Original Articles
The Practical Utility of Performing Peri-Ictal SPECT in the Evaluation of Children With Partial Epilepsy

https://doi.org/10.1016/S0887-8994(98)00019-8Get rights and content

Abstract

Peri-ictal brain single-photon emission computed tomography (SPECT) is increasingly being established as a useful test in localizing partial epilepsy in adults. However, obtaining an ictal injection and acquiring the SPECT images poses a greater challenge in pediatric patients, and few reports have specifically addressed the practical use of this technique in children. The Mayo Clinic experience of peri-ictal SPECT in the evaluation of children with partial epilepsy is reported here. Peri-ictal SPECT was attempted during 71 admissions involving 59 patients (median age 12 years, range 1 year 6 months-17 years). A peri-ictal SPECT injection was performed on 48 (67.6%) of these admissions in 43 (72.9%) patients, and only two patients could not be scanned. Of the 46 peri-ictal images successfully obtained, 30 (65.2%) were from ictal injection and 16 (34.8%) from post-ictal injections. Forty-two (91.3%) of the successfully obtained SPECT images, in 38 patients (92.3%), were classified as localizing (15 temporal, 24 extratemporal). We conclude that, with the appropriate unit setup and well-trained staff, peri-ictal SPECT scans can be obtained in most pediatric partial epilepsy patients. Moreover, the procedure provides specific localizing information in a high proportion of these patients.

Introduction

Peri-ictal single-photon emission computed tomography (SPECT) involves the intravenous injection of a radionuclide, such as technetium-99m hexamethylpropylene amine oxime (99mTc-HmPAO) or technetium-99m-ethyl cysteinate diethylester (99mTc-ECD), which has a rapid first-pass brain uptake with minimal redistribution. The resultant image provides a “snapshot” of the peri-ictal cerebral blood flow pattern that was present within 30-60 seconds of the injection 1, 2. Partial seizures have long been known to be associated with a transient focal increase in cerebral blood in the region of the seizure focus 3, 4, 5, 6, and this technique is becoming established as a useful test in the presurgical evaluation of partial epilepsy in adults, particularly in the lateralization of temporal lobe seizures 2, 7, 8, 9, 10, 11. More recently, extratemporal seizures have also been reported to be successfully localized with ictal SPECT 12, 13, 14, 15, 16.

However, ictal SPECT has been less well studied in children 12, 17, 18, 19, 20, 21. Obtaining an ictal injection and acquiring SPECT images pose a greater challenge in pediatric than in adult patients, and few reports have specifically addressed the practical aspects of this technique in children. The purpose of this report is to review our experience with peri-ictal SPECT in pediatric patients, especially regarding the success rate of performing an ictal injection and of acquiring satisfactory images, as well as the sensitivity and specificity of the SPECT localization.

Section snippets

Patients

All patients less than 18 years of age admitted to the Epilepsy Monitoring Unit at Mayo Medical Center, Rochester, from June 1993 to April 1997 with the presumed diagnosis of partial epilepsy, who had been scheduled to have a peri-ictal SPECT performed, were retrospectively identified. We determined the proportion of these patients in whom a successful peri-ictal injection was obtained and then the proportion of these that had a true ictal injection performed (i.e., while there was continuing

Clinical Information and Seizure Timing

Medical records were abstracted for demographic and clinical information. Seizure length and timing of injection were assessed by review of videotape of the injected seizures. The reviewer did not know the patients’ clinical history, the results of the SPECT imaging, the electroencephalogram (EEG) recordings, the magnetic resonance imaging (MRI) findings, and the surgical outcome. Seizure onset was considered to be the time of earliest indication of a warning (verbalized or pushing the call

Demographic and SPECT Injection Information

During the study period, ictal SPECT was scheduled for 71 admissions involving 59 pediatric patients. The mean age of these patients was 10 years 11 months, with a range of 1 year 6 months to 17 years (20.3%, 0-6 years; 40.7%, 7-12 years; and 40%, 13-17 years). Thirty-two were male, and 27 were female. A peri-ictal SPECT injection was successfully obtained during 48 (67.6%) of these admissions on 43 (72.9%) of the patients. The mean length of hospital stay was significantly longer for the

Discussion

This study represents the largest consecutive series of peri-ictal SPECT in children with partial epilepsy. More important, it is the first report that has specifically investigated the practical utility of performing peri-ictal SPECT in pediatric patients. Although a few studies have evaluated the sensitivity and specificity of peri-ictal SPECT images in selected groups of children 12, 17, 18, 19, 20, 21, none has reported their overall success rate of accomplishing a peri-ictal injection and

Acknowledgements

The authors acknowledge Timothy Hardyman, Division of Nuclear Medicine, Mayo Clinic, for technical assistance and advice and Dennis Hanson and Dr. Richard Robb, PhD, Department of Biomedical Imaging, for providing computer software and hardware support.

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