Bell’s Phenomenon
Sometimes the competition isn’t even close. Think Germany versus Brazil in the World Cup.
For those of you that have been doing ENG exams for years, back when electrode based testing was the norm. Do you remember how every time you would ask the patient to close their eyes, you would have to re-center the tracing because the recording had drifted up off the recording field? You may not have known it at the time, but you were dealing with Bell’s Phenomon.
Bell’s phenomenon refers to the rolling of the eyes superiorly and distally (up and out) when the eyes are closed. This phenomenon can be seen only when performing electrode-based ENG. When a patient closes his/her eyes, the tracing must be re-centered. This represents the eye rolling away from center with eyelid closure.
In the first publication regarding the use of Video goggles in vestibular testing, the author states, “In a few cases, patients who were tested with electrode ENG methods had abnormal or non-existent caloric responses. When their eyes were open in the IR (infrared) video goggle, the nystagmic response became readily evident and recorded by the electrodes. Thus, the eyes open without fixation is an important advantage of the IR/Video ENG System.”{{1}}[[1]]Waldorf, R. A. (1993). Observations of eye movements related to vestibular and other neurological problems using the House infrared/Video ENG system. In I. K. Arenberg (Ed.), Dizziness and balance disorders: An interdisciplinary approach to diagnosis treatment and rehabilitation (pp. 277–281). New York: Kugler[[1]]
One old trick we used if we got no response to caloric irrigation was to hold a large piece of dark-colored paper in front of the patient’s face, and ask them to open their eyes for a short period of time following the irrigation. The paper would cover their visual field. This would allow us to see the eye, but minimize the opportunities for the patient to visually fixate on a target and suppress any nystagmus.
Bottom line? No eye closure equals no Bell’s Phenomonom and one less chance for artifact. The winner? VNG by a mile.
Photo courtesy of: https://bigstory.ap.org/article/ap-photos-brazil-fans-shock-after-7-1-loss
