Caloric stimulation

Caloric Stimulation

Caloric stimulation is an audiological technique that uses cold or warm water or air to ride unusual eye movements. This eye movement is usually due to a brainstem disorder and is monitored for changes in latency and size. Depending on the type of eye movement observed, caloric stimulation can provide information on the integrity of the individual’s midbrain structures.

Preparation

Prior to the caloric stimulation procedure, a complete audiological evaluation must be performed. This includes a hearing test, an ear exam, and a vestibular assessment which includes an electronystagmography (ENG). For infants and young children, a tympanogram may also be needed. Additionally, a complete health history of the patient should be taken, to rule out any underlying health condition that could affect the caloric stimulation findings.

Types of Caloric Stimulation

Caloric stimulation can be conducted in two ways - cold and warm. During cold caloric stimulation, water or air is cooling below body temperature (33-34°C) and is periodically introduced to the ear. During warm caloric stimulation, water or air is heated above body temperature (38-39°C) and is periodically introduced to the ear.

Procedure

Caloric stimulation is conducted using a procedure called electronystagmography (ENG). During ENG, the patient is asked to lie on their back in a darkened room and remain still while an audiometer channels warm and cold air or water into the ear. This air or water triggers an involuntary eye movement, which is recorded by electrodes placed near the eyes. The size and latency of the eye movements is then compared to determine if there are any signs of abnormal activity in the midbrain structures.

Risks and Side Effects

Caloric stimulation is usually a safe procedure, and only rarely causes any side effects. However, some people may experience a temporary dizziness, nausea, or vertigo following the caloric stimulation. In rare cases, the warm water or air used for caloric stimulation may cause thermal burns or damage to the eardrum.

Why is Caloric Stimulation Performed?

Caloric stimulation is usually performed to evaluate the integrity of the individual’s brainstem structures. This procedure can help diagnose conditions such as Meniere’s disease, vestibular neuritis, and acoustic neuromas. It can also diagnose perilymph fistulae, which occurs when inner ear fluid leaks into the middle ear.

When is Caloric Stimulation Recommended?

Caloric stimulation is usually recommended in patients who are experiencing dizziness, vertigo, or other balance problems. It can also be helpful in diagnosing hearing loss, tinnitus, or other ear-related disorders. Additionally, caloric stimulation may be recommended if a patient is at risk for vestibular neuritis or acoustic neuromas.