OBJECT: Recent technological developments open the field of therapeutic 
application of focused ultrasound to the brain through the intact cranium. The 
goal of this study was to apply the new transcranial magnetic resonance 
imaging-guided focused ultrasound (tcMRgFUS) technology to perform noninvasive 
central lateral thalamotomies (CLTs) as a treatment for chronic neuropathic 
pain.
METHODS: In 12 patients suffering from chronic therapy-resistant neuropathic 
pain, tcMRgFUS CLT was proposed. In 11 patients, precisely localized thermal 
ablations of 3-4 mm in diameter were produced in the posterior part of the 
central lateral thalamic nucleus at peak temperatures between 51 ° C and 64 ° C 
with the aid of real-time patient monitoring and MR imaging and MR thermometry 
guidance. The treated neuropathic pain syndromes had peripheral (5 patients) or 
central (6 patients) origins and covered all body parts (face, arm, leg, trunk, 
and hemibody).
RESULTS: Patients experienced mean pain relief of 49% at the 3-month follow-up 
(9 patients) and 57% at the 1-year follow-up (8 patients). Mean improvement 
according to the visual analog scale amounted to 42% at 3 months and 41% at 1 
year. Six patients experienced immediate and persisting somatosensory 
improvements. Somatosensory and vestibular clinical manifestations were always 
observed during sonication time because of ultrasound-based neuronal activation 
and/or initial therapeutic effects. Quantitative electroencephalography (EEG) 
showed a significant reduction in EEG spectral overactivities. Thermal ablation 
sites showed sharply delineated ellipsoidal thermolesions surrounded by 
short-lived vasogenic edema. Lesion reconstructions (18 lesions in 9 patients) 
demonstrated targeting precision within a millimeter for all 3 coordinates. 
There was 1 complication, a bleed in the target with ischemia in the motor 
thalamus, which led to the introduction of 2 safety measures, that is, the 
detection of a potential cavitation by a cavitation detector and the maintenance 
of sonication temperatures below 60 ° C.
CONCLUSIONS: The authors assert that tcMRgFUS represents a noninvasive, precise, 
and radiation-free neurosurgical technique for the treatment of neuropathic 
pain. The procedure avoids mechanical brain tissue shift and eliminates the risk 
of infection. The possibility of applying sonication thermal spots free from 
trajectory restrictions should allow one to optimize target coverage. The 
real-time continuous MR imaging and MR thermometry monitoring of targeting 
accuracy and thermal effects are major factors in optimizing precision, safety, 
and efficacy in an outpatient context.