This is a radioanatomical study on the CT scans of 385 temporal bones to measure some parameters of the superior semicircular canals (SCCC) including bony thickness, diameter and projection into the middle cranial fossa. All measurements were performed on a reconstructed Poschl projection on a helical CT with 0.1 to 0.2 mm increments and slice thickness of 0.4 to 0.6 mm. The bony cover of the SCCC was classified into four stages: bone > 2.5 mm, bone < 2.5 mm, direct contact with the middle cranial fossa and opening into the middle cranial fossa. The mean age was 35 years with a nearly equal male to female distribution. The majority of studied temporal bones (88%) were within the normal range. Only 1.7% showed a radiological stage 4. The mean ages for the four stages were 24.6, 35.2, 47 and 65.4, respectively. There was a statistically significant difference between the mean ages of the examined scans between stages 1 and 2 and stages 3 and 4. There was a statistically significant difference in the diameter of the SCCC between the different age groups.
The authors conclude that SCCC dehiscence is most probably an acquired “ageing” of the bony skull base with progressive thinning leading ultimately to a pathological dehiscence which may be symptomatic.
However, this may not be completely true as the incidence of Minor syndrome is not restricted to older individuals and is mostly unrelated to these findings.