6q terminal deletion syndrome associated with a distinctive EEG and clinical pattern: a report of five cases.

PURPOSE: Mental retardation, facial dysmorphisms, and neurologic and brain abnormalities are features of 6q terminal deletions. Epilepsy is frequently associated with this chromosome abnormality, but electroclinical findings are not well delineated. We report five unrelated patients with 6q terminal deletions and a peculiar clinical, EEG, and neuroradiologic picture of epilepsy, mental retardation, and colpocephaly.
METHODS: These three male and two female patients underwent general and neurologic examinations, repeated awake and sleep EEGs, and brain magnetic resonance imaging (MRI). A cytogenetic study and fluorescent in situ hybridization (FISH) with chromosome-specific subtelomeric probes were carried out in all cases.
RESULTS: All subjects had seizures characterized by vomiting, cyanosis, and head and eye version, with and without loss of consciousness. In four cases, EEGs showed posterior spike-and-wave complexes, which were activated by sleep. No patient had status epilepticus or prolonged seizures. Brain MRI revealed colpocephaly and dysgenesis of the corpus callosum and brainstem in four patients; three of them also had hypertrophic massa intermedia. FISH analysis revealed a 6q terminal deletion in all patients, which ranged between 9 Mb (cases 2 and 3) and 16 Mb (case 4).
CONCLUSIONS: We suggest that epilepsy associated with 6q terminal deletions is a new entity. Patients with dysmorphic features associated with focal occipital epilepsy, colpocephaly, and dysgenesis of the corpus callosum, thalami, and brainstem should be considered candidates for testing for 6q subtelomere deletions.