There are many anatomical components involved in keeping your balance such as your vision, your proprioception (ability to feel your joint position – in particular your ankles in relation to contact with the ground), and your vestibular system. All three of these components must work together to give your brain accurate information for processing to keep your balance. In this article we will be focusing on the vestibular system, particularly the central components.
Before we dive into the inner workings of the vestibular system, let’s briefly go over some of the components of the anatomy and physiology of the peripheral and central vestibular systems
Peripheral Vestibular System Structures (inner ear)
Semicircular canals – are responsible for relaying information about angular motion of the head/body
Utricle and saccule – are responsible for relaying information about linear motion and tilting of the head
Vestibular nerve – is responsible for sending information from the semicircular canals, utricle, and saccule to the brain
Central Vestibular System Structures (brain/brainstem)
Vestibular nuclei – clusters of neurons located in the brainstem that recieve input from the vestibular nerve
Vestibulo-ocular reflex pathways – pathways that connect the vestibular nuclei to the oculomotor nuclei, allowing coordination of eye movements with head movements (VOR reflex)
Vestibulospinal tracts – descending pathways from the vestibular nuclei to the spinal cord to coordinate posture and balance
Cerebellum – recieves input from the vestibular nuclei and integrates vestibular information with other sensory inputs for motor coordination
Thalamo-cortical pathways – projections from the vestibular nuclei to the thalamus and then to the cerebral cortex; involved in conscious perception of spatial orientation and self-motion
Other connections – vestibular nuclei also have connections to reticular formation, hippocampus, and entorhinal cortex; these contribute to functions like spatial navigation and memory
Now that we understand where the information goes to get processed, how does our brain then interpret the information and create an action or output? There are three types of vestibular outputs that are utilized to maintain our balance. We have the vestibulo-ocular output which is part of our gaze stabilization (ability to maintain our eyes fixed on a target), vestibulo-spinal output which is for our overall postural control, and the vestibulo-cortical output which is gauged at body orientation and navigation.
In order to treat vestibular dysfunction, whether it is centrally or peripherally based, it is important for us to first determine where the dysfunction is happening. At any point along these pathways there can be a disruption to the system which may cause a dysfunctional output – in other words you may lose your balance either because the information is not getting “sensed” by your peripheral system or is not getting interpreted correctly by your central system.
Once we have determined where your dysfunctions are, and which outputs are affected, we are then able to tailor a vestibular rehabilitation program to address them. The three basic components of a vestibular rehabilitation program when dealing with central (and sometimes peripheral) vestibular dysfunction: adaptation, habituation, and substitution.
Adaptation Treatment
Aimed to induce long-term neurological changes to improve the vestibulo-ocular reflex (VOR) and gaze stability during head movements
Habituation Treatment
Involve repeated and systematic exposure to movements or positions that provoke dizziness or vertigo
The goal is to desensitize the vestibular system over time, leading to a reduction in symptoms
This of this as “exposure therapy” for the vestibular system
Substitution Treatment
Promote alternative strategies to compensate for impaired vestibular function and maintain gaze and postural stability
Think of substitution as “beefing up” your other body systems so you do not need to rely as much on your vestibular system
In summary, adaptation aims to retrain the vestibular system, habituation desensitizes the system to provocative stimuli, while substitution develops compensatory strategies using other sensory inputs when the vestibular system is impaired.
What is also important to note is that most often people are not just experiencing a vestibular dysfunction alone; they are often experiencing other potential limiting factors, such as cognitive dysfunction with Alzheimer's, fatigue with MS, spasticity with Parkinson’s, among others. When we treat a patient for vestibular dysfunction (peripheral or central), it is imperative you consider the patient’s whole picture and incorporate it into the treatment plan.
Info pulled from continuing education at the APTA Combined Sections Meeting 2024 in Boston, MA. Presenters were: Leland E. Dibble, PT, PhD, ATC, FAPTA: University of Utah; Colin R. Grove, PT, DPT, MS, PhD: Emory University; Brooke N. Klatt, PT, DPT, PhD: University of Pittsburgh.