Purpose: (1) To detect the presence of residual mesenchyme in temporal bone
s of adults and children above 5 years of age; (2) to evaluate its regressi
on with increasing age, and; (3) to detect pathologic conditions associated
with the presence of unresolved mesenchyme.
Materials and Methods: We examined 1,404 human temporal bones of donors fro
m 5 to 94 years of age for histopathologic evidence of mesenchyme. The pres
ence of stellate (star-shaped) cells with interdigitating processes and lar
ge nuclei embedded in a structureless ground substance was labeled as "pure
mesenchyme." Temporal bones showing these features and focal areas of fibr
osis, fibroblasts, and capillaries were classified as showing "transitional
mesenchyme." Selected sections were stained with Gomori's trichrome. Patho
logical features indicating otitis media and congenital anomalies of the ea
r were also documented. Case histories were reviewed, and any otologic comp
laints were noted. Statistical analysis was performed with the Chi-square t
est, analysis of variance, regression analysis, and confidence interval.
Results: Mesenchyme was found in 2.07% of temporal bones of patients from 5
to 81 years of age. Of these, 92.1% had transitional mesenchyme, whereas 7
.9% had pure mesenchyme. Seventy-six percent of the bones showed mesenchyme
in the mastoid air cells. In all 3 bones with pure mesenchyme, it was pres
ent in the round window niche. Otitis media was associated with residual me
senchyme in 84.2% of the temporal bones. No pattern of regression of mesenc
hyme with increasing age was observed in temporal bones from patients over
the age of 5 years.
Conclusions: Residual mesenchyme can be present in patients older than 5 ye
ars of age and can persist into adulthood, especially in the mastoid air ce
lls. Persistence of mesenchyme is closely associated with evidence of otiti
s media. Copyright (C) 1999 by W.B. Saunders Company.