IAC diverticula associated with pericochlear OS demonstrate different morphological features from isolated IAC diverticula. No morphological feature was associated with conductive hearing loss in isolated diverticula or with sensorineural hearing loss in diverticula with fenestral OS alone. Reduced neck:depth ratio, ill definition and angulation were all significantly associated with the presence of pericochlear OS ( p < 0.001), whilst only ill definition was associated with the presence of fenestral OS alone ( p < 0.05). Ninety-five isolated IAC diverticula were demonstrated in 54/978 patients (5.5%) without CT evidence of OS (31M, 23F, mean age 46), and 119 IAC diverticula were demonstrated in 71/306 patients (23%) with CT evidence of OS (23M, 48F, mean age 55). Continuous data was compared using Wilcoxon rank sum tests and categorical data with chi-squared and Fisher’s exact tests. Audiometric profiles were analysed for the isolated IAC diverticula and those with fenestral OS alone. Two independent observers evaluated the presence of IAC diverticula morphological features (depth, neck:depth ratio, definition of contour and angulation of shape), and these were correlated with the presence of fenestral and pericochlear OS. MethodsĬonsecutive temporal bone CT studies with ( n = 978) and without ( n = 306) features of OS were retrospectively assessed. We explored whether isolated IAC diverticula were morphologically different from those with additional CT features of OS, and whether IAC diverticula morphology influenced patterns of hearing loss. Structures that can be seen are facial and vestibulocochlear nerves.The association of internal auditory canal (IAC) fundal diverticula with otospongiosis (OS) and their clinical significance remain unclear. The anatomy of the internal auditory canal is best seen on high-resolution T2-weighted image sequences. Narrow duplicated internal acoustic canal 2 From here three bundles emerge: superior and inferior division of the vestibular nerve and the nerve from the posterior semicircular canal (see article: vestibulocochlear nerve (CN VIII) for further details). In addition to the three nerves which enter it, it also contains the vestibular ganglion ( ganglion of Scarpa). See mnemonic for the position of the nerves in the IAC. Inferior: cochlear nerve and inferior vestibular nerve (IVN) the cochlear nerve is situated anteriorly Superior: facial nerve and superior vestibular nerve (SVN) the facial nerve is anterior to the SVN and is separated from it laterally by Bill's bar, a vertical ridge of bone This horizontal ridge divides the canal into superior and inferior portions: Their position is most constant in the lateral portion of the meatus which is anatomically divided by the falciform crest. Superior vestibular nerve (component of CN VIII) Inferior vestibular nerve (component of CN VIII) Nervus intermedius (sensory component of CN VII)įacial motor root (motor component of CN VII) There are five nerves that run through the IAM: Labyrinthine artery (usually a branch of the AICA or basilar artery) The canal narrows laterally, and the lateral boundary is the fundus, where the canal splits into three distinct openings, one of which is the facial nerve canal. The margins of the opening are smooth and rounded, and the canal is short (1 cm), running laterally to the bone. The opening of the IAM, the porus acusticus internus, is located within the cranial cavity, near the posterior surface of the temporal bone.

Internal auditory canal ct