55 The Management of Temporal Bone Fractures



Gil Lahav, Ophir Handzel


Summary


Traumatic insults to the temporal bone (TB) in the pediatric population are not rare. TB trauma can result in life-threatening complications and severe functional loss. Correct and timely diagnosis and treatment may help reduce the risks and impact associated with these injuries. The focus of this chapter is to present the diagnostic and therapeutic approaches to TB trauma for the otolaryngologist, and to cite typical issues that need to be addressed for comprehensive patient assessment and treatment.




55 The Management of Temporal Bone Fractures



55.1 Introduction



55.1.1 Epidemiology


Temporal bone fractures in the pediatric population differ from those of adults in etiology and consequences.


The frequency of skull base fractures varies from 5% to 14% in children with head injuries, with a high prevalence of the temporal bone (as high as 62%), followed by the occipital, sphenoidal, and sphenoethmoidal complex and orbital portion of frontal bone. 1


Most traumatic injuries are blunt, and the common mechanisms are motor vehicle accidents, followed by falls, and bicycle and other recreational vehicle-related injuries. Frequency varies among the different age groups, with falls being a more frequent cause in young children (<5 years of age) and collision accidents in the older ages. 2 , 3


It is important to note that abuse is a common cause of traumatic brain injury and skull fractures in all age groups, especially in younger children where it accounts ~14% of cases. 4 , 5



55.1.2 Pathophysiology


Apart from the common head contusion–related injuries, there are specific aspects of temporal bone trauma which are related to the different structures that reside in or are adjacent to the temporal bone. These include the inner ear structures, the dura and CSF-containing spaces, blood vessels, nerves, middle ear structures, and the Eustachian tube.


The anatomical properties of children’s skulls differ from those of adults, thereby resulting in different skull base and temporal bone fractures characteristics. These differences vary with age, being most significant in infants, whose skull sutures are still open. The pediatric skull is more deformable, which enhances its energy absorption ability. An exception being the petrous part of the temporal bone, which is the most compact bone in the skeleton, and already well-developed in the newborn. This makes the forces that play a role in head trauma different specifically relative to the temporal bone. 6 The dissimilarity between adult and pediatric trauma mechanism is demonstrated by the lower incidence of facial nerve (FN) injury, and the higher rate of conductive hearing loss (CHL) in children compared to adults. 7



55.1.3 Classification


Historically, temporal bone fractures have been categorized as longitudinal or transverse, relative to the axis of the petrous ridge of the temporal bone. 8 Longitudinal fracture lines classically run through the mastoid bone cortex and air cells, squamous part of the temporal bone and the external canal wall (typically posterosuperior), with frequent involvement of the tympanic membrane. The fracture line of transverse fractures typically runs through the petrous bone (and commonly the otic capsule), and may also involve the foramen magnum posteriorly, the jugular foramen and the foramen lacerum anteriorly. A third type of fracture is the oblique or mixed, which according to some studies is actually the most frequent. 9 To improve the clinical relevance, the classification scheme has been modified according to the otic capsule involvement: otic capsule violating (OCV) vs. otic capsule sparing (OCS) fractures. According to several studies, the new classification method can better predict the risk for sensorineural hearing loss (SNHL), FN involvement, as well as cerebrospinal fluid (CSF) leak (all of which are more prevalent in OCV fractures). 8 , 10 These, however, do not separate adult from pediatric patients. In a study by Dunklebarger et al comparing the two systems, the OCS/OCV system had a better predictive value regarding SNHL, but neither system predicted CHL and FN involvement well. 11 This study showed 90:10 percent proportion of OCS/OCV fractures and 75:25 percent proportion of longitudinal/transverse fractures. Another study by Wexler et al found that neither system was a better predictor of FN injury, SNHL or CHL. 12



55.2 Diagnostic Approach



55.2.1 Initial Evaluation




  • Since temporal bone fracture is usually only part of a more complicated trauma, the primary concern should always focus on other more pressing life-threatening issues. The clinician must act according to the ATLS scheme, before approaching the specific temporal bone injury.


A temporal bone fracture could potentially pose a life danger if a main blood vessel is involved, namely the carotid artery or sigmoid sinus, but this is quite rare. Recording facial nerve function as early as possible is imperative. Particularly in unconscious patients or ones that are about to be sedated and/or intubated. An effort to establish facial nerve function will facilitate appropriate management of the paralyzed nerve. The window for this very early assessment typically closes before the otolaryngologist is involved, and should be included in the initial assessment by the trauma team.




  • Traumatic brain injury (TBI): Relating to head trauma, once the patient’s airway, breathing, and circulation status are stable, a neurological assessment should be performed. A detailed description of the neurologic examination is beyond the scope of this chapter; however, the main points are mentioned.


The Glasgow Coma Scale (GCS) is widely used to assess consciousness level. It has been adapted for children, and is easy to use for a general evaluation of the patient’s current neurological state: a score of 3 to 7 is severe, 8 to 12 is moderate, and 13 to 15 is mild. Other symptoms and signs to observe are confusion, somnolence, or irritability, as well as vomiting and pallor. With relation to temporal bone fractures, loss of consciousness and other intracranial injuries are present in about 60% of cases. 13 The wide spectrum of brain injury and neurological signs ranges from subtle focal deficits to signs of brain herniation. Either way, when TBI is suspected, further investigations and management are warranted. A key point, even in mild head trauma cases, where initial evaluation does not lead to the diagnosis of TBI, is repeating the neurologic examination several times during the first few hours, since the appearance of new neurological signs may indicate complications such as progressive brain edema or secondary intracranial hemorrhage or thrombosis. 6



55.2.2 Temporal Bone Fracture


Once the initial evaluation and stabilization are completed (principally by other members of the trauma team), it is time for the otolaryngologist to focus on the evaluation of the injured temporal bone. The diagnosis can be suspected on the basis of history and physical findings, although in some cases an imaging-based diagnosis may already be made at the time of the evaluation. The possibility of bilateral temporal fractures mandates the evaluation of both sides.


A detailed evaluation of each subsite is required, and will be further discussed, but at the initial “survey” two key-points require immediate attention: establishing the functional status of the facial nerve, and the presence of CSF leak. The management of the immediately completely paralyzed FN may require surgical intervention more frequently than the delayed paralyzed nerve. Other possible injuries require less urgent diagnosis and treatment.


Evaluation starts with a history if the patient is alert and cooperative. The patient (and/or parents) should be questioned about otalgia, ear fullness, loss of hearing, dizziness or vertigo, mechanism of trauma, past otologic history, and the presence of prior facial nerve dysfunction.


Next, a full ENT examination is performed, with a focus on neurotologic relevant pathologies:




  • External ear: The auricle should be inspected for lacerations. Postauricularly, ecchymosis which signifies base of skull fracture (Battle sign) may be seen. Next, the ear canal is examined. As mentioned, it is important to diagnose the presence of CSF otorrhea as early as possible, so one should look for the presence of a clear discharge.


Canal laceration and/or bony fragments may be present with or without stenosis of the canal (which will require further intervention). Foreign bodies may be detected in the external auditory canal (EAC).




  • Tympanic membrane (TM) and middle ear: The TM is often involved in temporal bone trauma, with a perforation more frequently encountered in longitudinal fractures. This will normally present with signs of fresh blood or clots in the canal. When the TM is not perforated, the pathognomonic hemotympanum is seen in about 80% of cases of temporal bone fractures. 7 Other middle ear involvement, including ossicular chain damage, will be difficult to diagnose with otoscopy at the time of initial evaluation.


Damage to middle ear structures is the most common reason for hearing loss. In most series, a CHL is the more common type (>50% of documented HL), followed by sensorineural hearing loss (SNHL) and mixed hearing loss (MHL). 3 , 7 , 12 In most instances, CHL is mild and resolves spontaneously. When the presentation is more severe, an ossicular disruption is the most probable pathology (▶ Fig. 55.1), and complete improvement is less likely. 14 , 15

Fig. 55.1 A 37-year-old male sustained blunt trauma to the left side of the head falling off a bicycle at a low speed. He noticed an immediate hearing loss. Otoscopy was normal. Audiometry revealed a 45-dB conductive hearing loss. Imaging depicts a separation of the incus body from the malleus head. No temporal bone fracture was present. Transcanal ossiculoplasty was successful in closing most of the air-bone gap (axial bone window temporal bones CT scan).



  • Inner ear: Otic capsule violation may include both the vestibular and cochlear components of the inner ear.


Vestibular bedside assessment in head trauma patient should take into account the possibility of concurrent central vestibular system involvement. Alsao, when examining the patient, head movements should be performed with caution, accounting for possibility of spinal injury. The bedside assessment includes the routine tests: evaluation of nystagmus, fistula test, Dix-Hallpike test, head thrust test, and post–head-shaking nystagmus. The most useful components to record in the initial evaluation are the characteristics of spontaneous nystagmus and head impulse test in the plane of the horizontal canal. Pathologic findings are expected in cases of acute vestibular paralysis, even without a fracture. The most common vestibular pathologies following temporal bone trauma are BPPV and vestibular hypofunction.


Hearing loss is present as a symptom in up to 33% to 80% of cases. 7 , 14 A bedside evaluation with the tuning fork test’s results may vary in different situation: unilateral vs. bilateral fractures, and type of hearing loss: conductive, mixed, or sensorineural (SN), but it is important to perform and document it at least for follow-up purposes.


An audiometry must be performed when possible. It is not urgent, since the patient’s cooperation is needed and hearing rehabilitation (surgical or conservative) will usually be done at a later stage. SNHL, second to CHL in incidence, may present on a wide scale, with temporary, mild, high tone loss to irreversible deafness. In general the more severe the hearing loss is on presentation, the higher the risk of some sort of sequelae.




  • CSF leak: CSF leak is not rare in temporal bone fractures in children (~20% of cases). 15 The natural history of quick spontaneous resolution probably contributes to its under-diagnosis. 15 A high index of suspicion is required.


Principally, a CSF leak resulting from temporal bone fracture can present as either otorrhea or rhinorrhea. In the latter, where the CSF drains through the Eustachian tube to the nasal cavity, the bedside diagnosis is more challenging because of a wider differential diagnosis of clear nasal discharge (rhinitis, which is very common in children, tears, etc.).


On examination one should look for clear discharge in the external canal. Irrigation of the canal should therefore be avoided. If the discharge is bloody and not clear, the long known halo or sign may a useful bedside tool. A small amount of discharge is placed on a white gauze pad. Blood will concentrate in the middle and a clearer halo will appear. However, the specificity of the ring sign is not ideal (it depends on the CSF concentration, and may be positive for fluids other than CSF), and usually more definitive tests are used. 16 , 17 Rhinoscopy and endoscopic nasal examination aid in determining the nature and source of nasal discharge, with direct visualization of the Eustachian tube orifices.


Collecting and testing the fluid for the presence of beta-2-transferrin is considered the gold standard laboratory test for diagnosis because of its high sensitivity and specificity. The presence of the protein in the discharge makes the diagnosis of a CSF leak certain. However, a negative test does not rule out a leak, as sampling and other technical errors may result in a falsely negative test. Former tests such as the fluid glucose levels have been abandoned since their accuracy is very low.


Once the diagnosis of CSF leak has been established, imaging studies are performed to locate its source. These are especially important when planning surgical intervention, when conservative management fails. The different modalities, namely CT and MRI scans including the use of intrathecal injections will be discussed in the management section.




  • Facial nerve injury: Facial nerve paralysis is one of the most devastating sequelae of temporal bone fractures, especially in the pediatric population. In most series, the incidence of FN paralysis is lower in children compared to adults, although the reported incidence varies greatly from 3% to 25%). 7 , 9 , 12 , 14 , 18


The facial nerve is the motor nerve with the longest intraosseous course in human body. As the Fallopian canal leaves no space for expansion of an edematous nerve, complete dysfunction of the nerve may result from injuries that do not significantly disrupt its continuation. The two most important factors influencing treatment of the injured FN are the timing of the onset of injury and its extent. An immediate complete paralysis may represent a complete transection (▶ Fig. 55.2). Delayed paralysis or paresis represents other injury mechanisms such as edema or hematoma. The determination of presence and/or timing of nerve injury can be impossible if the patient is unconscious when examined, although if some degree of consciousness exists, a facial movement can be elicited by a painful stimulation. Although it was originally developed for other purposes, the House-Brackman grading system is the most commonly used and best known. An important part of this is the degree of eye closure, which, if incomplete, may require protective eye measures.

Fig. 55.2 A 24-year-old male fell from a significant height. He suffered multiorgan and life-threatening injuries and loss of consciousness. Two weeks after his injury, facial nerve function could be evaluated and revealed complete peripheral paralysis on the left. The left facial nerve is severed at the proximal tympanic segment (arrow). Spontaneous recovery is impossible (axial bone window temporal bones CT scan).

Further investigations include imaging studies and electrophysiologic tests—electroneurography (ENOG) and electromyography (EMG). The combination of both helps the decision making regarding surgical intervention.

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Feb 8, 2021 | Posted by in HEAD AND NECK SURGERY | Comments Off on 55 The Management of Temporal Bone Fractures
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