1

Introduction

Facial nerve schwannomas (FNS) are unusual entities, and they are the most common tumors of facial nerve . FNS can involve any segments of facial nerve from cerebellar pontine angle segment to extratemporal main trunk.

There are over 600 reported intratemporal FNS in the literatures . Most reports contain relatively small case numbers, and those containing larger case series are limited. Kertesz et al. reported 88 facial nerve neuromas, but focused on anatomical and radiological features with neither clinical nor management details discussed. McMonagle et al. and O’Donoghue et al. analyzed the clinical and management details of 53 and 48 cases with FNS, respectively, but the great majority had normal or near-normal facial nerve function (House–Brackmann Grade I or Grade II). There have not been a study about a large series of intratemporal FNS with poor facial nerve function (Grade IV or worse), to our knowledge.

We aim to present a large series of intratemporal FNS with poor facial nerve function and present our experience of stripping surgery.

2

Materials and methods

A consecutive series of 17 patients of intratemporal FNS with poor facial nerve function, who were surgically treated in a tertiary referral center, were included in the study, and those patients with favorable facial nerve function (Grade III or better) who received expectant treatment other than surgical treatment were not involved. All diagnoses were confirmed pathologically. The stripping procedure was accomplished by the same surgeon. Intraoperatvie facial nerve monitoring and electrical stimulation were introduced to aid identification of facial nerve from the tumor tissues, and the key procedure was meticulous microdissection between nerve fibers and the tumor tissue under high magnification. The separation of fascicle and the tumors must be gentle to avoid facial nerve damage. Facial nerve was sacrificed when it was impossible to separate facial nerve from the tumors, and sural or greater auricular nerve was used as graft to fill the nerve deficit. Whether greater auricular nerve or sural nerve was used as the graft material was dependent on the length of nerve graft required. Greater auricular nerve was the preferred choice, since it was convenient to harvest, but sural nerve was adopted when longer nerve graft was required.

The surgical approach was mainly determined by tumor location. If the tumors were located at labyrinthine segment, geniculate ganglion, tympanic segment, or mastoid segment, transmastoid approach would be used. Middle cranial fossa combined with transmastoid approach was adopted when internal auditory canal was also affected. For adequate exposure of the region at geniculate ganglion or labyrinthine segment, incus was removed and placed back after tumor removal. The incus should be repositioned exactly to minimize hearing damage.

There were 9 female and 8 male among the case series, and mean age was 35.65 ± 1.53 years (range, 17 to 66 years). They were followed up for 43.94 ± 2.14 months (range, 15 to 80 months), with MRI examination to assess tumor recurrence. Hearing was measured by clinical audiometer. Their clinical features and outcomes of facial nerve are discussed.

2

Materials and methods

A consecutive series of 17 patients of intratemporal FNS with poor facial nerve function, who were surgically treated in a tertiary referral center, were included in the study, and those patients with favorable facial nerve function (Grade III or better) who received expectant treatment other than surgical treatment were not involved. All diagnoses were confirmed pathologically. The stripping procedure was accomplished by the same surgeon. Intraoperatvie facial nerve monitoring and electrical stimulation were introduced to aid identification of facial nerve from the tumor tissues, and the key procedure was meticulous microdissection between nerve fibers and the tumor tissue under high magnification. The separation of fascicle and the tumors must be gentle to avoid facial nerve damage. Facial nerve was sacrificed when it was impossible to separate facial nerve from the tumors, and sural or greater auricular nerve was used as graft to fill the nerve deficit. Whether greater auricular nerve or sural nerve was used as the graft material was dependent on the length of nerve graft required. Greater auricular nerve was the preferred choice, since it was convenient to harvest, but sural nerve was adopted when longer nerve graft was required.

The surgical approach was mainly determined by tumor location. If the tumors were located at labyrinthine segment, geniculate ganglion, tympanic segment, or mastoid segment, transmastoid approach would be used. Middle cranial fossa combined with transmastoid approach was adopted when internal auditory canal was also affected. For adequate exposure of the region at geniculate ganglion or labyrinthine segment, incus was removed and placed back after tumor removal. The incus should be repositioned exactly to minimize hearing damage.

There were 9 female and 8 male among the case series, and mean age was 35.65 ± 1.53 years (range, 17 to 66 years). They were followed up for 43.94 ± 2.14 months (range, 15 to 80 months), with MRI examination to assess tumor recurrence. Hearing was measured by clinical audiometer. Their clinical features and outcomes of facial nerve are discussed.

3

Results

Summary of the cases is listed in Table 1 .

Table 1

Summary of 17 cases with intratemporal facial nerve schwannomas.

Case no.	Location	Symptoms	FP duration (years)	Onset	PreFNF	PostFNF	SA	Nerve graft	FU (months)	Initial HL (dB)	Final HL (dB)
1	GG	FP	8	Recurrent	VI	VI	TM	No	58	10	10
2	TS, MT	FP, CHL, T	7	Insidious	VI	IV	TM	SN	80	40	20
3	TS	FP, CHL, T	1	Sudden	VI	IV	TM	GAN	76	50	35
4	IAC till MS	FP, V, MHL, otalgia	2/12	Sudden	VI	IV	MCF, TM	No	60	55	55
5	IAC till MS	FP, V, SNHL	2/12	Sudden	V	III	MCF, TM	GAN	42	45	45
6	GG	FP, xerophthalmia	18	Insidious	V	III	TM	No	24	10	10
7	IAC, TS	FP, CHL	7	Insidious	VI	VI	MCF, TM	No	62	45	15
8	GG, TS, MS, MT	FP	2	Insidious	VI	III	TM	No	50	5	20
9	GG, LS	FP, otalgia	3/12	Sudden	V	II	TM	No	29	15	20
10	LS	FP, otalgia	17	Insidious	VI	IV	TM	No	20	10	20
11	MS	FP, otalgia	3/12	Sudden	VI	III	TM	No	25	15	15
12	TS	FP, CHL, T	10	Insidious	VI	VI	TM	No	61	35	15
13	LS, GG, TS	FP, dysgeusia	2	Insidious	V	V	TM	GAN	15	10	25
14	LS, GG, MS, MT FP, CHL, V		50	Sudden	VI	VI	TM	No	18	60	45
15	TS, MS	FP	1	Insidious	IV	III	TM	SN	30	10	10
16	LS	FP	3/12	Sudden	IV	II	TM	No	66	15	15
17	LS, TS	FP	1	Insidious	V	III	TM	No	31	10	20

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