• Carlito Lagman, Joel S Beckett, Lawrance K Chung, Chen Cheng Hao Jacky CHJ Department of Neurosurgery, David Geffen School of Medicine, University of California, Los Angeles (UCLA), Los Angeles, California., Brittany L Voth, Bilwaj Gaonkar, Quinton Gopen, and Isaac Yang.
• Department of Neurosurgery, David Geffen School of Medicine, University of California, Los Angeles (UCLA), Los Angeles, California.
• Neurosurgery. 2018 Sep 1; 83 (3): 459-464.

BackgroundSuperior semicircular canal dehiscence (SSCD) is an osseous defect of the arcuate eminence of the petrous temporal bone. Strategies for measuring dehiscence size are variable, and the usefulness of such parameters remains in clinical equipoise.ObjectiveTo present a novel method of measuring dehiscence volume and to evaluate its potential as a predictor of symptom outcomes after surgical repair of SSCD.MethodsHigh-resolution computed tomographic temporal bone images were imported into a freely available segmentation software. Dehiscence lengths and volumes were ascertained by independent authors. Inter-rater observer reliability was assessed using Cronbach's alpha. Correlation and regression analyses were performed to evaluate for relationships between dehiscence size and symptoms (pre- and post-operative).ResultsThirty-seven dehiscences were segmented using the novel volumetric assessment. Cronbach's alpha for dehiscence lengths and volumes were 0.97 and 0.95, respectively. Dehiscence lengths were more variable as compared to dehiscence volumes (σ2 8.92 vs σ2 0.55, F = 1.74). The mean dehiscence volume was 2.22 mm3 (0.74, 0.64-0.53 mm3). Dehiscence volume and headache at presentation were positively correlated (Rpb = 0.67, P = .03). Dehiscence volume and vertigo improvement after surgery were positively correlated, although this did not reach statistical significance (Rpb = 0.46, P = .21).ConclusionSSCD volumetry is a novel method of measuring dehiscence size that has excellent inter-rater reliability and is less variable compared to dehiscence length, but its potential as a predictor of symptom outcomes is not substantiated. However, the study is limited by low power.

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