Radiation Injury Of The Temporal Bone

Temporal bone necrosis: diagnosis, classification, and management

OBJECTIVE

The goal of this study was to analyze temporal bone necrosis and classify its diagnosis and treatment according to extent of necrosis and cause.

METHODS AND MATERIAL

Twenty-six cases of temporal bone necrosis were retrospectively reviewed between 1988 and 1997 at the University of British Columbia.

RESULTS

Patients were classified on the basis of disease extent restricted to the tympanic bone or extension beyond the tympanic bone, as well as on the basis of the cause of disease; treatment based on classification. Patients with localized disease of the tympanic bone had minimal symptoms. Those with radiation-induced localized necrosis were less likely to respond to conservative medical management. Patients with diffuse disease were more likely to require surgical intervention.

CONCLUSIONS

Temporal bone necrosis comprises a spectrum of disease from idiopathic tympanic bone necrosis, which rarely requires surgery, to the more severe forms of radiation-induced diffuse temporal bone necrosis that may cause life-threatening complications requiring surgical intervention.

MR evaluation of radiation otomastoiditis

PURPOSE

The purpose of this study was to evaluate the incidence of radiation otomastoiditis, on using T2-weighted magnetic resonance (MR) imaging, in relation to radiation fields, doses, intervals, and clinical symptoms after radiotherapy that included the temporal bone in the fields.

METHODS AND MATERIALS

We performed follow-up MR examinations at various intervals after radiotherapy including the temporal bones for 270 ears of 114 patients with various diseases of the head and neck and intracranial regions. The middle ear and mastoid air cells on T2-weighted images were scored as follows; showing no high signal intensity, a local high signal intensity area, or a high signal intensity area occupying the entire middle ear and all mastoid air cells. The radiation fields as depicted on the lateral simulator films classed as anterior to the clival line, posterior to the clival line, or both.

RESULTS

The incidence of radiation otomastoiditis depicted on T2-weighted MR images increased in the patients who had received irradiation doses of 50 Gy or more. In the patients with doses of less than 50 Gy, the incidence was 18% within 6 months following radiotherapy, 13% at between 6 and 12 months, and 8% after 12 months, whereas it was more than 50% at any period after radiotherapy in the patients with 50 Gy or more. The incidence of radiation otomastoiditis was quite high in the patients whose radiation fields included region both anterior and posterior to the clival line.

CONCLUSION

The incidence of radiation otomastoiditis as demonstrated on T2-weighted MR images is increased at irradiation doses of 50 Gy or more. To reduce the incidence of severe radiation otomastoiditis, the irradiation fields of the temporal bone when the dose is 50 Gy or more should be limited to as small as possible. The clival line is considered to be a good landmark in reducing the irradiation field when doses of 60-70 Gy are delivered in curative radiotherapy.