Frequency specific hearing improvement in microvascular decompression of the cochlear nerve.
BACKGROUND
Microvascular compressions of the cochlear nerve can lead to hearing loss. Due to the tonotopic organization of the cochlear nerve any focal compression of the cochlear nerve will result in a frequency specific hearing loss. Decompressing the cochlear nerve could result in a frequency specific hearing improvement, without improving overall hearing.


METHODS
Thirty one patients underwent microvascular decompression operations of the vestibulocochlear nerve for vertigo or tinnitus. Preoperative audiograms were substracted from postoperative audiograms obtained 2 years after microvascular decompression. The frequencies of maximal hearing improvement postoperatively were determined.


RESULTS
Of the 31 patients studied, 19 had improvements of 5 dB or more at one or more frequencies postoperatively, and 15 patients had improvements of 10 dB or more. Three patients had improvements of 25 dB or more postoperatively. The postoperative hearing improvement was frequency-specific and related to the anatomical location of the vascular contact on the auditory nerve. The improvement of hearing becomes diluted when the difference between pre- and postoperative hearing thresholds are averaged over all audiometric frequencies. We therefore present results for each frequency that was tested.


CONCLUSIONS
Microvascular decompression of the cochlear nerve can improve hearing in selected patients. The improvement seems too small to justify decompressive surgery for the sole purpose of hearing improvement, but it could be considered if associated short vertigo spells, ipsilateral tinnitus, otalgia and cryptogenic hemifacial spasm are present. Decompression should be performed early, before BAEP changes become noticeable. 3D-MRI could become a valuable tool for selecting good surgical candidates.
De Ridder
D
D
Department of Neurosurgery and Otorhinolaryngology, University Hospital Antwerp, Belgium. dirk.de.ridder@uza.be
Ryu
H
H
De Mulder
G
G
Van de Heyning
P
P
Verlooy
J
J
Møller
A
A
D000328:Adult; D000368:Aged; D001488:Basilar Artery / Q000473:pathology / Q000503:physiopathology / Q000601:surgery; D002561:Cerebrovascular Disorders / Q000473:pathology / Q000503:physiopathology / Q000601:surgery*; D003056:Cochlear Nerve / Q000098:blood supply / Q000503:physiopathology / Q000601:surgery*; D003388:Cranial Fossa, Posterior / Q000033:anatomy & histology / Q000601:surgery; D019299:Decompression, Surgical / Q000379:methods* / Q000706:statistics & numerical data; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology; D005260:Female; D006319:Hearing Loss, Sensorineural / Q000209:etiology / Q000503:physiopathology / Q000601:surgery*; D006801:Humans; D008297:Male; D008866:Microsurgery / Q000379:methods / Q000706:statistics & numerical data; D008875:Middle Aged; D019635:Neurosurgical Procedures / Q000379:methods / Q000706:statistics & numerical data; D018579:Patient Selection; D010897:Pitch Discrimination / Q000502:physiology; D020127:Recovery of Function / Q000502:physiology; D016896:Treatment Outcome; D014656:Vascular Surgical Procedures / Q000379:methods / Q000706:statistics & numerical data; D015837:Vestibular Diseases / Q000473:pathology / Q000503:physiopathology / Q000601:surgery; D000160:Vestibulocochlear Nerve Diseases / Q000473:pathology / Q000503:physiopathology / Q000601:surgery*