Pediatric Trigeminal Schwannoma: A Case Report

Trigeminal schwannomas rarely present within the pediatric population. They most often occur sporadically and cause symptomology due to Schwann cell overgrowth resulting in dysfunction of the trigeminal nerve and/or adjacent structures. Management of these tumors is complicated by their benign nature, the need for long-term control in younger patients, and the potential for cranial nerve dysfunction with either observation or treatment. This report describes the clinical aspects of pediatric trigeminal schwannomas, including a literature review of the typical patient presentation with surgical outcomes. Furthermore, we assessed the feasibility of the mini-pterional approach for surgical exposure and tumor extraction for a dumbbell schwannoma. We report the case of a 14-year-old male who presented with an isolated sixth nerve palsy manifested by diplopia. [Fig. 1] is an MRI demonstrating a left-sided T1 contrast-enhancing lesion extending from the posterior fossa along the cisternal segment of the trigeminal nerve through Meckel’s cave into the cavernous sinus and into both the superior orbital fissure and foramen rotundum. Diffusion tensor imaging (DTI) was used to identify cranial nerves III, V, VII, and VIII along their anterior course. The DTI models were merged into an image-guidance-sequenced MRI for intraoperative use. A mini-pterional craniotomy was performed for an extended middle fossa approach with an anterior petrosectomy to gain access to the inferior aspect of the posterior fossa tumor component. [Fig. 2] contains intra-operative imaging obtained by a high-resolution microscope. Intraoperatively, the sixth nerve was compressed within Dorello’s canal. The tumor involved the ophthalmic and maxillary branches of the trigeminal nerve. Postoperative MRI demonstrated near-total resection with residual enhancement along the superior orbital fissure near the oculomotor nerve entry zone and foramen rotundum. Postoperatively, his sixth nerve palsy resolved; however, the patient developed left-facial numbness along the ophthalmic and maxillary divisions. The patient will undergo genetic testing for neurofibromatosis. A review of PubMed literature conducted for cases published within ten years revealed 11 cases treated by surgical resection and no published cases treated with radiosurgery. Results of the literature review are summarized in [Table 1]. The most common presenting symptom was trigeminal nerve dysfunction affecting seven cases. Other common presenting symptoms were four cases with cranial nerve VIII dysfunction, three with cranial nerve II dysfunction, and three with cranial nerve VI dysfunction. In conclusion, tumor location determines symptomatology and surgical approach. Most tumors in the literature are within the middle fossa with trigeminal nerve dysfunction. A case of pediatric trigeminal schwannoma type Mp treated surgically with a GTR via a mini-pterional approach and utilization of cranial nerve DTI is presented.