Disclaimer: The information contained within the Grand Rounds Archive is intended for use by doctors and other health care professionals. These documents were prepared by resident physicians for presentation and discussion at a conference held at Baylor College of Medicine in Houston, Texas. No guarantees are made with respect to accuracy or timeliness of this material. This material should not be used as a basis for treatment decisions, and is not a substitute for professional consultation and/or peer-reviewed medical literature. Temporal Bone Gunshot Wounds: Evaluation and Management With the significant increase in handgun availability since the 1960s, treatment of gunshot injuries is no longer limited to major trauma centers. Five thousand Americans under the age of 20 die annually from gunshot wounds in the United States alone, with many more victims surviving with significant injury. The easy availability of guns is seen in rural as well as in metropolitan areas across the country. Wound ballistics is the study of the effects of missiles striking tissues. Kinetic energy is directly proportional to the mass of the projectile and proportional to the square of the velocity at which the bullet is traveling. The most efficient missile enters tissues and imparts the majority of its kinetic energy to surrounding structures without exiting the victim. Traditionally, gunshot injuries could be classified as civilian or military. Civilian injuries were inflicted with low velocity weapons (90-210 m/sec) while military wounds typically were caused by high velocity weapons (610 m/sec and up). Due to medium to high velocity weapons appearing on the streets, more civilians are suffering from military-type injuries. Gunshot injuries to the temporal bone affect intracranial, vascular, middle or inner ear, cranial nerve, and external canal structures. Being the toughest bone in the body, the temporal bone deflects missles, often resulting in hidden injuries. Early intracranial injuries include skull fractures, subdural hematoma, foreign bodies, pneumocephalus and cerebrospinal fluid leaks. Temporal lobe abscess, meningitis, aphasia, hemianopsia, and hemiplegia are late intracranial complications. Venous injuries to the transverse and sigmoid sinuses, jugular system and cavernous sinus have been reported. Acute transection of internal or external carotid arteries is usually obvious while pseudoaneurysms and carotid-cavernous fistulae can develop later during the recovery period. Tympanic membrane perforations, ossicular disruption, labyrinthine destruction, and mixed longitudinal and transverse temporal bone fractures are the most commonly associated middle ear injuries. The majority of victims suffer acoustic injury inflicted either by direct damage from the bullet path or, more commonly, from blast effects. Fifty percent of victims will have facial nerve involvement with transections by far outweighing contusions. The vagus, hypoglossal, and abducens nerves are the next most frequently damaged cranial nerves. Bony and cartilaginous fractures, cicatricial scarring, temporomandibular joint displacement, canal cholesteatoma, and chronic bony infections can occur after gunshot injury involving the external auditory canal. Initial assessment includes a standard trauma workup with attention directed to life-threatening problems first. General and neurosurgical clearance is mandatory prior to thorough head and neck and otologic examination. Evaluation of the ear should be done with sterile instruments to avoid further soft tissue contamination. Computed tomography of the temporal bones is ordered once the patient is stable. Carotid and vertebral arteriograms should be obtained at the slightest suspicion of potential vascular involvement. Venous phases of these studies are important. Audiometric testing documents hearing at baseline and prior to any surgical manipulation of the otic structures and aids in selecting approaches to the middle ear and facial nerve. Vestibular testing may be obtained to document the nature and location of lesions in symptomatic patients and is useful to follow vestibular compensation. Patients are first stabilized from life-threatening injuries. Acute care for intracranial injuries includes intravenous steroids and osmotic diuretics. Antibiotic prophylaxis is key, especially if dural injury is suspected. Lumbar drainage and craniotomy should be employed as indicated. Embolization, packing at the skull base, and vessel ligation in the neck are options for vascular injuries. Mastoidectomy and tympanoplasty should be considered whenever remaining anatomy permits and residual hearing is documented. Debridement of the external auditory canal, labyrinthectomy and temporal bone obliteration should be used depending on the extent of destruction within the temporal bone and depending on the status of remaining critical structures. Presentation with a complete facial nerve paralysis signals a transection and should be managed aggressively. Exploration of the wound to localize damaged nerve endings is best done before 72 hours when distal nerve segments have not undergone degeneration. Exploration is often delayed while other injuries are treated. Exploration is then best completed in the subsequent 6 to 12 months. The best results are accomplished with end-to-end anastomosis. Due to local destruction from blast effects, end-to-end anastomosis is frequently not feasible mandating interposition grafting techniques. The great auricular nerve provides 5 cm to 7 cm of graft material while the sural nerve affords up to 30 cm of donor tissue. Delayed loss of facial nerve function most likely results from nerve edema or contusion and decompression suffices as definitive operative management. House-Brackmann grade 4 recovery or worse is expected with interposition grafting while up to grade 3 recovery has been documented from decompressions. Local eye care is mandatory to avoid exposure keratitis while nerve recovery progresses. Other cranial nerve injuries are managed symptomatically. Long-term follow-up is required since many of these patients will need secondary facial reanimation procedures. In conclusion, multispecialty assessment is required for patients with gunshot wounds involving the temporal bone. Life-threatening injuries are addressed first, followed by a thorough head and neck workup. Care must be taken to avoid missing hidden injuries induced secondary to blast effects or due to deflection of the missile off of the otic capsule. Indications for surgical exploration of the temporal bone include facial nerve paralysis, vascular injury, cerebrospinal leakage, chronic otitis media, conductive hearing loss and to debride necrotic tissue. Case Presentation A 44-year-old black male presented to the shock room at Ben Taub General Hospital with a single gunshot wound to the left preauricular area. On admission, he was awake and alert, with a complete left facial nerve paralysis. He had significant tissue loss on the left side of his face and in the left tonsillar area. After airway stabilization by endotracheal intubation, emergent computerized tomographic scanning of the head was negative for intracranial pathology and four vessel arteriograms showed no vascular injury. A barium swallow revealed no extravasation into the pharynx or esophagus. He was extubated after 48 hours. The left external auditory canal was remarkable for bloody discharge and squamous debris, with the Weber lateralizing to the right. The remaining cranial nerves were intact. No other injuries were found after thorough physical examination. The patient had swallowed the bullet that was originally presumed to be resting in his posterior oropharynx. Temporal bone CT scans revealed a comminuted left mastoid tip and fractured external auditory canal and temporomandibular joint. Audiogram showed no responses in the left ear and a moderate sensorineural loss on the right. No response could be elicited by nerve excitability testing on the left side. The patient was discharged after 11 days in the hospital. He was readmitted seven days later, at which time he underwent left radical mastoidectomy, complete facial nerve decompression, sural nerve grafting and meatoplasty. The patient did well postoperatively and has been followed regularly in clinic. He has a House-Brackmann grade VI recovery and is now, at two years postrepair, being considered for a secondary procedure to improve his facial tone and to gain left eye closure. Bibliography Brookes GB. Post-traumatic cholesteatoma. Clin Otolaryngol 1983;8:31-38. Byrnes DP, Crockard HA, Gordon DS, Gleadhill CA. Penetrating craniocerebral missile injuries in the civil disturbances in Northern Ireland. Br J Surg 1974;61:169-176. Coker NJ. Management of traumatic injuries to the facial nerve. Otolaryngol Clin North Am 1991;24:215-227. Coker NJ, Jenkins HA. Traumatic injury to the facial nerve. Exhibit Handout 1990. Coker NJ, Kendall KA, Jenkins HA, Alford BR. Traumatic intratemporal facial nerve injury: management and rationale for preservation of function. Otolaryngol Head Neck Surg 1987;97:262-269. Cushing H. A study of a series of wounds involving the brain and its enclosing structures. Br J Surg 1918;5:558-684. du Trevou M, Teasdale RB, Quin RO. 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Traumatic aneurysm of the internal carotid artery and epistaxis. J Laryngol Otol 1979;93:629-656. Singh SP, Adeloye A. Hearing loss in missile head injuries. J Laryngol Otol 1971;85:1183-1187. Grand Rounds Archive | Department Home page BCM Public | BCM Intranet | Privacy Notices | Contact BCM | BCM Site Map | ©2001-2006 Baylor College of Medicine
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