## Electronystagmography (ENG): A Comprehensive Guide
### Introduction
Electronystagmography (ENG) is a medical test that evaluates the function of the vestibular system, which is responsible for maintaining balance and equilibrium. This test detects involuntary eye movements (nystagmus) that occur in response to certain stimuli, such as head movements or cold or warm air.
### Procedure
ENG is performed in a specialized laboratory by a trained technician or audiologist. The test involves the following steps:
– **Caloric stimulation test:** Cold or warm water is irrigated into the ear canal to stimulate the vestibular system.
– **Rotational chair test:** The patient sits in a motorized chair that rotates in different directions.
– **Videonystagmography (VNG):** Video recordings of the patient’s eye movements are taken during the caloric and rotational tests.
– **Head impulse test:** The patient fixates on a target while the technician quickly moves their head to one side.
– **Ocular vestibular evoked myogenic potential (OVEMP):** Small electrodes are placed on the face to measure electrical activity in the muscles around the eyes.
### Diagnosis
ENG can help identify various conditions and diseases that affect the vestibular system, including:
– Vertigo (severe dizziness)
– Dizziness
– Motion sickness
– Labyrinthitis (inflammation of the inner ear)
– Meniere’s disease (a disorder of the inner ear)
– Vestibular neuritis (inflammation of the vestibular nerve)
– BPPV (Benign Paroxysmal Positional Vertigo)
– Multiple sclerosis
– Stroke
– Head injury
– Acoustic neuroma
### Importance
ENG is an essential diagnostic tool because it can:
– Confirm or rule out a vestibular disorder
– Determine the severity and nature of the disorder
– Help guide treatment decisions
– Monitor the progress of treatment
### Alternatives
Other tests that can assess vestibular function include:
– Vestibular evoked potentials (VEPs)
– Electroencephalography (EEG)
– Magnetoencephalography (MEG)
### Preparation
No special preparation is required for ENG. However, patients may be advised to:
– Avoid caffeine and alcohol before the test
– Wear comfortable clothing
– Bring a book or other entertainment for the duration of the test
### Duration
The duration of ENG varies depending on the specific tests performed. Typically, the test takes 30-45 minutes, but it may take longer in some cases.
### Recommendations
Additional tests that may be recommended in conjunction with or following ENG include:
– Audiometry (hearing test)
– Imaging studies (e.g., MRI, CT scan)
– Neurological examination
By understanding the purpose and procedure of ENG, patients can better prepare for the test and understand the significance of the results.
