Epilepsia Partialis Continua

Epilepsia partialis continua is a rare form of focal motor status epilepticus. It causes continuous, often rhythmic, focal muscle jerking, typically of the face, arm or leg on one side.

The jerking persists for hours, days or, in some cases, months to years, without spread to a generalised convulsion or loss of consciousness. It reflects continuous cortical epileptic discharge from a discrete area of the motor cortex.

Causes are diverse. They include structural lesions, inflammatory and infective encephalitis, metabolic derangement and, in specific geographical and epidemiological contexts, neurocysticercosis. The most notable encephalitis is Rasmussen encephalitis, a chronic, progressive inflammatory condition predominantly affecting children.

The underlying cause determines both the treatment approach and the prognosis.

Pathophysiology and causes

• Continuous, focal epileptiform discharge from a discrete cortical region, most commonly the primary motor cortex, produces the sustained, focal, often rhythmic muscle jerking. The cause determines the nature of the cortical abnormality.
• Structural causes include focal cortical dysplasia, tumour, stroke and, in endemic regions, an active neurocysticercosis lesion producing focal cortical irritation.
• Rasmussen encephalitis is a rare, chronic progressive inflammatory encephalitis of unknown but presumed autoimmune aetiology. It predominantly affects one cerebral hemisphere in children. It produces progressive epilepsia partialis continua together with progressive hemiparesis and cognitive decline over months to years. It is a particularly important cause because its pathology is, in some cases, surgically treatable.
• Metabolic causes include non ketotic hyperglycaemia, a well recognised precipitant particularly in elderly patients with poorly controlled diabetes, and other severe metabolic derangements. Epilepsia partialis continua typically resolves with correction of the metabolic abnormality, so identify and address this readily reversible cause promptly.

• The defining feature is continuous or near continuous, focal, often rhythmic clonic muscle jerking of a discrete body region. It persists without spread to a generalised convulsion and without loss of consciousness.
• The face, hand or arm are most commonly affected, reflecting their disproportionately large cortical representation in the motor homunculus.
• The jerking may persist continuously for extended periods, sometimes months to years with an underlying chronic progressive condition such as Rasmussen encephalitis.
• It is frequently, though not universally, resistant to standard antiepileptic medication, reflecting the often structural or actively inflammatory nature of the discrete cortical epileptogenic focus.
• Rasmussen encephalitis has a characteristic progressive course. It begins with focal seizures, which evolve into epilepsia partialis continua in the majority of affected patients. Progressive unilateral hemiparesis, cognitive decline and, in some cases, visual field deficit follow, reflecting a progressive, unilateral hemispheric inflammatory and atrophic process.
• Actively seek a relevant clinical context, because it points to the cause and guides targeted management: a known structural brain lesion, diabetes with poor glycaemic control, an epidemiological exposure for neurocysticercosis, or, in a child, a progressive course suggesting Rasmussen encephalitis.

• Electroencephalography typically shows focal epileptiform discharge corresponding to the affected cortical region.
• The electrographic correlate can be subtle or not clearly demonstrable on scalp electroencephalography alone, because the cortical discharge is sometimes deep or restricted. A normal or non diagnostic scalp electroencephalogram does not exclude the diagnosis where the characteristic clinical pattern is present.
• Magnetic resonance imaging of the brain is essential to identify any structural cause: tumour, focal cortical dysplasia, stroke or, in the appropriate epidemiological context, a neurocysticercosis lesion.
• In suspected Rasmussen encephalitis, serial imaging may show progressive unilateral hemispheric atrophy and signal change, supporting the diagnosis. Early imaging may be normal or show only subtle changes before the characteristic atrophic pattern becomes established.
• Full metabolic assessment is essential in every case, because a metabolic precipitant is readily identifiable and correctable. Check blood glucose (given the association with non ketotic hyperglycaemia), electrolytes, and renal and liver function.
• Where Rasmussen encephalitis is suspected from the clinical course and imaging, consider further evaluation including, in some cases, brain biopsy for histological confirmation (showing characteristic inflammatory changes). This is particularly relevant where surgery is contemplated and histological confirmation supports that decision.

• Treating any reversible underlying cause is the first priority.
• Correct non ketotic hyperglycaemia through careful, gradual glycaemic control, avoiding rapid overcorrection. This typically resolves the epilepsia partialis continua.
• Treat an underlying structural lesion: surgical resection where appropriate, or specific antiparasitic treatment for an active neurocysticercosis lesion (see neurocysticercosis).
• Trial standard antiepileptic medication, including sodium valproate, levetiracetam or other broad spectrum agents. Epilepsia partialis continua is frequently relatively resistant to drugs alone, particularly with an actively progressive process such as Rasmussen encephalitis, because of the persistent discrete cortical pathology driving the discharge.
• In Rasmussen encephalitis, immunotherapy (corticosteroids, intravenous immunoglobulin or plasma exchange) may give some symptomatic benefit and modest slowing of progression. It generally does not halt the progressive process.
• Functional hemispherectomy (surgical disconnection or resection of the affected, progressively dysfunctional hemisphere) is the definitive, most effective treatment for confirmed, progressive Rasmussen encephalitis. It can achieve complete seizure control and halt further decline.
• The anticipated consequence of hemispherectomy is a fixed contralateral hemiparesis and visual field deficit, generally well compensated over time, particularly in younger children.
• The decision for surgery requires careful, individualised discussion because of the significant, permanent functional consequences. It is generally reserved for confirmed, progressive disease with significant, disabling, medication refractory epilepsia partialis continua or other seizure activity.
• Timing matters: evidence suggests earlier intervention, before extensive bilateral functional reorganisation and further progressive decline, may be associated with better functional outcome.
• Rasmussen encephalitis needs multidisciplinary management, including paediatric neurology, epilepsy surgery, and rehabilitation input where surgery is pursued, together with ongoing family support given the substantial impact of this rare, complex condition.
• Management of epilepsia partialis continua from other, generally more readily identifiable and treatable causes follows the principles for that underlying condition.