Incidental Masticator Space Lesion in a Teenager

A teenage girl presentedwith new onset of bilateral upper extremity numbness and paresthesias. The rest of the clinical history and neurological examination was unremarkable. A magnetic resonance imaging (MRI) study of the brain and cervical spine obtained to evaluate for demyelinating disease demonstrated a normal brain and cervical cord, but an incidental T2 hyperintense lesion within the rightpterygoidmuscleswasnoted.Onfurther consultation with the otolaryngology department, the patient stated that she had not experiencedanysensationofamass, and results froma focusedotolaryngologicexamination were also normal. A dedicated fifth cranial nerveMRI examination performed to better characterize the lesion revealed a well-defined, lobulated T2 hyperintense lesion within the right pterygoid muscles without mass effect, adjacent edema, or other invasive features (Figure, A). Therewas a small focus of signal void on the T2-weighted images, suspicious for tiny calcification. On gadolinium administration, there was sequential increasedenhancementon thepostcontrastT1-weightedaxial images (Figure, B and C). Further imaging workup with single-proton emission computed tomography-CT (SPECT-CT) using technetium Tc 99m–labeled red blood cells (RBCs) demonstrated increased tracer pooling within the lesion (Figure, D). Quiz at jamaotolaryngology.com A B C D