Unilateral implantation of a vestibular prosthesis in patients with bilateral vestibular hypofunction showed a trend to improved posture, gait, and quality of life, but also reduced hearing in most patients, according to a recent study published in The New England Journal of Medicine.
“Approximately 1.8 million adults worldwide have severe bilateral vestibular hypofunction that results in chronic disequilibrium, oscillopsia, postural instability, and unsteady gait owing to failure of vestibular reflexes that stabilize the eyes, head, and body. Because affected persons must devote conscious effort to walking without falling, they have cognitive distraction, a risk of falling that is 31 times greater than that of an unaffected person, and the social stigma of ’walking like a drunk.’ They also have a disease-related economic burden and a reduction in health-related quality of life that are similar to those caused by adult-onset severe bilateral hearing loss or renal insufficiency,” wrote senior author Charles C. Della Santina, MD, PhD, of the Johns Hopkins University School of Medicine and Labyrinth Devices, Baltimore, and colleagues.
For this single-center, prospective, nonrandomized, single-group study, these researchers included eight patients (median age: 59 years; 62.5% women) with bilateral vestibular hypofunction of 2- to 23-years’ duration (seven: ototoxic, one: idiopathic) who underwent unilateral implantation of a prosthesis. Inclusion criteria were adult-onset bilateral vestibular hypofunction confirmed by clinical exam and objective testing for at least 1 year, 6 months of vestibular rehabilitation therapy, adequate hearing in at least one ear to support communication, and normal MRI and CT findings. Patients served as their own controls.
The implanted prosthesis was a self-contained system designed to electronically stimulate the three semicircular canal branches of the vestibular nerve to mimic nerve activity patterns representative of the speed and rotation of the head.
“Similar to a cochlear implant system, the device comprises an implanted stimulator, an electrode array, and an external processor. The stimulator is implanted unilaterally behind the ear that has poorer baseline hearing and vestibular function,” explained Della Santina and fellow researchers.
They compared baseline results in clinical outcomes such as balance, gait, gait speed, speech discrimination, and quality of life from baseline to 6 months after transplantation. Clinical and other outcomes were assessed using the following tests:
- Bruininks-Oseretsky Test of Motor Proficiency balance subtest (range: 0-36, higher scores=better balance).
- Modified Romberg test time to failure (range: 0-30 seconds).
- Dynamic Gait Index (range: 0-24; higher scores=better gait).
- Timed Up and Go test time.
- Puretone auditory detection thresholds.
- The Dizziness Handicap Inventory (range: 0-100).
- Vestibular Disorders Activities of Daily Living questionnaire (scale: 1-10 for 28 activities).
- 36-item Short-Form Health Survey (SF-36).
Balance improved from a baseline score of 17.5 to 21.0 at 6 months (median difference per participant: 5.5 points; 95% CI 0-10.0), as did time to failure on Romberg testing (3.6 versus 8.3 seconds, respectively; difference: 5.1; 95% CI 1.5-27.6).
Patients also exhibited improvements in median Dynamic Gait Index scores (12.5 versus 22.5; difference: 10.5 points; 95% CI 1.5-12.0), median times on the Timed Up and Go test (11.0 versus 8.7 seconds; difference: 2.3 95% CI -1.7 to 5.0), and median speeds on gait-speed testing (1.03 versus 1.10 m/sec; difference: 0.13; 95% CI -0.25 to 0.30).
Researchers also assessed six patients at 1 year, and the results were consistent with those seen at 6 months.
All but one patient experienced hearing loss in the ear containing the implant, and this was severe in three and diminished in four patients. Other adverse events included tinnitus, transient imbalance, dysgeusia, facial twitch, and tingling. Researchers put forth possible reasons for this hearing loss, including hypersensitivity to bone-conducted sound, “which can result from the presence of superior canal dehiscence or other conditions in which holes in the bone walls of the labyrinth alter the fluid dynamics of the inner ear.”
Participant-reported disability and quality of life were similar to changes in posture and gait. At 6 months, the median score on the Vestibular Disorders Activities of Daily Living decreased by 2 points (95% CI 0-4), while SF-36 utility scores increased by 0.10 points (95% CI 0.06-0.24).
“In eight participants with severe bilateral vestibular hypofunction who received artificial sensation of head movement through prosthetic vestibular stimulation for more than 6 months, some measures of posture, gait, and participant-reported quality-of-life outcomes improved from baseline and others were generally in the direction of improvement. Surgery for the implantation resulted in reduced hearing in the ear with the implant in seven participants,” concluded Della Santina et al.
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Upon unilateral implantation of a vestibular prosthesis for bilateral vestibular hypofunction, measures of posture, gait, and quality of life all improved from baseline measures at six months and one year.
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Adverse events included tinnitus, transient imbalance, and hearing loss in most patients.
Liz Meszaros, Contributing Writer, BreakingMED™
Senior authors Charles C. Della Santina, MD, PhD, and Johns Hopkins University report holding royalty interests in pending and awarded patents related to forms of technology discussed in this article, as well as equity interest in Labyrinth Devices, of which Della Santina is the founder and chief executive officer. Terms of this arrangement are managed in accordance with Johns Hopkins University policies on conflicts of interest.
This study was supported by the National Institute on Deafness and Other Communication Disorders of the National institutes of Health.
Della Santina holds royalty interests in pending and awarded patents related to forms of technology discussed in this article, as well as equity interest in Labyrinth Devices, of which Della Santina is the founder and chief executive officer.
Cat ID: 130
Topic ID: 82,130,730,130,192,925
