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Facial nerve palsy associated with a cystic lesion of the temporal bone.

Abstract

Facial nerve palsy results in the loss of facial expression and is most commonly caused by a benign, self-limiting inflammatory condition known as Bell palsy. However, there are other conditions that may cause facial paralysis, such as neoplastic conditions of the facial nerve, traumatic nerve injury, and temporal bone leions. We present a case of facial nerve palsy concurrent with a benign cystic lesion of the temporal bone, adjacent to the tympanic segment of the facial nerve. The patient's symptoms subsided after facial nerve decompression via a transmastoid approach.

Introduction

Facial nerve palsy results in the loss of facial expression and is most commonly caused by a benign, self-limiting inflammatory condition known as Bell palsy. (1) However, other conditions may result in injury of the seventh cranial nerve, such as neoplastic conditions of the facial nerve, traumatic nerve injury, and temporal bone lesions.

Facial nerve palsy attributable to a cystic lesion of the temporal bone is relatively rare. We present a case of facial nerve palsy concurrent with a benign cystic lesion of the temporal bone, adjacent to the tympanic segment of the facial nerve.

Case report

A 68-year-old woman presented with facial palsy of 14 days' duration. She had a history of left ventilation tube insertion because of serous otitis media 3 years previously. She had hypertension and was on medication. She had no other remarkable medical history. On physical examination, her left tympanic membrane was found to be thickened, with a few pits at the anterior portion of the pars tensa, and she presented with a left facial palsy of V/VI on the House-Brackmann scale.

An audiogram showed a normal hearing threshold on the patient's affected left side, but a conductive hearing loss (30 dB with an air-bone gap of 10 dB) on the right side. The stapedial reflex was absent, with a B-type tympanogram on the affected side. An electroneuronogram showed that the degeneration ratio was 40% on the affected side.

Because of the abnormal finding of the left tympanic membrane, a computed tomography (CT) scan of the temporal bone was obtained. The CT scan demonstrated a cystic lesion that seemed to compress the tympanic segment of the left facial nerve (figure, A). No significant erosive bony changes were observed. Afterwards, a magnetic resonance imaging (MRI) scan of the temporal bone was obtained, with and without gadolinium enhancement. A 5 x 5-mm cystic lesion was noted in the anterior epitympanic space abutting on the tympanic segment of the facial nerve. The lesion had low signal intensity on T1-weighted images, with or without gadolinium enhancement. Left facial nerve enhancement was noted on post-gadolinium images (figure, B). The lesion demonstrated high signal intensity on T2-weighted images (figure, C).

The patient underwent simple mastoidectomy. The mastoid bone was grossly well pneumatized. However, the tympanic segment of the facial nerve was focally pressed at the anterior epitympanum by the air cells, which were filled with yellowish fluid. They were removed with the fluid collection, and facial nerve decompression of the tympanic segment was accomplished around the cyst. A short part of the tympanic segment of the facial nerve at the anterior epitympanum was slightly edematous, but the facial nerve was grossly intact. Because such a small amount of fluid was collected, pathologic examination was nondiagnostic.

The patient's facial nerve function improved from a House-Brackmann score of V/VI to II/VI in 2 weeks. At 1 month follow-up after the operation, her facial nerve function became normal, I/VI on the HouseBrackmann scale.

Discussion

Aproximately half of facial nerve palsies are due to typical Bell palsy (1) and do not require radiologic images. However, the spectrum of diseases affecting the facial nerve is extensive and includes inflammatory conditions, primary neoplasms, secondary tumors of the facial nerve, traumatic conditions such as temporal bone fractures, and any temporal bone lesions close to the facial canal. Temporal bone lesions, such as mastoiditis and cholesteatomas adjacent to the facial canal, may cause bony erosion and may damage the facial nerve itself. (2) Cystic lesions of the mastoid that cause facial palsy are relatively rare, and there are only a few case reports of cystic lesion of the mastoid. (3,4)

In the present case, MRI and CT images of the temporal bone provided important clues as to the cause of the facial palsy and, thus, guided the treatment. The lesion was hypointense on TI-weighted images and showed nonenhancement with gadolinium, whereas it was hyperintesense on T2-weighted images. Not only the location of the lesion, but also the properties of the lesion, can be inferred from these image studies. (5) The chronic entrapment of fluid compressing the tympanic segment of the facial nerve might have caused our patient's facial palsy. The operative findings support such speculation.

A simple mastoidectomy with facial nerve decompression was sufficient for surgical removal of the fluid collection at the anterior epitympanic space. When the location of the lesion is more complex than can be approached with a simple mastoidectomy, other approaches such as infralabyrinthine, middle fossa, or trans-sphenoidal should be considered. (6)

Although we could not rule out the possibility that our patient's disease entity was Bell palsy with an incidental finding of a cystic lesion in the temporal bone, the imaging studies--CT and MRI scans of the temporal bone--provided beneficial information on the diagnosis and treatment of facial nerve palsy in our patient.

References

(1.) Alaani A, Hogg R, Saravanappa N, Irving RM. An analysis of diagnostic delay in unilateral facial paralysis. J Laryngol Otol 2005; 119(3): 184-8.

(2.) Chan EH, Tan HM, Tan TY. Facial palsy from temporal bone lesions. Ann Acad Med Singapore 2005;34(4):322-9.

(3.) Hwang PH, Jackler RK. Facial nerve dysfunction associated with cystic lesions of the mastoid. Otolaryngol Head Neck Surg 1998;119(6):668-72.

(4.) Ozttirk O, Inanli S, Sehitoglu MA. Facial paralysis in a patient with cholesterol cyst of the petrous bone. Otolaryngol Head Neck Surg 2005;133(4):643.

(5.) Arriaga MA, Brackmann DE. Differential diagnosis of primary petrous apex lesions. Am J Otol 1991;12(6):470-4.

(6.) Goldofsky E, Hoffman RA, Holliday RA, Cohen NL. Cholesterol cysts of the temporal bone; Diagnosis and treatment. Ann Otol Rhinol Laryngol 1991;100(3): 181-7.

Na Hyun Kim, MD; Seung-Ho Shin, MD

From the Department of Otorhinolaryngology, Yonsei University College of Medicine (Dr. Kim); and the Department of Otorhinolaryngology-Head and Neck Surgery, Ewha Womans University College of Medicine (Dr. Shin), Seoul, Korea.

Corresponding author: Seung-Ho Shin, MD, Department of Otorhinolaryngology-Head and Neck Surgery, School of Medicine, Ewha Womans University, 1071, Anyangcheon-ro, Yangcheon-gu, Seoul, Korea 158-710. Email: drshinsh@gmail.com
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Title Annotation:ORIGINAL ARTICLE
Author:Kim, Na Hyun; Shin, Seung-Ho
Publication:Ear, Nose and Throat Journal
Article Type:Case study
Date:Mar 1, 2014
Words:1101
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