Glial tumors and deep brain stimulation: An increasingly recognized association?

Occurrence of gliomas in patients with chronic deep brain stimulation (DBS) has been reported few. It has been speculated whether there could be a causal relationship. Here, we report the development of a pilocytic astrocytoma in close vicinity of a DBS electrode during the course of chronic DBS. A 38-year-old man with refractory dystonic head tremor underwent bilateral implantation of quadripolar DBS electrodes in the thalamic ventral intermediate nucleus. He benefited markedly from chronic DBS. At age 46 he was admitted with head and neck pain, attention deficits and sensory disturbances. Cranial computed tomography and magnetic resonance imaging (MRI) showed a subcortical tumor originating from the right pulvinar. Surgery was performed with neuronavigation guidance and the tumor was subtotally removed. The neuropathological examination revealed a pilocytic astrocytoma WHO Grade I. Postoperative MRI demonstrated a small remnant tumor without increase in size during 1 year follow-up after adjuvant radiation therapy. He had ongoing benefit of his tremor with continued DBS. To our knowledge, there have been only three case reports published before indicating such a co-occurrence. In all of these reports, the tumors were high-grade gliomas. It is estimated that about 160.000 patients have been treated with DBS worldwide to date. Even if one would take into account that glial tumors would develop only with chronic DBS after several years and that a significant number of patients didn't reach such long term follow-up the resulting probability of brain tumor development most likely wouldn't be higher as the expectation of mere coincidence.