Parapharyngeal neuroglial heterotopia presenting as a growing single locular cyst: MR imaging findings

Abstract

Heterotopic brain presenting as a giant, growing, single locular cyst at the parapharyngeal space has not been reported before, to our knowledge. We present such a case, with MR imaging findings, in a 13-month-old girl. A well-demarcated giant cystic mass was noted in the left parapharyngeal space from the skull base to the submandibular region. Airway compression and deformity of the left mandible with subluxation of the temporomandibular joint were noted. The cyst contained a clear fluid that was isointense to CSF with all pulse sequences. Wall enhancement was noted on contrast-enhanced T1-weighted images. No connection to intracranial structures was noted. Histologic findings were compatible with neuroglial heterotopia.

Fig 1.

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.

E, Islets of mature neuroglial tissue are noted in the fibrous tissue of cyst wall (H&E, original magnification ×100). F, Choroid plexus-like tissue is noted in the inner wall of cyst (H&E, original magnification x200). G, The mature neuroglial tissues are strongly staining for GFAP by immunohistochemical stain (original magnification ×200).