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AJNR - American Journal of Neuroradiology

A, An axial T1-weighted postcontrast image with fat saturation (600/13/2 [TR/TE/excitations]) demonstrates asymmetrical enhancement in the right orbicularis oculi muscle (O-R, arrowhead) as compared with the contralateral side (O-L). In addition, asymmetrical, abnormally intense enhancement along the descending mastoid segment of the right facial nerve (white arrow) as compared with the left (white arrowhead) is noted, consistent with perineural spread of neoplasm. Mildly asymmetrical enhancement of right-sided muscles of mastication is related to perineural spread of tumor along V3 (not shown).

B, A more inferior motion-degraded axial T1-weighted postcontrast image with fat saturation demonstrates intense enhancement in the right platysma (P, arrow) as compared with the left (arrowhead).

C, An axial fast spin-echo T2-weighted image with fat saturation (4000/102/1) slightly superior to the level shown in (B) demonstrates markedly increased signal intensity in the right platysma (P, long stemmed arrow), orbicularis oris (O, short stemmed arrow), and quadratus labii inferioris (Q, small black arrowheads). The contralateral muscles are poorly seen on this fat-saturated image, but clearly are not bright.

D, A coronal T1-weighted postcontrast image with fat saturation (650/13/2) demonstrates abnormally intense, continuous enhancement along the descending mastoid segment of the right facial nerve (arrowhead). The contralateral descending mastoid segment of the facial nerve is slightly posterior to this imaging plane and is not seen here

A, An axial T1-weighted postcontrast image with fat saturation (600/13/2) demonstrates an irregular mass centered at the right cerebellopontine angle (CPA). Enhancement extends into the right internal auditory canal (vertical white arrowhead) and along the tympanic segment of the right facial nerve (oblique white arrowheads). Contralateral IAC and tympanic segment are shown for comparison (vertical and oblique left-sided white arrowheads). A mass is also seen in Meckel's cave on the right (M), with abnormal enhancement extending anteriorly along foramen rotundum (small white arrowheads) and posterolaterally along the greater superficial petrosal nerve (small black arrowheads). The contralateral greater superficial petrosal nerve is demonstrated to show some mild normal enhancement (small black arrowheads on patient's left side).

B, A more inferior axial T1-weighted image postcontrast with fat saturation again demonstrates the right CPA mass. There is abnormal enlargement and enhancement of right V3 (vertical white arrowhead) compared with the normal left side (oblique white arrowhead), as well as abnormal asymmetrical enhancement along the descending mastoid segment of CN VII (F, horizontal arrowhead) compared with the left side (horizontal arrowhead). There is also marked enhancement of the right vidian nerve (double small arrowheads, V). The abnormal and asymmetrical enhancement and enlargement of V2 and V3, the facial nerve, the vidian nerve, and the greater superficial petrosal nerve are due to perineural extension of neoplasm.

C, A coronal T1-weighted image postcontrast with fat saturation (650/13/2) demonstrates marked asymmetrical enhancement of the right buccinator muscle (B) as compared with the left buccinator muscle (B).

D, An axial T1-weighted image (600/15/2) obtained 2 years earlier demonstrates marked enlargement of the third division of the trigeminal nerve on the right (white arrow) as compared with the left (white arrowhead). In addition, there is already subtle volume loss in the right muscles of mastication (M masseter, LP lateral pterygoid). The orbicularis oculi (small black arrowheads) and quadratus labii superioris (black arrowhead) appear symmetrical at this time