The inner ear (labyrinth) consists of a system of fluid-filled tubes. These include the cochlea, which is concerned with hearing, and the vestibule and semi-circular canals, which act like a spirit level, sensing head movements and assisting balance.
Labyrinthitis is inflammation of the inner ear, often due to an infection. Many cases are thought to be viral and some will be preceded by a common cold. It causes vertigo (dizziness with a spinning sensation) and this may be severe, often with vomiting. Temporary hearing loss and tinnitus (ringing or buzzing in the ear) may also be present. Labyrinthitis usually resolves spontaneously within a few weeks.
Although not caused by cycling, labyrinthitis may prevent you from being able to ride until you recover. There is no way to avoid it but, if severe, sometimes a course of anti-sickness tablets (such as prochlorperazine), or an antihistamine (such as cinnarizine) may be prescribed to ease the symptoms. No investigation or treatment is required in most cases. A full recovery is usual in a few weeks.
Other conditions can cause similar symptoms. These include BPPV (benign positional paroxysmal vertigo), which causes vertigo on specific head movements or positional changes. See your doctor if you have prolonged or recurrent symptoms, or if the diagnosis is uncertain.