|Year : 2014 | Volume
| Issue : 2 | Page : 89-91
A case of posttraumatic incudomalleolar disruption
Vivek Sasindran, Antony Joseph, Binu Babu, Pratibha George
Department of Otorhinolaryngology, Pushpagiri Institute of Medical Sciences and Research Centre, Tiruvalla, Kerala, India
|Date of Web Publication||3-May-2014|
Department of Otorhinolaryngology, Pushpagiri Institute of Medical Sciences and Research Centre, Tiruvalla - 689 101, Kerala
Source of Support: None, Conflict of Interest: None
Hearing loss following head trauma or head injury is a major medical problem. Trauma related conductive hearing loss can be due to injury to the ossicular chain, hemotympanum or laceration to the tympanic membrane. Sensorineural hearing loss is caused due to injury to the cochlea or organ of Corti. Head trauma associated with ossicular disruption should be suspected in patients with conductive hearing loss that persists after a healing process of 2 months. High-resolution computed tomography is the investigation of choice. Here, we present a case of traumatic isolated incudomalleolar disruption in a 46-year-old male following a road traffic accident. He presented with a persistent conductive hearing loss for 4 months following the incident.
Keywords: Incudomalleolar disruption, Posttraumatic hearing loss, Posttraumatic ossicular disruption
|How to cite this article:|
Sasindran V, Joseph A, Babu B, George P. A case of posttraumatic incudomalleolar disruption. Indian J Otol 2014;20:89-91
| Introduction|| |
Hearing loss following head trauma or head injury is a major medical problem.  Posttraumatic hearing loss is documented in 24-66% of individuals suffering from temporal bone fractures. 
One of the common causes of conductive hearing loss, following head injury is ossicular dislocation. Ossicular disruption should be suspected in patients with conductive hearing loss that persists after a healing process of 2 months. The most common ossicular dislocation is separation of the incudostapedial joint with or without dislocation of the body of the incus from the articulation with the malleus head. The second most common injury of the ossicular chain is fracture of the stapes crura. In our case, there was an isolated dislocation of the incudomalleolar joint which is not common.
| Case Report|| |
A 46-year-old male patient presented to us with a persistent decreased hearing in his left ear following a road traffic accident 4 months back. Otoscopic examination was found to be normal. Audiogram showed a conductive hearing loss of 50 dB with mixed component at 2 KHz and 4 KHz and an air-bone gap of 43.4 dB across speech frequencies. Impedance audiometry revealed a type A curve with reflexes absent.
A high-resolution computed tomography (HRCT) scan of the temporal bones revealed an oblique fracture involving the left mastoid temporal bone extending superiorly to involve the squamous temporal bone and disruption of the left incudomalleolar joint. Integrity of the ossicles was found to be maintained [Figure 1].
|Figure 1: High-resolution computed tomography of the temporal bone, axial section at the level of the epitympanum, showing the normal "ice-cream cone configuration" on the right side and the distorted configuration on the left side where the "ice-cream" appears to have fallen of the "cone." The red circle encloses the incudo-malleolar joint|
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An exploratory tympanotomy was carried out under general anesthesia. Intra operative findings revealed the malleus to be fixed initially. On exposing the attic, the head of the malleus was found to be dislocated from the incudomalleolar joint and displaced medially, under the body of the incus, thus restricting its mobility. The incudostapedial joint was intact, and the stapes were found to be mobile. A myringostapediopexy assembly with an incus autograft was achieved.
Air-bone gap was brought to 20 dB and a pure-tone average of 26.6 dB was obtained 6 months following surgery.
| Discussion|| |
Head injuries are often associated with fracture of the temporal bone. The common serious consequences of the temporal bone fractures are hearing loss and/or facial nerve paralysis.  The most common type of fracture of the temporal bone, from blunt trauma, is the longitudinal fracture. It comprises about 70-90% of temporal bone fracture. Longitudinal fractures involve the tympanic ring and are associated with conductive hearing loss. Transverse fractures of the temporal bone are associated with sensorineural hearing loss due to injury to the cochlea or organ of Corti. ,,
In a study of 820 temporal bone fracture patients, hearing loss was conductive in 21%, mixed in 22% and sensorineural in 57%. Most conductive hearing losses dissipated with time or were lost to follow-up and 5 patients underwent ossicular chain reconstruction for sustained loss.  High-frequency hearing loss, as seen in our patient, may be caused by concussion and intense acoustic stimulation, concussion being reversible. The peak loss is usually at 4000 Hz. Griffiths study (M.V. Griffiths) in 1979 showed a residual hearing loss in 14% of patients even after 6 months in cases of head injury with concussion without fracture. 
The most common surgically treatable complication of temporal bone fracture is ossicular chain disruption.  The most common ossicular dislocation is separation of the incudostapedial joint with or without dislocation of the body of the incus from the articulation with the malleus head. The second most common injury of the ossicular chain is fracture of the stapes crura.  Other varieties of ossicular chain disruption include incudomalleolar joint separation, dislocation of the incus, dislocation of the malleoincudal complex, and stapediovestibular dislocation. 
When a patient presents with conductive hearing loss that persists after a healing process of 2 months, following head trauma, with a normal otoscopic finding, ossicular chain pathology should be suspected. A HRCT-scan with 1 mm contiguous sections is the method of choice for assessing the etiology of a conductive hearing loss. ,
The incudomalleolar joint is a saddle-shaped diarthrodial joint, which is seen as an "ice-cream cone" on axial computed tomography planes. Head of the malleus resembles the scoop and the body and short process of the incus resembles the cone.  In incudomalleolar disruption, the "ice-cream" appears to have fallen off the "cone."
Preoperative audiogram is essential to assess the type and degree of hearing loss, for planning further management and explaining the possible postoperative hearing outcomes to the patient.
In patients where the ossicular injury is the cause of unresolved hearing loss, surgical intervention may be required. Reconstruction of the ossicular chain is considered if a patient has a conductive hearing loss of more than 30 dB. 
The surgical treatment of choice where ossicular disruption is confirmed or suspected is exploratory tympanotomy with subsequent ossicular chain reconstruction when required. Ossiculoplasty can be carried out with autografts (cartilage, ossicle) or other prosthesis, which include high-density polyethylene sponge (Plasti-Pore), aluminum oxide, ceramic, and hydroxyapatite. Many of the preferred methods attempt to utilize the patient's own tissue, but when this is not available prosthetic devices can be used depending on the type and extent of injury to the ossicular chain. ,, Prosthetic devices include incus prostheses, incus-stapes prostheses, partial ossicular replacement prostheses and total ossicular replacement prostheses.
Posttraumatic hearing loss is not an uncommon entity, especially following a road traffic accident. A conductive hearing loss persisting for more than 2 months following the incident should raise the possibility of ossicular discontinuity. A HRCT scan will aid in diagnosis and surgery with ossicular reconstruction is the definitive treatment.
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