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Cholesterol granuloma of the petrous apex: MR and CT evaluation.

We reviewed the clinical, CT, and MR findings in seven consecutive patients who had a total of nine cholesterol granulomas. Preoperative MR scans were available for five of the seven patients; two patients were studied with MR after treatment only (one had a recurrent lesion and the other was asymptomatic at the time of study). Preoperative CT scans were available for all patients, except one patient who was examined after developing a symptomatic recurrence. All lesions were detected by both imaging methods. Seven preoperative lesions (five patients) and one symptomatic recurrence (one patient) demonstrated increased signal intensity of both T1- and T2-weighted MR images. Three surgically drained lesions (three patients) showed a marked reduction in signal intensity on T1-weighted images. Pre- and postoperative lesions had different patterns of signal intensity on the chemical-shift images, which were obtained in two instances. The MR appearance of cholesterol granuloma differs from that of most other lesions that occur in the petrous apex. CT did not differentiate between pre- and postoperative lesions in all cases, while MR demonstrated a dramatic change on T1-weighted images and chemical-shift studies. Our findings indicate that MR is more specific than CT in suggesting the correct diagnosis of cholesterol granuloma and that MR appears to be the technique of choice in the follow-up of previously treated patients.