SPECT Ictal-Interictal Difference Imaging Reveals Thalamic and Brainstem Reticular Formation Involvement in Seizures
Abstract number :
1.243
Submission category :
Year :
2000
Submission ID :
1400
Source :
www.aesnet.org
Presentation date :
12/2/2000 12:00:00 AM
Published date :
Dec 1, 2000, 06:00 AM
Authors :
LeBron Paige, Christopher Bradley, David Chang, Colin Studholme, Rik Stokking, Andrew Norden, I G Zubal, Susan S Spencer, Hal Blumenfeld, Yale Univ, New Haven, CT; Yale Univ Sch of Medicine, New Haven, CT.
RATIONALE: Complex partial seizures cause loss of consciousness, yet involve only focal regions of the cerebral cortex. It has been hypothesized that this occurs through spread of activity to the thalamus and brainstem, structures known to be important for maintaining consciousness. Because of their deep location, the role of these structures in human seizures has not been thoroughly investigated. METHODS: We noninvasively imaged cerebral blood flow changes in the cortex, as well as in the thalamus and brainstem with SPECT ictal-interictal difference imaging coregistered with high resolution MRI scans. Seizure onset was classified as temporal, extratemporal, or uncertain, based on EEG, MRI, PET, neuropsychology testing, surgical pathology, and surgical outcome. RESULTS: We found that 34/45 patients admitted for epilepsy monitoring had SPECT ictal-interical changes of >20% in the medial thalami, pontomesencephalic reticular formation, or both regions. 14/20 patients with medial thalamic changes had seizures involving the temporal lobes, consistent with the known anatomic connections between these regions. In addition, for both temporal and extratemporal seizures, the time of injection in relation to the seizure determined which side showed greater perfusion changes. Thus, with early injections the medial thalamic and brainstem SPECT changes tended to be ipsilateral to the side of seizure onset, while with late injections (>30 seconds after seizure termination) the changes occurred contralateral to the side of seizure onset. CONCLUSIONS: These SPECT findings demonstrate bilateral sequential involvement of the medial thalami and pontomesencephalic reticular formation in some human seizures. Since these structures are known to be important for normal consciousness, this supports the hypothesis that involvement of these structures may cause loss of consciousness in certain seizures. Whether the thalamic and brainstem changes reported here are specifically correlated with impaired consciousness will be the subject of future study. Supported by the Dana Foundation, NIH NS02060, and a Pfizer fellowship.