Dizziness is the number one reason that people over the age of 60 visit their doctors. The term dizziness is used to describe a wide variety of symptoms including lightheadedness, spinning, floating, unsteadiness and imbalance. There are many causes of dizziness and imbalance including disorders of the vestibular system. The vestibular system includes the balance portion of the inner ear, nerve, and pathways in the brainstem and cerebellum. Physicians may recommend vestibular tests when it is suspected that symptoms may be related to abnormalities in the vestibular system.
Videonystagmography (VNG)/Electronystagmography (ENG) – This is the most commonly used test to evaluate the vestibular system (balance portions of the inner ear, nerve, and brain). When the head is in motion, the inner-ear balance organs send signals to the eye muscles to keep vision in focus. Therefore, eye movements can be used to evaluate the balance system. ENG testing uses electrodes placed near the eyes to record eye movements. Infrared video goggles, in lieu of electrodes, are used with VNG testing. Patients are asked to follow a moving light with their eyes and sit and lie in different positions. Each ear canal is also irrigated with small amounts of warm and cool water (caloric test) as the patient lies on an examination table. The water causes a temperature change that creates eye movements (nystagmus) that can be measured and compared for each ear. This component of the VNG test cannot be used with infants, very small children, or if there is a perforation (hole) in the eardrum. In these cases, rotary chair is the most appropriate test. The patient's physician uses the information obtained from the VNG, along with information from other clinical tests, to make a diagnosis and recommendations for treatment.
Rotary Chair Test – This test can be used to test patients of all ages, including infants. The patient sits in a chair in a small, dark booth. Small children and infants sit on a parent's lap for this procedure. Video goggles or electrodes are placed near the eyes and a computer-driven chair rotates gently back and forth at several acceleration rates. This motion stimulates the inner balance system and causes eye movements (nystagmus) that are recorded by a computer and monitored with an infrared camera. Unlike the VNG, rotary chair testing cannot provide specific diagnostic information about each ear individually. The rotary chair test is particularly useful when confirming a suspected loss of inner ear balance function in both ears and determining the extent of residual function. It is also a reliablemethod of monitoring the effects of ototoxic medications on the inner balance system over time.
Computerized Dynamic Posturography – This test evaluates the interrelationship of all three parts of the balance system; vestibular (inner ear and brainstem), vision, and proprioception (sensors in muscles and joints). This test may be used to evaluate functional balance in adults and older children. During posturography, the patient stands barefoot on a small platform surrounded on three sides by a padded wall. The platform and wall move slightly and the patient is asked to maintain balance while wearing a safety harness for support. A computer records the patient's shift in body weight and sway and these results are analyzed for patterns of imbalance. Posturography results should be interpreted in conjunction with the results of other clinical and vestibular tests.