Kouichirou Okamoto, Presenter: Nothing to Disclose

Tetsuya Furusawa MD, Abstract Co-Author: Nothing to Disclose

Kazuhiro Ishikawa MD, Abstract Co-Author: Nothing to Disclose

Keisuke Sasai, Abstract Co-Author: Nothing to Disclose

Susumu Tokiguchi MD, Abstract Co-Author: Nothing to Disclose

To evaluate a tiny T2 hyperintensity area demonstrated in the dorsal brain stem of patients with vestibular schwannoma.

We retrospectively reviewed postoperative MR images of 53 patients who had undergone neurosurgery for cerebellopontine angle tumor (CPAT). The MR images were obtained with a 1.5-T imager from May 2003 through March 2004. Acquired were 3 mm-thick spin-echo (SE) pre- and postcontrast T1-weighted axial images, 3 mm-thick fast SE (FSE) T2-weighted axial images and 0.8 mm-thick constructive interference in steady state (CISS) axial images in all patients. Surgical and histopathological diagnoses of the CPATs were as follows: vestibular schwannoma (41/53 = 77%), meningioma (7/53 = 13%), epdermoid cyst (3/53 = 6%), glioma with exophytic growth (1/53 = 2%), and chordoma (1/53 = 2%).

A tiny hyperintensity area was observed in the ipsilateral side of the dorsal pons in 6 patients (3 men and 3 women; age range 24 - 54 years, mean age 43 years) with vestibular schwannoma larger than 2 cm in the maximum diameter with compression of the middle cerebellar peduncle. The hyperintensity was seen at the lateral angle of the 4th ventricle floor on both 3 mm-thick T2-weighted FSE and CISS images. On CISS images, this hyperintensity was demonstrated on consecutive five (4/6 = 67%) or six (2/6 = 33%) images. Preoperative MR images with the same pulse sequences could be reviewed in these patients, and the hyperintensity area was seen in all these patients.

As the location of the hyperintensity area in the dorsal pons is compatible with that of vestibular nucleus, the hyperintensity area may represent degeneration of the nucleus. This hyperintensity should not be confused with a postoperative lesion or a small infarction. If such a hyperintensity is seen in a patient with large CPAT, the diagnosis of vestibular schwannoma could be suggested rather than schwannoma originating from other cranial nerves or other kinds of brain tumors.

Okamoto, K, Furusawa, T, Ishikawa, K, Sasai, K, Tokiguchi, S, A Tiny T2 Hyperintensity in the Dorsal Brain Stem Seen in Patients with Vestibular Schwannoma.  Radiological Society of North America 2004 Scientific Assembly and Annual Meeting, November 28 - December 3, 2004 ,Chicago IL. http://archive.rsna.org/2004/4409474.html