Hairline as a Neurosurgical Landmark

Hair is the first layer of the head. It is known from trichology that the hairline forms relatively constant patterns. However, its relation to the deeper structures has remained unexplored. Our goal was to analyze hairline topography with respect to the neuroanatomical structures, as well as to determine the accuracy and representativeness of the identified landmarks. A prospective study of two sequential groups of patients was conducted. The first group included 500 patients, in whom the general hairline structure and the level of its constancy were determined, depending on sex. The second group included 20 patients (40 head sides). In these patients, a radiopaque wire was fixed along the hairline, CT angiography (CTA) was performed and combined with incoming MRI, and finally, detailed topographic analysis was performed using 3D visualization. For descriptive purposes, we have developed a new anatomical terminology that divides the hairline into easily distinguishable points and segments. Using these landmarks, we found a clear relationship between the hairline and more than 20 cranial, cerebral, and vascular structures. Specifically, the hairline allows localization of the coronal and lambdoid sutures, sphenoidal and petrosal ridges, C2 vertebra, cortical sulci (Sylvian, central, precentral, superior, and inferior frontal), gyri (precentral, postcentral, all major frontal and temporal), and vessels (superficial temporal artery (STA), sinodural angle, and transverse-sigmoid sinus junction (TSSJ)). Discovered landmarks showed clinically acceptable spatial accuracy (overall shift 6.9±3.3 mm) and representativeness. The frontal region was constant in 85% of males (n=211) and 99% of females (n=249), while the temporal and occipital regions were from 95% (n=238) to 100% (n=250) of males and females. In conclusion, the hairline is topographically connected with deep layers. The novel data can be used to plan neurosurgical approaches, in addition to standard craniometric landmarks and neuronavigation.