Skull base chordomas presenting with abducens nerve deficits: clinical characteristics and predictive factors for deficit improvement or resolution

Skull base chordomas (SBCs) often present with cranial nerve (CN) VI deficits. Studies have not assessed the prognosis and predictive factors for CN VI recovery among patients presenting with CN VI deficits. The medical records of patients who underwent resection for primary chordoma from 2001 to 2020 were reviewed. Those presenting with CN VI palsy were identified. The extent of CN VI deficit was determined to be partial or complete based on the Scott-Kraft score. The change in deficit from baseline was recorded within 3 days of surgery and at the 6-month follow-up. The postoperative course was followed until partial and/or complete deficit recovery. Univariate logistic regression models were created to predict improvement or resolution of CN VI deficit. A total of 113 patients with primary SBC were identified, 34 of whom presented with CN VI deficits: 24 (73%) with partial and 9 (27%) with complete deficits. The extent of deficit in 1 patient was unable to be determined. The median duration of deficit preoperatively was 3.6 months, and CN VI was most commonly radiographically abutted at the prepontine cistern and Dorello's canal. Twenty-three (68%) patients experienced at least partial CN VI recovery (mean 61 days, range 2-174 days). Nineteen (56%) patients experienced complete CN VI recovery (mean 162 days, range 2-469 days). No patients whose CN VI deficit worsened immediately after surgery achieved improvement in CN VI function at 6 months (p = 0.001). Preoperative partial (relative to complete) CN VI deficit was associated with greater odds of CN VI deficit improvement by 6 months (OR 7.7, p = 0.028). Factors not associated with deficit resolution included duration of deficit, CN VI involvement by tumor, total segments abutted by tumor, sex, age at diagnosis, gross-total resection, tumor volume, and adjuvant radiation therapy, although this analysis may have been underpowered to detect small differences. Overall, 68% of patients achieved at least partial recovery in CN VI function after endoscopic skull base surgery. Among patients with partial CN VI palsy at baseline, 83% achieved CN VI recovery within 6 months and 75% achieved complete recovery within 14 months. For patients who presented with a complete CN VI deficit, within those same time frames, 33% and 11% achieved partial and complete recovery, respectively. Complete preoperative CN VI deficit was associated with lower odds of CN VI recovery by 6 months. The duration of preoperative deficit does not predict functional CN VI recovery.