Nasal Glial Heterotopia
Lester D. R. Thompson, MD
Key Facts
Etiology/Pathogenesis
Congenital malformation of displaced normal and mature glial tissue
Clinical Issues
Separated into extranasal and intranasal types
NGH usually presents during infancy
Radiographs are prerequisite to avoid post-biopsy complications
Recurrences (up to 30%) if incompletely excised
Microscopic Pathology
Gliosis pattern in glial tissue
Fibrosis frequently obliterates or obscures glial tissue; special stains required to confirm
Ancillary Tests
Glial tissue: S100 protein and GFAP positive
Top Differential Diagnoses
Fibrosed nasal polyp, cutaneous meningioma
 Low magnification shows intact skin with adnexal structures (hair follicles  ) surrounding a haphazard collection of neural elements (glial tissue). |
 High magnification shows the intermingling of glial elements with fibrosis. This is a very subtle finding, highlighting the reason for performing special studies in many cases. |
TERMINOLOGY
Abbreviations
Nasal glial heterotopia (NGH)
Synonyms
Glioma (implies tumor, and should be discouraged)
Definitions
NGH is congenital malformation of displaced normal, mature glial tissue (choristomas)
Continuity with intracranial component usually obliterated
Encephalocele represents herniation of brain tissue and leptomeninges through defect of skull
Continuity with cranial cavity is maintained
ETIOLOGY/PATHOGENESIS
Developmental Anomaly
NGH is congenital malformation of displaced normal and mature glial tissue
