Scalp biopsy remains a gold standard for the definitive diagnosis of alopecia. The hair count parameters of each scalp area still need to be clarified. The present study determined hair count values at different scalp locations from histopathology and established reference values for each part of the scalp. 

It obtained biopsy specimens from the frontal, vertex, temporoparietal and occipital areas of the scalps of normal deceased subjects and evaluated them for the number of follicular units, hair counts, hair types and stages of the hair cycle. 

The study observed:

• Collection of 240 specimens from 60 cadavers.
• Among all scalp sites, the temporoparietal area showed the lowest mean hair count, the number of follicular units, terminal and vellus hairs and terminal-to-vellus hair ratio.
• Comparable average anagen-to-telogen hair ratio across all scalp sites.
• No significant association of hair parameters with gender differences or increasing age in all scalp areas. 

This study highlights the diversity of the hair index among different scalp areas and suggests that normal hair count values should be separately standardized on each scalp region. The findings will provide reference values for the histopathological evaluation of hair disorders in Asians.

Source: Rutnin S, Chanprapaph K, Pakornphadungsit K, et al. Variation of hair follicle counts among different scalp areas: a quantitative histopathological study. Skin Appendage Disord. 2022;8(1):24-30.