Abstracts

Rationale: The pathophysiology of generalized spike and wave is unclear with reticular, thalamic and cortical origins proposed. fMRI has been used most commonly to study hemodynamic changes during absence seizures. ASL has also shown activation in candidate regions but surprisingly only rare observations of thalamic involvemnent in some series. We observed PASL changes on routine MRI in a subject with generalized epilepsy. Methods: 29-year-old female with onset of absence seizures and tonic-clonic seizures in childhood which were controlled with Valproate. Multiple EEGs over years had shown generalized 3 hertz spike and wave. Due to concerns of teratogenicity, anticonvulsant medication was switched to levetiracetam at patients request. Breakthrough seizures occurred every few months due to either medication failure or stress of work and sleep deprivation. MRI was done because of report of intermittent focal neurological symptoms. Results: EEG revealed 3 Hz spike and wave discharges with prominent activation by hyperventilation. Routine MRI sequences did not demonstrate any focal abnormalities. PASL images were found to show a discrete area of hyperperfusion in the medial, bilateral thalami. Simultaneous EEG was not obtained at the time of MRI acquisition. Conclusions: Demonstration of thalamic activation using ASL sequences has not been perforemd as frequently as fMRI. The failure to identify this response in some cases may be due to a number of reasons including spike frequency, MRI magnet strength and subtle electroclinical differences. Our case shows thalamic PASL activation in a case of primary generalized epilepsy which has only reported on rare occasions in secondary generalised epilepsy to our knowledge. More studies with larger numbers of patients are needed to clarify these findings.