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Skull Base Deficiency in Superior Semicircular Canal Dehiscence (SSCD): Evidence for Incomplete Development

William R Schneider¹, Douglas J Totten², Hunter L Elms²

¹Department of Otolaryngology- Head & Neck Surgery, Indiana University School of Medicine.

Otology & Neurotology : Official Publication of the American Otological Society, American Neurotology Society [And] European Academy of Otology and Neurotology

|April 6, 2026

Abstract

Objective:

Determine whether Superior semicircular canal dehiscence (SSCD) patients have thinner skull bases compared with controls and spontaneous cerebrospinal fluid leak (sCSFL) patients.

Study Design:

Case control.

Setting:

Tertiary referral center.

Patients:

Radiographically confirmed SSCD, temporal bone sCSFL, matched (BMI and age), and unmatched control cohorts.

Intervention:

Measurement of calvarium, zygomatic arch, and lateral skull base thickness.

Main Outcome Measures:

Compare BMI, average skull base, calvarial, and zygomatic arch thicknesses of controls and sCSFL patients.

Results:

SSCD patients have an average [SD] BMI similar to unmatched controls (29.2 [7.7] vs. 31.4 [7.9] kg/m 2 , P =0.18), but significantly lower BMI than sCSFL patients (29.2 [7.7] vs. 38.5 [10.6] kg/m 2 , P <0.001). The average skull base thickness of SSCD patients was 50% thinner than matched control patients (2.12 [0.92] vs. 4.23 [1.13] mm, P <0.001, Cohen d =2.05) and 33% thinner than sCSFL patients (2.12 [0.92] vs. 3.13 [1.46] mm, P <0.001, Cohen d =0.83). No significant difference in skull base thickness was observed between symptomatic and asymptomatic SSCD patients ( P =0.45). SSCD patients had a small yet significantly reduced calvarium to zygomatic arch thickness ratio compared with controls (0.44 [0.09] vs. 0.51 [0.11], P <0.001, Cohen d =0.70), but not sCSFL patients (0.44 [0.09] vs. 0.47 [0.12], P =0.09).

Conclusions:

SSCD patients possess dramatically thinner skull bases than control and sCSFL patients, despite a lack of predisposing factors like obesity. These data implicate a developmental deficiency in the pathophysiology of SSCD.

Keywords:

CSF leak Cerebrospinal fluid leak Intracranial hypertension SSCD Skull base development Superior semicircular canal dehicse

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