Surgical Outcomes and Complications after Resection of Foramen Magnum Meningiomas

Background: Foramen magnum meningiomas are rare tumors that often present with insidious onset of symptoms over years. They are complex lesions to treat due to the adjacent lower cranial nerves and posterior circulation. Surgical approach depends on tumor location with the far-lateral and midline suboccipital approaches being most common. Here, we reviewed our surgical outcomes and complications after resection of foramen magnum meningiomas.

Methods: A retrospective review of 2,120 patients who underwent surgery for resection of meningioma from 1985–2015 meningiomas was conducted. Clinical information was extracted from the chart using electronic medical records, radiology data, and pathology data. All records of patient’s with foramen magnum meningioma were reviewed. Demographic data, presenting symptoms, surgical management, outcomes and complications data were collected. Logistic regression was used to evaluate for risk factors associated with complications.

Results: Of 2,120 patients with meningioma, we identified 27 patients with foramen magnum meningiomas (1.3%). The average age at diagnosis was 56 years and 70.4% were female. Median follow up was 4.9 years. Ninty-three percent of tumors were WHO Grade I, and 7% were WHO Grade II. There were no WHO Grade III tumors. One patient had had prior surgery. Presenting symptoms included numbness/paresthesias (12), ataxia (8), headache (7), extremity weakness (7), neck pain (6), incidental finding (3), and cranial nerve deficit (1). Tumor location within the foramen magnum was classified as anterior (n = 3, 11%), posterior (n = 2, 7%), lateral (n = 6, 22%), anterolateral (n = 11, 40%) or posteriolateral (n = 5, 19%). Arterial encasement occurred in 33% of cases, with 26% completely encasing the vertebral artery, and 7% partially encasing it. The average size was 18 +/− 20 cm3. The far-lateral (n = 21, 78%) and sub-occipital (n = 6, 22%) approaches were used to reach the tumor. Gross total resection was achieved in 33% of cases, and subtotal in 56% of cases. Post-op imaging was unavailable on 3 patients. One tumor recurred. A total of 20 complications occurred in 6 patients (22%), and included worsened extremity weakness (n = 7, 26%), new lower cranial nerve deficits and dysphagia (n = 3, 11%), hydrocephalus (n = 3, 11%), cerebrospinal fluid leak (n = 3, 11%), pseudomeningocele (n = 3, 11%), pneumonia (n = 1, 3.7%). There were no strokes or vascular injuries. Eight patients underwent post-operative radiation for residual tumor. Pre-operative extremity weakness was associated with an increased risk of any complication (p = 0.01). Anterior location was significantly associated with post-operative worsening of weakness (p = 0.01). Gross total resection and smaller size were associated with fewer complications (p = 0.004).

Conclusion: Foramen magnum meningiomas are relatively rare and complex tumors that typically present with symptoms secondary to mass effect on the upper spinal cord. They can be effectively treated with microsurgical resection, most commonly via far lateral or sub-occipital approach. Anterior location and pre-operative extremity weakness are associated with increased morbidity.