Abstracts

Rationale: It is now widely accepted that after drug resistance is established, Epilepsy Surgery, if a defined seizure focus is identified and functional impairment minimized, should be entertained. Scalp EEG and MRI may not adequately define a focus, and this is Exaggerated in children, whom, unlike adults, isolated MTS is not the dominant Epilepsy causing lesion. Functional Imaging such as Subtraction SPECT when co-registered with MRI may be extremely helpful in lateralizing and localizing a designated epileptiform target. Degradation and stability of the radio-isotope, rapidity of injection, rapidity of seizure spread, and availability of the scanner are potentially all impediments to acquiring an adequate study. Scans are often limited to 9 hours of acquisition at our center but are often limited by time of maximal seizures (drowsiness or sleep), and the half-life of the isotope often lasting up to 8 hours for an adequate study. The two isotopes utilized at our center, Neurolite and Ceretec, were compared for efficacy in acquisition of SPECTS and there localizing value in defining the epileptogenic zone. Ceretec seemed to have less stability, is colored which affects visability and has a shorter half-life. It also requires a filter prior to pushing the isotope, which slightly reduces the speed of the injection. We therefore theorized that Neurolite would have better localizing value than its counterpart.Methods: The Epilepsy database was retrospectively reviewed for all patients with prior SPECT Scans done between July 2010 and January 2015. The numbers of attempted studies versus successful subtraction studies were compared. Sensitivity and specificity of Neurolite versus Ceretec, in acquiring useful data were compared. Scalp EEG, seizure semiology and in cases where intracranial recordings were available, cortical recordings defined ictal onset zones were collected for analysis. IRB for database review was approved by SETON family of Hospitals.Results: 195 studies were attempted and ictal and inter-ictal studies were able to be carried out in 122 (62.56%). 77 were injected with Ceretec and 45 with Neurolite. 52/77(67.53%) Ceretec scans successfully revealed BOLD signals and 33/45 (73%) Neurolite scans. 15 Revealed bilateral uptake (9 Ceretec, 6 Neurolite) but all had similar bilateral uptake on EEG. SPECT was more concordant with intracranial electrode placement and subsequent resection than scalp EEG.Conclusions: This study revealed a higher yield of successful subtraction (SISCOM) studies than most prior studies with yields as low as 38% in temporal lobe epilepsy and 36% non-temporal lobe epilepsy (Sulc V et al. Neurology, 2014). In most cases the information obtained was useful in lateralizing and localizing the seizure focus. There was a trend towards Neurolite having better value in localization than Ceretec, however it was not statistically significant. In Pediatric cases of drug resistant epilepsy, Subtraction SPECT still offers significant value in better defining the Epileptogenic Zone.