Standardization of amygdalohippocampectomy with intraoperative magnetic resonance imaging: preliminary experience

Intraoperative magnetic resonance imaging (IMRI) is an extremely useful neurosurgical tool in surgeries in which the extent of resection is known to have a significant impact on outcome. Residual hippocampus is the most common cause of recurrent seizures after temporal lobectomy for medial temporal lobe epilepsy. Although the risk/benefit ratio of a policy of universal radical hippocampal resection is not known, we hypothesized that IMRI would aid in the intraoperative assessment of the extent of hippocampal resection and assist in accomplishing a complete hippocampectomy.

Five consecutive patients with medically intractable medial temporal lobe epilepsy underwent a radical amygdalohippocampectomy as part of the their surgery for epilepsy. IMRI was used before surgery and after an initial resection. The quality of images was assessed. Postoperative MR images were evaluated by a radiologist to determine the extent of resection of the amygdala, hippocampus, and parahippocampal gyrus.

There were no perioperative infections. After a mean follow-up of 10 months, all patients are seizure free. T(1)-weighted coronal intraoperative images were judged adequate at visualizing the medial structures in all patients. T(2) and fluid-attenuated inversion recovery (FLAIR) images did not provide useful information. Postoperative MR images indicated that a complete hippocampectomy had been achieved in all patients.

IMRI is a useful adjunct in the surgical treatment of medial temporal lobe epilepsy and perhaps the most reliable method of standardizing a complete hippocampectomy. T(1)-weighted coronal images are the most helpful sequence.