Prognostic factors affecting the surgical outcome of anterolateral benign tumors in the foramen magnum region

• This study firstly investigates the prognostic factors of all types of benign tumors located anterolateral to FM region.
• Far lateral approach was an independent predictor of postoperative neurological deficits.
• The role of the suboccipital approach to the anterolateral FM tumor may be underestimated and should be further evaluated.

IntroductionAnterior and anterolateral tumors in foramen magnum region are rare and surgically challenging although most of them are benign. The optimal approach is debatable and prognostic factors affecting surgical outcome remains unclear. We aimed to identify factors including surgical approach determining postoperative outcome.MethodsThe data of 49 patients diagnosed benign tumors involving the anterior and anterolateral foramen magnum were retrospectively analyzed in our institution from January 2009 to January 2015. The demographic, clinicoradiological, surgical and follow-up information were collected. Primary surgical outcome was new neurological deficits. A multivariate analysis was performed to determine predictors of postoperative neurological deficits.ResultsPatients were operated on either via suboccipital (31 cases, 63.3%) or far lateral (18 cases, 36.7%) approach. Newly developed neurological deficits occurred in 11 (22.4%) patients, improved over time in 6 (12.2%) patients. 2 (4.1%) patients died within 3 month after operation and 2 (4.1%) suffered tumor recurrence. 44 (93.6%) out of 47 survivors had good functional outcome (postoperative Karnofsky performance score ≥80) at last follow-up period. Patients with postoperative new neurodeficits harbored tumors which tended to more frequently involve lower third clivus (p = 0.083), to be meningiomas (p = 0.059), were more likely to be removed through far lateral approach (p = 0.010) and have extradural extension (p = 0.024). Multivariate analysis showed that the far lateral approach was the sole predictor independently related to postoperative neurological deficits (p = 0.029).ConclusionsThe far lateral approach to benign tumors anterolateral to foramen magnum experienced higher rate of immediate new neurological deficits compared to suboccipital approach. The role of the suboccipital approach may be underestimated and should be further evaluated.