Normal hair and hair from patients with pili annulati, pili torti, trichorrhexis nodosa, and monilethrix have been examined using the scanning electron microscope. Study of the fine architecture of the hair shaft surface has been greatly facilitated with this technique. New findings described in this study are longitudinal ridging of the internodes in monilethrix and distinctive surface irregularity of the wider abnormal bands in pili annulati.
Dawber R, Comaish S. Scanning Electron Microscopy of Normal and Abnormal Hair Shafts. Arch Dermatol. 1970;101(3):316-322. doi:10.1001/archderm.1970.04000030060009