Schwannoma of the greater superficial petrosal nerve

Abstract

The authors report the clinical features, imaging and surgical findings, and follow-up of 5 rare cases of schwannoma of the middle fossa with possible origin from the greater superficial petrosal nerve (GSPN). All patients presented to a single neurosurgical institution. The study design was a prospective follow-up of 5 cases of schwannomas of the middle fossa that most likely originated from the GSPN. The presenting features were burning pain in the eyes in 2 cases, epilepsy and behavioral changes in 2 cases, and headache in 1 case. Imaging studies showed a subtemporal mass on the anterosuperior aspect of the petrous bone in all cases. An enhancing tail on the MR images was highly suggestive of the origin of the tumor from the GSPN. All tumors were removed through a subtemporal extra- or intradural approach. Partial to complete peripheral facial nerve palsy was encountered after surgery in 3 cases, which recovered completely. Dry eye was the long-term permanent deficit in all cases. Mid- to long-term follow-up of the cases has not revealed any tumor recurrence. The 5 cases of schwannoma of the middle fossa with possible origin from GSPN were managed successfully, and their clinical presentation, differential diagnosis, and management are discussed.

Greater Superficial Petrosal Nerve Schwannoma: 3 Case Reports and Review of Literature

“…In order of decreasing frequency these schwannomas in petrous bone, can arise from tympanic, vertical, labyrinthine, geniculate, and meatal segment of the facial nerve [5]. In the middle cranial fossa, schwannomas can arise from the geniculate ganglion or GSPN.…”

“…Tumor size and main symptom helps in determining to choose between intra or extra dural subtemporal corridor [5]. Relatively big tumor indenting in to the temporal lobe or seizure as a presenting symptom usually require intradural exploration also.…”

“…Benign-appearing bony scalloping and remodeling of the bony boundaries in the anterosuperior aspect of the petrous bone is usually a characteristic of schwannoma of the GSPN. It can be easily misunderstood by schwannoma originating from geniculate ganglion, which usually causes bulbous enlargement of the geniculate fossa [5,4,13]. Therefore, Careful inspection of the skull base and anterosuperior aspect of the temporal bone is mandatory [8,16].…”

The Appropriate Surgical Approach to a Greater Petrosal Nerve Schwannoma in the Setting of Temporal Lobe Edema

“…This anatomic feature does not mean that the patient will present with xerophthalmia. 9 It is difficult to determine whether a tumor originates from the GPN based solely on these symptoms. However, Schirmer test …”

“…Xerophthalmia and facial nerve paralysis are the most common complications after surgery. 1,[5][6][7][8][9][10] We present a case of GPN schwannoma associated with temporal lobe edema in which the patient was operated on by an extradural and intradural middle fossa approach. To the best of our knowledge, GPN schwannomas associated with temporal lobe edema have not been reported previously.…”