Case No. :	20
Month :	August
Year :	2000
Contributor :	Dr. Rohit Mailik

Clinical Profile | Radiological Findings | Differential Diagnosis & Discussion

Clinical Profile:

A 12- year- old boy presented with intermittent seizures since two years. To begin with, there was facial twitching followed by focal convulsions which had progressed to generalised tonic-clonic convulsions .There was a history of low grade fever and weight loss since two years .Born of a normal delivery, the pt had had delayed milestones; dysmorphic features were present. He was born of a non consanguineous marriage & and had normal siblings. Clinical examination revealed no cervical lymphadenopathy Mantoux test was positive. The head circumference was marginally more than the normal for age . Kernig's sign was positive. A diagnosis of tuberculous meningitis was made & a CT scan performed.

 

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Radiological Findings :

Plain and contrast enhanced CT scans of the were done. This revealed sparse white matter on the right side. Abnormal areas of heterotopic gray matter were noted. There was decreased sulcation on the right cerebral hemisphere. The right lateral ventricle was irregularly enlarged - mainly the frontal horns and body. No abnormal focal enhancing areas were noted.There was no evidence of abnormal meningeal enhancement. The rest of cerebral parenchyma, ventricles & calvarium were normal.

Differential Diagnosis and Discussion :

The clinical diagnosis of tuberculous meningitis or a tuberculoma could not be justified in the light of the scan findings. However, sometimes tuberculous meningitis may present with no enhancing exudates and be associated with hydrocephalus alone; however, this is generally obstructive and symmetrical and hence this possibility was ruled out. In view of the differing size of the cerebral hemispheres, the possibility of Dyke - Davidoff hemiatrophy was considered. But in this case, the large lateral ventricle was ipsilateral to the atrophic side. There was no compensatory ipsilateral skull thickening or enlargement of the paranasal and mastoid sinuses. In addition, there was no midline shift or sulcal enlargement. Hence this possibility too was eliminated.

Hemimegalencephaly was the next differential diagnostic consideration. In this case, the ipsilateral lateral ventricle is enlarged with respect to the enlarged hemisphere, the frontal horn is enlarged and curved with the concavity being laterally There is heterotopic gray matter with minimal ipsilateral white matter hypoplasia. These findings are typical of hemimegalencephaly.

Discussion: Hemimegalencephaly was first described in 1835 by Sims as an idiopathic condition associated with cerebral hemihypertrophy and cortical dysplasia and migrational anomalies. It is known to be associated with Klippel Weber Trenauny Syndrome, neurofibromatosis, epidermal naevus syndrome, Canavans disease, Sotos syndrome etc.

The postulated etiopathogenesis is that this occurs due to insults during the second trimester of pregnancy, wherein the neurons which are unable to form synaptic connections are not eliminated and hence they accumulate. There may be abnormal accumulation of metabolic products in the brain tissue.

The treatment includes control of seizure disorder. A hemispherectomy may be indicated in severe cases.