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Epilepsia Partialis Continua

Overview

Introduction

Epilepsia partialis continua (EPC) was a name first introduced by Kojewnikoff on January 21, 1894 when he presented his description of a unique type of prolonged focal seizure in four patients at a meeting of the Moscow Neurological and Psychiatric Society.
Since then, this name has been ascribed to various nosological entities, with the condition being described as a variation of jacksonian epilepsy, jacksonian status epilepticus, myoclonus epilepsy, an extrapyramidal syndrome, or continuous, localized myoclonia.

EPC can be considered the status epilepticus (SE) equivalent of focal onset seizure with retention of awareness. It can manifest as focal motor or sensorimotor clonic seizures without jacksonian march. Seizures remain localized to the part of the body in which they originate, and motor activity is often persistent, even during sleep, lasting for at least 60 minutes and  up to hours, days, weeks, or even longer. Consciousness is usually preserved, since the thalamus is spared and seizures remain unilateral in most cases. Postictal weakness (also known as Todd’s paralysis) is frequently evident.

In the vast majority of cases, the seizures are of cortical origin; however, subcortical mechanisms also have been proposed.
EPC can be an expression of a stable neurologic lesion or a progressive disease, such as Rasmussen syndrome.
Antiepileptic drugs, with a few notable exceptions, do not seem to significantly alter the course of this condition.
While the localized nature of EPC is one of its most striking features, occasional spread is seen in otherwise typical cases, and using spread as an exclusion criterion is not warranted.

Historical perspective and definition

Kojewnikoff (1895),
Bruns (1895),
Orlovskij (1896),
and Choroschko (1907)
all reported a similar condition characterized by intermittent muscular twitching of a body part while consciousness is unaffected. Kojewnikoff described 4 cases in which the patient experienced seizures, consisting of constant jerking movements of high frequency that were resistant to treatment and involving only one part of the body.
He recognized that this type of seizure could have many causes, such as a tumor, an abscess, syphilis, edema, embolism, or localized encephalitis. He postulated, without postmortem studies, that the seizures resulted from focal cortical encephalitis and localized the inflammation of the brain in the motor pathway.
This original description of EPC has been extensively discussed,
and its incidence in Russian spring-summer encephalitis has been recently reviewed.

From 1904-1907, Speilmeyer and Mills reported,
under the name of jacksonian epilepsy, cases in which EPC may have been present. Since then, a number of clinical and pathological studies have further defined the syndrome, its location, and its etiology.

In 1966, Juul-Jensen and Denny-Brown defined EPC as “clonic muscular twitching repeated at fairly regular short intervals in one part of the body for a period of days or weeks.”
They also differentiated it from myoclonus by characterizing the latter as “more rapid, lasting less than half a second, involving a variable number of muscles… at irregular intervals,” but recognized the existence of transition forms, which are difficult to classify.

In 1977, Thomas et al defined EPC as “a partial somatomotor SE… for a minimum of one hour and recurring at intervals of no more than 10 seconds.”
They carefully described the features of EPC in 32 patients. EPC had a sudden onset in 17 of 25 patients; its durations varied from 4 hours to 18 years. Movement frequency was 0.5-10 Hz, and the duration varied from 25-600 milliseconds, with twitches often recurring every 2-3 seconds. Spike or sharp wave on scalp EEG preceded the movement in 9 of 12 patients, and all 5 corticographies revealed a cortical origin. Seventeen of 25 patients had a poor response or no response to anticonvulsants, and 6 of the 7 responders had acute brain lesions so that the therapeutic success could have been coincidental. Interestingly, cortical excision failed to stop the seizures in 4 of 5 patients.

In 1983, Gastaut defined EPC as a subtype of somatomotor focal with retained awareness SE, which was itself a form of elementary focal SE; this definition made the point that there are as many types of SE as there are types of seizures.
Several subsequent reviews have used this definition.

In 1985, Obeso et al defined epilepsia partialis continua as spontaneous regular or irregular clonic muscle twitching of cerebral cortical origin, confined to one part of the body and continuing for a period of hours, days, or even weeks.
The addition of “irregular” to the description recognizes the fact that the interval between motor twitches can vary but, in the author’s view, makes a clear distinction from myoclonus impossible.

Cockerell et al (1996)
and Shorvon (1994)
defined EPC as “a syndrome of continuous focal jerking of a body part occurring over hours, days, or even years” and restricted the definition to jerks of cortical origin; they proposed the name “myoclonica continua” for jerks of subcortical origin. While this distinction is attractive in principle, in practice localizing the exact origin of the seizures is often difficult, and clinical activity indistinguishable from EPC has been associated with subcortical pathology (eg, multiple sclerosis).

Wilson and Winkelman, (1924)
Hess and Sethi, (1990)
and Biraben and Chauvel (1998)
restricted EPC to local and elementary motor signs, regardless of whether it was associated with spreading seizures at times.

In current practice, EPC is defined as a form of focal SE with simple motor manifestations that are maintained for over 1 hour, with clonic activity restricted to one body part and recurring at fairly regular intervals. The following modifying factors apply:

Motor activity often is modified by sensory stimuli

Frequency is usually 0.1-6 Hz

Epilepsia partialis continua can continue for long periods (sometimes years) without spreading, although spread can occur at times

Epilepsia partialis continua often is associated with postictal or interictal weakness

Clonic activity in EPC can involve any muscle group and is most common in the upper extremities. Although it is typically invariant and remains localized to a single muscle group in most patients, it may be accompanied by jacksonian spread of the seizure, which may even lead to a focal seizure with loss of awareness or secondarily generalized seizure. This syndrome also may be accompanied by other neurological and psychopathological symptoms.

Bancaud classification

Bancaud et al (1982)
classified EPC into 2 groups. Both entities start with similar seizures, but type 2 proves to be intractable and progressive. See the Table below.

Table. Bancaud Classification (Open Table in a new window)

Type 1 ( Classic)

Type 2 (Rasmussen)

Rolandic fixed lesion

Normal developmental and history until seizure onset

Neurological deficit

Preceding focal motor

Preceding focal motor seizures

Following myoclonic jerks

Following myoclonic jerks

Abnormal EEG background with focal and diffuse paroxysmal abnormalities

Focal abnormalities on EEG

Progressive course

Nonprogressive course

Intractable epilepsy

Surgery usually effective

 

Bancaud divided the clinical course of type 2 into 3 stages. The first stage features only focal motor seizures with retained awareness or focal seizures with loss of awareness, but EPC may occur. In the second stage, EPC is seen in the setting of progressive neurologic deficit and mental deterioration. The third stage is characterized by arrest of deterioration and decrease or disappearance of seizures.

Go to Epilepsy and Seizures, Status Epilepticus, and Partial Epilepsies for an overview of these topics.

Patient education

For patient information, see the Brain and Nervous System Center, as well as Epilepsy.

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