The purpose of rotational chair testing is to determine if the inner ear, known as the vestibular, or the neurological system is causing a balance disorder. When someone turns their head, the vestibular system sends continuous signals to the brain that update it on the head’s position. This causes additional signals to be sent to the muscles of the eyes via the vestibular ocular reflex (VOR). For every head movement in one direction, there is eye movement in the opposite direction. This phenomenon is the basis for the rotational chair testing.
Rotational chair testing can be very helpful in detecting bilateral loss (no function in both ears) of vestibular function or if there are cerebellar ocular motor abnormalities. In recent studies, many people with neurological problems or vestibular ocular reflex (VOR) have been diagnosed with the use of the rotary chair very successfully.
Rotational chair testing is usually ordered in addition to VNG testing to confirm a specific diagnosis and increase accuracy. This allows the audiologist to see precisely what head movement speeds are affected by the inner ear disturbance if one is noted during the VNG testing exam. This cannot be achieved with any other test and ensures that the audiologist has an accurate diagnosis specific to the problem within the inner ear.
The rotational chair is the gold standard in diagnosing bilateral vestibular loss, and is used to investigate whether dizziness may be due to a disorder of the inner ear or the brain.
- There are three parts to the test:
- The chair test measures nystagmus (jumping of the eyes) while the patient turns slowly in a motorized chair. Persons with inner ear disease become less dizzy than do normal persons.
- The optokinetic test measures nystagmus caused by viewing of moving black and white stripes (like the VNG Optokinetic test). Optokinetic testing is sometimes useful in diagnosis of bilateral vestibular loss and central conditions.
- The fixation test measures nystagmus as the person rotates, while they are looking at a dot of light that is rotating with them. Fixation suppression is impaired by central nervous system conditions and improved by bilateral vestibular loss.
With the Rotary Chair, all six semicircular canals of the inner ear can be assessed, at real-time head velocities, to determine which (if any) of them are malfunctioning – this is far superior to the caloric irrigation test, which has commonly been the “go-to” test for decades to assess inner ear function.