Diplopia and Esophoria Induced by Medial Thalamic Deep Brain Stimulation (P6.308)

Abstract

OBJECTIVE: To describe esophoria caused by medial thalamic deep brain stimulation (DBS) for Tourette syndrome (TS). BACKGROUND: DBS of the thalamic centromedian/parafascicular complex (CM/Pf) ameliorates symptoms of TS. Stimulation-induced eye movement abnormalities have not been described. DESIGN/METHODS: A 44-year-old with debilitating TS since childhood that was refractory to pharmacotherapy underwent DBS, with leads (3387 Medtronic) implanted in bilateral thalamic CM-Pf region. Lead locations were left x -4.3, y -5.3, z 1.0, and right x 4.6, y -4.7, z 0.6. RESULTS: Following DBS programming, dramatic tic relief occurred, with preoperative Yale Global Tic Severity Score of 86 improving to 42 postoperatively. Final stimulation parameters were left 7.2 mA and right 6.0 mA, bilateral contact 0-3+, pulse width (PW) 90usec, 130Hz. At baseline, eye movements were full with no esophoria. He had a congenital ability to independently adduct his right eye. Monopolar review of each contact was conducted using ascending current (mA), case positive, PW 90 usec , 130 Hz, and contralateral DBS off. Patient reported dizziness and diplopia worse with left gaze. Esophoria in left gaze was induced with left or right stimulation, most severe with ventral contacts, with lower threshold for left lead (thresholds left contact 0 four mA, contact 3 six mA, right contact 0 five mA, contact 3 eight mA). The esophoria spread to central position and right gaze with higher amplitude or longer duration stimulation. No abduction defect was seen. Tic relief was best with ventral contacts. CONCLUSIONS: Thalamic DBS may influence descending supranuclear convergence pathways traveling through the medial thalamus to rostral midbrain, disinhibiting convergence neurons and causing esodeviation. Left-sided predominant esophoria that spreads to central and right gaze with increasing current from either lead suggests bilateral innervation of supranuclear convergence pathways. This case may shed light on convergence pathways and explain patients' subjective diplopia and dizziness observed during medial thalamic stimulation.

Disclosure: Dr. Changizi has nothing to disclose. Dr. Cho has received personal compensation for activities with Merz Pharma, CogniMed, and US WorldMeds. Dr. Kopell has nothing to disclose. Dr. Rucker has nothing to disclose.