Facial Nerve Paralysis after Silver Nitrate Application

Facial Nerve Paralysis after Silver Nitrate Application

Corresponding author: Dr. Richard Vincent, University of Maryland Medical Center, 1727 Gough Street, United States, Tel: 302-383-0818; Email: rvincent@smail.umaryland.edu

Abstract

Objective: This study aims to report the first case of temporary facial paralysis secondary to silver nitrate cauterization of a canal wall down mastoidectomy cavity.

Methods: Case report with review of the literature.

Results: The patient underwent cauterization of an area of granulation tissue below the tympanic portion of the facial nerve in her mastoid bowl. She presented two days later with a House-Brackmann III facial paralysis that progressed over ten days to a House-Brackmann IV. She was treated with antibiotics, oral steroids, and topical steroids, and returned to clinic a month later with complete resolution of her paralysis.

Conclusion: Silver nitrate cauterization in the post-operative mastoid bowl is generally a safe procedure; however, it is not with- out risks. This case report highlights the importance of carefully identifying middle ear landmarks and minimizing application time, when chemically cauterizing granulation tissue in a mastoidectomy cavity.

Keywords: Facial Nerve Paralysis; Mastoidectomy; Canal Wall Down; Silver Nitrate

Introduction

Silver nitrate is commonly used as a cauterizing agent for treatment of granulation tissue. It was first described in the otologic literature in 1848, when William Wilde used it to stimulate closure of tympanic membrane perforations and lat- er to cauterize granulation tissue within the middle ear [1]. It acts as an oxidizing agent producing free radicals that lead to tissue coagulation and bacterial protein denaturation and has been shown to decrease hypertrophic granulation tissue and enhance wound healing [1]. Today it is used when treating the canal wall down [CWD] mastoidectomy cavity post-operative- ly. This is the first reported case of temporary facial paralysis following silver nitrate cautery of mastoid cavity granulation tissue.

Case-Report

A 51-year old woman with a history of chronic otitis media and previous tympanoplasty presented with chronic otorrhea. On exam she was noted to have a deep attic retraction pocket. The CT scan demonstrated soft-tissue filling the epitympanum and mastoid, with scutal and ossicular erosion, and she underwent uneventful CWD mastoidectomy with tympanoplasty. Two years later she presented with otalgia and otorrhea. She was noted to have an area of cicatrix below the tympanic portion of the facial nerve with trapped epithelium which was debrid- ed. On follow-up she had granulation tissue in the same area.

Cite this article: Richard Vincent. Facial Nerve Paralysis after Silver Nitrate Application. J J Otolaryn. 2016, 2(1): 028.

Silver nitrate was applied for approximately 2 seconds and Ciprodex drops were prescribed. Two days later she present- ed to an Emergency Department with facial weakness and otalgia, was started on Levaquin and Prednisone. She was ex- amined in our institution the following day, and was noted to have a House-Brackmann (HB) III/VI facial weakness. The dif- ferential diagnoses considered viral reactivation after nerve manipulation, inflammatory neuritis from granulation tissue, and cautery injury from silver nitrate. Antibiotics and the ste- roid taper were continued. Ten days later she had persistent facial weakness with progression to HB IV/VI. On exam there was no longer evidence of granulation tissue but there was an area of dehiscence with prolapse of the facial nerve near the cochleariform process.

Figure 1. Axial T1-weighted magnetic resonance image following administration of gadolinium. The arrow points to area of high sig- nal intensity in perigeniculate and prox tympanic segments of facial nerve

Figure 2. Coronal non-contrast temporal bone computed tomogra- phy. The arrow points to soft-tissue density contiguous with area of dehiscence in proximal tympanic segment of Fallopian canal.

Topical steroid soaked gelfoam was applied in the office. Diagnostic imaging was performed. MRI showed a mild asymmetric enhancement of the tympanic segment of the left facial nerve (Figure 1), and CT demonstrated evidence bony dehiscence over the tympanic segment of the facial nerve (Figure 2). The patient completed her steroid taper and returned to clinic one month later with complete resolution of paralysis and no sequelae.

Discussion

CWD mastoidectomy has well-described indications and the benefit of a decreased rate of recidivistic disease [2,3]. One potential drawback is a large cavity requiring frequent debridement, which may lead to trapped epithelium and granulation tissue. These can be treated with topical agents, however, persistent and extensive granulation tissue may require cauterization with agents such as silver nitrate.

There are no detailed reports in the literature of facial nerve paralysis after application of silver nitrate. Wachter et al [4] reported a patient referred for chronic, complete paralysis fol- lowing application of silver nitrate, prompting a study looking at the functional and histological effects of silver nitrate on the rat sciatic nerve. They concluded that an increased dura- tion of cauterization leads to more severe injury, with mini- mal paralysis and nerve loss after 1 second applications but increased damage after 5 and 10 second applications. Details of this patient’s clinical presentation prior to application of silver nitrate, particulars of the clinical management, and imaging findings prior to presentation for facial rehabilitation are unknown. Their patient had no return of facial function, thus our patient is the first with documented recovery following treatment.

Identifying landmarks in an open cavity mastoid can be challenging, and caution must be used when using cauterizing agents. Although the risk of facial nerve paralysis is low and should not preclude the use of chemical cauteriza- tion, it is recommended the surgeon minimize application time to decrease the likelihood of injury. Further studies compar- ing nerve damage caused by silver nitrate versus other agents such as trichloroacetic acid or 5-FU [5] may help better define the safety profile for treatment of persistent granulation tissue in the mastoid cavity.

References
  1. Hanif J, R.A. Tasca, A. Frosh et al. Clinical Otolaryngology and Allied Sciences, 2003, 28(4): 368-370.
  2. Thomas J McDonald. Canal Wall Down Mastoidectomy. In: Haberman, Rex, ed. Middle Ear and Mastoid Surgery. Ed New York, NY: Thieme, 2004.
  3. Chang CC, Chen MK. Canal-wall-down tympanoplasty with mastoidectomy for advanced cholesteatoma. J Otolaryngol. 2000, 29(5): 270-273.
  4. Wachter BG, Leonetti JP, Lee JM et al. Silver nitrate injury in the rat sciatic nerve: A model of facial nerve injury. Otolaryn- gology Head and Neck Surgery. 2002, 127(1): 48-54.
  5. Atef AM, Hamouda MM, Mohammed AH et al. Topical 5-flu- orouracil for granular myringitis: a double-blinded study. The Journal of Laryngology and Otology. 2010, 124(3): 279-284.

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