The Site of Lesion in Hearing Loss: Advances in Otoneuroradiology

*Giorgio Conte, Silvia Casale, Sara Sbaraini, Federica Di Berardino and Diego Zanetti*

### **Abstract**

The last decade has witnessed significant advances in imaging of the middle and inner ear and the auditory pathways. High resolution computerized tomography (CT) scanners and new magnetic resonance (MR) sequences have been implemented in clinical practice as valuable supportive tools for the Audiologist in the identification of the site of lesion and for the surgical planning by the Otologist. The purpose of this chapter is to review the current advanced methods of neuroradiological evaluation of patients with sensorineural hearing loss (SNHL), either congenital or acquired, especially focusing on the assessment of candidates to cochlear implantation (CI), with plenty of explicative images.

**Keywords:** sensorineural hearing loss, congenital inner ear malformations, acquired inner ear disorders, flat panel CT, high-resolution MR-sequences

#### **1. Introduction**

The imaging assessment of the inner ear and the auditory pathway requires high-resolution techniques because their anatomical structures are small and complex. In the last 10 years, computed tomography (CT) and magnetic resonance (MR) has reached much higher spatial resolution for bony and neural structures.

Multi-section CT (MSCT) is the technique of choice for the study of the temporal bone, thanks to its high spatial resolution. However flat panel CT (FPCT) constitutes the newest alternative technique, since it guarantees some additional advantage compared with MSCT in terms of ultra-high isotropic spatial resolution (~150 × 150 × 150 μm3 ) and reduction of the effective dose of up to 40% [1–3].

On the other hand, 3 Tesla MR scanners, thanks to the high-resolution sequences such as tridimensional (3D) T2 weighted sequence (3D-T2w, spatial resolution: 0.4 × 0.4 × 0.6 mm3 , field of view: 140 × 140 mm, time of scan: 5′ 32″) and 3D Fluid Attenuated Inversion Recovery (FLAIR), have provided new insight to detect changes in the inner ear [4, 5]. MR is technique of choice to study the peripheral and central auditory pathways.

The purposes of this chapter is to review the state of the art of pre-operative neuroradiological assessments of patients with sensorineural hearing loss (SNHL) especially focusing on candidates to a cochlear implant (CI). Advanced imaging of the morphology and the integrity of anatomical structures will be presented in order to show the current capabilities of correct site of lesion identification.
