Abstracts

Rationale: The benign occipital epilepsies of childhood include Panayiotopoulos Syndrome and Gastaut syndrome; a third syndrome, Idiopathic photosensitive occipital epilepsy may also begin in childhood. These syndromes are defined according to age of onset, seizure semiology and EEG features including photosensitivity. We describe siblings with a novel occipital epilepsy syndrome and localize their interictal epileptiform activity using EEG with functional MRI (EEG-fMRI). Methods: A sister and brother presenting with refractory occipital seizures were identified and detailed electroclinical information obtained. Functional imaging was performed at 3 Tesla with EEG recorded during continuous acquisition of gradient-recalled echoplanar images. In-scanner EEG was reviewed off-line, all interictal epileptiform discharges were marked as events of interest, and an event related analysis using SPM8 was performed. Results: Seizure began at 12 years in the girl and 10 years in her brother. Seizure semiology involved elementary visual phenomena or visual loss. In longer seizures, head and eye deviation to the right was noted in the girl and to the left in the boy. At times, loss of awareness and post-ictal headache was seen in the girl. The boy often experienced headache while awareness was preserved. Neither sibling experienced autonomic symptoms. The boy has had a single seizure with fever at age 2 but other seizure types were not seen. They developed frequent refractory seizures (10 or more daily) despite multiple anti-epileptic drugs. The ketogenic diet substantially reduced seizure frequency in the 17 year old sister and has recently been commenced in her 11 year old brother. They were the only children to unrelated parents with no family history. EEGs demonstrated a normal posterior dominant rhythm with episodic occipital slowing. Occipital fast activity and sharp and slow discharges occurred bilaterally, with left-sided predominance in the boy. Seizures were recorded in both and confirmed a localized occipital onset. There was no fixation-off sensitivity. Structural imaging was normal. Siblings had normal intellect without regression. Celiac serology, mitochondrial and POLG mutation screening were negative. Both subjects demonstrated BOLD signal change in the occipital cortex during fMRI. The sister showed bilateral negative BOLD in the lingual gyrus while her brother showed positive BOLD change in the left middle occipital gyrus. There was positive BOLD signal change in the cerebellum, bilaterally in the girl and left lateralized in the boy. The girl also demonstrated bilateral anterior thalamic positive BOLD. Conclusions: This novel childhood onset genetic occipital epilepsy syndrome is characterized by frequent, brief, refractory occipital seizures with onset at around 10 years of age. Functional imaging suggests a network involving occipital and cerebellar circuits is important for seizure generation. The striking electro-clinical concordance in siblings provides strong evidence for a genetic basis, but it is unclear if the etiology is monogenic or polygenic.