Limb Preference Changes after Focused-Ultrasound Thalamotomy for Tremor

Area of Science:

• Neurology
• Neurosurgery
• Biomedical Engineering

Background:

• Magnetic resonance-guided focused-ultrasound (MRgFUS) thalamotomy is a key treatment for essential tremor, targeting the ventrointermedius (Vim) nucleus.
• While effective, MRgFUS thalamotomy carries risks like balance and gait disturbances, potentially linked to proprioception disruption.

Purpose of the Study:

• To quantitatively assess the impact of MRgFUS thalamotomy on proprioception and limb use in essential tremor patients.
• To investigate the hypothesis that lesioning the sensorimotor Vim thalamus affects proprioception.

Main Methods:

• Utilized the Kinarm exoskeleton robot to measure proprioception in 18 essential tremor patients.
• Collected data pre-operatively and at 1 day, 3 months, and 1 year post-surgery.
• Assessed motor coordination, postural control, goal-directed movement, bimanual planning, position sense, and kinesthesia through four tasks.

Main Results:

• Observed immediate post-surgery improvements in posture speed and a temporary preference for the untreated limb in bimanual tasks.
• Found no significant changes in proprioception parameters following MRgFUS thalamotomy.
• No correlation was found between measured outcomes, lesion size, or lesion overlap with the dentato-rubro-thalamic tract.

Conclusions:

• This study provides the first quantitative evaluation of proprioception and limb preference after MRgFUS thalamotomy.
• Results indicate that MRgFUS lesioning of the Vim thalamus does not degrade proprioception.
• Transient alterations in limb preference suggest a potential
• relearning
• process in the treated limb.