Thalamic deep brain stimulation: Effects on the nontarget limbs

Unilateral thalamic ventral intermediate (VIM) deep brain stimulation (DBS) is now accepted as an effective treatment for essential tremor (ET) and tr emor related to Parkinson's disease (PD). The effects of unilateral placeme nt on the side ipsilateral to the surgical site have not been carefully eva luated. To systematically assess the effects ipsilateral to the surgical si de and to determine the effects of device inactivation on the baseline trem or, we evaluated tremor in 73 patients approximately 3 months after their u nilateral thalamic placement. Assessment included blinded and unblinded rat ings using the Unified Parkinson's Disease Rating Scale for PD patients and a modified Tremor Rating Scale in ET patients. All measures of tremor cont ralateral to the implantation site improved significantly and robustly in b oth PD and ET. Implantation did not worsen tremor by any measure on the ips ilateral side. There was mild ipsilateral improvement as measured by lower observed tremor scores in ET (6.0 +/- 1.8 to 5.0 +/- 1.9, P < 0.005), but n ot PD. There was no rebound augmentation of tremor in either hand after the devices were deactivated in either group. We conclude that VIM DBS may mil dly improve ipsilateral ET, and that concerns about meaningful ipsilateral tremor augmentation after device deactivation are not warranted. (C) 2001 M ovement Disorder Society.