Complex Partial Status Epilepticus



Complex Partial Status Epilepticus


Peter D. Williamson



Introduction

Nonconvulsive status epilepticus (SE) is divided into two categories: absence SE (ASE) (spike-wave stupor, petit mal status) and complex partial SE (CPSE).4,71,102,114,117 ASE is discussed in detail in the following chapter (see Chapter 60). ASE will be examined here only in comparison to CPSE. Until relatively recently, CPSE has been considered very rare. Twenty-three years ago, Ballenger4 reviewed the literature and concluded that there were only 17 well-documented cases of CPSE. Subsequently and certainly related to the exponential growth in epilepsy centers, there has been a significant increase in reports critically examining nonconvulsive SE and CPSE.14,18,44,62,91,114,115,116,127,129,133 This includes several studies in which CPSE was studied using intracranial electrodes.53,129,133 Even so, the limits and definitions of nonconvulsive SE in general, and CPSE in particular are still imprecise.125 Consequently, controversies over several important issues persist. As will be discussed, differentiating the two types of nonconvulsive SE is often difficult and sometimes not possible at the time of initial clinical presentation.

The term “complex partial” has recently been called into question by the ILAE Task Force on Classification and Terminology.9 This was largely based on the difficulty encountered when trying to define consciousness. The term “dyscognitive” was suggested to replace “complex partial.” Dyscognitive SE would greatly simplify the condition and overlook many of the complicated and complex characteristics of the condition. This is even further confounded by a recent recommendation of a new classification of SE in which dyscognitive status is further subdivided into three subcategories.93 For the purposes of this discussion, the term CPSE will be retained in the hopes of avoiding confusion. This is consistent with the recommendations of the ILAE task force.


History

CPSE with electroencephalographic (EEG) documentation was first reported by Gastaut et al.38 in 1956. Almost 70 years earlier, however, during his Tuesday lectures, Charcot provided a fascinating and colorful account of a patient he had examined who had multiple, prolonged, ambulatory fugue states.16,41 Charcot was convinced that this form of poriomania was indeed an example of epileptic fugue and, as such, would now be considered a type of nonconvulsive SE. Although an argument has been presented implying Charcot’s case was an example of ASE,41 an equally strong case could be made for CPSE. Jackson50 also described cases of prolonged twilight states presumed to be epileptic. Whether these and other descriptions found in scholarly writings from ancient times up to Gastaut’s report in 1956 are examples of nonconvulsive SE can only be conjectural, since most modern authorities would agree that EEG criteria are needed to make the diagnosis.14,17,30,45,53,91,114,115,124

SE of any type was only rarely described before the 19th century,110 but as reviewed by Shorvon,102 isolated early descriptions of fatal convulsive SE date from the neo-Babylonian era. In ancient times, it can be assumed that most nonconvulsive varieties of SE were not recognized as epilepsy. For example, a patient with probable nonconvulsive SE is described in The Sacred Illness written by an unknown student of Hippocrates, but this manifestation was specifically excluded as a form of epilepsy.110 Hunter49 made the ironic observation that descriptions of SE increased with the introduction of bromide therapy, implying a causal relationship between the introduction of effective antiepileptic drug (AEDs) and the increased frequency of SE, presumably a consequence of withdrawal of medication.


Definitions

SE is defined as “a condition characterized by epileptic seizures that are sufficiently prolonged or repeated at sufficiently brief intervals so as to produce an unvarying and enduring epileptic condition.”36 Although this definition is generally accepted, it has some definite drawbacks and limitations. What constitutes “enduring? Time constraints were suggested only after the definition was proposed and have since generated considerable debate and controversy. Although the duration of convulsive SE may have prognostic significance, it is of much less importance in most cases of nonconvulsive SE, even in extreme examples.18,77,133 In a study of patients with CPSE reported from the Yale epilepsy program,133 several patients had repeated flurries of partial seizures, some lasting for less than 30 minutes and others lasting for hours. No fundamental difference was noted between the longer and the shorter episodes in terms of clinical seizure manifestations or intracranial electrographic findings. Are patients with prolonged postictal confusion examples of SE? The answer to this question depends on specific circumstances. Most examples of prolonged postictal states following complex partial seizures are exactly that—prolonged nonepileptic disturbances of cortical function following a discrete seizure. As such, this should not be considered SE. Occasionally, however, prolonged “postictal” states are due to continued seizure activity, either localized or diffuse, following a typical discrete complex partial seizure53 (see patient 2 in case descriptions). This latter possibility clearly constitutes an enduring seizure state and is a form of SE.

Similarly, “unvarying” in the definition of SE is misleading. Some examples of nonconvulsive SE are very unvarying, whereas others present with widely variable clinical features. Some patients within a single episode of CPSE have stereotyped as well as highly variable clinical and electrographic manifestations.127,129,133 The definition of SE therefore must be less restrictive to encompass a wide variety of types.


Shorvon102 reviewed the limitations and proposed the following definition: “SE is a condition in which epileptic activity persists for 30 minutes or more, causing a wide spectrum of clinical symptoms, and with a highly variable patho-physiological, anatomical, and aetiological [sic] basis.”

Although this avoids most of the limitations of the traditional definition of SE, there have been objections to the time constraints for nonconvulsive SE, for the reasons cited earlier. Also, this definition implies continuous seizure activity which is clearly not true in many examples of SE. Recently, the recommendations for minimal seizure duration in nonconvulsive SE have been 10 minutes.103 This seems in much better agreement with clinical observations.

Gastaut37 stated that there are as many types of status as there are types of epileptic seizures. The traditional separation of nonconvulsive SE into ASE and CPSE has, however, been questioned.102,114,115 The definition of CPSE must be re-examined, and this will be done when describing clinical and electrographic seizure activity.


Epidemiology

Considering that the concept of CPSE is evolving and has yet to be defined precisely, the fact that there are no good epidemiologic studies of the condition should come as no surprise.125 Although earlier studies concluded that CPSE was very rare, almost a medical curiosity,4,71,74,117 more recent investigations report that CPSE is under-reported and more common than previously thought.18,102,114,115,133 The current belief that CPSE is not rare is undoubtedly related to improved methods of detection, particularly through the use of intensive monitoring.45 Although it is admittedly a crude approximation, Shorvon102 estimates that CPSE occurs in 35 per 1,000,000 persons in the general population. Nonconvulsive status in the mentally handicapped population was similarly calculated at 100 to 200 per 1,000,000 persons.102 In one hospital-based population study, an incidence of nonconvulsive SE was 1.5 per 100,000 per year.114 Approximately half of these patients were thought to have CPSE. Two studies found that 19% to 25% of all types of SE were nonconvulsive, but the majority were considered ASE.15,25 DeLorenzo et al.24 attempted a prospective study of all types of SE. CPSE was very uncommon. This is not in agreement with other recent reports, which indicate that it can no longer be considered rare.114,116,133 Treiman116 notes that over 200 well-documented cases of CPSE have been reported. Furthermore, CPSE is probably even more common if, as suspected, the condition is under-reported.14,24,56,102,114,133 Finally, as discussed later, many examples of what appear to be ASE occur in patients with localization-related epilepsy and are therefore examples of CPSE.49,91,102,115,116,117 Nonconvulsive SE, in general, is estimated to comprise one third of all types of SE.133 A PubMed search of “complex partial SE” from 2000 to present yielded 666 citations.


Etiology

The etiologies of CPSE are many and varied. Approximately one third to one half of patients with CPSE are initially seen without an antecedent history of epilepsy.102,114 In one study of nonconvulsive SE that included CPSE, the most common precipitants were generalized tonic–clonic (GTC) seizures and changes in AEDs, either due to noncompliance or under medical direction.114 A recent study related CPSE to increased levels of carbamazepine-10,11-epoxide secondary to comedication.108 Other causes of CPSE include various acute diseases of the nervous system, including encephalitis and stroke.62 A case of alcohol-induced CPSE has been reported.35 Nonconvulsive SE has also been precipitated by intrathecal metrizamide during myelography and electroconvulsive therapy.122,123 CPSE has been described in several reports of patients with presumed benign childhood rolandic epilepsy.19,32,54 A type of autonomic status is characteristic of Panayiotopoulos syndrome,59,66,81 and recurrent refractory CPSE is a component of the ring chromosome childhood epilepsy syndrome.3 Over 30 reports relate tiagabine with the development of new CPSE.58 CPSE has even been reported to occur after temporal lobectomy,12 but this may have been in a patient with two separate types of epilepsy.

The causes of CPSE in patients with known focal seizures are the same as the causes of localization-related epilepsy. These include gliotic scars, tumors, vascular malformations, cerebrovascular disease, hamartomas, and congenital malformations. Precipitants include drug and alcohol withdrawal, physical and emotional stress, sleep deprivation, and metabolic disturbances. CPSE can produce transient abnormalities on neuroimaging studies that may or may not have etiologic and localizing significance.5,61,96,109,113

The anatomic site of seizure origin may be important in the development of SE. Until recently, CPSE was equated with temporal lobe SE.30,37,74,98,102 In many cases, temporal lobe seizure origin was diagnosed on the basis of interictal scalp recording or simply implied because of clinical seizure characteristics. However, except for the four cases described by Wieser,127,129 and several patients who have benefited from temporal lobectomy,18,48 there have been very few well-documented examples of CPSE of temporal lobe origin (also see patients 1 and 3 in case descriptions). In one report, CPSE was recorded in eight of 87 patients with medically intractable localization-related epilepsy who were undergoing presurgical evaluations with intracranial electrodes.133 Seizure origin was extratemporal in these eight patients, whereas CPSE developed in none of the 60 patients from this series with seizure origin in the medial temporal lobe. Extratemporal seizure origin and CPSE has been observed by others.73,102 The association of frontal lobe epilepsy and convulsive SE has been the subject of several reports.15,51,85 A similar association of nonconvulsive SE and frontal lobe seizure origin has also been reported.7,10,13,41,114,115,130,134 In conclusion, CPSE is not analogous to temporal lobe SE, but is often related to extratemporal seizure origin, possibly with a frontal lobe preponderance.


Pathophysiology

Less is known about the pathophysiology of SE than of isolated seizures. Although the onset of isolated seizures and the initiation of an episode of SE are probably an expression of the same physiologic mechanisms, exactly how seizures start is not known. Even less is known about the mechanisms of seizure termination, but here is undoubtedly the key to understanding SE. It is known that the cessation of status per se is not due to energy failure, but presumably is related to the activation of those systems that stop single seizures.33,34,86 The development of SE must represent failures of different systems, producing a cascade of neurophysiologic, neurochemical, and probably neuroanatomic changes that serve to perpetuate and prolong the epileptic process.75,101 Self-sustaining feedback loops have been postulated in limbic status.120,121 At the neurochemical level, depletion of γ-aminobutyric acid (GABA) during nonconvulsive status was reported,126 but these results could not be duplicated in other studies.105 Status-induced cell damage and the role of excitotoxins is discussed elsewhere in this volume, but the experimental evidence of CPSE-induced cell death must be described briefly because of its effects on long-term prognosis. In the kainic acid (KA) model of limbic SE, disseminated brain damage occurs, particularly in the hippocampus.82 Pretreatment with diazepam abolishes this effect, thus demonstrating that cell damage is not due to the direct excitotoxic effect of KA.6 Remote hippocampal damage occurs following prolonged perforant pathway stimulation.104,106 Hippocampal cell damage does not occur following multiple (thousands of)
single seizures.8 How these observations relate to clinical CPSE is discussed in the sections on treatment and consequences.


Clinical Features

The initial descriptions of CPSE using EEG documentation defined two types: one with clinically apparent recurrent seizures, and another that exhibited a continuous seizure state.30,39,69,74 Treiman and Delgado-Escueta,117 after reviewing the literature and examining cases of their own, concluded that epileptic twilight states consisted of continuous and cyclic varieties of seizures, with CPSE being of the latter type—that is, all examples of CPSE consisted of recurrent complex partial seizures with incomplete clearing between episodes. The continuous type was thought to be ASE. This was in disagreement with previous reports (including one of their own), and is not supported by other studies. For example, Wieser127 described a patient, studied using depth electrodes, who, during an episode of CPSE had continuous and discontinuous clinical and electrographic seizure activity. Subsequent reports of patients with CPSE, some studied using intracranial electrodes, confirmed the existence of both cyclic and continuous varieties, with some patients exhibiting both types of CPSE in single or different seizures.14,92,114,115,129,133 Treiman,116 in a recent communication, described CPSE presenting as a continuum between continuous altered conscious and recurrent discrete complex partial seizures, and he believed that CPSE originating in the medial temporal lobe structures was more likely to be of the cyclic variety, whereas frontal lobe CPSE was more likely to be continuous. However, this concept had been refuted by intracranial electrode studies.129,133 Finally, variable or cyclic clinical patterns have been described in patients with ASE.114,115 CPSE, therefore, does not always present with consistent or readily identifiable clinical characteristics, but rather is associated with a wide variety of clinical patterns, some of which may be indistinguishable from ASE. Others may mimic psychiatric disease.53,91

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Aug 1, 2016 | Posted by in NEUROLOGY | Comments Off on Complex Partial Status Epilepticus

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