Improved Dexterity after Chronic Electrical Stimulation of the Motor Cortex for Central Pain: A Special Relevance for Thalamic Syndrome

Objectives: To demonstrate that motor cortex stimulation (MCS) could improve motor function in patients with neuropathic pain. Methods: In this prospective clinical study of 38 patients referred for MCS as treatment for their neuropathic pain, we collected any declaration of improvement in motor performance that could be attributed to MCS. Results: Ten patients (26%) declared a benefit in their motor function. Eight presented objective evidence of recovered dexterity for rapid alternating movements. A minor proportion had improvement in dystonic posture (n = 2), but none had detectable increased motor strength or tonus changes. Overall, 73% of the patients with limb ataxia declared a benefit after MCS. In 6 out of 10 patients (60%), the anatomic lesion responsible for pain was restricted to the lateral aspect of the thalamus. All of them had either clinical or electrophysiological evidence of lemniscal dysfunction (proprioceptive ataxia). No correlation was found between the scores of pain relief and the modification of motor status. The correlation between thalamic lesions and benefits in motor performance was significant (Fisher's exact test, two-tailed, p = 0.0017). Conclusions: Up to 26% of patients estimated that MCS improved their motor outcome through recovered dexterity and in cases of lateral thalamic lesions.