Clinical Vignette

A 40-year-old woman experiences episodic numbness that spreads from the left thumb to the hand, arm, and then to the face over a period of about 30 seconds. These occur sporadically and are stereotypical in nature. She maintains alertness throughout the events. Since starting antiepileptic medications, these events have abated.

This history represents typical simple partial seizure (SPS). During the episodes, patients are conscious, aware of their surroundings, and able to respond appropriately. Partial seizures originate and develop within a discrete area of the cerebral cortex (Fig. 14-3). They may have a “Jacksonian march” wherein the cortical epileptic discharges spread along contiguous cortical regions. The brain area involved determines the clinical signature of the event. Symptoms may be somatosensory, as in the above vignette, when the origin is in the parietal lobe, motor when discharges arise from the frontal or motor cortex, and visual when they begin in the occipital lobe. However, the relation of focal cortical location to clinical expression is not absolute. Seizures may start in a “silent” cerebral cortical area with the manifest ictal symptoms representing the result of the discharge spreading to neighboring cortical areas. SPSs may occasionally have autonomic, psychic, or cognitive manifestations. Other seizure types may start off as SPS and then evolve into broader disruptions. By definition, these simple ictal events do not include any change in level of consciousness and it is this preserved responsiveness to the external environment that characterizes SPSs. Auras, a warning that a patient experiences prior to altered or loss of consciousness, are, in effect, SPS.

Figure 14-3 Classification of Partial Seizures.

Clonic phases of partial motor seizures that continue uninterrupted for prolonged periods, with no progression into other body segments, are known as epilepsia partialis continua, or Kojevnikov syndrome, and are discussed below.

The clinical evaluation of patients with partial epilepsy must include an EEG, a neuroimaging test, and laboratory testing. Although routine EEG recordings may often be normal in patients with unequivocal seizure disorders, it remains of paramount importance for the correct diagnosis and classification of the ictal events. Even when the neurologist suspects a seizure disorder from the clinical description, the EEG, if positive, may serve as an important confirmatory test when the episode is not well described. It should be remembered, however, that a routine EEG represents only a limited time sample and that sporadically firing interictal discharges can, therefore, be easily missed in patients with unequivocal seizure disorders. Long-term seizure telemetry units and ambulatory EEG monitoring are now available to increase recording time and enhance detection rates. The EEG hallmark of partial epilepsy is focal spikes or spike-and-wave discharges. Because delta-wave non-REM sleep activates or disinhibits epileptiform discharges, the EEG is preferably recorded during both wakefulness and sleep to increase the probability of making the correct diagnosis and defining the focal origin (Fig. 14-4). A definitive result is often obtained only during sleep recordings. Repeated recordings may be necessary if the nature of the episode is unclear or if psychogenic nonepileptic seizures are suspected. In contrast, the EEG in patients with epilepsia partialis continua contains spike-wave discharges in a variably continuous manner, often in the contralateral frontal lobe. A small number of individuals in the healthy population have abnormal EEG containing focal spikes but do not go on to have seizures later in life. This emphasizes that an abnormal EEG can only be interpreted in light of the presenting clinical symptoms and that it does not, on its own, define a seizure syndrome or dictate treatment. At best, the EEG may capture an ongoing seizure and greatly clarify its origin. It may also help to localize the epileptogenic pathology, guiding surgery if medical treatment fails.

Figure 14-4 Electroencephalography.

Neuroimaging studies, especially MRI, are vital to the evaluation of new-onset or changing-pattern seizures. Brain computed tomography is a useful screening technique when MRI is not available. The onset of new partial seizures strongly suggests the development of a new pathologic process, including tumors (primary or metastatic) or abscess in the adult population, stroke from emboli or rarely vasculitis in older age groups, and focal encephalitis such as Rasmussen encephalitis in children, herpes simplex encephalitis in children or adults, or head trauma (Fig. 14-5). However, sometimes a patient with a lesion, for example, mesial temporal sclerosis or an AVM, does not present with partial seizures until adulthood. Rarely, acute-onset partial seizures may be caused by metabolic abnormalities, such as nonketotic hyperglycemia or hypoglycemia.

Figure 14-5 Causes of Seizures.

Clinical Vignette

A 37-year-old patient experiences episodic events that start with a rising feeling in the stomach followed by a blank stare with loss of awareness. Subsequently, he has nonpurposeful movements of the hands lasting several minutes followed by somnolence.

This patient’s history represents a typical example of complex partial seizures (CPSs). The clinical manifestations of this seizure type include changes in alertness or level of consciousness, partial amnesia, and automatisms (Fig. 14-3). Patients often perform simple motor tasks and even may walk during the seizure. CPSs usually arise from mesial temporal structures but can also originate in other extralimbic temporal structures or the inferior frontal lobe and spread via the uncinate fasciculus and other pathways to the mesial temporal area.

Partial seizures of frontal lobe origin are frequently confused with a CPS of temporal origin but are distinguished by brief auras with rapid generalization or versive head and eye movements with tonic posturing of the arms. Rarely, a fall is the only clinical feature. Nocturnal frontal lobe seizures often produce odd complex behaviors suggestive of psychogenic nonepileptic seizures but should be kept in mind in those with fairly consistent patterns and no obvious secondary gain.

Because complex seizures are of focal origin, patient evaluation is similar to that undertaken for SPS. Typically, the interictal EEG (i.e., obtained between seizures) reveals spike discharges in one or both anterior temporal lobes. The ictal EEG is usually abnormal, with recurrent focal spikes or rhythmic activity. Brain MRI with special attention given to the temporal lobes shows that these patients often have mesial temporal lobe sclerosis with cell loss and atrophy (see Fig. 14-5).

Clinical Vignette

A 40-year-old patient experiences events in which he suddenly stiffens, cries out, loses consciousness, and progresses to have rhythmic tonic–clonic movements of all four extremities lasting several minutes. The events are associated with incontinence, tongue bites, muscle soreness, and ultimately a state of somnolence. Several hours later, the patient was awake and back to normal but had no recollection of the event.

This type of seizure represents the classic picture that the public and medical community generically perceives as epilepsy. Generalized seizure begin with simultaneous and almost equal involvement of both hemispheres from the onset and, unlike partial seizures with focal cortical abnormalities, involve the deeper thalamic, subcortical, and brainstem structures in a feedback loop to the cortices. Tonic–clonic (grand mal) seizures are often preceded by nonspecific, vaguely defined prodromes lasting at times up to hours or have no promontory symptoms at all. Seizures with specific auras, on the other hand, usually are of a focal origin with secondary generalization.

Grand mal seizures start with loss of consciousness, a cry, generalized tonic muscle contraction, and a fall (Fig. 14-6). Autonomic signs are often present during the tonic phase, including tachycardia, hypertension, cyanosis, salivation, sweating, and incontinence. The tonic muscle contraction becomes interrupted relatively soon and is followed by the clonic phase of the seizure with brief relaxation periods progressively lengthening until the seizure eventually abates. Patients may remain stuporous for a moment and eventually awaken confused with postictal headaches, lethargy, disorientation, and myalgia that may persist for up to a few days.

Figure 14-6 Generalized Tonic–Clonic Seizures.

A single generalized grand mal seizure does not warrant the diagnosis of epilepsy. In the vignette above, the patient later admitted that during the previous year, he was worried about his business and had been abusing alcohol and sedatives. He had recently discontinued these and had not had alcohol or sedatives for 48 hours. EEG and neuroimaging studies were normal. The seizure described above represents a reactive type of generalized grand mal seizure secondary to drug withdrawal. Similar seizures may occur from severe sleep deprivation, withdrawal from other drugs, trauma, central nervous system (CNS) infection, and various metabolic conditions.

Clinical Vignette

A 10-year-old boy is noted to have abrupt and brief (~10-second) episodes of impaired alertness. These can be brought out particularly when he hyperventilates. Eye fluttering is often noted during the episodes and occasional lip movements. The child returns to normal right after the episodes and the neurologic examination is normal.

This is the typical history of a child with generalized absence (petit mal) seizures. Petit mal epilepsy is the classic example of benign primary generalized epilepsy, which tends to remit in adulthood. Brief lapses in consciousness without an aura or any postictal symptoms are the main features (Fig. 14-7). Automatic movements may be observed but are generally simple and brief. The neurologic examination is usually normal.

Figure 14-7 Absence (Petit Mal) Seizures.

EEG provides the best diagnostic confirmation and typically demonstrates brief generalized bilaterally synchronous 3-Hz spike-and-wave discharges. Hyperventilation may precipitate petit mal seizures and the classic EEG changes describe above. There is neither focal interictal EEG epileptic activity nor focal initiation of the spike-and-wave pattern.

Atypical Absence Seizures

Atypical absence seizures differ from typical absence seizures because motor symptoms are more prominent and sometimes have a focal preponderance. Additionally, some patients have postictal confusion. Usually beginning during childhood, atypical absence seizures tend to occur over a longer lifetime period than classic petit mal seizures. Children with atypical absence seizures tend to have multifocal or generalized cerebral pathology, clinically associated with a lag in attaining normal developmental milestones.

The EEG demonstrates a slow (1.5- to 2.5-Hz) spike-and-wave pattern. This clinical constellation with its associated seizures and EEG pattern are characteristic of the Lennox–Gastaut syndrome. Generally, these patients also have other seizure types, and treatment of the seizures is difficult, usually requiring multiple anticonvulsants.

Clinical Vignette

A 20-year-old college student reports a history of muscle jerks involving either arm for the past several years, which tended to occur in the morning. She also had two recent unexplained falls, without lapse of consciousness during the falls. Her neurologic examination results were normal. On two occasions, once after staying up late studying for exams, and another after drinking alcohol to excess and missing her medications, she had a generalized tonic–clonic seizure.

One of the most frequently observed settings for myoclonus is the postanoxic syndrome (Lance–Adams syndrome) following prolonged cardiac arrest and resuscitation. Prognosis for full recovery in those who display myoclonus is generally poor. In the adult population, myoclonus is one of the classic findings in the prion-induced dementing illness or transmissible spongiform encephalopathy (Creutzfeldt–Jakob disease). This disease usually occurs in middle to late life. The EEG in Creutzfeldt–Jakob disease has a classic appearance with periodic sharp and slow wave complexes recurring usually at 1–2 Hz. The background EEG is abnormal. Myoclonus is also a nonspecific term that describes brief nonepileptic muscle jerks. They may involve a body segment or be generalized, may be single or repetitive, and may be spontaneous or provoked by sensory stimulation (reflex) or limb action. Myoclonus may be mediated by cortical, subcortical, brainstem, or spinal cord mechanisms.

The above-described patient has juvenile myoclonic epilepsy (JME), a primary generalized epilepsy syndrome that usually begins during the teenage years and is associated with morning myoclonic jerks soon after awakening. Many of these patients have occasional generalized seizures, especially under period of physiologic stress. The EEG typically demonstrates bilaterally synchronous, irregular spike-wave or polyspike discharges at variable 4- to 6-Hz repetition rates but no focal epileptic discharges. Paradoxically, the EEG discharges usually have no clinical myoclonic accompaniment. This condition responds generally well to antiepileptic medication and sometimes remits spontaneously in later years.

Myoclonic seizures also may occur in children with a variety of epileptic syndromes such as the Lennox–Gastaut syndrome, infantile spasms (West syndrome), and early myoclonic encephalopathy. Myoclonus also may be a part of CNS storage diseases. In the past, myoclonus occurred as a significant manifestation of a rare late form of measles or subacute sclerosing panencephalitis. This illness presented with poor school performance, mental changes, and myoclonus in teenagers, with periodic EEG complexes occurring regularly every several seconds.