BACKGROUND: Already in the late 1960s and early 1970s, targeting of the 
"posterior subthalamic area (PSA)" was explored by different functional 
neurosurgical groups applying the radiofrequency (RF) technique to treat 
patients suffering from essential tremor (ET). Recent advances in magnetic 
resonance (MR)-guided focused ultrasound (MRgFUS) technology offer the 
possibility to perform thermocoagulation of the cerebellothalamic fiber tract in 
the PSA without brain penetration, allowing a strong reduction of the 
procedure-related risks and increased accuracy. We describe here the first 
results of the MRgFUS cerebellothalamic tractotomy (CTT).
METHODS: Twenty-one consecutive patients suffering from chronic (mean disease 
duration 29.9 years), therapy-resistant ET were treated with MRgFUS CTT. Three 
patients received bilateral treatment with a 1-year interval. Primary relief 
assessment indicators were the Essential Tremor Rating Scale (Fahn, Tolosa, and 
Marin) (ETRS) taken at follow-up (3 months to 2 years) with accent on the hand 
function subscores (HF16 for treated hand and HF32 for both hands) and 
handwriting. The evolution of seven patients with HF32 above 28 points over 32 
(group 1) differentiated itself from the others' (group 2) and was analyzed 
separately. Global tremor relief estimations were provided by the patients. 
Lesion reconstruction and measurement of targeting accuracy were done on 2-day 
post-treatment MR pictures for each CTT lesion.
RESULTS: The mean ETRS score for all patients was 57.6 ± 13.2 at baseline and 
25.8 ± 17.6 at 1 year (n = 10). The HF16 score reduction was 92 % in group 2 at 
3 months and stayed stable at 1 year (90 %). Group 1 showed only an improvement 
of 41 % at 3 months and 40 % at 1 year. Nevertheless, two patients of group 1 
treated bilaterally had an HF16 score reduction of 75 and 88 % for the dominant 
hand at 1 year after the second side. The mean patient estimation of global 
tremor relief after CTT was 92 % at 2 days and 77 % at 1-year follow-up.
CONCLUSIONS: CTT with MRgFUS was shown to be an effective and safe approach for 
patients with therapy-refractory essential tremor, combining neurological 
function sparing with precise targeting and the possibility to treat patients 
bilaterally.