Neuropsychological Assessment of Patients with Epilepsy

Generalized seizures

Tonic–clonic (in any combination)

Absence

Typical

Atypical

Absence with special features

Myoclonic absence

Eyelid myoclonia

Myoclonic

Myoclonic atonic

Myoclonic tonic

Clonic

Tonic

Atonic

Focal seizures

Unknown

Epileptic spasms

In the 2010 ILAE classification, one finds the well-known distinction between generalized seizures and focal seizures, differing in the characteristics of their underlying seizure networks, which are known to be bilaterally distributed in the case of generalized seizures and more localized in focal seizures. Generalized seizures can include tonic–clonic seizures, which is the most obvious and dramatic symptom of epilepsy, in addition to more subtle types of generalized seizures such as absence attacks and myoclonic seizures, which are seen mostly in childhood epilepsy syndromes.

Terms such as “simple” and “complex” partial seizures have been dropped from the new classification as a result of common misuse or misunderstanding of those terms. The current classification makes much less specification regarding focal seizures, placing more emphasis on describing these seizures based on features that are most useful for a given purpose. The symptomatic characteristics of focal seizures are varied and reflect functional characteristics associated with the brain region from which they originate. For this reason, neuropsychologists and other professionals interested in the study of behavior have shown a marked interest in focal epilepsy and its tendency to provide a “window” into underlying brain mechanisms.

Focal seizures often begin with an aura, which commonly reflects the anatomic origin of the initial site of abnormal brain activity. Seizures originating in temporal or limbic zones will often be preceded by onset of a visceral feeling or behavioral manifestations involving cognition or emotion. For example, seizures originating from the hippocampus are commonly characterized by mnestic changes, such as the well-known déjà vu phenomenon whereas those involving the amygdala might have more of an affective component, such as the subjective feeling of fear. Auras emanating from more posterior brain regions might involve somatosensory or visual changes associated with parietal or occipital regions respectively. Details regarding these auras provide valuable information about the localization of the seizure onset in addition to helpful clues about the nature of the functional impairment that might exist when the individual is not having seizures.

The evolution of focal seizures can be varied in nature, with the variability reflecting the track of abnormal electrical activity through a complex neural network involving subcortical and cortical brain regions. Some seizures will not evolve beyond the level of the aura, which makes them brief and simple in their characteristics. Other focal seizures will spread into a generalized tonic–clonic convulsion. In between these extremes, seizures will involve varying changes in consciousness, which are often difficult to characterize. In some cases, individuals are totally aware of their surroundings. In other cases, individuals might experience changes in consciousness accompanied by behaviors that seem out of their control. These behavioral “automatisms” have formed the basis of much debate on the role of consciousness in behavior, both from a medical and legal perspective. Table 1.2 includes a summary of terms that are now used to describe the range of impairment associated with focal seizures. Neuropsychologists are urged to become familiar with the terminology from this table as a starting point for providing a full clinical description of the phenomena reported by their patients.

Table 1.2

Descriptors of focal seizures according to degree of impairment during seizure—ILAE Revised (2010)

Without impairment of consciousness or awareness with observable motor or autonomic components. This roughly corresponds to the concept of “simple partial seizure.” “Focal motor” and “autonomic” are terms that may adequately convey this concept depending on the seizure manifestations.

Involving subjective sensory or psychic phenomena only. This corresponds to the concept of an aura, a term endorsed in the 2001 Glossary.

With impairment of consciousness or awareness. This roughly corresponds to the concept of complex partial seizure. “Dyscognitive” is a term that has been proposed for this concept.

Evolving to a bilateral, convulsive seizure (involving tonic, clonic, or tonic and clonic components). This expression replaces the term “secondarily generalized seizure.”

Epilepsy Syndromes

In the past, clinicians evaluating and treating patients with epilepsy focused primarily on seizure types and EEG abnormalities when classifying various forms of epilepsy. With technological developments in brain imaging and molecular genetics, clinicians now focus more on characterizing epilepsy syndromes, which now extend beyond the disorder’s electroclinical characteristics. A listing of the syndrome recognized by the ILAE is provided in Table 1.3. Neuropsychologists working with epilepsy patients are encouraged to be well acquainted with these syndromes.

Table 1.3

Electroclinical syndromes and other epilepsies—ILAE Revised (2010)

Electroclinical syndromes arranged by age at onset
Neonatal period
Benign familial neonatal epilepsy (BFNE)
Early myoclonic encephalopathy (EME)
Ohtahara syndrome
Infancy
Epilepsy of infancy with migrating focal seizures
West syndrome
Myoclonic epilepsy in infancy (MEI)
Benign infantile epilepsy
Benign familial infantile epilepsy
Dravet syndrome
Myoclonic encephalopathy in nonprogressive disorders
Childhood
Febrile seizures plus (FS+) (can start in infancy)
Panayiotopoulos syndrome
Epilepsy with myoclonic atonic (previously astatic) seizures
Benign epilepsy with centrotemporal spikes (BECTS)
Autosomal-dominant nocturnal frontal lobe epilepsy (ADNFLE)
Late onset childhood occipital epilepsy (Gastaut type)
Epilepsy with myoclonic absences
Lennox–Gastaut syndrome
Epileptic encephalopathy with continuous spike-and-wave during sleep (CSWS)
Landau–Kleffner syndrome (LKS)
Childhood absence epilepsy (CAE)
Adolescence—Adult
Juvenile absence epilepsy (JAE)
Juvenile myoclonic epilepsy (JME)
Epilepsy with generalized tonic–clonic seizures alone
Progressive myoclonus epilepsies (PME)
Autosomal dominant epilepsy with auditory features (ADEAF)
Other familial temporal lobe epilepsies
Less specific age relationship
Familial focal epilepsy with variable foci (childhood to adult)
Reflex epilepsies
Distinctive constellations
Mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE with HS)
Rasmussen syndrome
Gelastic seizures with hypothalamic hamartoma
Hemiconvulsion–hemiplegia–epilepsy
Epilepsies that do not fit into any of these diagnostic categories can be distinguished first on the basis of the presence or absence of a known structural or metabolic condition (presumed cause) and then on the basis of the primary mode of seizure onset (generalized vs. focal)
Epilepsies attributed to and organized by structural-metabolic causes
Malformations of cortical development (hemimegalencephaly, heterotopias, etc.)
Neurocutaneous syndromes (tuberous sclerosis complex, Sturge–Weber, etc.)
Tumor
Infection
Trauma
Angioma
Perinatal insults
Stroke
Etc.
Epilepsies of unknown cause
Conditions with epileptic seizures that are traditionally not diagnosed as a form of epilepsy per se
Benign neonatal seizures (BNS)
Febrile seizures (FS)

A full discussion of the pediatric epilepsy syndromes is beyond the scope of the current discussion. Excellent reviews of this material are provided in Chaps. 2 and 12. However, from the perspective of a neuropsychologist working with adults with epilepsy, it is important to remember that many forms of the disorder are developmental in nature, meaning that patients seen as adults might have experienced one of these developmental syndromes during childhood. This is particularly true for adults with focal epilepsy beginning in childhood secondary to perinatal stroke, brain tumor, traumatic brain injury, or any one of a number of causes of localized brain disturbance. It is important to recognize that cognitive deficits in these early onset cases will appear different from those in cases where seizures develop in adulthood. In other cases, epilepsy syndromes resulting from genetic or metabolic causes will be exhibited in adults as causes of intellectual disability. It is clear that the scope of the neuropsychological evaluation will be affected by specific characteristics and needs of the patient.

Most pediatric epilepsy syndromes characterized by the presence of absence or myoclonic seizures do not extend into the adult years. There are, however, some important exceptions. Juvenile myoclonic epilepsy (JME) is a form of epilepsy developing in adolescence or early adulthood characterized by bilateral repetitive myoclonic jerks occurring predominately in the upper extremities. These are, in many cases, accompanied by generalized tonic–clonic seizures and possibly absence attacks. While the condition is considered a form of generalized epilepsy, neuropsychological studies find that affected patients exhibit a pattern of neuropsychological test performance characterized by intellectual functioning within the average range and deficits in executive functions including planning, concept formation, and verbal fluency (Piazzini, Turner, Vignoli, Canger, & Canevini, 2008). More generalized patterns of neuropsychological dysfunction have been identified in patients with idiopathic generalized epilepsy (Shehata & Bateh Ael, 2009). There is now interest in determining whether there are, in fact, structural brain abnormalities in patients with generalized epilepsies that might provide an explanation as to why some forms, such as JME, show more localized patterns of neuropsychological dysfunction.

Neuropsychologists working with epilepsy patients should become very familiar with focal epilepsy syndromes as these are seen in more than half (60 %) of patients with epilepsy and are those most often referred for assessment of cognitive functioning. Temporal lobe epilepsy is the most well known and frequent of the focal epilepsy syndromes, occurring in approximately 70–90 %. Most of these patients demonstrate an onset of seizures emanating from the medial temporal lobe region, involving structures such as the hippocampus and amygdala. This form of the disorder, often referred to as mesial temporal lobe epilepsy (P. D. Williamson et al., 1993), is often seen in individuals with a history of febrile convulsions, auras of a visceral nature, and seizures beginning in the first decade of life. Hippocampal sclerosis, a condition characterized by gliosis and atrophy of the hippocampus, is the most common pathological feature. Patients with temporal lobe seizures originating from a more lateral neocortical onset often have auras involving illusory auditory or visual phenomena in addition to more complex behavioral automatisms (Pacia et al., 1996). The cause of epilepsy in these cases is varied with etiologies ranging from brain tumors, cortical dysplasia, to head trauma.

From a neuropsychological standpoint, patients with mesial temporal lobe epilepsy are known to have intact intelligence with particular deficits in word finding and memory retention (B. P. Hermann, Seidenberg, Schoenfeld, & Davies, 1997). Memory deficits in these patients are believed to result from a primary disruption of consolidation processes secondary to the hippocampal pathology. These patients are thought to differ on a neuropsychological basis from patients with lateral temporal lobe seizures, who are thought to exhibit more difficulty with memory encoding in addition to a more pronounced impairment in naming skills (Hamberger, Seidel, Goodman, Perrine, & McKhann, 2003).

Frontal lobe epilepsy is the second most frequently observed form of focal epilepsy. Seizures in patients with frontal lobe seizures include a combination of unusual movements and/or vocalizations often accompanied by abnormal motor activity (Patrikelis, Angelakis, & Gatzonis, 2009). Like temporal lobe epilepsy, one encounters seizures manifested specifically by changes in awareness or consciousness, previously referred to as complex partial seizures. Differentiating patients with frontal lobe epilepsy from those with temporal lobe epilepsy based on neuropsychological testing has proven more difficult than what was suggested by the early literature (Barr & Goldberg, 2003; B. P. Hermann, Wyler, & Richey, 1988; Milner, 1964). However, there is now published evidence indicating that patients with frontal lobe epilepsy exhibit more impairment in motor programming and deficits on tests of response inhibition (Helmstaedter, Gleibner, Zentner, & Elger, 1998).

Seizure localization in posterior cortical regions is much less common than those originating from the temporal and frontal lobes. Given the infrequency of the posterior cortical epilepsies they are often lumped into a general classification of “extratemporal seizures.” Seizures originating from the occipital lobe are characterized by visual auras, eye blinking, alterations in consciousness, and motor phenomena (Jobst et al., 2010). Those with an onset in the parietal lobe are often accompanied by somatosensory phenomena but little else that is specific to a disruption of that part of the brain (P. D. Williamson et al., 1992). Deficits in attention and processing speed are seen in some patients with occipital lobe seizures, but neuropsychological evidence of disruption of higher or visuoperceptual or language functions associated with focal seizures originating from the posterior cortex is mixed (Guerrini et al., 1997).

It is important to remember that focal epilepsy can be the result of any one of a number of different pathological processes. Brain tumor is the second most frequent cause of seizures. Stroke is another common cause of epilepsy with seizures known to develop at a higher rate following embolic events and from cerebrovascular events involving the middle cerebral artery. While neuropsychological profiles in patients with seizures resulting from one of these conditions are clearly influenced by lesion location, one must also consider the influence of seizure variables, medication effects, and other medical and emotional characteristics of the patient (Morrison & Nakhutina, 2007).

Treatment of Epilepsy

Nearly every patient with an established diagnosis of epilepsy will undergo some form of medication management with antiepileptic drugs (AEDs). While these drugs are known to be effective in reducing seizures through effects on neuronal irritability, they also have a simultaneous effect on neuronal excitability, which has the potential to reduce cognitive efficiency. Many of the most commonly used AEDs, their indications, and their effects on cognition are listed in Table 1.4. There is an interesting history to some of the older drugs, where their effectiveness for reducing seizures was identified “accidentally” in laboratory studies with animal models. While these drugs are known to be effective in treating multiple types of seizures in humans, they are also known to have significant effects on cognition, which was not a focus of study when the use of these drugs was first initiated. As a result, many of the newer AEDs were developed with the goal of modulating alternative neuronal mechanisms with the ultimate goal of improving seizure reduction with minimal effects on cognition.

Table 1.4

Cognitive side effects of antiepileptic drugs (AEDs)

	Epilepsy type	Cognitive effects
Older AEDs
Phenobarbital	Generalized, focal	Significant
Phenytoin	Focal, generalized	Moderate
Carbamazepine	Focal	Moderate
Sodium valproate	Generalized, focal	Moderate
Newer AEDs
Felbatol	Focal	Mild
Lamotrigine	Generalized, focal	Mild
Vigabatrin	Focal, generalized	Mild
Gabapentin	Focal	Mild
Topiramate	Focal, generalized	Moderate
Tiagabine	Focal	Mild
Oxcarbazepine	Focal, generalized	Mild
Zonisamide	Focal	Mild
Levetiracetam	Focal, generalized	Mild

Many patients require treatment with more than one AED to achieve adequate seizure control. Clinicians prescribing these medications must consider the balance between the need to minimize seizure recurrence and the desire to reduce side effects as polypharmacy is the number one treatment factor known to affect cognitive functioning (Loring, Marino, & Meador, 2007). Surprisingly little is known about the profile of cognitive side effects associated with specific AEDs. Most of this is the result of the multitude of methodological challenges one faces when attempting to conduct controlled studies on AEDs in patient samples (Kwan & Brodie, 2001). Some of this has been the result of a failure of neuropsychology, as a field, to agree upon a set of measures to evaluate cognitive functions in randomized controlled drug trials, much in the manner that the Alzheimer’s Disease Assessment Scale – cognitive subscale (ADAS-Cog) is used in Alzheimer’s disease studies (Mohs et al., 1997).

What is known from existing research is that the newer drugs have less severe side effects than the older drugs. It is generally known that phenobarbital is the drug with the most potent cognitive side effects. Based on the older literature, it has generally been assumed that other drugs, such as phenytoin and carbamazepine, have more moderate level effects on attention, processing speed, and memory retrieval. At one point, investigators were arguing whether these drugs’ influence on processing speed was the primary result of attentional or motoric factors (Dodrill, 1975, 1992; Trimble & Thompson, 1983).

Findings on newer AEDs have shown more generalized effects on cognitive functioning. Many note that some drugs, such as lamotrigine, have only minor CNS side effects in addition to some “alerting” properties associated with beneficial effects on mood (Kwan & Brodie, 2001; Loring et al., 2007). Topiramate, an extremely effective antiepileptic agent, is the one among the newer drugs that stands out as having differential effects than the other newer drugs. Patients taking this drug have been described as having more effects on cognition than other drugs with additional effects reported on executive functions and language skills including naming and verbal fluency. It has been demonstrated that these effects can be reduced with careful titration and minimal dosing, when possible (Loring, Williamson, Meador, Wiegand, & Hulihan, 2011).

In practice, neuropsychologists need to recognize that patients with epilepsy will require variable levels and types of medications to control their seizures. Some patients tend to report more cognitive side effects than others. In counseling patients receiving medication management, one should emphasize that, based on results of experimental studies, the AED effects on cognition are known to be minimal. The clinician should also inform them that the initial cause of the epilepsy and the ongoing effects of seizures are likely to be exerting an effect on their cognition and that their subjective sense of attention or memory disturbance is not likely to be caused solely by the drugs they are taking. They also need to be reminded that while the drugs are known to have some side effects, these are likely to be minimal in comparison to the decline in cognitive functioning that would potentially result if one were to discontinue medication management altogether, which would lead to uncontrolled seizures in many patients taking AEDs and the possibility of a steady decline in cognitive functioning.

While most patients with epilepsy achieve adequate seizure control with AED treatment, there remain a substantial number who become “drug-resistant,” which is defined as a failure following an appropriate trial of two (or more) appropriately used medications. It is now estimated that 30–40 % of patients will eventually become refractory to treatment, defined by medical terms (Kwan, Schachter, & Brodie, 2011). One must also consider a number of other factors when determining whether an individual has reached a treatment refractory state. One of these involves whether the patient has “socially disabling” seizures, which are seizures that reach a point where they have a marked detrimental effect on one’s lifestyle. It is important to recognize that some patients, possibly in the context of intellectual disability, can tolerate the occurrence of daily seizures, if they are residing in a safe and supportive environment. Other patients, such as those working in professional roles or with family responsibilities, might not be able to tolerate one seizure per year without sustaining a substantial disruption on their lives. It is important to realize that cognitive functioning, as assessed through neuropsychological testing, can provide significant information in helping to determine whether patients are achieving optimal treatment of their seizures.

There are a number of alternatives to drug treatment for epilepsy, although most are used in combination with drugs in the majority of cases. Surgery is the most well known of these treatments, with results demonstrating that significant relief from seizures can be obtained in approximately 70 % of patients undergoing surgical resection of the epileptic focus (Wiebe, Blume, Girvin, Eliasziw, & Effectiveness and Efficiency of Surgery for Temporal Lobe Epilepsy Study Group, 2001). However, it is recognized that there is risk to decline in verbal memory and naming following these procedures, with greater levels of impairment observed in those undergoing left side surgery (Sherman et al., 2011). More details about the neuropsychological aspects of epilepsy surgery can be found in Chap. 4. Vagal nerve stimulation is another one of the other available nondrug treatments involving surgical placement of a programmable pulse generator in the patient’s chest. While the efficacy of this treatment is considered somewhat modest, there have been some suggestions that it has less of an effect on cognitive functioning with possible improvement seen in some patients. Information about cognitive functions associated with some of the newer epilepsy treatments such as electrical or pharmacological stimulation is currently limited.

Neuropsychological Assessment

Clinical neuropsychologists are considered essential members of the interdisciplinary teams found at most epilepsy centers. In fact, guidelines established by the National Association of Epilepsy Centers consider doctoral level neuropsychologist among the staff members recommended for staffing at all Level 3 and 4 epilepsy specialty centers (NAEC Guidelines, 2010). The guidelines encourage neuropsychologists working in these settings to have postdoctoral training in neuropsychology with specific experience in using neuropsychological tests for evaluation of epilepsy surgery along with a background in interpreting results of intracarotid amobarbital procedures (Wada Tests).

Neuropsychologists play a number of important roles in an epilepsy center by virtue of the unique training they have received. While many associate neuropsychologists with assessment services, the role they play in specialized epilepsy centers often extends far beyond testing. As found in many clinical settings, neuropsychologists are valued for their ability to integrate information obtained through various sources. As a result, they are often the only clinicians present on the team who are in a position to provide a comprehensive and balanced description of the patient based on their medical, cognitive, emotional, and psychosocial characteristics. Neuropsychologists are also able to provide valuable input to the treatment team by taking into account unique characteristics of the patient’s social and cultural background when making clinical recommendations.

There are numerous reasons to conduct a neuropsychological assessment on a patient with epilepsy. Some of these recommended by the NAEC are listed in Table 1.5. While most attention is typically based on assessment for epilepsy surgery (see Chap. 4), there are many other questions that can be addressed by performing neuropsychological testing on a patient with epilepsy.

Table 1.5

Guidelines for neuropsychological services: National Association of Epilepsy Centers (NAEC, 2010)

1. Comprehensive neuropsychological test batteries for:

(a) Evaluation of cerebral dysfunction for vocational and rehabilitative services.

(b) Localization of cerebral dysfunction in evaluation for epilepsy surgery.

2. An established referral arrangement for comprehensive management of psychogenic nonepileptic events.

3. Clinical psychological services for assessment and basic treatment of emotional disorders associated with chronic epilepsy.

Neuropsychological assessment is often requested in situations when there is a need to know a patient’s particular strengths and weaknesses. This knowledge will be put to use in different ways depending on the patient’s age and the context of their daily activities. For example, a student in college might need this information to receive academic accommodations while another patient might benefit from receiving information from testing to guide vocational planning. Other patients complaining of cognitive difficulties will appear for testing with the goal of verifying whether their subjective sense of memory or concentration impairment is “real” and finding if there is a way that something can be done to reduce it.

Evaluations by neuropsychologists are also commonly obtained when the treatment team desires input on cognition to help in making a differential diagnosis. This information might come in handy when there is a need to determine whether a geriatric patient’s reported memory disturbance is related more to the influence of ongoing seizures or to the effects of an underlying neurodegenerative process such as Alzheimer’s disease. In other cases, testing can be useful in monitoring effects of nonsurgical treatments such as the side effects of medications.

While neuropsychological assessment of a patient with epilepsy generally focuses on evaluation of cognitive functions it is important to recognize that clinicians working in epilepsy centers also play a role in addressing mental health issues. As listed in Table 1.5, neuropsychologists often play a significant role in evaluating and treating patients with psychological nonepileptic seizures (PNES) and other types of psychiatric disorders. Details regarding these types of evaluations are provided in Chaps. 9 and 11.

Clinical Interview

Many consider the neuropsychologist’s clinical interview to be the most important component of the assessment process. In many cases, it is the opportunity for the clinician to obtain a direct description of symptoms and important historical elements while observing the patient’s behavior in an open-ended condition. The Russian neuropsychologist, A.R. Luria, emphasized the “preliminary conversation” as the point where the clinician develops initial theories about the patient and his or her condition that will guide the choice of assessment procedures (Luria, 1966). The interview often serves as the time when the clinician arrives at a set of relevant hypotheses that will either be confirmed or disconfirmed through the results of formal testing. In a patient with epilepsy, the clinical interview provides an occasion for the neuropsychologist to pose questions directly to the patient regarding the characteristics of their seizures in addition to how the seizures affect their cognitive and behavioral functioning.

Before considering the elements of a clinical interview with an epilepsy patient, it is useful to present a model for understanding how epilepsy affects behavior and cognition. In a comprehensive review published in 1984, Bruce Hermann and Steven Whitman provided a model for understanding epilepsy’s effects on behavior and personality, which can be adapted easily to explain cognitive factors (B. P. Hermann & Whitman, 1984). The model conceptualizes behavior in patients with epilepsy as influenced by various effects, beginning with brain-related factors, such as the initial cause of the epilepsy or the effects of seizures. Secondly, one must consider treatment effects, particularly the influence of AEDs and surgery. Lastly, one needs to acknowledge that various “non-brain” variables will affect behavior, including social variables and the effects of mood. Figure 1.1 provides a depiction of the relative contributions of these various factors. Characterizing the effects of these three variables on cognition can be very helpful to clinicians when attempting to integrate information relevant to the assessment and when providing feedback to patients regarding the effects of the epilepsy on their attention and memory functioning.

Fig. 1.1

Factors contributing to cognitive and behavioral impairment in epilepsy (from Kwan & Brodie, 2001. Reproduced with permission)

When beginning the interview, the neuropsychologist should start with a description of the nature and purposes of the testing. The examinee must have the ability to provide informed consent to proceed with the evaluation, consistent with the ethical principles of the American Psychological Association (APA, 2002). During this point of the evaluation process, the examiner should be in a position to address any questions the patient might have about the testing or their condition and life in general. It is also important to inform the patient that a report will be prepared and will be sent to the referring party. One might also ask whether the report should be sent to any other parties and what arrangements will be made to provide direct feedback to the patient regarding the final results.

The information-gathering portion of the interview should begin with the patient’s subjective description of their symptoms and how the symptoms affect their daily lives. Based on research findings, we know that approximately 70 % of patients with epilepsy experience a subjective disturbance of memory, making this the most common cause for a referral for neuropsychological assessment (Thompson & Corcoran, 1992). However, the clinician should always remember that patients and referral sources are not psychologists and, as a result of a lack of knowledge, may refer to cognitive difficulties more generally as memory difficulties in cases when attention or executive functions are the actual domains that are affected. One will encounter many cases where a patient with epilepsy will complain of memory difficulties and it is discovered that their major problem is more consistent with impairment in executive functions such as organization or planning. A guided description of the patient’s symptoms and the context in which they arise will provide the neuropsychologist with valuable insights into the presenting problem.

After coming to an understanding of the patient’s cognitive complaints it is important to turn to their seizure history. To begin with, it is important to have a good idea of when the seizures began. While this might be assumed to be when the patient first came to medical attention, that is not likely to be the exact point when the seizures first appeared. Many patients will describe unusual experiences occurring during their lifetime that, in retrospect, were likely to have been the effects of focal seizures, long before they received medical treatment. It also helps to differentiate when in life the patient developed habitual seizures, as opposed to other types of seizures that had appeared at some point during their lifetime. In this context, it is important, for example, to determine whether a patient ever experienced a febrile seizure during infancy or early childhood (<3 years), which is known to be a strong risk factor for mesial temporal epilepsy in a patient presenting later in life with a history of focal seizures.

At some point, the interview will turn to the patient’s own description of their seizures. It is often useful to obtain these descriptions in spite of the fact that the medical record might contain detailed information on their seizure history. As in other contexts, it is often good to go back to the original source for a full description. Coming to an understanding of the patient’s subjective account of the seizure, as opposed to what others have told them, will help the interviewer determine to what degree consciousness is affected during the seizure and whether there are any specific subjective phenomena that might provide clues to localization. Negative information, such as the patient claiming to be totally amnestic for the seizures, can also be extremely helpful, as it has been shown that those who are amnestic for seizure activity are more likely to experience bitemporal abnormalities on EEG (Palmini, Gloor, & Jones-Gotman, 1992).

A number of studies over the past 40 years have examined the effects that various seizure variables have on neuropsychological test performance. From a neuropsychological perspective it is important to estimate the age of onset of the epilepsy, as it is known that an onset of seizures early in life will have a more generalized and detrimental effect on test performance (Dikmen, Matthews, & Harley, 1975; Elger, Helmstaedter, & Kurthen, 2004). In terms of seizure type, it is clear that generalized tonic–clonic seizures provide a greater impact on neuropsychological functioning than other types of focal seizures (Dodrill, 1986). It is also important to determine whether the patient has ever experienced status epilepticus, a condition characterized by prolonged or clustered seizures, which is known to provide a significant long-term disruption to memory and other functions in some patients (Dodrill & Wilensky, 1990).

Patients often have a difficult time quantifying the frequency and severity of their seizures. While many are asked to keep a diary on their seizure activity, these are often found to be inaccurate as a result of the fact that some patients are not aware that a seizure has occurred and, without the help of a reliable collateral informant, might not be able to specify how many seizures they are having with any acceptable degree of reliability. While it is clear that having frequent seizures is not good for one’s cognitive functioning, it is not totally clear how “seizure burden,” a concept designed to capture a combination of seizure type and frequency, affects performance on neuropsychological testing. Further research on this topic is clearly needed.

A good clinical interview will also address the etiology of the epilepsy, as this is likely to have a major impact on neuropsychological functioning, independent of the effects of seizures. This should start with a detailed neurodevelopmental history, beginning with details on the patient’s birth and early maturation. This will include information regarding the age at which the patient began walking and talking. One will also want to learn details of the patient’s school history and whether there was any evidence of learning disability (LD) or attention deficit hyperactivity disorder (ADHD) identified by parents, school, or medical personnel. Information regarding the patient’s favorite subjects in school, or those subjects they disliked immensely, has the potential of providing valuable input to cognitive deficits that might have originated in childhood. It is also important to learn about the patient’s social development, in terms of their ability to establish friendships and peer relationships. One might also ask if they remember being bullied or excluded from activities as a result of their seizures.

In patients with a history of focal seizures, it is important to obtain medical information on the causative factor, as this will also have a likely impact on neuropsychological functioning. In those patients with a history of brain tumor, one should understand when symptoms of the tumor first appeared and whether that coincided with the onset of epilepsy. One must also know the pathological type and grade of the tumor in addition to whether any surgery has been performed. In cases of traumatic brain injury (TBI), it is necessary to gain information on the nature of the initial injury, including whether there was a loss of consciousness, post-traumatic amnesia, or coma. One must come to an understanding of the overall severity of the injury, as it is clear that epilepsy will occur much more frequently following a severe level of TBI as opposed to mild TBI (Lowenstein, 2009). Neuropsychologists will also need to obtain details regarding illness and onset of seizures in patients with epilepsies resulting from infectious and other medical causes.

One must always remember that a patient with epilepsy is first and foremost a person living their life who will face the same medical, psychological, and social factors that affect all other individuals undergoing a neuropsychological evaluation. The clinician must be in a position to determine whether there are any ongoing medical factors, such as hypertension, hypercholesterolemia, diabetes, or cardiac abnormalities that might affect the patient’s neuropsychological functioning. One must know whether the patient has undergone any type of surgical procedure, whether or not it is related to treatment for epilepsy. It is important to have information on the full regimen of medications the patient is taking. While the cognitive side effects of AEDs are reviewed above, one must also determine whether the patient is taking any other medications for other physical illnesses or ailments with a potential for similar side effects. The interviewer should be aware if there is a family history of epilepsy or any other types of family based neurological or neuropsychiatric disorders. As with any evaluation, the clinician should determine whether there is any history of alcohol or drug abuse.

Patients with epilepsy are known to have a higher rate of mental illness than the general population. This topic is covered in detail in Chap. 9. It is estimated that approximately 30 % of patients with epilepsy will encounter depression at some point in their lives (Kanner, 2013). A substantial number of patients with epilepsy also experience anxiety disorders. Clinicians should ask whether the patient has ever been under any form of psychological or psychiatric treatment. The neuropsychologist will need to conduct a detailed assessment of mood disorder symptoms during the clinical interview and should be in a position to refer for psychiatric treatment, if indicated. While seen more rarely, one should also be on the lookout for the presence of psychotic symptoms, either emerging in the context of seizure clusters or occurring totally independent of seizure activity.

It is helpful to learn details about the patient’s social background. One might ask questions on where they were born and raised. At this point, one can get information about the family background, including the number of siblings. It is often helpful to know details about family members and their educational and occupational backgrounds. As a result of the condition and its effects on cognition and education, some patients with epilepsy may be prone to feeling as if they have achieved less than others in their family, which can have an effect on them from a psychosocial perspective.

It is very important for the neuropsychologist to have a full understanding of the patient’s cultural background before proceeding with the evaluation. One must know first whether English is the patient’s native language. The vast majority of neuropsychological tests used in North America are developed and normed in English. When planning the evaluation, it is important to understand whether or not the patient can complete the testing with the use of standard instruments, or whether testing in their native language will be required. More detailed discussion of this issue is provided in Chap. 14. Secondly, it is known that patients’ and families’ understanding and perception of illness and seizures varies widely among cultures. Neuropsychologists, by virtue of their specialized training, are in a position to recognize many of these factors and integrate them into their evaluation and interpretation of the test findings.

Turning back to the patient, it is helpful to learn details about their educational history. One will also want to obtain a detailed occupational history with emphasis on how seizures and cognitive effects were expressed during the course of the individual’s employment and how employers, supervisors, and coworkers reacted to these issues. It is often helpful to break down the patient’s workday and activities to determine if any workplace accommodations are warranted if supported by the neuropsychological test findings.

Finally, one will want to know details about the patient’s home and social life. Asking about who is living with the patient in their current home environment is a good way to address relationship issues without any ties to traditional values. It is important to understand the quality of relationships and how these individuals react and support the patient in terms of their epilepsy. At this point, one might also obtain information about the patient’s interests and their daily activities. One might also query on how seizures and/or cognitive issues affect their ability to perform and enjoy these activities.

Neuropsychological Testing

Background on Testing

While the specific roles that clinical neuropsychologists will play in each epilepsy center might vary, their responsibilities will almost always include neuropsychological assessment as a primary function. It is important to remember that the process of neuropsychological assessment is rather broad and encompasses test selection, interpretation of the data, and integrating the findings with clinical information obtained from other sources. One must not confuse the assessment process with that of test administration, which is clearly an important component of the overall assessment process, but requires less extensive training with heavy reliance on procedural guidelines provided in test manuals.

It is recognized that professional preparation for practice in neuropsychological assessment requires extensive coursework and clinical training in neuropsychology and knowledge about epilepsy syndromes and effects of seizures and treatments on cognitive functions. In terms of education and training, this typically requires a doctoral degree in professional psychology (e.g., Ph.D. or Psy.D.), clinical training in generic clinical psychology, and 2 years of postdoctoral training in clinical neuropsychology.

Practice in clinical neuropsychology requires a professional license in psychology, consistent with local state or provincial laws. The scope of knowledge and skills required for effective practice in clinical neuropsychology, with its focus on the study of the science of psychology, statistical methods, and psychometrics, is distinctly different from the education and training obtained in receipt of a typical medical degree or in other health care fields, which do not include a comparable level of education in any of these topics. It is becoming more and more common for clinical neuropsychologists to obtain board certification (e.g., ABCN) to formally document their training and proficiency. Commensurate with the medical model and the expectations made of our physician colleagues, obtaining board certification is highly recommended for those planning to work in comprehensive epilepsy centers.

Results from professional surveys indicate that over 50 % of neuropsychologists utilize ancillary staff, such as graduate school trainees or technicians, to administer neuropsychological tests under their direct supervision (Sweet, Meyer, Nelson, & Moberg, 2011). Results of a survey conducted on neuropsychologists practicing specifically in epilepsy centers indicate that 63 % employ technicians to assist with test administration (Djordjevic & Jones-Gotman, 2011). The process is analogous to that of a radiologist who interprets images produced from the work of a technician rather than obtaining the images directly. The professional component lies in the interpretation and communication of the results, rather than from collecting the data. This practice, when used by neuropsychologists, is recognized legislatively in nearly every state and is reimbursed by third-party payers across the country including the Centers for Medicare and Medicaid Services (CMS) with specific Current Procedural Terminology (CPT) codes (e.g., CPT code 96119). Interested readers can obtain further details about the use of technicians in neuropsychological testing through published statements provided by professional organizations including Division 40 of the APA (APA Division 40, 1991), the National Academy of Neuropsychology [NAN, (Puente, Adams, Barr, Bush, & N. P. P. Committee, 2006)], and the American Academy of Clinical Neuropsychology (AACN, 1999).

Neuropsychological tests provide an empirically based method for evaluating and measuring cognition and behavior. Successful use of these tests requires adherence to standardized administration guidelines and the proper use of psychometric and normative principles when interpreting the results. The guidelines for neuropsychological services provided in Table 1.5 above include general reasons for administering test batteries. However, from a purely empirical basis, the information provided by standardized testing is most useful in advising the treatment team regarding three basic questions: (1) has there been a general decline in the patient’s level of intellectual functioning, (2) are there weaknesses or impairments in specific aspects of cognitive functioning, and (3) has there been a relevant and identifiable change in performance or functioning on testing performed between Time 1 and Time 2?

Clinicians treating patients with epilepsy are very interested in knowing whether a given patient is experiencing any form of cognitive decline that can be attributed to the epilepsy or seizures. Results from longitudinal studies indicate that a progressive pattern of cognitive decline can be identified in adults with epilepsy with duration of illness appearing to be the most reliable predictor of its occurrence (Seidenberg, Pulsipher, & Hermann, 2007). More detailed information about this issue can be found in Chap. 3. Scores from neuropsychological testing naturally provide the optimal data for addressing this issue. Empirical documentation of cognitive decline can be provided by demonstrating a statistically rare discrepancy between current test performance and measures used to estimate expected “premorbid” levels of functioning or through demonstrating on repeat testing that the interval change in test scores exceeds what is expected by “chance” or as a result of “practice effects.” Clinicians using neuropsychological tests to address these questions must therefore be adept at using psychometric principles for interpreting base rates of discrepancy between test scores and formal statistical methods for assessing changes in test scores over time.

Based on contents of the clinical descriptive literature, we are well aware that patients with epilepsy can exhibit “normal” levels of intellectual functioning while experiencing specific deficits in cognitive areas such as attention, executive functions, and/or memory. However, identifying specific weaknesses in cognitive functioning in a valid and reliable manner through neuropsychological testing can be a challenge to even the most seasoned clinical neuropsychologist. When using a comprehensive battery of tests, one must be very careful to avoid making a Type I statistical error resulting from erroneously identifying a deficit based on what might be statistically “chance” findings. The field of neuropsychology has been paying more attention to this issue in recent years with an increasing number of published papers demonstrating the frequency of “abnormal” test scores found in healthy control samples who have completed neuropsychological testing (Binder, Iverson, & Brooks, 2009; Schretlen, Testa, Winicki, Pearlson, & Gordon, 2008). Neuropsychologists working in epilepsy centers must be aware of these base rates of abnormal test findings and exercise care when reviewing a sheet of scores from a neuropsychological test battery by making sure that a sufficient number of scores are in the abnormal range and that the pattern of abnormal scores fit some reasonable conception of an identifiable cognitive deficit.

One of the most powerful uses of neuropsychological testing is to identify the presence of cognitive changes over time. Making inferences from changes in test scores obtained over two or more evaluations provides information that is useful for measuring treatment effects from medication and/or surgery and, as discussed above, can be helpful in identifying changes associated with a pattern of cognitive decline. Neuropsychologists working in the field of epilepsy have been at the forefront of developing empirical methods for assessing interval change. Valuable information from a pioneering set of studies performed in the 1990s has been used to determine “normal” patterns of change over time in samples of epilepsy patients using a variety of different tests (Chelune, Naugle, Luders, & Awad, 1991; B. P. Hermann et al., 1996). Data from these studies, combined with empirical methods for assessing change, such as the reliable change index (RCI) and standardized regression-based (SRB) methods, have provided the field with a statistically rigorous methodology for assessing change associated with drug treatment, surgery, and other factors (Barr, 2002). Neuropsychologists are encouraged to use this information when assessing changes in their patients.

Neuropsychological Test Battery

There is no universally accepted approach to conducting a neuropsychological assessment in epilepsy patients or in those with any other clinical condition. Over the years, methodological approaches to neuropsychological testing have fluctuated between an emphasis on purely empirical or quantitative methods, such as that which is characterized by use of a fixed-standardized approach such as the Halstead-Reitan Neuropsychological Test Battery (HRNB) (Reitan & Wolfson, 1985) and an emphasis on purely flexible approach using clinical or qualitative methods, such as what might be found using the Boston Process Approach (Kaplan, 1988) to assessment. However, according to recent surveys, a more hybrid approach to assessment is now used by the majority of practicing neuropsychologists, characterized by what is termed as a flexible battery of tests, chosen for use with specific patient groups. This approach is based on the use of a core battery of tests with various patient groups supplemented by adding or subtracting certain tests from the battery depending on characteristics and needs of the patient. This is the approach recommended for use when evaluating patients with epilepsy.

A neuropsychological test battery for epilepsy, based significantly on use of measures from the HRNB, was developed by Carl Dodrill in the 1980s (Dodrill, 1978). However, based on results from experimental studies on cognition in epilepsy, most clinicians evaluating patients with epilepsy using a flexible battery of tests for assessment of adults are encouraged to include measures of general intelligence, attention, executive functions, language, and memory. There is currently no universally accepted battery of tests. Common with traditions in neuropsychology, individuals from various centers tend to use tests that are most familiar to them based on a number of scientific and nonscientific factors including the preference of their clinical supervisors. This has led to differences in test usage based on the regional location of the epilepsy center. There are efforts in the field of neuropsychology to phase out the tendency to choose tests based on comfort level in favor of selecting a set of measures that has been validated for clinical decision-making through empirical research (Chelune, 2010).

Clinicians aiming to develop a clinical test battery are often informed by learning which tests are used by their colleagues. Several surveys of neuropsychological test usage among clinicians have been published (Rabin, Barr, & Burton, 2005), including some conducted on neuropsychologists working in specialized epilepsy centers. Djordjevic and Jones-Gotman (2011) conducted a recent survey from 75 respondents working in epilepsy centers spanning across 17 countries, with the majority (65 %) of them from North America. The results of the survey are listed in Table 1.6. The findings demonstrate that, on average, the duration of neuropsychological evaluations performed in epilepsy centers is 5.6 h. The number of tests administered varies widely, with a range from 12 to 56 tests considered part of a “standard” battery. Neuropsychologists across the globe are in general agreement about the domains of functioning assessed in patients with epilepsy and the type of core battery that is used, although there is certainly evidence that many centers continue to use their own specific choice of tests for many applications.

Table 1.6

Summary of survey of neuropsychological test usage among neuropsychologists working in specialized epilepsy centers (Djordjevic & Jones-Gotman, 2011)

Domain	Most use (>50 %)	Many use (20–50 %)
Intelligence		WAIS/WASI
Attention	WAIS Digit Span	Letter-Number Sequencing
	WAIS Digit Symbol	WMS Spatial Span
	Trail making Test
Executive	WCST	Stroop
	Letter Fluency (COWAT)
	Category Fluency
Motor	Grooved Pegboard	Finger Tapping
		Motor Strength
Language	Boston Naming Test	Token Test
	WAIS Vocabulary	WRAT
Visuospatial	WAIS Block Design	Judgment of Line Orientation
	WAIS Picture Completion	Facial Recognition Test
	Rey Complex Figure Copy
Memory	WMS	RAVLT
	Rey Complex Figure Recall	CVLT
Mood		BDI
		BAI
Personality		MMPI
		PAI

BAI Beck Anxiety Inventory, BDI Beck Depression Inventory, COWAT Controlled Oral Word Association Test, CVLT California Verbal Learning Test, MMPI Minnesota Multiphasic Personality Inventory, PAI Personality Assessment Inventory, RAVLT Rey Auditory Verbal Learning Test, WCST Wisconsin Card Sorting Test, WAIS Wechsler Adult Intelligence Scale, WASI Wechsler Abbreviated Scale of Intelligence, WMS Wechsler Memory Scale, WRAT Wide Range Achievement Test

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