The purpose of this study is to determine whether patients with primary ciliary dyskinesia (PCD) have reduced or absent otolith function.The otolith system is a specific part of the inner ear vestibular (balance) system that detects linear movement.

Primary ciliary dyskinesia (PCD) is a genetically inherited condition. It is due to structural abnormalities of cilia, which are microscopic hairs found in organs and cells throughout the body. Patients with this condition typically develop upper respiratory tract symptoms such as sinusitis and glue ear, lower respiratory tract problems such as recurrent chest infections, and fertility problems. There is currently no evidence that patients with PCD have a higher incidence of balance problems. However, recent animal studies have shown that cilia may also be important in the development of part of the inner ear balance (vestibular) system, specifically the part that detects linear movement known as the otolith system.

The investigators hope to determine whether patients with PCD have absent or reduced otolith function compared to the normal population. Balance problems are not currently screened for in PCD patients, and could be unrecognized and therefore untreated. It is also possible that PCD patients have compensated for absent otolith function and so are unaffected under normal circumstances; any additional insult to their balance system would cause more pronounced difficulties than expected and treatment might need to reflect this.

Inclusion Criteria:

• aged 16-30 years
• Confirmed diagnosis of PCD under the care of the PCD team at the Royal Brompton Hospital

Exclusion Criteria:

• Aged under 16 years
• Unconfirmed or "suspected" PCD
• Previous history of balance disorders or diagnoses
• Previous history of sensorineural hearing loss
• Previous middle or inner ear surgery (other than grommet insertion)

Ten patients from the PCD clinic at the Royal Brompton Hospital, London.