Eye Movement Biomarkers in Autoimmune Stiff Person Syndrome A Case Series and Review

Background Stiff Person Syndrome (SPS) is a rare autoimmune neurologic disorder characterized by progressive rigidity, painful spasms, and significant functional disability. Oculomotor dysfunction remains an underrecognized feature despite its potential as a sensitive marker of central nervous system involvement. Given the role of GABAergic inhibition in eye movement control, detailed neuro-ophthalmologic evaluation may uncover abnormalities indicative of SPS pathophysiology. Case Presentation We present two illustrative cases of anti-GAD positive SPS with distinct oculomotor abnormalities identified via videonystagmography. The first case, a 40-year-old male, exhibited vertical smooth pursuit impairment, vertical saccadic dysmetria atenuated with repeated stimulation and upward gaze-induced facial spasms. The second case, a 44-year-old female, demonstrated severe pursuit deficits, saccadic dysfunction, saccadic intrusions, ocular flutter. Both patients showed significant improvement in oculomotor findings following immunomodulatory therapy. Conclusion Oculomotor abnormalities—particularly vertical pursuit impairment, saccadic dysmetria, and gaze-holding failure—are valuable, noninvasive indicators of central involvement in SPS. These findings, often overlooked, underscore the importance of structured neuro-ophthalmologic assessment in suspected SPS. Early detection of such abnormalities may facilitate timely diagnosis, prompt immunotherapy, and improved clinical outcomes.