Parapharyngeal Neuroglial Heterotopia Presenting as a Growing Single Locular Cyst: MR Imaging Findings

Thirteen-month-old female infant with neuroglial heterotopia in the parapharyngeal space.

A and B, Axial T1-weighted MR images before (A; TR, 450 ms; TE, 11 ms) and after (B; TR, 566 ms; TE, 11 ms) gadolinium administration at the oropharynx level. A huge, thin-walled cystic lesion is noted in the left parapharyngeal space, obliterating the normal parapharyngeal fat associated with compression and narrowing the oropharynx air column. The cyst displaces the carotid space posteriorly, the masticator space anteriorly and laterally, and the parotid space laterally. There is a thin fat plane (white arrows) seen between the parotid gland and the lesion, excluding the possibility of a lesion from the deep lobe of parotid gland. Note the parapharyngeal triangular fat clearly identified on the contralateral side (black arrow). Mild enhancement is seen along the wall of the cyst after gadolinium administration (arrowhead).

C and D, Axial T2-weighted MR images at a lower level (C; TR, 3000 ms; TE, 56.7 ms) and coronal T2-weighted (D; TR, 4800 ms; TE, 47.7 ms) images. The cyst appears to have no septum and no mural nodule or focal wall thickening. The cystic contents are isointense to CSF for all pulse sequences. The left mandibular arch is eroded, thinner and deformed when compared with the contralateral side (arrow). No communication between the cyst and intracranial structures is noted. The skull base over the left middle cranial fossa is intact.