Cochlear Implant Candidates and Patients Should Receive Vestibular Testing: ICS Impulse vHIT and ICS Chartr EP 200 VEMP are the Perfect Tools
Janky and Givens published a very thoughtful and concise article regarding vestibular, visual acuity and balance outcomes in children with cochlear implants. Batuecas-Caletrio A. et al. evaluated an adult population pre and post implantation using vHIT and caloric testing and obtained the Dizziness Handicap Inventory. Here are the highlights but please read the full articles.
In the Pediatric Population: Access publication
Vestibular loss in children: It has been reported that vestibular loss in children is more commonly found when the inner ear in its entirety are physiologically affected (Cushing et al 2013). This is children with meningitis, cytomegalovirus, inner ear anomalies and Connexin 26 mutations (Cushing et al 2013). Vestibular loss is more likely to occur as hearing loss increases (Brookhouser et al 1991). These children described above are also those who are more likely to receive a cochlear implant. It has also been reported that an estimated 10% are at an additional risk of vestibular loss directly related to the process of cochlear implantation (Jacot et al, 2009).
Testing for children with potential vestibular loss: “Combined cVEMP, OVEMP, and vHIT are ideal for testing the pediatric population, as they do not induce dizziness and provide information not only about each of the individual vestibular receptors (otolith and canal) but also about the right and left ears separately.”
Impact of vestibular loss on a child: “In children, vestibular loss relates critically to both gross motor development delay and abnormal visual acuity. As young as in infancy, children with vestibular loss demonstrate motor delays; they hold their head and independently walk significantly later than their typically developing peers (12 to 33 months versus 10 to 12 months) (Kaga et al 2008; Inoue et al 2013). Reading acuity has been found to be related to dynamic visual acuity (DVA) scores, with poorer DVA scores being associated with poorer reading acuity and adjustment of or larger print size needed for effortless reading, increasing the significance of assessing DVA (Braswell & Rine 2006). DVA is also related to balance function, whereas children with poorer DVA scores exhibit significantly poorer balance function (Martin et al 2012).
ICS Impulse results: “Currently findings confirm that vHIT can be completed in the pediatric population and furthermore that in this small sample, gain is a stable outcome parameter, not affected by age/maturation. vHIT gains were all significantly associated with rotary chair gains. Given its close estimation to rotary chair, vHIT is preferable test, as it provides ear-specific and canal-specific information regarding semicircular function without causing symptoms of dizziness and is easier to perform than both rotary chair and caloric testing. Likewise, the similarity of the vHIT gain in children to adult data makes the vHIT a preferable test compared to rotary chair test, as higher rotary chair gains have been reported in children compared to adults (Valente 2007, Charpiot et al 2010, Maes et al 2014a).”
Vestibular loss for the population in this study: The subjects has their cochlear implant for 5-17 years. 46.7% had semicircular canals abnormalities using vHIT, 55% with abnormal cVEMP and 45% with abnormal OVEMP results. 31% had bilateral loss of vestibular function. All children were tested post implantation. None were tested pre-implantation. “In our small sample children with cochlear implants and vestibular loss demonstrated poor DVA and balance function, and amount of vestibular loss predicted performance on some of these measures.”
Why is identifying a vestibular loss in these children important? “Children with congenital (or early acquired) vestibular loss will not frequently complain of blurred vision, or dizziness for that matter; therefore, the relationship between degree of vestibular loss and reduced DVA can be helpful in predicting performance and targeting children who might be good candidates for physical therapy, specifically vestibular rehabilitation. A common assumption is that children with vestibular loss will recover functionally, due to plasticity. However, Janky and Givens reported a small cohort of children with cochlear implants, of whom 50% have significant vestibular loss, demonstrating significant reductions in both DVA and some aspects of motor function performance. This preliminary evidence suggests that children with vestibular loss do not naturally recover to levels of their healthy peers, particularly with activities that utilize vestibular input and that attention should be given to vestibular loss in the pediatric population. To minimize the risk of additional vestibular loss, pre-implant vestibular testing is recommended and should be considered when choosing the appropriate ear for cochlear implantation”
In the Adult Population: Access publication
Dizziness caused by cochlear implantation: Subjective postoperative dizziness is said to affect between 2% and 47% of patients (Kubo et al 2001 & Vibert D et al 2001).
Testing for adults with potential vestibular loss: “vHIT is an excellent test to evaluate vestibular function not only in the lateral canals but also the vertical canals. Indeed, it may be more sensitive than other tests to detect insufficient vestibular function.”
Vestibular loss for the population in this study: All subjects had normal vestibular function before surgery. Thirty-three percent of patients exhibited changes in the caloric test or in the vHIT after cochlear implant surgery. In three patients, vHIT gain became abnormal and caloric response were reduced. In three patients, vHIT gains were reduced but caloric did not change. In four patients, vHIT gain did not become abnormal but saccades appeared (covert & overt in two cases and overt in one case) and caloric was unchanged. The additional vHIT abnormalities identified are clinically relevant because there is a relationship to subjective vestibular handicap in the Dizziness Handicap Inventory. Note: “Performing vHIT only in the horizontal plane could underdiagnose some deficits in vertical canals, mainly concerning posterior semicircular canal deficits.”
Recommendations: “Although symptomatic vestibular impairment after cochlear implant appears to be short-term in most cases, with long-term disability unlikely, the possibility of vestibular disturbance by cochlear implant, especially bilateral cochlear implant, should be explained to the patients preoperatively. The occurrence of post-op cochlear implant vestibular disturbance is especially important for the elderly and pediatric populations in which not only is vestibular function sometimes affected but other important balance systems also are affected such as vision and proprioception. Batuecas-Caletrio et al reports “vHIT is an excellent procedure to test vestibular function before and after some otologic surgeries such as cochlear implant. It could offer more information about vestibular changes than other test like calorics.”