The authors presented a case report and systematic review assessing the outcomes of patients from cochlear implantation (CI) following radiotherapy treatment for vestibular schwannoma (VS). Outcomes of cochlear implantation in these patients are uncertain due to the combination of both tumour and radiotherapy effect on the cochlear nerve and if electrical transmission along the nerve would be affected, especially in the long term. The authors analysed 33 patients from 14 studies, which were mostly case reports or series. The majority of patients had neurofibromatosis type 2 (NF2) except one who had sporadic VS. The type of radiation used varied, ranging from stereotactic radiosurgery, gamma knife and fractionated stereotactic radiotherapy. Cochlear nerve function was assessed preoperatively in most studies, either by electrical promontory stimulation, electrically evoked compound action potential or auditory brainstem response. There was heterogeneity in reporting hearing outcomes although, in general, outcomes were measured using speech discrimination for monosyllables, phonemes, or sentences both in quiet and noise. Follow-up varied across the studies ranging between six weeks to five years. The majority of patients showed some improvement in hearing both objectively and subjectively, although there were three patients experiencing little or no improvements. A number of patients scored poorly on objective testing. However, despite this, they reported subjective benefit, improvement in hearing-related quality of life and tinnitus, and remained daily users. The authors were unable to perform statistical analysis due to heterogeneity in the data. In general, it appeared most patients derived benefit, although the amount of benefit experienced was highly variable. There were also two patients who suffered from decline in performance at one and three years post implantation respectively. It would be interesting to see the long-term outcome of these patients. In summary, there appears to be a role for cochlear implantation in patients post radiotherapy for VS but cautious counselling about hearing outcomes would be required. Further work on predicting postoperative hearing outcomes would be useful.
Cochlear implantation following radiotherapy treatment of vestibular schwannomas
Reviewed by Wai Sum Cho
Cochlear Implantation After Radiotherapy of Vestibular Schwannomas.
