"Lateral Angle" of the Internal Auditory Canal: Non-Association with Temporal Bone Pneumatization

Abstract:  The "lateral angle," the angle with which the posterior wall of the internal auditory canal meets the posterior fossa plate, is arguably wider in females (>45°) than males (<45°). Not previously addressed, however, are repeatability of angle determination, and whether the extent of temporal bone pneumatization is a confounder. Forty-one adult human cranial specimens (82 clinically normal temporal bones) were studied; no sex information was available for this United States sample. Two casts were created from each ear; each cast was independently categorized twice. No association of lateral angle with mastoid size was found. Repeatability was good. Although bilateral symmetry was suggested (phi = 0.60, p  = 0.05), two crania had oppositely categorized right-left angles. We observed a new finding: narrowed but clinically normal canals in 10% of crania. The lateral angle is a good candidate to be a morphological method in determination of sex.