title: Diffusion tensor imaging of the auditory nerve in patients with long-term single-sided deafness.
abstract: A cochlear implant (CI) can restore hearing in patients with profound sensorineural hearing loss by direct electrical stimulation of the auditory nerve. Therefore, the viability of the auditory nerve is vitally important in successful hearing recovery. However, the nerve typically degenerates following cochlear hair cell loss, and the amount of degeneration may considerably differ between the two ears, also in patients with bilateral deafness. A measure that reflects the nerve's condition would help to assess the best of both nerves and decide accordingly which ear should be implanted for optimal benefit from a CI. Diffusion tensor MRI (DTI) may provide such a measure, by allowing noninvasive investigations of the nerve's microstructure. In this pilot study, we show the first use of DTI to image the auditory nerve in five normal-hearing subjects and five patients with long-term profound single-sided sensorineural hearing loss. A specialized acquisition protocol was designed for a 3 T MRI scanner to image the small nerve bundle. The nerve was reconstructed using fiber tractography and DTI metrics - which reflect the nerve's microstructural properties - were computed per tract. Comparing DTI metrics from the deaf-sided with the healthy-sided nerves in patients showed no significant differences. There was a small but significant reduction in fractional anisotropy in both auditory nerves in patients compared with normal-hearing controls. These results are the first evidence of possible changes in the microstructure of the bilateral auditory nerves as a result of single-sided deafness. Our results also indicate that it is too early to assess the degenerative status of the auditory nerve of a subject-specific basis.
authors: Department of Otorhinolaryngology and Head & Neck Surgery, University Medical Center Utrecht, Utrecht, The Netherlands; Image Sciences Institute, University Medical Center Utrecht, Utrecht, The Netherlands; Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht, The Netherlands. Electronic address: ent-research@umcutrecht.nl.
authors: Sjoerd B
authors: SB
authors: Vos
authors: Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands; Department of Forensic Medicine & Comparative Medicine Lab, Aarhus University, Aarhus, Denmark.
authors: Wieke
authors: W
authors: Haakma
authors: Department of Otorhinolaryngology and Head & Neck Surgery, University Medical Center Utrecht, Utrecht, The Netherlands; Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht, The Netherlands.
authors: Huib
authors: H
authors: Versnel
authors: Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands.
authors: Martijn
authors: M
authors: Froeling
authors: Department of Otorhinolaryngology and Head & Neck Surgery, University Medical Center Utrecht, Utrecht, The Netherlands.
authors: Lucienne
authors: L
authors: Speleman
authors: Department of Pediatric Urology, University Children's Hospital UMC Utrecht, Utrecht, The Netherlands.
authors: Pieter
authors: P
authors: Dik
authors: Image Sciences Institute, University Medical Center Utrecht, Utrecht, The Netherlands; Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht, The Netherlands.
authors: Max A
authors: MA
authors: Viergever
authors: Image Sciences Institute, University Medical Center Utrecht, Utrecht, The Netherlands; Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht, The Netherlands.
authors: Alexander
authors: A
authors: Leemans
authors: Department of Otorhinolaryngology and Head & Neck Surgery, University Medical Center Utrecht, Utrecht, The Netherlands; Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht, The Netherlands.
authors: Wilko
authors: W
authors: Grolman
mesh_terms: D000328:Adult; D000368:Aged; D016880:Anisotropy; D016022:Case-Control Studies; D003056:Cochlear Nerve / Q000473:pathology*; D056324:Diffusion Tensor Imaging; D005260:Female; D006319:Hearing Loss, Sensorineural / Q000473:pathology*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008297:Male; D008875:Middle Aged; D009410:Nerve Degeneration; D010865:Pilot Projects; D011237:Predictive Value of Tests