A Case of Epilepsia Partialis Continua Due to Linear Nevus Syndrome with Hemimegalencephaly.

Epilepsia partialis continua (EPC) is a form of focal status epilepticus often refractory to anticonvulsant therapy. A wide range of abnormalities such as inflammatory, vascular, metabolic-toxic, developmental malformations, and neoplasia cause EPC. Linear nevus syndrome with hemimegalencephaly is one of the developmental malformations that can present with EPC.

INTRODUCTION

Epilepsia partialis continua (EPC) is a rare form of focal status epilepticus with a prevalence of one to two per million population.[1] It is defined as a regular or irregular, clonic muscular twitching affecting limited parts of the body occurring for a minimum of 1 hour, and recurring at intervals of no more than ten seconds.[2] The etiology of EPC is multiple and varied ranging from inflammatory (infectious and immune-mediated), vascular, metabolic-toxic, cortical malformations, and neoplasia. The clinical course and prognosis also vary widely according to the etiology. Herewith, we report a case of EPC associated with hemimegalencephaly with linear nevus syndrome.

CASE VIGNETTE

A 6-year-old male child presented to us with a history of recurrent focal seizures involving his right hand and foot since his 4th month of life. He is the second child born out of normal delivery. His perinatal period was uneventful. His milestones were delayed globally. His mother noticed weakness of his right-sided limbs since 1 year of age. For the past 1 year, he has almost continuous seizures involving fingers of the right hand, especially index finger, and right great toe.

Examination revealed large head with a head circumference of 52 cm (>95th percentile), asymmetrically enlarged left side of the skull, linear brownish pigmentation in the mid-forehead extending from bridge of the nose to the scalp [Figure 1]. He had mental subnormality, could speak only a few words. He also had right facial lag and right hemiparesis. There were frequent, recurrent clonic twitching of his right thumb and index finger, and at times right great toe. His optic fundi were normal. There was no hypertrophy of the limbs.

Figure 1

Linear midline nevus in the forehead and the right facial lag

Magnetic resonance imaging brain revealed a large left hemisphere with pachygyria, dilatation of ipsilateral lateral ventricle, and altered signal intensity of the white matter [Figures 2–4]. EEG showed spikes and sharp waves from the left hemispherical leads.

Figure 2

Magnetic resonance imaging brain T1-weighted axial image showing unilateral megalencephaly on the left side with enlarged ventricle

Figure 4

Coronal fluid-attenuated inversion recovery sequence showing pachygyria and white matter changes

Magnetic resonance imaging brain T2-weighted image showing unilateral megalencephaly on the left side

He is under treatment with multiple anticonvulsants. Hemispherectomy was advised, but parents were not willing for any surgical procedure. The child continues to have recurrent partial seizures in spite of multiple anticonvulsants.

DISCUSSION

EPC is a rare form of simple focal motor seizures characterized by continuous, involuntary, focal muscle jerking at least every ten seconds for at least 1 hour not impairing awareness. Clinically, EPC can occur in any age but in a third of cases start before 16 years of age.[1] It was first described by Kojewnikoff and Besondere in 1895.[3] It may last for hours, days, or even years without spreading to other parts of the body.[4] The jerks can occur singly or in clusters and can be aggravated by physical exercise, sensory stimuli, and psychic exertion. Upper rather than lower half of the body is more frequently involved, and distal parts are affected more than the proximal parts. The jerks tend to persist during sleep.[5] The diverse causes of EPC include encephalitis (Rasmussen, infectious) 15%–19%, vascular (stroke, vasculitis, and venous thrombosis) 24%–28%, neoplasms (glioma, hemangioblastoma, meningioma, and lymphoma) 5%–16%, metabolic-toxic (nonketotic hyperglycemia, mitochondriopathy, and Alpers syndrome) 6%–14%, and unknown in 19%–28%.[6] The most frequent cause of EPC in adults include vascular and neoplastic diseases whereas in children it is usually due to Rasmussen encephalitis. Nonketotic hyperglycemia is the most common reversible cause.[7] Our child has EPC involving fingers and great toe on the right side which persist even during sleep for the past 1 year.

Hemimegalencephaly or unilateral megalencephaly is a congenital disorder in which there is hamartomatous overgrowth of all or part of a cerebral hemisphere.[89] The affected hemisphere may have focal or diffuse neuronal migration defects with areas of polymicrogyria, pachygyria, and heterotopias. The cause is unknown. It is postulated that it occurs due to a genetically programmed developmental defect related to cellular lineage and establishment of symmetry.[8] The typical clinical presentation includes intractable epilepsy, psychomotor retardation, and contralateral motor deficit.[10] The epilepsy pattern can be partial seizures or spasms as in epileptic encephalopathy. Neuroimaging shows a dysplastic cortex and abnormal white matter. The lateral ventricle in the enlarged brain is larger in proportion to the lateral ventricle of the smaller hemisphere.[9] Brain single-photon emission computed tomography and positron emission tomography demonstrate hypometabolism in the affected hemisphere.

There are three types of hemimegalencephaly - the isolated form without hemicorporal hypertrophy or a cutaneous lesion, syndromic form associated with epidermal nevus syndrome, neurofibromatosis type I, hypomelanosis of Ito, Klippel–Weber–Trenaunay syndrome, and tuberous sclerosis. The third and least common type is total hemimegalencephaly in which there is additional enlargement of the ipsilateral half of the brainstem and cerebellum.[11] Our child has a syndromic hemimegalencephaly with linear nevus syndrome.

The linear nevus is a brown hairless waxy plaque located in or near the midline in scalp and face, usually present at birth or in early childhood. There is a high incidence of congenital anomalies of central nervous system, cardiovascular system, eyes, and urogenital system associated with linear nevus syndrome. As many as 50% of these lesions involve central nervous system including hemimegalencephaly, unilateral lissencephaly, schizencephaly, colpocephaly, and heterotopic gray matter.[12] Although various abnormalities have been described with linear nevus syndrome, hemimegalencephaly may be an important feature of this syndrome contributing to the developmental delay and refractory seizures associated with this syndrome.[13]

Typically, EPC is resistant to pharmacotherapy and treatment should focus on the underlying etiology. The outcome is variable and highly dependent on underlying cause. Hemispherectomy is the treatment of choice in refractory epilepsy with hemimegalencephaly. Potential benefits on cognition and development are important factors which necessitate an urgency to properly evaluate and treat these children with an early surgical option. More than 90% reduction in seizure frequency is obtained in three-fourths of the patients operated on before the age of 3 years.[14] The integrity of the nonhemimegalencephalic hemisphere is considered an important factor in the postsurgery prognosis.[14] Despite the risks, early surgery should be preferred for major reduction in seizure frequency and better developmental outcome.[15]

CONCLUSION

Hemimegalencephaly is one of the causes for EPC and should be suspected in a child with a linear nevus.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.