The role of diffusion tensor imaging in idiopathic sensorineural hearing loss: is it significant?

Introduction
To assess the role of diffusion tensor imaging metrics in the evaluation of the microstructural integrity of the central auditory tract in patients with idiopathic sensorineural hearing loss (SNHL), and to compare these patients with healthy controls.

Material and methods
This prospective study, which was conducted upon 30 subjects (21 males, 9 females; age range from 16 to 65 years, mean age 45years) with SNHL proven by audiometric tests. Ten age- and sex-matched healthy volunteers were included as a control group. Patients (n = 30) and volunteers (n = 10) underwent conventional magnetic resonance imaging and diffusion tensor imaging of the brain. Both fractional anisotropy and mean diffusivity (MD) of 3 points along the acoustic tract (inferior colliculus, lateral lemniscus and superior olivary nucleus) were measured bilaterally in all patients and correlated with controls.

Results
Mean fractional anisotropy (FA) values were reduced bilaterally at the superior olivary nucleus and/or lateral lemniscus and more significantly at the inferior colliculus of subjects with SNHL in comparison to the volunteers. In patients of unilateral SNHL, similar results were obtained in the contralateral side when compared to controls with statistically significant difference at the 3 regions (p = 0.001). No significant changes were noticed in the MD parame­ters either in patient or control groups.

Conclusions
The FA value was a valuable non-invasive biomarker in evaluating the subtle microstructural abnormali­ties of the central auditory tract in idiopathic SNHL and correlated well with hearing impairment.