Lower Cranial Nerve Schwannomas: Institutional Case Series and Literature Review

Introduction: Schwannomas originating from the lower cranial nerves are rare and pose a significant surgical challenge. Resection has been the mainstay of treatment, but often at the cost of significant morbidity. Sparse data exists on factors affecting surgical outcome.

Methods: A retrospective review was performed for pathologically proven LCNS between 2003 and 2022 at a single institution. A formal literature review was also performed.

Results: Twenty-seven patients met criteria, with a median age was 47 years (range: 17–71), 14 females (52%), and patients had a median duration of 7 months of symptoms prior to neurosurgical presentation (range: 1–60). The most common presenting symptoms were dysphagia (52%), voice changes (41%), headaches (37%), dysarthria (33%), imbalance (33%), hearing loss or tinnitus (30%), and painless neck/throat mass (30%). Median maximum tumor diameter found on preoperative imaging was 4.0 cm (range 1.2–8.2). Bony erosion was found in 33% of patients, brainstem compression was seen in 56%, and 30% of patients had radiographic evidence of hydrocephalus. Most of the lesions were centered in the cerebellopontine angle and jugular foramen (59%), with 41% having parapharyngeal-predominant tumor mass. Retrosigmoid craniotomy was the most common surgical approach (37%), followed by anterior neck dissection (30%), far lateral (22%), combined neck and cranial (7%), and midline suboccipital (4%). Gross total resections were obtained in 14 patients (53.8%), with most remnants in the jugular foramen (62%) and cranial nerve 9–12 rootlets (25%). Vasal schwannomas made up 81% of the lesions, followed by spinal accessory (7%), hypoglossal (7%), and glossopharyngeal (4%) schwannomas. Postoperatively, 67% had clinical deterioration, most commonly hypophonia/hoarseness (63%), dysphagia (59%), hypoglossal weakness (19%), hearing loss (15%), and facial weakness (11%); 11% required PEG tubes and 4% tracheostomy. Median follow up was 60 months (range: 3–231). Seventeen (94%) of those patients demonstrated clinical improvements at follow up, with 11 (41%) undergoing vocal cord augmentation or thyroplasty. Eleven patients (41%) underwent adjuvant radiation or radiation for disease progression at a median of 5 months postsurgery (range: 2–32). 96% of all patients demonstrated tumor stability or no recurrence at last radiographic follow-up. In our literature review, we identified 22 studies that fulfilled our inclusion criteria with a total of 350 patients. Most tumors had extracranial extension (56%), though this highly varied. Gross total resection was achieved in 84% of the cohort. In individual studies, this ranged from 33 to 100%. Glossopharyngeal was the most identified site of origin (28%), followed by hypoglossal (26%), vagus (21%), and accessory (4%). At most recent follow-up, 93% of patients achieved tumor stability or had no tumor recurrence with individual studies ranging from 53% to 100%.

Conclusions: Surgical resection of LCNS carries a significant risk, including major cranial nerve deficits. Our study found that the growth into the CPA was associated with bony erosion, hydrocephalus, mass effect on the brainstem, and subtotal resection. This is pertinent as these lesions are most often found after significant growth. Although these are surgically high-risk lesions, aggressive surgical intervention is possible with good ultimate clinical outcomes and long-term durable tumor control.

Publication History

Article published online:
01 February 2023