The development of “miners’ nystagmus” in an individual who had lived in complete darkness for at least 2 years because of migraine is believed to be the first modern-day report of the condition and suggests that previous descriptions of the disorder were probably genuine.
In the current case report, the patient was found to have physiologic changes in the brain as well as severe eye oscillations after living in the dark for several years because of photophobia associated with migraine. These effects resolved after treatment with gradually increasing exposure to light.
The authors say this demonstrates the extent to which neuroplastic and perfusion changes in the visual pathways are reversible even when exposed to extremes of physiology.
“These findings demonstrate the remarkable plasticity of the brain and show how neural pathways can recover even after many years of not being used. This could have implications for other conditions in which some area of brain function is lost, for example, after a stroke,” coauthor Diego Kaski, MBBS, PhD, told Medscape Medical News.
The case is described in a letter to the Annals of Internal Medicine published online on February 23.
Kaski, a consultant neurologist at the National Hospital for Neurology and Neurosurgery, London, United Kingdom, explained that miners’ nystagmus, characterized by irregular eye oscillation, was reported by miners in the 1800s after they had spent years working underground, but it was not considered to be a real disease.
“It was believed the miners were making it up to get compensation, so it has not been included in medical textbooks,” he noted.
The current case report describes a 57-year-old woman who reported having persistent and severe daily throbbing migraine headaches over a period of years. The migraines were associated with motion sensitivity and severe phonophobia and photophobia. The photophobia led her to live in complete darkness; her home was totally blacked out, and only a small camping light set to nocturnal settings was used for illumination in the bathroom. She wore a mask over her eyes when she ventured outside.
The patient was referred to Kaski and colleagues after developing gradual-onset oscillopsia (jumping vision) associated with the appearance of a halo around objects. Videonystagmography conducted in the dark revealed binocular pendular torsional nystagmus in the primary position with occasional rapid upbeat jerk nystagmus. “Our results showed extreme and violent shaking of the eyes,” Kaski said.
A structural MRI of the brain was normal, but perfusion imaging hinted at abnormal blood flow in the occipital cortex, likely as a consequence of the visual deprivation, which was due in turn to pathology of anterior visual pathways, the authors state.
“The lack of light induces abnormal eye oscillation,” Kaski elaborated. “For visual pathways to work properly, the brain needs some feedback from the eyes ― it needs light to process the image. Without light, the visual pathways become unstable, and the eyes start to oscillate.”
The patient’s migraines were eventually successfully treated with botulinum toxin injections, intravenous magnesium sulphate, and some psychological input. The nystagmus was addressed with a program of gradually increasing exposure to light using dimmer switches and a lux monitor.
By week 5, she was able to tolerate 1 lux for 8 hours a day, and by week 13, she could tolerate 50 lux for 12 consecutive hours a day. Her nystagmus and oscillopsia resolved completely by 8 months, the authors report.
“The gradual exposure to light allowed her visual pathways to revive,” Kaski said. “This was a very dramatic journey. The patient’s extreme behavior of living completely in the dark caused the visual pathways to stop working. But these pathways are obviously plastic enough to remold themselves and return to normal once exposed to light again.”
He added: “We have never come across this phenomenon before, and the diagnosis and treatment of this patient involved experts from several different fields, including an eye specialist, a psychologist, and myself, a neurologist with special interest in eye movements.”
Kaski says the case is particularly interesting from a human perspective. It shows how particular symptoms can lead patients to extremes of behavior; in this situation, the patient’s symptoms pushed the visual physiology over its limits. It also demonstrates the remarkable plasticity of the brain even under such extreme circumstances.
“We saw physiological changes in the brain ― at the worst stages of nystagmus, the blood flow was reduced to the area where vision is processed, and this returned to normal when the patient became tolerant of light again,” he commented.
Ann Intern Med. Published online February 23, 2021. Abstract