Anesthetic Management of Stiff-Person Syndrome During Prolonged Lateral Skull Base Surgery: A Case Report and Phenotype-Informed Review

Background: Stiff-person syndrome (SPS) is a rare autoimmune neurological disorder characterized by progressive rigidity and episodic spasms. Perioperative evidence consists mainly of case reports, underscoring the importance of incorporating heterogeneity across the stiff-person spectrum disorder (SPSD) into perioperative assessment. To our knowledge, this is the first published report of SPS management during prolonged lateral skull base surgery. Case Presentation: A 56-year-old man with anti-amphiphysin antibody-positive, lower-limb-predominant SPSD without documented generalized spasms and a skull base phosphaturic mesenchymal tumor underwent an 11 h radical resection. Total intravenous anesthesia with propofol, remifentanil, and dexmedetomidine was used without neuromuscular blocking agents because facial and lower cranial nerve monitoring was required. Bispectral index values were maintained at 30–50, and serial quantitative train-of-four monitoring showed four responses with ratios of 100–125% throughout the procedure. No intraoperative spasm, movement, or hemodynamic instability occurred. The patient was extubated 3.5 h after intensive care unit admission, and serum phosphorus normalized within 48 h. A focused review of published reports identified no previous lateral skull base surgery in SPS and limited prolonged quantitative neuromuscular monitoring data. Conclusions: Prolonged muscle-relaxant-free total intravenous anesthesia was feasible in this selected SPS phenotype. Perioperative planning should integrate individual spasm history, bulbar or respiratory involvement, medication burden, surgical requirements, and SPSD phenotype. The proposed phenotype-informed framework organizes these considerations for individualized perioperative planning and provides a basis for future evaluation.