A 25-year-old man presents with complaints of right-sided hearing loss. This began the previous month, after he got involved in a car accident that led to his hospitalization. He denies having tinnitus or vertigo. Recalling the accident, he says he was a passenger in a vehicle that rolled over. He passed out and regained consciousness a few days later in the hospital. He was told there was some bleeding from his ear after the accident. His tympanogram was a type Ad. His audiogram is on the right.
Diagnosis: Temporal Bone Fracture
In movies, bleeding in the ear is always an ominous sign. If a movie character gets into an accident or falls from a significant height and bleeds from the ear, it usually means that he or she is dead. However, bleeding from the ear generally indicates a temporal bone fracture sustained after trauma. Most temporal fractures cause a laceration of the skin in the bony canal, which results in bleeding from the ear canal. It certainly does not mean a death sentence! However, it may cause hearing loss.
Hearing loss due to temporal bone fracture can come in different varieties. The degree and type of hearing loss primarily depends on the type of temporal bone fracture. Temporal bone fractures have been traditionally classified as either longitudinal or transverse fractures. A longitudinal fracture is usually caused by a lateral blow to the head where the impact is around the ear and temporal bone. The fracture line starts at the lateral cortex of the mastoid, and extends into the middle ear and commonly into the Eustachian tube as well. This type of fracture generally communicates with the ear canal and causes a laceration of the ear canal skin. If hearing loss were to occur after a longitudinal fracture, it would be as a result of a disruption in the joint between the malleus and the incus. Longitudinal fracture causes a disruption in the capsule of the incudomalleal joint and leads to scar formation between the malleus and the incus. Hearing loss due to this type of fracture occurs shortly after the injury and is typically mild. Over time, and as more scar tissue builds up, the degree of conductive hearing loss worsens, though generally no more than 30 to 40 dB. The tympanogram of patients with this condition will often be type As due to the stiffness of the ossicles. Patients with temporal bone fracture may also have a mild or moderate high-frequency sensorineural hearing loss due to a cochlear concussion. Cochlear concussions generally occur as a result of severe trauma to the head. These are not usually sustained after mild head trauma in the absence of a fracture. Uncommonly, a longitudinal bone fracture may involve the otic capsule (cochlea and vestibular structures) and lead to severe to profound sensorineural hearing loss. Longitudinal bone fractures are also much less likely to lead to facial paralysis.
A transverse temporal bone fracture generally occurs after significant trauma to the head. The fracture traverses the petrous pyramid in a perpendicular direction compared with a longitudinal fracture. Transverse temple bone fractures usually result from more severe traumatic injuries. These fractures are much more likely to cause a disruption in the otic capsule and lead to a total or near complete sensorineural hearing loss. In addition, these fractures are more likely to cause facial paralysis. A transverse temporal bone fracture is much less likely to cause a disruption of the ossicular chain since the fracture line is most commonly medial to the middle ear structures, running from the front to the back. Some patients with severe head trauma may develop a mixed fracture, which is a combination of longitudinal and transverse fractures.
More recently, a classification system has been introduced that divides fractures into otic capsule sparing and otic capsule disrupting fractures. An otic capsule sparing fracture can be a longitudinal or transverse type of fracture that does not disrupt the cochlea or the vestibular structures. An otic capsule disrupting fracture is any type of fracture that courses through the cochlea or the vestibular structures. This classification system has been developed since it is thought to be more clinically useful to know whether the fracture involves the otic capsule, regardless of its direction.
The best method to detect the type and extent of a temporal bone fracture is to obtain a high-resolution CT scan of the temporal bone that outlines the structures involved in the fracture. These fractures disrupt the mucosal lining of the mastoid, revealing traces of blood that help detect the fracture line.
This patient's CT shows that the longitudinal fracture did not disrupt the otic capsule (Figs. 1, Figs. 2, Figs. 3). Looking at the middle ear structures, however, the incus appears to be missing from the middle ear. A closer examination of the CT scan shows that the incus has been dislocated and displaced into the mastoid.
Hearing rehabilitation options for this patient includes the use of an air conduction hearing aid or a bone conduction device. The patient may also undergo a surgical procedure using a partial ossicular reconstruction prosthesis (PORP) or the incus as an interposition graft. In this patient, the incus interposition will require a mastoidectomy. The patient is awaiting recovery from his orthopedic injuries before making a decision. When dealing with patients with temporal bone fractures, it is advisable to wait for a few months to confirm that the conductive hearing loss is permanent. In this patient, however, hearing will not improve due to the complete dislocation of the incus.
BONUS VIDEOS: VISUAL DIAGNOSIS
Read this month's Clinical Consultation case, then watch the accompanying videos from Hamid R. Djalilian, MD, to review the patient's imaging for yourself.
- Video 1. Axial CT of the right temporal bone demonstrating the fracture.
- Video 2. Axial CT of the left temporal bone showing the normal anatomy of the same patient on the left.
- Video 3. Coronal CT of the right temporal bone demonstrating the position of the incus in the mastoid.
- Video 4. Coronal CT of the left temporal bone in the same patient showing the normal mastoid and middle ear.
- Video 5. Sagittal CT of the right temporal bone demonstrating the transcanal view (looking from the side). The incus is located at the mid-canal level.
- Video 6. Sagittal CT of the left temporal bone showing the normal transcanal view (looking from the outside of the ear inward).
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