X-linked focal epilepsy with reflex bathing seizures: Characterization of a distinct epileptic syndrome

We recently reported a Q555X mutation of synapsin 1 (SYN1) on chromosome Xp11-q21 in a family segregating partial epilepsy and autistic spectrum disorder. Herein, we provide a detailed description of the epileptic syndrome in the original family.

A total of 34 members from a large French-Canadian family were evaluated. Family members with seizures or epilepsy underwent (when possible) clinical, neuropsychological, electrophysiologic, and neuroimaging assessments.

Epilepsy was diagnosed in 10 family members (4 deceased, 6 living). In addition to occasional spontaneous complex partial seizures, seven family members clearly had reflex seizures triggered by bathing or showering. Hippocampal atrophy was found in two of five epileptic family members family members who underwent magnetic resonance (MR) imaging. Video-electroencephalography (EEG) recordings of three triggered seizures in two affected members showed rhythmic theta activity over temporal head regions. Ictal single-photon emission computed tomography (SPECT) showed temporoinsular perfusion changes. Detailed neuropsychological assessments revealed that SYN1 Q555X male mutation carriers showed specific language impairment and mild autistic spectrum disorder. Female carriers also exhibited reading impairments and febrile seizures but no chronic epilepsy.

Available evidence suggests that impaired SYN1 function is associated with hyperexcitability of the temporoinsular network and disturbance of high mental functions such as language and social interaction. The presence of reflex bathing seizures, a most peculiar clinical feature, could be helpful in identifying other patients with this syndrome.