Otologic and Temporal Bone Injuries, Triage, and Management

Key points

  • Temporal bone trauma requires a large amount of force, meaning that patients will presents with multiple injuries and the temporal bone injury is often incidentally found. Focus should first be on assessing and treating the ABCs before management of temporal bone injuries.

  • The physical examination should include inspection of the face and soft tissue for lacerations, assessment of cerebrospinal fluid leakage, assessment of the facial nerve, an otoscopic examination of the ear, a tuning fork examination with a 512-Hz tuning fork, and a complete cranial nerve examination.

  • If a temporal bone fracture is suspected, a fine-cut computed tomography scan of the temporal bone is indicated.

  • One of the most important physical examination findings for patients with temporal bone injuries is function of the facial nerve immediately after the injury. This must be assessed as soon as it is possible, and an assessment may be performed in an unconscious patient.

  • If the facial nerve is not functioning immediately following the injury, workup by an otolaryngologist for potential facial nerve exploration is indicated.

  • If a cerebrospinal fluid leak is identified from the ear or from the nose, workup by an otolaryngologist and neurosurgeon is indicated.

  • Early audiology consultation is indicated if there is any hearing loss.

  • Conductive hearing loss immediately following these injuries can be a result of traumatic tympanic membrane perforations, hemotympanum, cerebrospinal fluid in the middle ear, or ossicular chain disruption.

  • Traumatic sensorineural hearing loss is typically the result of noise-induced trauma, otic capsule disruption, or perilymphatic fistulas.

Introduction

Injury to the temporal bone requires a great deal of force: the lateral force required for a temporal bone fracture is estimated at greater than 1875 lb of force. Trauma may result in fractures through the temporal bone, including through the otic capsule, injury to the facial nerve, ossicular chain discontinuity, tympanic membrane perforation, perilymphatic fistulas, cerebrospinal fluid (CSF) leaks, and injuries to the carotid artery.

Temporal bone contents can be injured by blunt trauma, penetrating trauma, and barotrauma. The most common cause of temporal bone trauma in civilian hospitals is motor vehicle accidents, followed by assaults and falls. Gunshot injuries to the temporal bone are less common. Within the military population, tympanic membrane perforations caused by blast injury are fairly common. A series from Brooke Army Medical Center found that 16% of patients sustaining blast injuries had tympanic membrane perforations.

In the case of a gross CSF leak or hemorrhage from the ear, emergent action is necessary. Otherwise, injury to the temporal bone is infrequently life-threatening in and of itself. Given the amount of force required for a temporal bone injury, concomitant injuries are common, and attention should be paid to any airway, breathing, and circulation injuries first.

This article explores the initial evaluation and management of temporal bone trauma and auricular injuries.

Introduction

Injury to the temporal bone requires a great deal of force: the lateral force required for a temporal bone fracture is estimated at greater than 1875 lb of force. Trauma may result in fractures through the temporal bone, including through the otic capsule, injury to the facial nerve, ossicular chain discontinuity, tympanic membrane perforation, perilymphatic fistulas, cerebrospinal fluid (CSF) leaks, and injuries to the carotid artery.

Temporal bone contents can be injured by blunt trauma, penetrating trauma, and barotrauma. The most common cause of temporal bone trauma in civilian hospitals is motor vehicle accidents, followed by assaults and falls. Gunshot injuries to the temporal bone are less common. Within the military population, tympanic membrane perforations caused by blast injury are fairly common. A series from Brooke Army Medical Center found that 16% of patients sustaining blast injuries had tympanic membrane perforations.

In the case of a gross CSF leak or hemorrhage from the ear, emergent action is necessary. Otherwise, injury to the temporal bone is infrequently life-threatening in and of itself. Given the amount of force required for a temporal bone injury, concomitant injuries are common, and attention should be paid to any airway, breathing, and circulation injuries first.

This article explores the initial evaluation and management of temporal bone trauma and auricular injuries.

History

There are a number of critical pieces of historical information that the facial trauma specialist needs to obtain when evaluating a patient with head, neck, and temporal bone trauma. Often for the isolated temporal bone fracture discovered from a routine trauma head computed tomography (CT) scan, this information can be obtained from the patient, but care should be taken to collect this information from alternative sources if the patient is unconscious or otherwise unable to communicate.

The mechanism of injury and associated injuries should be obtained first. Next, it should be determined if there is or was any facial nerve function after the injury, for reasons will we go into further later in this article. To assess injuries to the otic capsule and the cochlear nerve, determine if there is hearing loss, tinnitus, or vertigo. Ask specific questions regarding CSF leaks, including otorrhea, watery rhinorrhea, and salty taste in the back of the mouth.

Physical examination

A facial trauma specialist should perform a complete head and neck examination. Grossly, the head and neck should be evaluated for CSF leaks and otorrhea. The skin should be examined for abrasions, laceration, and open fractures, including evaluating the entire scalp for lacerations. Identify lacerations and hematomas of the auricle. Hematomas, particularly those involving the auricle, should be drained and bolstered to prevent “cauliflower ear.” Postauricular and periocular ecchymosis should be identified and recorded, as these can be evidence of a basilar skull fracture. Anterior nasal endoscopy with a standard otoscope should be performed to rule out gross CSF rhinorrhea.

A complete examination also includes otoscopy, a tuning fork examination, a facial nerve examination, and comprehensive cranial nerve examination ( Fig. 1 ).

Fig. 1
Basic tool kit for initially assessing temporal bone trauma. Note the 512-Hz tuning fork on the left, the otoscope in the center, and the various sizes of specula on the right. The smallest specula (3 mm and 4 mm, on the bottom and middle right, respectively), are typically used in small children and infants.

Otoscopy

The otoscopic examination is one of the most important components of the examination for temporal bone trauma, but it can also be the most challenging because of debris in the ear canal, the inability of the patient to be able to turn his or her head because of cervical spine stabilization, and operator inexperience with the otoscopic examination.

The angle of the external auditory canal becomes larger and more horizontal as the patient ages. For newborns and small children, it may be necessary to gently tug the pinna posteroinferiorly with a small (size 3 mm or 4 mm) otoscopic speculum for adequate evaluation. Adults can typically accommodate a larger speculum (size 5 mm), but may still require gentle tugging of the pinna to obtain an adequate view of the tympanic membrane.

The external auditory canal should be evaluated for any lacerations, canal edema, debris, blood, or CSF. Some of the debris may only be cerumen ( Fig. 2 ). Cerebrospinal fluid is typically a thin, clear liquid. Careful examination of the external auditory canal may also reveal fractures of the temporal bone visible through the thin skin of the canal wall. This is also important to document. Occasionally, the external auditory canal wall skin can grow into the fracture, resulting in a canal wall cholesteatoma years later.

Fig. 2
Cerumen debris on otoscopic examination. Remove under binocular microscopy to allow for appropriate view of the tympanic membrane.

The tympanic membrane, if visible, should then be assessed ( Fig. 3 ). Fluid behind the tympanic membrane should be identified. Clear fluid, occasionally with air bubbles within the fluid, can suggest CSF, although it may also suggest a serous otitis, particularly in a child. Hemotympanum will be obvious as dark red or black fluid behind the tympanic membrane. The tympanic membrane should also be assessed for perforation. The perforation should be described based on the quadrant and the percentage of the tympanic membrane perforated ( Fig. 4 ).

Fig. 3
This is the appearance of a normal, healthy appearing right tympanic membrane. The tympanic membrane is translucent, there is no red or brown discoloration behind it, and there is no air fluid level or air bubbles.

Fig. 4
This is a view of a patient’s right ear with extensive myringosclerosis, evident as a chalky appearing tympanic membrane, as well as having a 40% anterior-inferior tympanic membrane perforation.

Tuning fork examination

In temporal bone trauma, hearing loss is a common complaint. Hearing loss can be divided into 2 broad categories that can help narrow the differential diagnosis. Conductive hearing loss occurs because of obstruction of the sound waves from reaching the tympanic membrane, noncompliance or perforation of the ear drum, or poor of movement of the ossicular chain. Sensorineural hearing loss is caused by injuries to the cochlea or to the cochlear nerve.

The tuning fork examination is a simple examination that can rapidly determine the type of hearing loss a patient has. There are 2 parts to this examination, the Weber test and the Rinne test. Both should be used as a piece of information within the clinical context of the patient, and not used in isolation.

These examinations require a conversant patient. For both, a 512-Hz tuning fork is preferred. Care is taken to strike the tuning fork on a soft surface to prevent high-pitched overtones.

In the Weber test, an oscillating tuning fork is placed in the midline, typically on the maxilla or forehead. The most reliable results, however, come when the tuning fork is placed on the upper incisors ( Fig. 5 ). In conductive hearing loss, the patient will hear the sound of the vibrating tuning fork louder on the affected side. In sensorineural hearing loss, the patient will hear the tuning fork louder on the contralateral side. If a patient can hear the sound louder in one ear (typically the difference of 3–5 dB), the Weber is said to lateralize to that side. If the patient hears the sound in the middle, it is said to be midline or normal.

Fig. 5
The Weber test is performed with a 512-Hz tuning fork on a midline structure, and it can distinguish a 3-db difference between ears. The most reliable location for this test is on the premaxillary incisors.

The Rinne test is used in conjunction with the Weber ( Fig. 6 ). The oscillating tuning fork is first placed on the patient’s mastoid and then right in front of the ear. The patient is then asked which they hear louder. If they hear the sound louder with the tuning fork on the mastoid, bone conduction (BC) is said to be greater than air conduction (AC). In normal, or positive, Rinne, AC is greater than BC. At our institution, we record this as AC>BC, BC>AC, or AC = BC. The test then is repeated for the contralateral ear. If BC is louder than AC, this suggests a conductive hearing loss of greater than 20 dB. AC greater than BC is found in either a normal-hearing ear or in the presence of sensorineural hearing loss.

Fig. 6
The Rinne test is performed first with the tuning fork on the mastoid ( A ), followed by placing it in front of the ear ( B ). The patient is then asked which is louder. In a patient with conductive hearing loss, placing the tuning fork on the mastoid ( A ) will appear to sound louder than placing it in front of the ear ( B ); in other words, bone conduction will be greater than air conduction.

For example, if a patient has decreased hearing in the right ear, and the Weber test lateralizes to the left ear with a normal Rinne in both ears (AC>BC), this would suggest the patient has a sensorineural hearing loss. On the other hand, if the Weber test lateralized to the right side, and the Rinne was negative (BC>AC) on the right ear, this would suggest a conductive hearing loss instead.

Facial nerve examination

The first and most important consideration for the facial nerve is to determine timing of a facial nerve injury. Often, immediate loss of facial nerve function suggests transsection or severe compression of the nerve. Gradual loss, however, suggests edema or reactivation of a virus. This is information that guides whether or not surgical intervention is indicated. Therefore, it is essential to obtain an adequate facial nerve examination when the patient initially presents, preferably before muscle relaxants are given and the patient is intubated.

The facial nerve’s principal responsibility is to control the muscles of facial expression. Loss of function is disfiguring and can cause significant morbidity. The motor branch of the facial nerve has 5 major branches: temporal, zygomatic, buccal, marginal mandibular, and cervical. Asymmetry across branches is worrisome for a facial nerve injury within the temporal bone, but individual extracranial branches may also be injured in facial trauma. Identifying the injured branches helps drive surgical management, as we explore later in this article. Testing is simple in the conscious patient:

Jan 23, 2017 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Otologic and Temporal Bone Injuries, Triage, and Management
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