Late onset generalised epilepsy in a case of periventricular heterotopia

Malformations of the cortical development are relatively rare but important causes of developmental disabilities and epilepsy. Periventricular nodular heterotopia is one of the best known and described cortical dysplasias that in the era of magnetic resonance tomography are easily and accurately diagnosed while alive. It is characterized by subependymally localized contiguous ovoid nodules of gray matter, which may occur ipsilaterally or bilaterally along the wall of the lateral ventricles. Although periventricular nodular heterotopia shows mostly a X-linked dominant inheritance pattern and manifests among women, there are also cases of autosomal recessive inheritance, as well as cases associated with chromosome 5p anomalies. Former doubts whether seizures originate directly from these neuronal migration disorders, or are simply associated consist no more since depth-electrode studies have proved the epileptogenity of gray matter heterotopias. Most patients present focal epileptic seizures during infancy, childhood or adolescence. However, late-onset epilepsy can rarely also be attributed to regional brain cortical dysplasia including bilateral nodular periventricular heterotopia. The incidence of neurological signs in this patients' group is lower. Mental retardation is moderate or absent, thus allowing a fairly normal way of living. Drug resistance is rare and the response rate to applied antiepileptic medication is good.

We present the uncommon case of late-onset primary generalized epilepsy in a 34 years old female patient with normal mental and motor development with known history of typical migraine attacks. Her family history suggested no pattern of inheritance. She presented 3 typical Grand Mal seizures on awakening within a period of six months, without reports of any prior disorders of consciousness. Computed tomography of the brain revealed bilateral periventricular uncalcified hyperintensities, which were later identified by means of magnetic resonance tomography as almost contiguous, ovoid, not enhancing nodules of gray matter density. The typical imaging findings excluded the differential diagnostic alternative of tuberous sclerosis and established the diagnosis of periventricular nodular heterotopia of cortical tissue as highly uncommon cause of late-onset generalized epilepsy in a patient with no other apparent epileptogenic lesions.

The present case report suugests periventricular nodular heterotopia as rare but probable cause of symptomatic epilepsy and underlines the importance of magnetic resonance tomography as essential and crucially important part in the diagnostic workup of all patients irrespective of age and gender with newly manifest epileptic seizures.

Key words: Epilepsy, seizures, periventricular heterotopia, magnetic resonance imaging.