From the unfortunate circumstance that capillary nevi, the "port-wine marks" of the vernacular, occur with especial frequence on the face, their appearance is but too well known and there are few of us who can not recall among friends or acquaintances instances of this lesion.
There is a topographical peculiarity of these vascular stains, however, which has received but little attention from writers in English. This peculiarity lies in the close correspondence which often exists between their field of distribution and the skin fields sensitized by one or more of the main divisions of the trigeminal nerve; for the blemish often demarcates with considerable accuracy the territory of the ophthalmic, maxillary or mandibular branches and in exceptional cases may even outline the trigeminal skin-field in its entirety.
The metameric boundaries of the nevus are not always anatomically exact, for the stain may to some extent overlap the adjoining fields or
CUSHING H. CASES OF SPONTANEOUS INTRACRANIAL HEMORRHAGE ASSOCIATED WITH TRIGEMINAL NEVI.. JAMA. 1906;XLVII(3):178-183. doi:10.1001/jama.1906.25210030020002e