1

Introduction

Facial nerve schwannomas (FNS) are rare and benign tumors. Despite their rarity among the population, they are the most common tumors of facial nerve . FNS may involve any segments of facial nerve from intracranial segments to intratemporal segments and extracranial segments.

The ultimate treatment of FNS is surgical removal, but complete tumor removal and nerve grafting invariably lead to not better than HB Grade III recovery of facial nerve . Apparently, most patients will be reluctant to accept immediate surgery if the facial nerve function is normal or mildly abnormal. Therefore, ENT doctors tend to choose observation, decompression, stereotactic radiosurgery or subtotal resection for those patients with favorable facial nerve function (Grade III or better) to maintain good facial nerve function for a period . However, the tumors are still left in nature, and there is risk of tumor growth and subsequent facial nerve deterioration in the long run, especially for the younger patients. Many of them may finally have to turn to complete tumor removal and nerve grafting, and recover to not better than Grade III.

Surprisingly, stripping surgery, which could preserve facial nerve integrity and maintain good facial nerve function after complete tumor removal, has been attempted by a few surgeons . We hereby present a larger series of 18 FNS with favorable facial nerve function in which stripping surgery is attempted.

2

Materials and methods

18 patients, all of whom had favorable facial nerve function, were involved in the study, and those who were lost follow-up were excluded. They were pathologically diagnosed as having facial nerve schwannomas between 2000 and 2009 in a tertiary referral center. There were 8 males and 10 females, and the mean age was 36.40 ± 1.62 years (range, 18 to 70 years).

Stripping surgery was attempted by the same surgeon. During surgery, intraoperative facial nerve monitoring and electrical stimulation were used to aid identify facial nerve from the tumors (the tumors showed no response to electrical stimulation while the nerve was responsive). The tumors were separated from facial nerve at the plane of tumor capsule and nerve sheath, and the separation must be gentle enough to prevent facial nerve damage. The whole process was accomplished under high magnification. Facial nerve decompression without tumor removal was performed when the tumors were found to be distributed throughout facial nerve.

The surgical approach was mainly determined by tumor location. Transmastoid approach was used to remove tumors at tympanic segment, or mastoid segment, and middle cranial fossa approach was utilized when geniculate ganglion, labyrinthine segment or internal auditory canal segment was affected by the tumors. Middle cranial fossa combined with transmastoid approach was used when both the former and latter sites were affected.

They were followed up for 5.8 ± 1.4 years (range, 4 to 8 yearss). MRI was used to assess tumor recurrence, and hearing level was measured by clinical audiometer. Facial nerve outcomes after surgery were discussed.

2

Materials and methods

18 patients, all of whom had favorable facial nerve function, were involved in the study, and those who were lost follow-up were excluded. They were pathologically diagnosed as having facial nerve schwannomas between 2000 and 2009 in a tertiary referral center. There were 8 males and 10 females, and the mean age was 36.40 ± 1.62 years (range, 18 to 70 years).

Stripping surgery was attempted by the same surgeon. During surgery, intraoperative facial nerve monitoring and electrical stimulation were used to aid identify facial nerve from the tumors (the tumors showed no response to electrical stimulation while the nerve was responsive). The tumors were separated from facial nerve at the plane of tumor capsule and nerve sheath, and the separation must be gentle enough to prevent facial nerve damage. The whole process was accomplished under high magnification. Facial nerve decompression without tumor removal was performed when the tumors were found to be distributed throughout facial nerve.

The surgical approach was mainly determined by tumor location. Transmastoid approach was used to remove tumors at tympanic segment, or mastoid segment, and middle cranial fossa approach was utilized when geniculate ganglion, labyrinthine segment or internal auditory canal segment was affected by the tumors. Middle cranial fossa combined with transmastoid approach was used when both the former and latter sites were affected.

They were followed up for 5.8 ± 1.4 years (range, 4 to 8 yearss). MRI was used to assess tumor recurrence, and hearing level was measured by clinical audiometer. Facial nerve outcomes after surgery were discussed.

3

Results

Summary of the cases is listed in Tables 1 and 2 . 15 of 18 cases (83.3%) presented with facial palsy, followed by hearing loss in 7 cases (38.9%), tinnitus in 5 cases (27.8%) and vertigo in 2 cases (11.1%). Geniculate ganglion was most commonly affected, which was involved in 11 cases (61.1%) followed by tympanic segment (8 cases, 44.4%), mastoid segment (7 cases, 38.9%), labyrinthine segment (6 cases, 33.3%), and internal auditory canal segment (3 cases, 16.7%). There was multi-segment involvement in 14 cases (77.8%).

Table 1

Summary of 11 cases who underwent stripping surgery.

No.	Symptoms	Location	PreFNF	PosFNF	Surgical approach	Initial hearing (dB)	Final hearing (dB)	Recurrence	Follow-up (years)
1	T	IAC, GG	I	I	MCF	5	5	No	5
2	FP	GG,LS	III	II	MCF	10	10	No	6
3	FP, V	GG, LS	II	II	MCF	15	15	No	4
4	FP, CHL	GG, TS, MS	III	II	TM, MCF	55	55	No	6
5	T, MHL	LS, TS, MS	I	II	TM, MCF	35	30	No	8
6	CHL, T	TS, MS	I	I	TM	40	25	No	7
7	FP	TS, MS	II	III	TM	15	15	No	6
8	FP	LS	III	II	MCF	10	10	No	5
9	FP	GG, TS	II	I	TM,MCF	5	5	No	4
10	FP, CHL	GG, TS, MS	III	II	TM,MCF	50	20	No	8
11	FP	IAC	III	III	MCF	10	10	No	7

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