Irradiation of cochlear structures during vestibular schwannoma radiosurgery and associated hearing outcome.
OBJECTIVE
The purpose of this study was to measure the dose of radiation delivered to the cochlea during a Gamma knife surgery (GKS) procedure for treatment of patients with vestibular schwannomas (VSs), and to analyze the relationship between cochlear irradiation and the hearing outcome of these patients.


METHODS
Eighty-two patients with VSs were treated with GKS using a marginal dose of 12 Gy. No patient had neurofibromatosis Type 2 disease, and all had a Gardner-Robertson hearing class of I to IV before treatment, and a radiological and audiological follow-up of at least 1-year after GKS. The dosimetric data of the volume of the cochlea were retrospectively analyzed and were correlated with the auditory outcome of patients.


RESULTS
The mean radiation dose delivered to the cochlear volume ranged from 1.30 to 10.00 Gy (median 4.15 Gy). The cochlea received significantly higher radiation doses in patients with worsening of hearing after GKS. A highly significant association between the cochlear and the intracanalicular dose of radiation delivered during GKS was found.


CONCLUSIONS
During GKS for VSs, relatively high doses of radiation can be delivered to the cochlea. Worsening of hearing after GKS can be the consequence of either radiation injury to the cochlea or the irradiation dose delivered into the auditory canal, or both.
Massager
Nicolas
N
Gamma Knife Center, University Hospital Erasme, Brussels, Belgium. nmassage@ulb.ac.be
Nissim
Ouzi
O
Delbrouck
Carine
C
Delpierre
Isabelle
I
Devriendt
Daniel
D
Desmedt
Françoise
F
Wikler
David
D
Brotchi
Jacques
J
Levivier
Marc
M
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003051:Cochlea / Q000502:physiology / Q000528:radiation effects; D003056:Cochlear Nerve / Q000502:physiology* / Q000528:radiation effects; D005260:Female; D005500:Follow-Up Studies; D006309:Hearing; D034381:Hearing Loss / Q000209:etiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009464:Neuroma, Acoustic / Q000601:surgery*; D011183:Postoperative Complications; D011874:Radiometry; D016634:Radiosurgery / Q000009:adverse effects*; D012189:Retrospective Studies; D016896:Treatment Outcome; D014725:Vestibular Nerve / Q000601:surgery*