Diffusion tensor imaging to evaluate commissural disconnection after corpus callosotomy

Corpus callosum transection can prevent propagation of epileptic discharges. If seizures persist after surgery, assessment of the efficacy of the transection requires knowledge that the commissural fibers have been disrupted. We evaluated whether diffusion tensor imaging (DTI) and diffusion tensor fiber tracking can assess the degree of callosal transection and determine which white matter pathways remain intact. This HIPAA-compliant retrospective study was performed after Institutional Review Board approval. Patients who underwent corpus callosotomy with postoperative magnetic resonance imaging (MRI) that included DTI were identified. Axial DTI was performed with either 15 or 25 noncollinear directions of encoding. MRI and DTI were reviewed by two board-certified neuroradiologists to evaluate commissural disconnection. One hundred eleven patients underwent corpus callosotomy with postoperative MRI, of which 32 had postoperative DTI. Of these 32, there were 16 males and 16 females, with a mean age of 12.2 +/- 6.3 years (range 0.24 to 32.8 years, median 12.3). Eighteen patients had undergone complete callosal transection and 14 patients had partial callosal transection. Seventeen of 18 patients undergoing complete callosal transection had structural and diffusion tensor fiber tracking (DT-FT) evidence of complete transection. The forceps major was intact in all patients undergoing partial transection. At least some commissural fibers originating from the precuneus, postcentral gyrus, and posterior cingulate were intact in all six partial transections which spared the callosal isthmus. DTI and DT-FT aid in the postoperative characterization in patients with callosal transection for seizure control. This can confirm whether the intended fibers have been disconnected, helping in the planning for possible further surgical intervention versus other therapies.