[Solitary intraparotid neurofibroma of the facial nerve. Symptomatology, biology and management]

Collision tumor of the facial nerve: a synchronous seventh nerve schwannoma and neurofibroma

OBJECTIVE

To report a novel case of a collision tumor involving an intraparotid neurofibroma and a mastoid segment facial nerve schwannoma.

STUDY DESIGN

Clinical capsule report.

SETTING

Tertiary academic referral center.

PATIENT

A 29-year-old woman with a 2-year history of an asymptomatic enlarging left infraauricular mass and normal FN function presented to a tertiary care referral center. Computed tomography and magnetic resonance imaging demonstrated a cystic lesion in the deep portion of the parotid gland extending into the stylomastoid foramen.

INTERVENTION

The patient underwent superficial parotidectomy, and a cystic parotid mass was found to be intrinsic to the intraparotid facial nerve. A portion of the mass was biopsied, and intraoperative frozen section pathology was consistent with a neurofibroma. A mastoidectomy with FN decompression was then performed until a normal-appearing segment was identified just proximal to the second genu. After biopsy, proximal facial nerve stimulation failed to elicit evoked motor potentials, and en bloc resection was performed.

RESULTS

Final pathology demonstrated a schwannoma involving the mastoid segment and a neurofibroma involving the proximal intraparotid facial nerve.

CONCLUSION

We report the first case of a facial nerve collision tumor involving an intraparotid neurofibroma and a mastoid segment facial nerve schwannoma. Benign FN sheath tumors of the parotid gland are rare but should be considered in the differential diagnosis of a parotid mass.

Intra-parotid facial nerve multiple plexiform neurofibroma in patient with NF1

INTRODUCTION

Primary neurogenic tumours of facial nerve are uncommon with the majority found intra-temporally. Intracranial and intra-parotid neoplastic involvement of cranial nerve VII is much less common. There are 11 reported cases, in the English-language literature, of intra-parotid facial nerve plexiform neurofibromas with eight of them associated with NF1.

MATERIALS AND METHODS

A child, 10 years old, with NF1, reached us for a cheek swelling, slowly increased in previous 8 years. At the age of 3 years, a plexiform neurofibroma was diagnosed by biopsy of the lesion. Clinical examination and NMR showed in the sub-cutaneous tissue of the right cheek, two contiguous nodular lesions, about 2 cm x 1.5 cm in diameter; a third neoformed lesion, about 1cm in diameter, was located above the ipsilateral labial commissure. No facial nerve impairment was seen. The patient underwent superficial parotidectomy with removal of the lesions and preservation of the facial nerve.

RESULTS

The patient had a considerable regional swelling in the immediate post-operative course; no facial nerve impairment was observed. The swelling of the cheek did not show a fully regression in the post-operative course. Ultrasonography at 3 months showed a recurrence of disease.

DISCUSSION

Plexiform neurofibromas should be distinguished due to their risk of malignant transformation seen in up to 15% of patients affected by NF1. Surgery is the only effective option currently available for the treatment of PNF. However, success of surgical intervention is limited by the infiltrating nature of the tumours, resulting in a high rate of tumour re-growth. Facial nerve preservation during surgery is unlikely and significant morbidity can result from their excision. The age of the patient at surgical resection seemed to influence outcome: tumours resected before age 10 years recurred in 60% of cases compared with only 30% recurrence in patients older than the age of 10 years.

CONCLUSION

Indication and timing of surgery, in paediatrics patients with NF1, are complex. To avoid eventual physical and psychological consequences, it seems prudent to delay surgery as long as it is feasible for otherwise asymptomatic paediatric patients with facial plexiform neurofibroma.