Focus localization in patients with partial epilepsy with 99Tcm-HMPAO SPECT under continuous surface EEG monitoring

Neuropsychological, intellectual, and behavioral findings in patients with centrotemporal spikes with and without seizures

Forty children (23 boys, 17 girls) with centrotemporal spikes (rolandic focus) with and without seizures (mean age 8.4 years +/- 4.8 SD), and 40 healthy controls matched for age, sex, and socioeconomic status were assessed for their neuropsychological, intellectual, and behavioral outcome. Compared with the controls, patients were significantly impaired in their IQ, visual perception, short-term memory, in their psychiatric status and in some subtests in a fine motor performance task. No significant differences could be computed for a simple finger-motor speed exercise or a linguistic performance test. In patients, deficits in IQ were significantly correlated with frequency of spikes in the EEG, but not with frequency of seizures, lateralization of the rolandic focus, or time since rolandic focus was diagnosed. It was concluded that a rolandic focus is not as benign as once thought.

The relative contributions of MRI, SPECT, and PET imaging in epilepsy

Functional and structural neuroimaging techniques are increasingly indispensable in the evaluation of epileptic patients for localization of the epileptic area as well as for understanding pathophysiology, propagation, and neurochemical correlates of chronic epilepsy. Although interictal single photon emission computed tomography (SPECT) imaging of cerebral blood flow is only moderately sensitive, ictal SPECT markedly improves yield. Positron emission tomography (PET) imaging of interictal cerebral metabolism is more sensitive than measurement of blood flow in temporal lobe epilepsy. Furthermore, PET has greater spatial resolution and versatility in that multiple tracers can image various aspects of cerebral function. Interpretation of all types of functional imaging studies is difficult and requires knowledge of time of most recent seizure activity and structural correlates. Only magnetic resonance imaging (MRI) can image the structural changes associated with the underlying epileptic process, and quantitative evidence of hippocampal volume loss has been highly correlated with seizure onset in medial temporal structures. Improved resolution and interpretation have made quantitative MRI more sensitive in temporal lobe epilepsy, as judged by pathology. When judged by electroencephalography (EEG), ictal SPECT and interictal PET have the highest sensitivity and specificity for temporal lobe epilepsy; these neuroimaging techniques have lower sensitivity and higher specificity for extratemporal EEG abnormalities. Regardless of the presence of structural abnormalities, functional imaging by PET or SPECT provides complementary information. Ideally these techniques should be used and interpreted together to improve the localization and understanding of epileptic brain.

Technetium-99m HmPAO brain SPECT and outcome of hemispherectomy for intractable seizures

With recent descriptions of the modified hemispherectomies and hemicorticectomy, there has been renewed interest in hemispherectomy for treatment of intractable seizures with hemiparesis. Because long-term outcome remains uncertain, patient selection remains difficult. 99mTc-HmPAO brain SPECT has been a helpful adjunct in the evaluation of epilepsy surgery candidates. We report SPECT scan findings in 7 patients who underwent hemispherectomy and compare these results with scalp EEG findings. Six patients had unilateral SPECT findings and all had a favorable outcome, regardless of surface EEG findings.

Memory complaints, memory disorders and focus localization in patients with partial epilepsy

Our study aimed at analysing effects of epileptic foci on memory function in patients with partial epilepsy. Twenty-eight patients with spontaneous memory complaints and psychometrically established memory disorders were assessed by 21-channel electroencephalography recorded both during cognitive testing and during 99mTc-HMPAO single photon emission computed tomography (SPECT). Computed tomography (CT) was performed on the same day. None of the epilepsy-related factors (seizure type, seizure frequency, type of epilepsy, age at onset of the seizures, type of antiepileptic treatment) could be related directly to severity or type of memory impairment (classified into the categories 'global', 'verbal' and 'non-verbal'). Remarkably, this study found no significant relationship between EEG focus localization and severity of measured memory impairment. Most areas with hypoperfusion on the SPECT were found in the group with global (severe) amnesia, typically with a right frontal localization. Abnormalities on CT were predominantly found in the same group, however, with a right-sided parietal localization. An unanticipated finding was that the majority of temporal CT and SPECT lesions were found in the group with relatively better memory performance.