The Influence Of Cochlear Implantation On Vestibular Function

ObjectiveTo observe the influence of cochlear implantation on vestibular function.Patients and MethodsA total of 12 patients aged >6 years who underwent cochlear implantation more than half years ago performed by the same surgeon at 1st Affiliated Hospital of Fujian Medical University between 2001 and 2009,and were followed up between Nov 2009 and Jan 2010 are included.One patient who discontinued use of the implant other than for vestibular reasons is excluded. Vestibular function are detected by spontaneous nystagmus and bithermal caloric test useing Video-Nystagmography ,and vestibular evoked myogenic potentials. P13 and N23 latencies, amplitude of VEMP-inducing wave,spontaneous nystagmus, directional preponderance and cannal paresis are observed.ResultsThere are 3 cases suffered from vertigo before surgery , one relieved after cochlear implantation. The frequence of subjective vertigo is 16.67%, while the abnormal rate of VEMP and bithermal caloric test is 66.67% and 100% respectively.The occurrence rate of P13,N23 wave evoked by the bilateral tone burst are 50%.There are no statistical significance between operate ears and non-operate ears considering P13 and N23 latencies(P>0.05). There are no statistical significance between operate ears and non-operate ears consideringâ–³P13-N23 (P>0.05).The amplitude of VEMP-inducing wave in operate ears are significantly lower than in non operate ears(t=3.75, P<0.05).41.67% of the patiens (5 cases) developed bilateral cannal paresis, while 58.33% (7 cases) unilateral cannal paresis and 41.67%(5 cases) directional preponderance.Conclusions1. vestibular dysfunction after cohlear implantation doesn't always lead to clinical balance disturbance.2. The occurrence of subjective vertigo is lower than the abnormal rate of vestibular function ,which may be attributed to the vestibular compensation.3. The patient with vestibular dysfunction are fragile to develop subjective vertigo.4. The abnormal vestibular function are higher in patients with inner ear malformation than in the patients with a naormal inner ear.5. The function of the saccules and the horizontal semicircular cannal can be measured by using VEMP and bithermal caloric test.The implantation doesn't influence the conduction of the VEMP,but may lower the amplitude of VEMP-inducing wave,which can be related with the effect of surgery or electrode implantation on the function of the saccule. Operate ears are inclined to develop the dysfunction of horizontal semicircular cannal and contralateral directional preponderance, which may come from positional nystagmus and the vestibular trauma caused by placing long-term electrodes.6. The vestibular function examination can be widely applied in the vestibular evaluation before and after the cochlear implant.