A clinicopathological study of 15 patients with neuroglial heterotopias and encephaloceles of the middle ear and mastoid region

Objectives/Hypothesis: Heterotopic masses of neuroglial tissue involving no n-midline structures, specifically, the middle ear region, are exceptional. The pathogenesis of these lesions and, in particular, their relation to en cephaloceles, is uncertain. Study, Design and Methods: H&E-stained sections from 15 lesions diagnosed as neuroglial heterotopias or encephaloceles inv olving the middle ear region were reviewed. Radiographic or operative evide nce of a central nervous system (CNS) relation and clinical factors possibl y 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 re lation to the CNS, were composed of varying proportions of neurons and glia with associated chronic inflammatory cells and reactive gliosis, No signif icant ependymal or choroid plexus component was present. Operative findings revealed that two lesions had definite CNS connections and two were unrela ted to the CNS; this relation could not be determined in the remaining case s. Seven of 10 patients for whom clinical information was available had a h istory 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, h ad no predisposing factors. Conclusions: Most neuroglial heterotopias of th e middle ear are probably acquired encephaloceles. These lesions occur in o lder patients than do their midline counterparts. Determination of the rela tion of these lesions to adjacent CNS structures must be done radiographica lly or using operative findings, because histology alone cannot be reliably used to render an accurate diagnosis.