Revisiting bilateral thalamotomy for tremor.

MRI guided focused ultrasound surgery (MRgFUS) has been FDA approved for unilateral treatment of essential tremor (ET). Before this non-incisional lesioning method can be applied to the treatment of both hemispheres the previous experience with bilateral thalamic ablation must be addressed. In particular, the high incidence of worsening of speech and balance associated with bilateral surgical thalamotomy, a rationale for the development of deep brain stimulation. The highest incidence of these complication occurred in the early years of surgery for movement disorders, when neither MRI nor current stereotactic methods were available. The vast majority of these initial patients suffering these complications had Parkinson's disease where approximately 30% developed worsening dysarthria and ataxia after bilateral thalamotomy. Patients suffering these complications commonly had baseline abnormalities in speech and balance or worsening symptoms after a first unilateral procedure. The more contemporary experience with bilateral thalamotomy in the ET population is both much more limited in patient numbers (includes patients after Gamma Knife radiosurgery), and shows a much lower rate of these complications (approximately 5%). This more recent experience suggests that bilateral thalamotomy using closed incisionless methods such as MRgFUS has the potential to safely improve ET patients with axial or bilateral limb involvement, if done in a staged manner excluding patients with baseline dysarthria or ataxia or transient worsening of these symptoms following a unilateral procedure.