Abstracts

Rationale: Secondarily generalised tonic-clonic seizures (SGTCS) in patients with temporal lobe epilepsy (TLE) correlate with unfavourable outcome after surgical resection. Extensive hypometabolism remote to the temporal focus is found in patients with SGTCS (Wong et al 2010). Different propagation patterns of temporal lobe seizures with and without secondarily generalisation have been described (Blumenfeld et al 2009, Yoo et al 2014). The purpose of this study is to evaluate seizure propagation in TLE with and without SGTCS using ictal perfusion patterns. Methods: A total of 42 seizures from 35 patients (age 39.93 ± 14.00 years) with TLE who underwent video EEG monitoring for pre-surgical evaluation and had ictal single photon emission computed tomography (SPECT) using Technetium Tc-99m ethyl cysteinate dimer (ECD) during admission were examined. Seizures with ECD injected after secondary generalisation were excluded. Images were analysed using statistical parametric mapping (SPM2). Ictal and Interictal SPECT images were pre-processed using Ictal-interictal SPECT Analysis by SPM (ISAS). Images of right sided TLE were flipped to the left to assess changes ipsi- or contralateral to onset. Ictal hyperperfusion was studied in SGTCS and focal seizures with impaired responsiveness (FS) by applying paired-wise t test in each group respectively. Intergroup difference of perfusion changes between SGTCS and FS was determined by applying the multi-group conditions and covariates model in SPM. Significant voxels were thresholded at P<0.01, with an extent threshold K = 125 at cluster level. Results: Of 42 seizures in the group, 6 focal seizures with impaired responsiveness (14.3%) progressed to SGTCS and 36 focal seizures did not (FS group). In the FS group, ictal hyperperfusion was detected in ipsilateral temporal lobe, insula, bilateral basal ganglia and cerebellum. In patients with SGTCS, ictal hyperperfusion involved similar structures and extended further to involve ipsilateral posterior neocortical temporal and parietal lobe. Group comparison between FS and SGTCS showed significantly greater hyperperfusion in ipsilateral lateral-temporal lobe and ipsilateral parietal region (Fig 1). Conclusions: The ictal hyperperfusion pattern is different in the seizures of TLE with and without SGTCS. SGTCS are associated with significant hyperperfusion in posterior lateral temporal cortex extending into the inferior parietal region. This region is similar to that demonstrated by intracranial EEG recording in patients with TLE with SGTCS (Yoo et al., 2014). We did not find significant differences in the involvement of brainstem, thalami, basal ganglia or the cerebellum between focal seizures of temporal onset with and without progression to tonic clonic seizures.