Unit:
Κατεύθυνση Ακοολογία–ΝευροωτολογίαLibrary of the School of Health Sciences
Author:
Tsarpalis Dimitrios
Supervisors info:
Θωμάς Νικολόπουλος, Καθηγητής, Ιατρική Σχολή, ΕΚΠΑ, Επιβλέπων
Παύλος Μαραγκουδάκης, Αναπληρωτής Καθηγητής, Ιατρική Σχολή, ΕΚΠΑ
Αλέξανδρος Δελίδης, Επίκουρος Καθηγητής, Ιατρική Σχολή, ΕΚΠΑ
Original Title:
Electronystagmography caloric test - its use in clinical pratice (a systematic review)
Translated title:
Electronystagmography caloric test - its use in clinical pratice (a systematic review)
Summary:
Electronystagmography caloric test has stood the test of time and has been proven to be clinically invaluable when dealing with dizzy or vertigo patients. It is an objective test to diagnose vestibular disorders (peripheral and central). It is named after the DC potential that naturaly exists between the cornea and the retina (the corneo-retinal potential) used to track eye movements in electrooculography. It evaluates the vestibular system by testing the vestibulo-ocular reflex (VOR).
Since Fitzgerald and Hallpike first described the alternate binaural bithermal caloric test (ABBT) in 1942, the ice water caloric test (IWCT), the monothermal caloric screening test (MCST), the simultaneous binaural bithermal caloric test (SBBT) and the monothermal differential caloric test (MDCT) have been developed. Even nowadays, the alternate binaural bithermal caloric test (ABBT) remains the standard caloric test used because each horizontal semicircular canal is serially examined, its caloric response is reproducible and overall the test is well tolerated. However, we should keep in mind that certain studies have shown that this laboratory test in up to 25% of patients failed to aid physicians to draw any conclusions as the caloric test is a low frequency sinusoidal harmonic acceleration test of around 0.004 Hz, assessing partially the function of each horizontal semicircular canal.
Normal ENG caloric test results do not necessarily imply a normal vestibular function. It is reported that up to 35% of patients suffering from dizziness of peripheral vestibular etiology will have normal caloric test findings. A no response to caloric stimulus does not mean a non-functioning peripheral vestibular organ, as its middle and high-frequency function have not been examined as well as the other two semicircular canals. Many ENG caloric abnormalities are non-localizing; therefore, clinical history and otologic examination as well as other laboratory methods are needed to formulate a diagnosis and treatment plan. In terms of cost-effectiveness for evaluating vertigo, it has been shown that hearing testing followed by electronystagmography and especially caloric testing is the most effective method. ENG caloric test findings are more accurate than clinical symptoms in predicting whether imaging tests will be abnormal. Based on its results, the decision to proceed with more expensive tests like MRI is made. Duration, frequency (beats/time period), mean peak slow-phase-eye velocity of nystagmus (spv) (degrees/second) as well as unilateral weakness (UW), directional preponderance (DP), baseline shift (BS), gain asymmetry (GA), bilateral weakness (BW), hyperactivity and fixation index (FI) are being measured or calculated.
Main subject category:
Health Sciences
Keywords:
Electronystagmography, Caloric test, Nystagmus, Mean peak slow-phase-eye velocity of nystagmus, Vestibular weakness, Directional preponderance, Fixation index
