Cochlear Implants and Balance: A Two-Part Series for Vestibular and Physical Therapists - Part 2
In Part 1 of this series, we explored the basics of cochlear implants, their candidacy criteria, and their remarkable benefits for individuals with severe-to-profound hearing loss. In Part 2, we'll focus on the potential vestibular consequences of these devices and the crucial role of vestibular and physical therapists in managing them.
A Case of Cochlear Implants and Balance
A gentleman in his early 60s recently presented to my clinic with a history of bilateral cochlear implants. Reviewing his intake form, I noted his implants and was curious about his vestibular function. Upon meeting him, it was evident that he was struggling. He exhibited significant balance difficulties, anxiety, and fear of falling. He reported a history of bilateral BPPV that would come and go, along with severe instability.
During the examination, his fear and anxiety were palpable. He struggled to complete basic balance tests due to his intense fear of falling. His plea to stop the Sensory Organization Test (SOT) on the Bertec CDP-IVR system was a stark reminder of vestibular disorders' profound impact on a person's life.
This case underscores the crucial role of vestibular specialists in identifying and managing the potential vestibular consequences of cochlear implantation. Your vigilance and expertise are vital in ensuring the overall well-being of our patients.
Pre-existing Vestibular Issues: A Hidden Factor
Recognizing that some individuals may have underlying vestibular issues before cochlear implantation is essential. These pre-existing conditions can be exacerbated by the surgical procedure or the changes in sensory input associated with the implant.
Therefore, a thorough pre-operative vestibular assessment is crucial to identify any pre-existing balance disorders and establish a baseline for comparison. This allows for better management of potential post-operative complications such as increased dizziness, vertigo, or imbalance and helps differentiate between pre-existing and implant-related vestibular dysfunction.
Mechanisms of Vestibular Dysfunction
Several mechanisms can contribute to balance problems in cochlear implant recipients:
Surgical Trauma
Direct Damage: The surgical procedure to implant the cochlear electrode array can inadvertently damage delicate vestibular structures, such as the semicircular canals and otolith organs. This can disrupt these structures' normal fluid dynamics and hair cell function, leading to vestibular symptoms (Parietti-Winkler et al., 2015).
Nerve Injury: The vestibular nerve, which transmits balance information from the inner ear to the brain, is near the cochlea and can be injured during surgical manipulation.
Scar Tissue Formation: Scar tissue can form around the implant and surrounding tissues, potentially compressing or restricting the movement of vestibular structures.
Inner Ear Alterations
Changes in Fluid Dynamics: Inserting the electrode array into the cochlea can disrupt the normal flow of endolymph and perilymph, the fluids that fill the inner ear. This can affect the hair cells within the vestibular organs, impairing their ability to sense head movement accurately (Jang et al., 2017).
Pressure Changes: The implant can create pressure changes within the inner ear, potentially affecting the delicate balance mechanisms.
Sensory Mismatch
Introducing new auditory input through the cochlear implant can create a sensory mismatch for the brain, especially if the individual has been deaf for a prolonged period. The brain needs time to adapt and re-process this new auditory information with vestibular and visual inputs. This adaptation period can be accompanied by dizziness (Phillips et al., 2005).
Other Potential Mechanisms
Electromagnetic Interference: The implant's electrical signals can interfere with the normal functioning of vestibular hair cells or nerves.
Individual Susceptibility: Some individuals may be more prone to vestibular dysfunction, making them more prone to experiencing balance problems after cochlear implantation.
Clinical Presentation
The vestibular consequences of cochlear implantation can vary widely, ranging from mild dizziness and unsteadiness to more severe balance disorders and debilitating vertigo.
As I have experienced with my patients, individuals with cochlear implants may present with:
Benign Paroxysmal Positional Vertigo (BPPV) (Gürkov et al., 2014)
Postural instability
Fear of falling
Anxiety and panic related to balance and visual difficulties.
Severe gaze stabilization challenges
Cervical pain and epiphenomenal dizziness
Assessment and Management
A comprehensive vestibular assessment is crucial for identifying and managing balance disorders in cochlear implant recipients. This may include:
Oculomotor and Vestibular Tests: Video Head Impulse Test (vHIT), caloric testing, and rotational chair testing can help assess the function of the vestibulo-ocular reflex (VOR) and identify specific vestibular impairments (Van de Berg et al., 1998).
Balance Function Tests: The Sensory Organization Test (SOT), Clinical Test of Sensory Interaction on Balance (CTSIB), Berg Balance Scale (BBS), Dynamic Gait Index (DGI), or Functional Gait Assessment (FGA) can assess balance and gait function, identify fall risk, and guide treatment planning.
Subjective Questionnaires: The Dizziness Handicap Inventory (DHI), Activities-specific Balance Confidence (ABC) Scale, and anxiety questionnaires can provide valuable information about the patient's perceived limitations, quality of life, and emotional state.
Vestibular Rehabilitation Therapy: A Comprehensive Approach
Vestibular rehabilitation therapy (VRT) is a cornerstone in managing balance deficits in cochlear implant recipients. To optimize outcomes, VRT should be combined with a thorough sensory strategy analysis and identification of sensory mismatches, as described by Tjernström et al. (2016). This approach involves:
Sensory Organization Testing: Identifying the patient's reliance on visual, vestibular, and somatosensory cues for balance control.
Sensory Mismatch Identification: Recognizing specific sensory conflicts, such as visual-vestibular mismatch (VVM/VSVM) or somatosensory-vestibular mismatch (SVM/SVVM), may contribute to dizziness and instability.
Targeted Exercises: Implementing exercises that address the identified sensory mismatches and promote central adaptation.
This comprehensive approach allows for a more targeted and effective VRT program, improving balance, reducing dizziness, and enhancing the quality of life for cochlear implant recipients.
Practical Tips for Physical Therapists
Awareness and Education
Recognize the phenomenon: Cochlear implants can cause vestibular dysfunction, even in patients without previous balance issues.
Educate patients: Inform patients about the potential for balance problems and encourage them to report any dizziness or unsteadiness they experience.
Collaborate with audiologists: Maintain open communication with audiologists involved in the patient's care to share information and coordinate treatment strategies.
Thorough Evaluation
Detailed history: Obtain a thorough history, including the type of cochlear implant, date of surgery, and any pre-existing balance disorders.
Comprehensive examination: Conduct a comprehensive vestibular and balance assessment, including oculomotor tests, balance and gaze function tests, and subjective questionnaires.
Specific tests: Consider using the Sensory Organization Test (SOT) and the Clinical Test of Sensory Interaction on Balance (CTSIB) to identify specific sensory integration deficits. Remember to use the correct terminology to describe these sensory strategies, such as VVM (Visual-Vestibular Mismatch) and SVM (Somatosensory-Vestibular Mismatch).
Individualized Treatment
Vestibular rehabilitation therapy (VRT): Implement individualized VRT programs tailored to the patient's needs and impairments.
Exercises: Include exercises to improve gaze stability, postural control, and balance confidence.
Patient education: Educate patients about their condition and empower them to manage their symptoms.
Specific Considerations
BPPV: Be vigilant for signs and symptoms of BPPV, as it is more common in cochlear implant recipients. Perform appropriate diagnostic maneuvers and canalith repositioning techniques as needed.
Anxiety and fear: Address anxiety and fear related to balance difficulties, as these can exacerbate symptoms and hinder progress. Consider incorporating relaxation techniques and strategies to promote psychological well-being.
Ongoing Monitoring
Regular follow-up: Monitor patients to assess their progress and adjust the treatment plan.
Long-term management: Provide ongoing support and education to help patients manage their balance disorder and maintain their quality of life.
Conclusion
Cochlear implants offer significant benefits for individuals with hearing loss, but it is essential to recognize the potential impact on balance. As vestibular and physical therapists, we play a vital role in assessing, managing, and educating patients about balance deficits related to cochlear implantation. By integrating comprehensive vestibular testing, targeted VRT interventions, and collaborative care, we can help optimize patient outcomes and improve their overall quality of life.
References (Part 1 and 2)
Agrawal, Y., & Carey, J. P. (2016). Balance Disorders in Adults with Cochlear Implants. Otol Neurotol, 37(10), 1437-1442.
Ajalloueyan, M., Lin, F. R., & Litvak, L. M. (2016). Oscillopsia and Cochlear Implants. Otol Neurotol, 37(10), e404-e408.
Grimm, A. M., Carey, J. P., & Agrawal, Y. (2018). Vestibular rehabilitation outcomes in patients with cochlear implants: a systematic review. J Neurol Phys Ther, 42(1), 3–10.
Gürkov, R., Keçeci, H., Topuz, A., et al. (2014). Benign paroxysmal positional vertigo after cochlear implantation. Cochlear Implants Int, 15(Suppl 1), S44-S47.
Jang, J. H., Kim, S. H., Park, M. S., et al. (2017). Evaluation of Vestibular Function Using the Dizziness Handicap Inventory and Posturography in Cochlear Implant Recipients. Clin Exp Otorhinolaryngol, 10(1), 34-39.
Parietti-Winkler, C., Lion, A., Montaut-Verient, B., Grosjean, R., & Gauchard, G. C. (2015). Effects of Unilateral Cochlear Implantation on Balance Control and Sensory Organization in Adult Patients with Profound Hearing Loss. Biomed Res Int, 2015, 621845.
Phillips, K. A., Tadros, S. F., & Hain, T. C. (2005). Vestibular and balance function following cochlear implantation in children. Otol Neurotol, 26(1), 104-108.
Tjernström, F., Cervin, J., Magnusson, M., & Sternad, D. (2016). Balance training with virtual reality and sensory augmentation in patients with bilateral vestibular loss. Gait & Posture, 49, 262-270.
Van de Berg, R., Mulder, J. J., & Kingma, H. (1998). Vestibular function after cochlear implantation in adults. Acta Otolaryngol, 118(3), 301-304.
Ward, B. K., & Carey, J. P. (2017). Dizziness and Cochlear Implantation. Otol Neurotol, 38(10), 1440-1446.