Diffusion tensor imaging tractography to visualize the relationship of the optic radiation to epileptogenic lesions prior to neurosurgery.

PURPOSE

About one-third of patients with epilepsy are refractory to medical treatment and may be amenable to surgery. However, in patients with lesions on or near the presumed course of the optic radiation, the potential benefits of resection must be balanced against the risk of a visual field deficit. This study demonstrates the utility of diffusion tensor imaging (DTI) tractography in delineating the course of the optic radiation and its relationship to the epileptogenic lesion prior to epilepsy surgery.

METHODS

Anatomic and DTI scans were acquired on 10 patients with medically refractory epilepsy undergoing presurgical evaluation at the National Hospital for Neurology and Neurosurgery. Five patients underwent surgery and repeat scans postoperatively. The optic radiation was delineated and visualized in relation to the lesions on anatomic images and in three-dimensional (3D) reconstructions. Preoperative and postoperative visual fields were acquired by Goldmann perimetry.

KEY FINDINGS

The entire optic radiation was reliably delineated bilaterally in all patients. The results provide helpful additional information in informing the patient of the risks of surgery and in planning the surgical procedure and approach. Postoperative imaging findings correlated with the visual field data.

SIGNIFICANCE

The optic radiation shows significant anatomic variability, but can be reliably delineated by tractography. Because surgical disruption of the optic radiation has serious consequences for the patient, DTI tractography is a useful technique in this population. Future integration with real-time neuronavigation will minimize the risks of neurosurgery.