A rare case of greater petrosal nerve schwannoma

Abstract

Background:Facial nerve schwannomas include only 0.8% of all intrapetrous mass lesions, and schwannomas originating exclusively from the greater petrosal nerve (GPN) are extremely rare. To date, only 13 reports have been described. In this case, the tumor was thought to originate from the GPN on the basis of clinical, radiological, and operative findings.Case Description:A 23-year-old girl presented an acute left facial palsy, a disturbance in tear secretion of the ipsilateral eye, and a left-sided conductive hypoacusia. Computed tomography (CT) scan and magnetic resonance imaging (MRI) showed an extradural mass in the left middle fossa. A subtemporal approach was performed and the lesion, originating from the proximal portion of the GPN, was excised. The post-operative course was satisfactory, except for a xerophtalmia, which was treated with artificial teardrops.Conclusion:GPN schwannomas can originate anywhere alongside the course of the nerve, from its proximal segment near the facial hiatus to its distal segment near the foramen lacerum. For these reasons, it requires differential diagnosis with trigeminal nerve schwannomas or with injuries arising from the geniculate ganglion, because it can be easily confused with those lesions. However, in less severe cases, an early diagnosis can be able to preserve the function of the facial nerve by reducing iatrogenic injuries caused by surgical maneuvers.

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

“…Xerophthalmia, although pathognomonic of GSPN schwannoma may not be there in all patients and only present if parasympathetic nerve fibers have been destroyed by the tumor [7][8][9][10][11]. In previously reported cases only 6 patients had xerophthalmia [1,[12][13][14]. Other reported manifestations include diplopia due to abducens nerve palsy [1], trigeminal nerve involvement [15], seizure [12], eye pain, headache etc.…”

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

“…4,5,9 Some cases have curvilinear calcification of the tumor rim. 1,9,13 Bone-targeted high-resolution CT scanning is superior to MRI because delineation of the complex bone structures within the petrous bone is important to determine tumor location and extension and involved surrounding structures. For surgery, the relationship of the mass and the bony destruction of the carotid canal should be noted.…”

“…1,15 Also, to prevent postoperative xerophthalmia, the tumor capsule should be left on the middle fossa floor. Rupture of the ICA secondary to tumor adherence during dissection has been reported.…”

“…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.…”

“…Facial nerve schwannomas are rare lesions that constitute only 0.8% of all intrapetrous mass lesions. [1][2][3] The labyrinthine, tympanic, and vertical segments are the most common sites. 4,5 Tumors originating in and restricted to the greater petrosal nerve (GPN) are the least frequent.…”