Patients with Vestibular Disorders can present with problems of: balance; vertigo; dizziness; nausea and vomiting.
These problems in older people can be linked to degenerative process in the vestibular system. The vestibular system is made up of the peripheral and central systems:
The Peripheral Vestibular System:
· The Peripheral Apparatus
This is the balance portion of the inner ear (the non-auditory parts) and concerning three semi-circular canals and two otolith organs. They detect angular motion and linear acceleration/deceleration.
· The Vestibular Nerve
Also known as cranial nerve VIII, the vestibular nerve connects the inner ear to a section in the brain called the Brainstem.
The Central Vestibular System:
· The Brainstem
This is a stalk like structure, which connects the Cerebrum of the brain to the spinal cord. As well as regulating vital functions such as heart rate and breathing, it controls balance, co-ordination, and reflexes.
· The Cerebellum
This structure is located at the back of the brain, and among other functions it is responsible for making postural adjustments to maintain balance.
· Thalamic Relays
The Thalamus is a structure in the brain which receives information from lots of areas including the eyes, ears, and receptors in the body (for pain, pressure and temperature), and it relays these onto other appropriate areas of the brain accordingly.
· The Vestibular Cerebral Cortical Network
This collectively covers other areas in the brain involved in the processing of vestibular function, including the temporoparietal junction.
Aging Processes in the Peripheral Vestibular System
These can be associated with nerve and hair cell loss in the peripheral apparatus (semi-circular canals and otolith organs of the inner ear), and also degeneration of the vestibular nerve.
Furthermore, otoconia (ear crystals) which are contained in the otolith organs undergo degenerative changes where they fracture/fragment. These changes are associated with a condition called Benign Paroxysmal Positional Vertigo (BPPV), causing vertigo on certain head positional movements. BBPV has been linked to the crystal debris being dislodged from the otolith organs and into the semi-circular canals.
While BBPV is perhaps the most common cause of vertigo in older people, the good news is that it can be treated effectively with manoeuvres, and those able to carry out these include specially trained Physiotherapists.
Interestingly, within the peripheral vestibular system - the semi-circular canals lose hair cells at a greater rate than the otolith structures. Specifically, it is a loss of Type I hair cells which are associated with age related decline in vestibular function.
In contrast, Meniere’s Disease (associated with symptoms of vertigo, tinnitus, hearing loss, hearing sensitivity and a sensation of pressure in the ears), is linked to the loss of Type II hair cells.
Approaches to the management of Meniere’s include prescription of antihistamine and vertigo medication in the acute phases. Additionally, lifestyle changes including low salt diet, and relaxation may help. Furthermore, while vestibular rehabilitation has historically been employed after surgical procedures for the condition, some research has found benefit once acute symptoms have settled in conservatively managed cases.
Finally, degenerative changes in the peripheral vestibular system have also been linked to dysfunction in the Vestibule-Ocular Reflex (VOC) reflex. This is a reflex which stabilises gaze during head movements. Under the supervision of an experienced clinician, including Physiotherapists specialising in vestibular rehabilitation, specific exercises can be prescribed targeting the VOC reflex.
Aging Processes in the Central Vestibular System
The Central Vestibular System is composed of the Brainstem and Cerebellum. After the age of 40, there is a 3% loss of nerve cells in the vestibular nuclei – which are groups of cells located in the Brainstem and receive information from the inner ear via the vestibular nerve.
In aging processes, the Cerebellum (which receives vestibular information from the Brainstem), reduces in volume and cell density. It is thought that aging processes in the Cerebellum may directly affect the VOC reflex.
Additional to age related changes in the Brainstem and Cerebellum, patients with a history of Stroke affecting these areas present with vestibular problems. Most research has focussed on rehabilitation for disorders affecting peripheral systems (and indeed the Cochrane Library holds a systematic review of research in this field). However, a recent systematic review of research indicated in favour of vestibular rehabilitation for Stroke patients, though it was highlighted more larger scale studies of higher quality are needed.
Further information, from the Stroke association on Balance Disorders can be found here: https://www.stroke.org.uk/resources/balance-problems-after-stroke
Of final relevance, Dementia is a condition known to be associated with shrinkage of the hippocampus within the brain, and problems with memory are linked to this. Patients living with Dementia, can also present with spatial orientation problems which are bilateral (affecting both sides). Spatial orientation relates to a person’s ability to maintain body orientation and/or posture in relation to the surrounding environment at rest and during motion. More recently, this has been attributed to lesions in an area of the brain called the temporoparietal junction, rather than hippocampus. Traditionally, rehabilitation for patients with Dementia who present with mobility/falls problems have been adapted from approaches used generically in older people’s rehabilitation to strengthen the legs and challenge balance. However, in view of known changes in the central vestibular systems of these patients, addition of more and specifically targeted vestibular exercises may be indicated.
References:
Allen, D., et al. (2016) ‘Age-related vestibular loss: current understanding and future research directions’, Front. Neurol, 7(231). Doi: 10.3389/fneur.2016.00231.
Gottshall, K.R., Hoffer, M.E., Moore, R.J., and Balough, B.J. (2005) ‘The role of vestibular rehabilitation in the treatment of Meniere’s Disease’, Otolaryngology–Head and Neck Surgery, 133, pp. 326-328.
McDonnell, M.N., and Hillier, S.L. (2015) ‘Vestibular rehabilitation for unilateral peripheral vestibular dysfunction’, Cochrane Database of Systematic Reviews, Issue 1. Art. No.: CD005397. DOI: 10.1002/14651858.CD005397.pub4.
Tsubasa, M., Takeshi, I., and Tanaka, R. (2020) ‘The effects of vestibular rehabilitation on gait performance in patients with Stroke: a systematic review of randomized controlled trials’, J Stroke Cerebrovasc Dis, 29(11). Doi: 10.10116/j.jstrokecerebrovasdis.2020.105214.
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