Downbeat Nystagmus Causes

Nystagmus is an eye disorder characterized by periodic involuntary movement of the eyes. Downbeat refers to one particular type of the disorder; the eyes move downward in the first phase. The first phase is generally the most intense stage of the condition. Nystagmus, and downbeat in particular, results from several causes that affect the process by which humans control their eyes.

Arnold-Chiari Malformation

• Arnold-Chiari malformation is seen as a cause of downbeat nystagmus. It is a structural defect in the cerebellum, the part of the brain that controls balance. Skull formation was smaller than normal and did not provide enough space for the cerebellum, causing it to be pushed down under pressure. This pressure causes headaches, dizziness, numbness, balance problems and vision problems. Downbeat nystagmus appears for some people with the condition. Surgery to correct the malformation is the only option available for downbeat nystagmus. Medications only treat symptoms like headaches, not the vision problems.

Lesions of the Cerebellum

• Lesions in the area of the cerebellum that control balance cause downbeat nystagmus. Those lesions are the result of a trauma, stroke, multiple sclerosis, brain stem encephalitis and tumors, according to Medscape Reference. Lesions also result from alcohol abuse and anti-seizure medications.

Heat Stroke

• Heat stroke results from the elevation of the body's temperature, or hypothermia, up to 106 degrees Fahrenheit. It occurs generally on very hot days after exercise in the sun when the body is unable to keep itself cool by sweating. It is considered to be a medical emergency causing physical and neurological problems, including vision disorders like dizziness, hallucinations and downbeat nystagmus. Seek medical treatment immediately to lower the body temperature.

Drugs and Nutrition

• Two causes of downbeat nystagmus are the drug lithium and magnesium deficiency. A hypomagnesemic patient developed downbeat nystagmus while taking lithium carbonate for depression, according to an article in the "Neurology Journal." No other cause is identified for the nystagmus. Whenever the lithium was stopped, the nystagmus disappeared. Blood testing revealed that lithium levels were not in the toxic range. The article concluded that the magnesium deficiency may have enhanced the effects of lithium, thus causing downbeat nystagmus. Besides magnesium, another nutritional deficiency that causes the condition is insufficient vitamin B12.

Caudal Brain Stem Compression

• Caudal brain stem compression caused by the vetebral artery, one of the main arteries supplying blood to the brain, was identified as a cause of downbeat nystagmus, according to an article in the "Journal of Neuro-Ophthalmology." This cause was revealed as a result of magnetic resonance imaging of the head.