Abstracts

Rationale: Periventricular nodular heterotopia is a disorder of gray matter migration that often presents clinically with seizures in the second decade of life. Typically the ectopic tissue has a nodular appearance overlying the ventricular walls. The heterotopia rarely presents as thin layers of periventricular grey matter curved around the frontal horns. It is still unclear how a structural abnormality, present since birth, may manifest with seizures only in the second decade. We are reporting a case of thin layer curvilinear heterotopia at the frontal horns without associated periventricular nodular tissue. Methods: The work-up has included a complete neurological assessment, brain MRI, video-EEG recording in the Epilepsy Monitoring Unit (EMU), ictal and interictal SPECT scans and a Wada test. Results: The patient is a 19-year-old male with a history of seizures for at least two years. Typical episodes consisted of staring accompanied by automatisms of the upper and lower extremities. He had no risk factors for epilepsy. The brain MRI showed thin curvilinear bands of gray matter around both frontal horns of the lateral ventricles, more prominent over the left side. There were no accompanying nodular periventricular heterotopia and no other structural abnormalities. Hippocampi appeared unremarkable and symmetric. The interictal epileptiform EEG consisted of 2 Hz spike and slow waves over the left frontal leads or generalized with left frontal emphasis. The EEG ictal onset showed an electrodecrement with low amplitude fast activity, generalized but with subtle left frontotemporal and central emphasis. In a few seconds it evolved into a diffuse rhythm with intermixed faster frequencies. The ictal SPECT study demonstrated left frontal lobe hyperperfusion. Even if the patient was right handed, the work-up disclosed various degrees of left hemisphere impairment: the dexterity of the dominant right hand was reduced compared with that of the left hand and the Wada test demonstrated right hemisphere language representation. There was no family history of left handedness. Conclusions: Isolated thin curvilinear heterotopia in the periventricular frontal region, without associated nodular tissue, represents a novel finding. The ictal and interictal electrographic abnormalities recorded in this patient appear different from those previously described in series of patients with periventricular heterotopia. The finding of a right hemisphere language representation without a family history of left handedness suggests that subclinical dysfunction of the left hemisphere may precede the onset of epilepsy by a wide time margin.