The inner ear comprises two sensory organs, the cochlea which is important for hearing, and the vestibular organ which is important for balance, in addition to their respective nerves, the auditory nerve and the vestibular nerve (see diagram 1).
The vestibular organ and the cochlear together are collectively known as the labyrinth.
The vestibular system refers to the vestibular organ and the vestibular nerve. The vestibular organ itself is made up of 5 sensory organs: 3 semicircular canals and 2 otolith organs, the saccule and the utricle (see diagram 2).
The role of the vestibular system is to monitor the position and motion of your head in space:
The two vestibular organs work together and send information to the areas in the brain that provide co-ordination of the movement of your eyes and head. The brain also integrates the information from the vestibular system with other sensory systems (vision and somatosensation) to maintain your balance.
When a problem occurs in the vestibular system or in the areas of the brain important for maintaining balance individuals can experience dizziness and/or vertigo in addition to problems with their balance.
Dizziness and vertigo are commonly mistaken to mean the same problem but are in fact distinct symptoms.
Dizziness describes a variety of different sensations such as giddiness, wooziness or feeling light-headed. Although in many cases the inner ear is the problem there are however a number of other potential causes for dizziness including: a sudden drop in blood pressure, heart problems, side effect of medications, anxiety disorders and some neurological disorders, just to list a few.
Vertigo is described as the environment or yourself moving, typically it is felt as a spinning sensation in a rotational direction. Vertigo is commonly due to an inner ear problem but it can also be caused by problems in certain areas in the brain.
In addition to dizziness, vertigo and unsteadiness, other symptoms commonly reported include: nausea; vomiting; visual blurring; fatigue; and poor concentration.
For some individuals these symptoms may be mild and they can manage to get through their day. However, for others it can be very debilitating, affecting their ability to perform work duties, household chores, exercise/sporting activities, social outings or drive a car. This can subsequently lead to decreased physical activity; increased risk of falling and falls; anxiety; depression; fear and social isolation.
Vestibular problems can occur through different mechanisms including age, disease, adverse reaction to certain medications (ototoxicity) or trauma. Here is a brief description of some of the more common vestibular conditions:
Benign Paroxysmal Positional Vertigo – crystals from the otoliths floating into one of the semicircular canals causing brief episodes of vertigo triggered by changes in head position relative to gravity.
Vestibular Neuritis – a viral infection of the vestibular nerve that causes an acute episode of vertigo, nausea/vomiting and loss of balance.
Vestibular Migraine – a variant of migraine where the predominant symptom is dizziness or vertigo rather than headache which is often reported as mild.
Meniere’s Disease – a circulatory problem where fluid accumulates in the inner ear causing fluctuating episodes of vertigo, tinnitus, hearing loss and unsteadiness.
Acoustic Neuroma/Vestibular Schwannoma – a slow growing benign tumour on the vestibulocochlear nerve causing a gradual loss of hearing in one ear and unsteadiness. Requires an MRI to confirm a diagnosis.
It is always advisable to discuss your symptoms with your General Practitioner (and not rely on all the information you find on Google Doctor). There are a number of other medical conditions that can mimic a vestibular problem and the treatment required will vary depending on the underlying cause.
To diagnose a vestibular condition and exclude other possible causes a detailed medical history and physical examination is required. Your GP will likely refer you to a vestibular specialist, either an ENT surgeon, Neurologist or Vestibular Physiotherapist, who has undergone additional training. Vestibular specialists understand the normal function of the vestibular system and also know the signs and symptoms of the different vestibular conditions.
Referral for additional tests such as vestibular function (balance) tests with a trained vestibular audiologist may also be necessary to help confirm if there is a problem in the vestibular system causing an individual’s symptoms. Imaging of the brain (CT and/or MRI) may also be required to help assess for other possible causes.