What Are the Causes of Horizontal Nystagmus?

Nystagmus is the involuntary movement of the eye in a rhythmic motion. The specific direction of eye movement, whether horizontal (side to side), vertical (up and down) or oscillating (circular), is not indicative of the cause. For the person suffering from nystagmus, the eyes feel as though they are bouncing or wobbling. Episodes of nystagmus can last anywhere from 30 seconds to several minutes, and in severe cases nystagmus is constant. During nystagmus, the sufferer cannot maintain a steady gaze.

Congenital

• Nystagmus that begins during infancy, through six months of age, is referred to as early-onset nystagmus or congenital nystagmus. It is typically an inherited trait that results from a neurological dysfunction or an optical condition. Congenital nystagmus is usually mild and does not worsen as the child gets older.

Neurological Diseases

• Voluntary eye movement is controlled by the brain. The brain sends signals to the optic nerve via the central nervous system (CNS). Involuntary eye movements can occur when the nerves in the body are diseased. The signals traveling along the optic nerve are altered and, as a result, eyes can move involuntarily. Multiple Sclerosis is one disease that affects the CNS. Nystagmus is a very common symptom of MS. Other diseases of the CNS that are marked with nystagmus as a common symptom include Schindler Disease and Friedreich's Ataxia. Also, brain tumors involving the part of the brain responsible for dictating eye movement can cause nystagmus.

Vestibular Disorders

• The vestibular system is what controls the balance in the body. The vestibulo-ocular reflex is responsible for the reflexive eye movements in response to signals from the non-auditory parts of the inner ear as movement is sensed. When the inner ear is disturbed or damaged, reflexive eye movements are affected as though the body were moving, even when it is still.

  Disorders of the vestibular system that cause nystagmus generally have vertigo as a major symptom and include labyrinthitis, Meniere's disease and benign paroxysmal positional vertigo (BPPV). Labyrinthitis is the inflammation of the inner ear canal. It can be caused by a viral or bacterial infection that occurs after a cold, flu or middle ear infection. Meniere's disease occurs when the fluid-filled sacs within the inner ear become swollen. BPPV is the most common vertigo-inducing disorder. Its cause is oftentimes unknown and episodes are dependent on the position of the head.

Other Causes

• Other conditions responsible for causing nystagmus include head injuries from car accidents and strokes that cause blood vessel blockage in the brain.