Objective: To evaluate the therapeutic effect of chronic stimulation of posterior limb of the internal capsule in two subjects affected by fixed dystonia of the upper and lower limb (respectively) due to ischemic subcortical stroke.

Background: Fixed dystonia syndrome consists of abnormal postures of a body segment, (following ischemic or hemorrhagic events involving CNS) that never return to the normal position. It has obviously to be distinguished from the typical clinical picture of mobile dystonia, and carries a poor prognosis, being usually resistant to all conservative treatments. Our previous unsuccessful attempt at treating a fixed dystonia patient with GPI DBS led us to target the pyramidal system.

Methods: Two patients affected by post-stroke fuxed dystonia of the upper and of the lower limb, respectively, were submitted to DBS of the posterior limb of the internal capsule (IC) contralateral to the affected limb, under intra-operative neurophysiological monitoring (microelectrode recording and electromyography) and stereotactic computerized equipment.

Results: Follow-up is 7 years for patient 1 (lower limb fixed dystonia) and 9 months for patient 2 (upper limb fixed dystonia ); in patient 1, immediate improvement was noticed, with reversal of the previous inward rotation of the right foot. Such improvement persists at the last follow-up. In patient 2, there was a reduction of >40 % in the Disability of Shoulder, Arm, and Hand Scale (DASH) score; this score reports subjective measures of hand dexterity and related functional improvements. In this patient, the abnormal posture consists of hyperflexion of metacarpophalangeal joint of all five fingers of the right hand. Post-operative imaging demonstrated the correct posistioning of the electrodes within the IC.

Conclusions: Chronic DBS of IC posterior limb could be an alternative approach to conservative treatments in patients affected from abnormal fixed postures. Intraoperative neurophysiological monitoring confirmed correct targeting of the IC, with muscle activation of the affected segment of the body through intraoperative stimulation with DBS electrode; postoperative parameters were mantained subthreshold for tonic muscular contrations or other clinical side effects. It is not clear, though, if the therapeutic effect is attributable to activation of motor fibers or to cortico-striatal fiber.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/improvement-of-post-stroke-fixed-dystonia-of-upper-and-lower-limb-following-dbs-of-internal-capsule-report-of-two-cases/