Correlation of cephalic anthropometric parameters and microsurgical anatomy of the optic nerves: a cadaveric morphometric study.

ABSTRACT

BACKGROUND: This study was designed to elucidate the possible correlation of cranial anthropometric measurements with the chiasm to limbus sphenoidale distance to facilitate preoperative estimation of this distance and to choose a better surgical approach. METHODS: Thirty-three fresh adult cadaver heads (22 males and 11 females) were evaluated for cranial anthropometric measurements. The precraniotomy anthropometric measurements included (A) inion to nasion distance and (B) the longest intermeatal meridian. Subsequently, with a standard craniotomy, the following intervals were measured (C) optic chiasm to falciform ligament, (D) anterior aspect of optic chiasm to limbus sphenoidale, and (E) limbus sphenoidale to inner nasion. A combined ratio parameter, labeled as (F), was calculated from the following equation F = B/E x 10. RESULTS: The mean values and standard errors of the mean of parameters A to F were 195.8 +/- 14.53 mm, 374.7 +/- 25.29 mm, 10.47 +/- 1.89 mm, 9.93 +/- 2.01 mm, 38.46 +/- 3.17 mm, and 9.81 +/- 1.11, respectively. The parameter D had significant correlation to the parameters B, C, E, and F. The most significant correlation was seen between parameters D and F (p < 0.001). According to linear regression assessment between parameters D and F, the following regression equation was obtained D = 4.24 + 0.58F. CONCLUSIONS: Optic nerve topography and dimensions show inter-personal variations that may be anticipated to some extent with cranial anthropometric data. Calculating of F ratio gives us an acceptable estimation of the actual distance of chiasm to limbus sphenoidale, which in turn can help the surgeon to select the approach to tumors of intrasellar region. However, the role of meticulous imaging studies cannot be overemphasized to confirm the anticipated estimations.