Interaction between vestibular compensation mechanisms and vestibular rehabilitation therapy: 10 recommendations for optimal functional recovery
Authors Michel Lacour and Laurence Bernard-Demanze
Page 7 suggests, “Adaptation is usually described in the literature as two separate mechanisms called sensory substitution and behavioral substitution, even though this categorization can differ according to authors. The common characteristic of these two recovery mechanisms is that they constitute learning processes, which are acquired actively and require dynamic interactions of the subject with the environment. In both cases, the lost function is not restored but replaced by a new operating mode using either other sensory cues or a newly elaborated behavioral strategy. This means that adaptation is a qualitative variation of the response, resulting from positive learning.”
Professor Dr Margie Sharpe says, ‘Why Favour Vestibular Adaptation rather than Habituation Processes in Vestibular Rehabilitation Therapy?
Let’s consider; learning a new routine or adapting to our condition is what is required by many during the vestibular rehabilitation process…
We adapt to many situations during the course of our life and of course life is one long adaptation process resulting in evolution. Therefore, it’s natural for a person to wish to adapt to their environment and condition and to return to a place of control and ease.
In this instance, for the vestibular patient, adaptation is a recovery mechanism, where we need to learn new processes to achieve results; we need to be active and interact with our environment to adapt and learn as the loss of vestibular function is frequently something which is not restored.
What once was, is often replaced by using either other sensory cues (sensory substitution) or a new behavioural strategy (behavioural substitution).
As therapists, our aim is to teach our patients new strategies and sensory substitution, and we encourage the brain to engage and reorganise itself to cope with this apparent new loss of function.
For example, in tech speak, covert saccades are thought to substitute for the deficient dynamic VOR function in vestibular patients thereby helping to maintain near normal gaze stability during quick head movements, thus enabling the vestibular patient to focus. On the other hand, covert saccades have been reported during passive and rapid head rotations in patients with vestibular insufficiency. The trigger for these covert saccades triggered by passive head rotations remains an open question.
Commonly, vestibular patients select a new reference frame for control of posture and spatial orientation. This is achieved by re-weighting the remaining sensory cues.
For example, vision compensates for the loss of vestibular information to control earth vertical for posture and trunk stability and becomes the new frame of reference for postural control and spatial orientation.
This sensory substitution varies widely among vestibular patients and as we are all unique, there is no uniform or “one hat fits all” approach.
Some in our industry suggest people should form new habits as a way to teach our patients coping strategies. However habituation is defined as learning a new routine over and over — to the point where we become desensitised to it. It is a passive process, unlike adaptation which is active.
Therefore, active adaptation process has more positive results.
Paper Reference
Interaction between vestibular compensation mechanisms and vestibular rehabilitation therapy: 10 recommendations for optimal functional recovery
Authors Michel Lacour and Laurence Bernard-Demanze
ABSTRACT
This review questions the relationships between the plastic events responsible for the recovery of vestibular function after a unilateral vestibular loss (vestibular compensation), which has been well described in animal models in the last decades, and vestibular rehabilitation (VR) therapy elaborated on a more empirical basis for patients with vestibular loss.
The main objective is not to propose a catalogue of results but to provide clinicians with an understandable view on when and how to perform VR therapy, and why VR therapy may benefit from basic scientific knowledge and influence the recovery process. With this perspective, 10 major recommendations are proposed as ways to identify an optimal functional recovery.
Among them are the crucial role of active and early VR therapy, coincidental with a post-lesion sensitive period for neuronal network remodeling, the instructive role that VR therapy may play in this functional reorganization, the need for progression in the VR therapy protocol, which is based mainly on adaptation processes, the necessity to take into account the sensorimotor, cognitive, and emotional profile of the patient to propose individual or “Ã la carte” VR therapies, and the importance of motivational and ecologic contexts. More than 10 general principles are very likely, but these principles seem crucial for the fast recovery of patients with vestibular loss to ensure positive functional outcomes and a good quality of life.