Early diagnosis of this condition is important as aggressive management is necessary to avoid morbidiy and mortality. The louder the sound the bigger the vibration, the lower pitch the sound the slower the vibration. This sound then reaches the tympanic membrane, and causes it to vibrate. Differential diagnosis includes cholestatoma and squamous cell carcinoma of the EAC. The external ear/pinna funnels sound waves into a unidirectional wave, and is able to direct it into the auditory canal. Temporal bone osteomyelitis is seen as increased density of the bone, with linear periosteal reaction, and accompanied by a soft tissue density around the EAC and mastoid. Involvement of the TM joint is seen as widening of the joint space, with irregularity of the articular margins. Involvement of the temporalis muscle leads to formation of a temporalis abscess, which is seen as diffuse muscle thickening with hypodensity. CT scan demonstrates the presence of an asymmetric soft tissue density in the EAC, with or without extension into the surrounding structures. The ear canal (external acoustic meatus, external auditory meatus, EAM) is a pathway running from the outer ear to the middle ear. The infection soon spreads into the adjacent structures such as the temporomandibular (TM) joint, middle ear, mastoid air cells, and skull base. It is commonly seen in the elderly and in diabetic patients. Malignant otitis externa is a result of infection of the EAC with Pseudomonas aeruginosa. Mortality has currently decreased to 20% from 30-40% due to good improved antibiotics. Malignant otitis externa is a misnomer as it is not a malignant condition it is termed “malignant” because of the aggressive clinical behavior and high mortality associated with it. 3D reconstructed images should demonstrate the volume of the middle ear cavity and also the distance from the middle ear structures to the atretic EAC and reveal any other anomalies of the external ear. Its initial direction is superoanterior and it ends in a inferoanterior direction. Additional anomalies need to be looked for as well, such as the presence of severe incudomallear dysplasia, which when present has to be resected, as well as dysplastic stapes, which may need to be replaced by a prosthesis. The external auditory canal is a sigmoid shaped tube lined with skin and cartilage and supported by the temporal bone. In addition, we also need to look for structures that may cause problems during surgery such as reduced volume of the middle ear cavity and poor pneumatization of the temporal bone. The stenosis of EAC is narrowing of the width of the EAC. Preoperatively, the radiologist should look for contraindications for surgery such as atretic oval and or round window and unfavorable course of the facial nerve. The external auditory canal (EAC) is formed by lateral cartila ginous and medial bony part. HRCT of the temporal bone is indicated for preoperative planning. The outcome of surgeries performed in the presence of middle and inner ear dysplasia are not encouraging. Isolated EAC atresias are amendable to surgery. Atresia of the EAC can occur in isolation or it may be associated with middle ear and inner ear dysplasia.
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