Biometric Study of the Optic Canal during Cranial Development

Abstract

To study optic canal dimensions and symmetry during cranial development, 146 silicon rubber left- and right-side models of the optic canal were cast from 51 dry skulls and 22 individual bones. The sample was divided in three age groups: fetuses (including newborns), children and adults with ages ranging from seven months of fetal life to 68-year-old. A digital caliper was used to measure the optic canal orbital and cranial diameters as well as model length. Results for the right and the left sides were, respectively, in millimeters: a) Maximum diameter of the orbital opening: fetuses, 4.68/4.47--children, 5.51/5.41--adults, 5.43/5.34; b) Minimum diameter of the orbital opening: fetuses, 2.89/2.84--children, 3.54/3.61--adults, 3.78/3.73; c) Diameter of the cranial opening: fetuses, 3.79/3.76--children, 4.67/4.72--adults, 5.24/5.43; d) Length of the optic canal: fetuses, 3.27/3.05--children, 3.93/3.71--adults 4.94/5.21. The diameter of the cranial opening of the optic canal increases significantly (p < 0.001) during the fetal period and throughout child and adulthood. The greater and smaller orbital apertures increase during the fetal period and during childhood, keeping the same size in adulthood. Optic canal length increases at some point between childhood and adulthood. Concerning symmetry, the only significant difference found was greater right than left optic canal diameter on the orbital side.

Monitoring of Intracranial Pressure by CT‐Defined Optic Nerve Sheath Diameter

“…The anterior opening is oval in outline and measures 5‐6 mm in its longer diameter; the central part is circular, with an average diameter of 5.5 mm; the posterior portion is generally considered to be flattened from above downwards. Combining the previous and current data, the length of the canal varies significantly from 4 to 12 mm . Anomalies of the sphenoid bone and of the skull in general, various tumors, the ophthalmic artery aneurysm, and other abnormalities can affect the shape of the OC.…”

“…Current descriptions of the dimensions of the OC can be misleading because expressions like “average optic canal width,” “mean diameter of the optic canal orbital aperture,” or “diameter of the orbital opening” do not provide the practitioner with practical information in cases when the ONSD is used for ICP monitoring. For proper implementation of the ONSD technique, only the minimal cross‐sectional area/diameter of the canal's lumen is important.…”

“…However researchers of ONSD‐ICP relations overlook the OC being concentrated on the ONSD itself and do not mention the diameters of the canal in their papers. The average length of the OC and its diameters vary from 3.57×4.82 mm to 5.5 mm in different publications causing a discrepancy …”

A 2-year prospective surveillance of pediatric traumatic optic neuropathy in the United Kingdom

“…Thus, differences in the presentation and natural history of the condition might be expected between adults and children. 2 The published literature on TON mainly consists of retrospective case series, and management of TON remains controversial in both adults and children. The recommendation to treat TON with steroids was based on data extrapolated from the National Adult Social Care Intelligence Service studies of megadose steroids for spinal cord injuries.…”

Optic Nerve Sheath Diameter on Brain Magnetic Resonance Imaging: A Single Center Study

“…Third, myopia, congenital and acquired glaucoma, retinoblastoma and some other disorders can change the size of the eyeball [11]. Forth, the optic canal of the sphenoid bone can be wide, normal, or narrow and specifically its orbital opening can be wide or narrow that can influence the ONSD because the sheath acts as periosteum of the sphenoid bone inside the canal [12]. All these variations might influence the accuracy of the ONSD method of intracranial pressure monitoring.…”