High-resolution 3 T magnetic resonance findings in cochlear hypoplasias and incomplete partition anomalies: a pictorial essay

Abstract

Main purposes for cross-sectional imaging in patients with sensorineural hearing loss (SNHL) are: to identify a possible malformation of the inner ear, define the anatomy of the temporal bone, study the auditory pathway from the cochlear nerve to the auditory cortex, identify associated brain anomalies and identify prognostic factors. 1 MRI with three-dimensional (3D) heavily T 2 weighted gradient-echo sequence allows a spatial resolution of up to 0.4 mm. Sagittal, coronal and oblique reconstructions can be performed. This means that not only cochlear and facial nerves can be better displayed, but also the modiolus, lamina spiralis and interscalar septum (ISS) can be visualized in details (Figure 1). 2 High-resolution CT is not able to show neither early cochlear obliteration nor central causes of hearing loss, 3 but is still necessary for pre-operative assessment of cochlear implants. 4 Of note, cone beam CT is an increasingly used tool that has shown to be able not only to assess middle ear and ossicular anomalies with superior performances compared to multidetector CT, but also to depict inner ear structures with extraordinary anatomical detail and with lower radiation dose. 5

Temporal bone and intracranial abnormalities in syndromic causes of hearing loss: an updated guide

“…1). According to the new histological classification of cochlear malformations [1,13] this specific appearance falls into the category of cochlear hypoplasia type 4 (CH 4) with a cochlear height smaller than normal values and relatively preserved internal partitioning and basal turn [14,15]. We suggest measuring the cochlear height in a coronal plane perpendicular to the oval window ( Fig.…”

“…3D) and shortening/ calcification of the middle ear ligaments [11]. Atresia or stenosis of the external auditory canal may also be present [1].…”

“…Temporal bone imaging show pathognomonic bilateral and symmetrical incomplete partition type III anomaly (IP-3) [1,50,51,55,56], characterized by a normal sized cochlea with absent modiolus and lamina spiralis but preserved interscalar septum giving a "corkscrew appearance" (Fig. 7B).…”

“…Internal acoustic meatus is enlarged, bulbous with wide communication between the end of the acoustic meatus and the cochlea, leading to an abnormal communication between the subarachnoid space and the perilymph and increase of perilymphatic pressure [49]. Minor vestibular and semicircular canal abnormalities, and an abnormal course of the facial nerve which lies above the cochlea have been reported [1,49]. The VIII nerve is present and the otic capsule is remarkably thin, consisting of only the endosteal layer.…”

“…Approximately half of pediatric cases of sensorineural hearing loss (SNHL) are due to a genetic cause and a third of these are syndromic [1]. Multiple systemic anomalies are present in these patients and specific combination of findings in different parts of the body (such as the kidney, eye, musculoskeletal system, central nervous system and skin) allows diagnosis [2].…”