Evaluation of Bilateral Gamma Knife Thalamotomy in Patients Presenting With Severe Essential Tremor

Essential tremor (ET) is the most frequent movement disorder. Its prevalence is about 1/200 implying that at least 300 000 peoples are concerned in France. Its frequency increase with age (14% of patients 65 yo). The diagnostic criteria are postural and kinetic tremor that can be associated with head/voice tremor. ET induces a social impairment but also difficulties to perform any task requiring dexterity. With time, tremor can be so severe that every activity of daily living is impaired with loss of autonomy. Treatment such as betablockers, primidone or antiepileptics might have some efficacy at the beginning. But as the severity of the tremor increases, there is lack of efficacy. Deep Brain stimulation (DBS) of the ventral intermediate nucleus (VIM) of the thalamus can be proposed. However, in case of medical or surgical contra-indication, Gamma Knife (GK) radiosurgery thalamotomy can be an alternative option. Patients will be included with a minimum of 12 months after having the first thalamotomy (Gamma Knife 1) (done on the most annoying side) subject to no significant deterioration in cognitive assessment, voice assessment and balance and postural assessment or neuroradiological abnormality. Patients will be assessed with Magnetic resonance imaging (MRI) cerebral, clinical assessment (tremor rating scale) impairment of activity of daily living, neuropsychological evaluation, voice assessment and balance and postural assessment. The second thalamotomy (Gamma Knife 2) will be proposed and a monitoring at M6 and M12 will be done. This study will demonstrate the feasibility and tolerance of bilateral GK radiosurgery thalamotomy in ET patients with severe impairment.