Value and Limitations of “True” Ictal 99mTc Ethyl Cysteinate Dimer Single Photon Emission Computed Tomography inpatients with Epilepsy
Authors: Sasagawa Mutsuo , Kameyama Shigeki , Fukuda Masafumi , Wachi Manabu , Tanaka Kou , Kanazawa Osamu , Oda Junichi , Hasegawa Seiichi 
Published: August 2009

Purpose: The goal of this study was to analyze the value of ictal 99mTc ethyl cysteinate dimer (ECD) single‐photon‐emission computed tomography (SPECT) in 30 patients undergoing presurgical evaluation for intractable seizures.

Methods: After reducing all medication, we closely monitored each patient to detect spontaneous seizures. Patients were injected intravenously with 600 MBq of ECD after a seizure was noted. All injections were administered in conjunction with long‐term EEG‐VCR monitoring. The EEG‐VCR documented the exact timing of the injection relative to the seizure onset, characteristics, and termination. We analyzed the time period between the ictal ECD injection and the termination of the seizure pattern on the EEG. We visually compared the ictal perfusion and interictal images of each patient. When the ictal SPECT image clearly identified the localization or laterality or both of the epileptic foci, we diagnosed the patient as “ictal positive”.

Results: The patient group consisted of 15 patients diagnosed with temporal lobe epilepsy (TLE), 11 with frontal lobe epilepsy (FLE), and four with other types of epilepsies. Twenty of the 30 patients underwent surgery: a temporal lobectomy was performed on 11 patients and a frontal corticectomy on nine. The mean ages of the patients diagnosed with TLE, FLE, and other types of epilepsies were 28.2, 17.9, and 17.9 years, respectively. The mean delay between seizure onset and ictal ECD injection was 15 s (range, 4–31 s) for patients with TLE, 7 s (range, 3–22 s) for those with FLE, and 8 s (range, 4–15 s) for those with other types of epilepsies. The mean period from seizure onset to termination as observed on the EEG was 54 s (range, 14–95 s) for patients with TLE, 34 s (range, 6–80 s) for those with FLE, and 17 s (range, 4–33 s) for those with other types of epilepsies. The percentage of ictal‐positive patients was 83% for those with TLE, 69% for those with FLE, and 50% for those with other types of epilepsies. The percentage of ictal‐positive cases was 50% for those with simple partial seizures (SPSs) at the time of injection, 77.3% for those with complex partial seizures (CPSs), and 72.7% for those with CPSs that evolved into generalized tonic‐clonic seizures. The mean delay between seizure onset and ictal ECD injection was 11.9 s for the ictal‐positive cases for all types of epilepsies; however, it was 8.1 s for the ictal‐negative cases. The mean duration between the ictal ECD injection and the termination of the seizure pattern observed on the EEG was 44.6 s for the ictal‐ positive cases and 31.9 s for the ictal‐negative cases. No patient was considered to be ictal positive when the mean duration between the ictal ECD injection and the termination of seizure pattern was <13 s.

Conclusions: ECD is stable for 6 h after preparation, enabling us to determine the laterality or localization of epileptic foci with “true” ictal SPECT. The percentage of ictal‐positive cases with TLE (83%) was higher than that with FLE (69%). However, there were no statistically significant differences between them because of the small size of the series. There was also no statistically significant differences between the types of epileptic seizures at the time of injection. A very short period between ECD injection and the termination of the seizure might result in no significant findings for a true ictal SPECT.