Objectives/hypothesis: Heterotopic masses of neuroglial tissue involving non-midline structures, specifically, the middle ear region, are exceptional. The pathogenesis of these lesions and, in particular, their relation to encephaloceles, is uncertain.
Study design and methods: H&E-stained sections from 15 lesions diagnosed as neuroglial heterotopias or encephaloceles involving the middle ear region were reviewed. Radiographic or operative evidence of a central nervous system (CNS) relation and clinical factors possibly related to pathogenesis were analyzed.
Results: All 15 lesions (from six men and nine women; mean age, 49 y; range, 16-67 y), regardless of their relation to the CNS, were composed of varying proportions of neurons and glia with associated chronic inflammatory cells and reactive gliosis. No significant ependymal or choroid plexus component was present. Operative findings revealed that two lesions had definite CNS connections and two were unrelated to the CNS; this relation could not be determined in the remaining cases. Seven of 10 patients for whom clinical information was available had a history of chronic otitis media or mastoiditis or both; four of these seven patients also had a history of previous trauma or surgery. Three patients, including both patients whose lesions had no demonstrable CNS attachment, had no predisposing factors.
Conclusions: Most neuroglial heterotopias of the middle ear are probably acquired encephaloceles. These lesions occur in older patients than do their midline counterparts. Determination of the relation of these lesions to adjacent CNS structures must be done radiographically or using operative findings, because histology alone cannot be reliably used to render an accurate diagnosis.