BPPV is a common presentation to an ENT department, accounting for approximately 25% of referrals to specialised dizziness clinics. 1 The mainstay of treatment has been medical or particle-repositioning manoeuvres, but for a small cohort of patients, approximately 1%, this treatment is ineffective. 2,3 Parnes and McClure introduced posterior semicircular canal occlusion surgery (PSCCO) for intractable BPPV in the 1990s. 4 The procedure is based on the theory that obstruction of the semicircular canal lumen will prevent endolymph flow, fixing the cupula and therefore make it unresponsive to freefloating particles in endolymph, or are no longer able to cause deflection of the PSCC cupula because they are physically separated from the ampulla. 2,4 The surgical procedure has been described in several articles, and commonly the following steps are taken; a cortical mastoidectomy adequate to expose the lateral and posterior SCC is made. The PSCC is skeletonised carefully over its presenting curvature. A small fine diamond burr is used to blue line the PSCC. A dome is created over the proposed fenestration site, and a stapedectomy hook is used to lift the dome. The canal is plugged with bone dust and fibrin sealant, and the site closed with temporalis fascia. 2,4 None of the published articles state how the PSCC was located.Temporal bone anatomy can be challenging, but needs to be fully understood for surgeons addressing various ear pathology. Many mainstream textbooks and temporal bone dissection course manuals explain and describe the morphological features of the temporal bone. 5 However, there is a lack of precise measurements and accurate correlation between different structures. A particular area of the temporal bone containing the posterior semicircular canal (PSCC) can be difficult to locate, and this is clinically important for PSCCO.The objective of our study was to provide the knowledge of the three measurements between the lateral semicircular canal (LSCC) and PSCC to enable the surgeon to locate the PSCC more readily and perform a limited cortical mastoidectomy for PSCCO.
Materials and methodsThe material consisted of 10 human adult cadaveric temporal bones which were preserved using Thiel, of which six were paired. Thiel is a soft embalming technique involving intravascular injection and then immersion of a body using a preservation fluid comprised of salts, boric acid, ethylene glycol and low level of formaldehyde. It results in preservation of plasticity of the tissues and longevity compared to fresh-frozen cadavers. These bones were obtained and approved for the use of the study from the Anatomy Department, University of Dundee, Ninewells Hospital.
TechniqueEvaluation of the distance between (i) the anterior turn of the LSCC to PSCC, (ii) from the incus to the PSCC and (iii) the posterior end of the LSCC to the PSCC (see Figs 1-4).The measurement was determined independently by each of the four assessors using a microscope at magnification level 0.6 and callipers with 0.5 mm accuracy.The temporal bones ...
