The inner ear
Each inner ear contains three semicircular canals that detect rotation of the head and two otolith organs that detect tilt and straight-line movement. Fluid and tiny hair cells in these structures convert movement into nerve signals many times a second.
The brain
Signals from both ears travel to the brainstem and cerebellum, where they are combined with what the eyes see and what the joints and muscles report. The brain uses this to keep the eyes fixed on a target while the head moves, to adjust posture, and to give a sense of where you are in space. Because the system integrates three sources, the brain can compensate when one is faulty, which is the principle behind vestibular rehabilitation.
When it goes wrong
Displaced crystals in a canal cause BPPV, brief spinning on turning over or looking up. Infection of the nerve or inner ear causes days of severe vertigo followed by weeks of imbalance. Migraine can disrupt processing and cause episodic dizziness. Head injury, ageing, some medications and Meniere's disease also affect it. The symptoms are vertigo, dizziness, unsteadiness, visual blurring with head movement, nausea, and a sense of the world moving.
Why it matters for treatment
Dizziness is a symptom with many causes, and treatment depends on which part of the system is involved. Assessment of eye movements, positional testing and balance identifies the source. BPPV is treated with a repositioning manoeuvre; other causes with exercises that use the brain's ability to recalibrate.
At Omnia
Vestibular First at our Chiswick clinic assesses the whole system and treats accordingly, with tai chi available for longer-term balance training.