Brain Advance Access published online on April 1, 2009
Brain, doi:10.1093/brain/awp027
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Clinical use of ictal SPECT in secondarily generalized tonic–clonic seizures
1 Department of Neurology, Yale University School of Medicine, New Haven, Connecticut, USA 2 Department of Neurology, Columbia University College of Physicians & Surgeons, New York, USA 3 Department of Nuclear Medicine, Columbia University College of Physicians & Surgeons, New York, USA 4 Department of Neurology, University of Alabama School of Medicine, Birmingham, Alabama, USA 5 Department of Nuclear Medicine, Yale University School of Medicine, New Haven, Connecticut, USA 6 Department of Neurosurgery, Yale University School of Medicine, New Haven, Connecticut, USA 7 Department of Neurobiology, Yale University School of Medicine, New Haven, Connecticut, USA
Correspondence to:
Hal Blumenfeld, Yale Departments of Neurology, Neurobiology, Neurosurgery 333 Cedar Street, New Haven, CT 06520-8018, USA E-mail: hal.blumenfeld{at}yale.edu
Partial seizures produce increased cerebral blood flow in the region of seizure onset. These regional cerebral blood flow increases can be detected by single photon emission computed tomography (ictal SPECT), providing a useful clinical tool for seizure localization. However, when partial seizures secondarily generalize, there are often questions of interpretation since propagation of seizures could produce ambiguous results. Ictal SPECT from secondarily generalized seizures has not been thoroughly investigated. We analysed ictal SPECT from 59 secondarily generalized tonic–clonic seizures obtained during epilepsy surgery evaluation in 53 patients. Ictal versus baseline interictal SPECT difference analysis was performed using ISAS (http://spect.yale.edu). SPECT injection times were classified based on video/EEG review as either pre-generalization, during generalization or in the immediate post-ictal period. We found that in the pre-generalization and generalization phases, ictal SPECT showed significantly more regions of cerebral blood flow increases than in partial seizures without secondary generalization. This made identification of a single unambiguous region of seizure onset impossible 50% of the time with ictal SPECT in secondarily generalized seizures. However, cerebral blood flow increases on ictal SPECT correctly identified the hemisphere (left versus right) of seizure onset in 84% of cases. In addition, when a single unambiguous region of cerebral blood flow increase was seen on ictal SPECT, this was the correct localization 80% of the time. In agreement with findings from partial seizures without secondary generalization, cerebral blood flow increases in the post-ictal period and cerebral blood flow decreases during or following seizures were not useful for localizing seizure onset. Interestingly, however, cerebral blood flow hypoperfusion during the generalization phase (but not pre-generalization) was greater on the side opposite to seizure onset in 90% of patients. These findings suggest that, with appropriate cautious interpretation, ictal SPECT in secondarily generalized seizures can help localize the region of seizure onset.
Key Words: epilepsy; cerebral blood flow; grand mal; surgery; nuclear medicine
Received August 28, 2008.
Revised January 26, 2009.
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