Abstracts

Gelastic, partial and generalised seizures are characteristic of the progressive epilepsy syndrome associated with hypothalamic hamartoma (HH), yet the relationship between seizure origin, propagation and epileptogenesis is poorly understood. We used subtraction peri-ictal ^99mTc-HMPAO SPECT, co-registered with MRI in standard space, to study seizure origin and spread in 20 patients with HH and refractory seizures. HH hyperperfusion was analysed with respect to patient factors, timing of injection, seizure semiology and epilepsy characteristics. An index of the asymmetry of HH attachment to the hypothalamus was compared to a hemispheric hyperperfusion asymmetry index [(right[ndash]left)/(right+left)]. Thirteen patients had HH hyperperfusion, including all 7 with ictal laughter or crying (p=0.045). HH hyperperfusion was also significantly associated with true ictal injection (p=0.029) and longer seizure duration (p=0.006). Analysis of pooled subtraction studies revealed focal cortical hyperperfusion in common regions, including the orbitofontal, mesial frontal, anterior and posterior cingulate gyri, temporal pole, superior temporal gyrus, supramarginal gyrus and thalamus. Mesial temporal hyperperfusion was infrequent. No cortical regions of hyperperfusion were correlated with ictal laughter or tonic seizures. Cerebral hyperperfusion was asymmetric and linearly correlated with asymmetry of HH attachment to the hypothalamus (r=0.78, p[lt]0.001).[figure1] Subtraction peri-ictal SPECT confirms a role for the HH in all seizure types in this syndrome. Gelastic seizures are associated with HH hyperperfusion, while asymmetric hemispheric hyperperfusion is correlated with HH attachment asymmetry. Cortical propagation appears more frontal than temporal and temporal propagation is more neocortical than mesial. Thalamic and cingulate hyperperfusion may be relevant to the evolution of symptomatic generalised epilepsy in some patients. (Supported by NHMRC Postgraduate, University of Melbourne and Murdoch Childrens Research Institute research scholarships (JLF).)