A systematic review of extraocular movement-related schwannomas (CN III, IV, VI). Part II: Surgical outcomes and prognostic factors for postoperative nerve function.

OBJECTIVE

Extraocular movement-related schwannomas (EOMS)-arising from the oculomotor (CN III), trochlear (CN IV), or abducens (CN VI) nerves-are rare, and comparative data on nerve-specific surgical outcomes and prognostic factors are limited. This paper represents Part II of a two-part study on EOMSs. While Part I addressed tumor localization, clinical features, and surgical approaches, the present paper focuses on surgical outcomes and prognostic factors for postoperative neurological function.

METHODS

Systematic review identified surgically treated EOMS. Of 156 patients found, 117 had complete pre-/postoperative data; with the three institutional cases, 120 patients were analyzed. Variables extracted were tumor size, extent of resection (EOR), cavernous sinus involvement (CSI), and postoperative function of the nerve of origin. Univariate and multivariable logistic regression identified predictors of persistent postoperative origin nerve-related deficits.

RESULTS

The cohort comprised 52 CN III (43.3%), 34 CN IV (28.3%), and 34 CN VI (28.3%) tumors. Mean diameter was 30.1 mm. CSI occurred in 43.3% (more frequent in CN III and CN VI). Gross-total resection (GTR) was achieved in 69.2% overall and more often in CN IV (94.1%). Preoperative nerve deficits were present in 73.3%; among these, postoperative improvement occurred in 31.8%. New postoperative palsy developed in 40.6% of patients without preoperative palsy. At final follow-up, persistent nerve-of-origin deficits were present in 60.0%. On multivariable analysis, tumor diameter ≥ 35 mm (OR 2.47, 95% CI 1.06-5.73; p = 0.0354), CSI (OR 2.56, 95% CI 1.05-6.27; p = 0.039), and trochlear origin versus abducens (OR 3.24, 95% CI 1.03-10.1; p = 0.0438) were independently associated with persistent origin nerve-related deficits.

CONCLUSION

Persistent nerve-of-origin deficits are common after EOMS surgery. Larger tumors (≥ 35 mm), CSI, and trochlear origin confer higher risk, whereas EOR does not independently determine functional outcome. For high-risk subsets, a function-preserving strategy may better balance tumor control and neurological function.