Delayed neural degeneration following gamma knife radiosurgery in a patient with an arteriovenous malformation: a diffusion tensor imaging study.

Gamma knife surgery (GKS) is a proven modality for the treatment of arteriovenous malformations (AVMs), but neural degeneration is a serious complication of GKS. In this study, we report on a patient who displayed delayed neural degeneration following GKR, using diffusion tensor imaging (DTI). A 43-year-old male patient was diagnosed with an intraventricular hemorrhage (IVH) due to rupture of an AVM in the right middle cerebellar peduncle, and exhibited cognitive impairment, quadriparesis, and ataxia after IVH onset. He underwent GKS 5 weeks after onset. Brain MRIs performed at 6 weeks, 7 months, and 21 months post-onset revealed encephalomalactic lesions in the right pons, middle cerebellar peduncle, and medulla oblongata. DTI at 6 weeks post-onset suggested neural injuries of the right corticospinal tract (CST), right middle cerebellar peduncle (MCP), and right inferior cerebellar peduncle (ICP). DTI at 7 months suggested that the right CST and right ICP had recovered to some extent, which concurred with improved clinical manifestations. However, at 21 months, four neural tracts (right CST, right MCP, and both ICPs) appeared to have degenerated, which was in-line with aggravation of corresponding clinical manifestations. Experiences of this patient suggest DTI is a useful technique for the detection of neural degeneration after GKS.