Nystagmus

Original Editor - Lucinda hasmpton

Top Contributors - Lucinda hampton, Kim Jackson, Alyssa Brooks-Wells and Uchechukwu Chukwuemeka  

Introduction

Nystagmus refers to rapid involuntary movements that may cause one or both eyes to move from side to side, up and down, or around in circles. The nystagmus may be defined by the type of movement observed:

• Jerk nystagmus: a slow beat in one direction and a fast beat in the other
• Pendular nystagmus: the same speed and amplitude in both directions
• Rotary nystagmus: rotational beat on the Z-Axis

These movements can reduce vision, and affect depth perception, balance, and coordination

Some underlying conditions which cause nystagmus can be treated, especially childhood cataracts and strabismus and there are therapies for some neurological conditions and otologic conditions.

Etiology

Nystagmus is caused by an abnormal function in the areas of the brain that control eye movements and/or its connection with the vestibular system. Nystagmus may be either present at birth or develop later in life.

• Infantile nystagmus usually develops by three months of age. It is characterized by a horizontal movement and has correlations with conditions such as albinism, congenital iris absence, underdeveloped optic nerves, or congenital cataracts. Children 6 months to 3 years of age can have a form of nystagmus known as spasmus nutans. This form usually improves without intervention between ages 2 through 8 years. Characteristically, children will often nod or tilt their heads with this type of nystagmus, and the eyes may move in any direction.
• Acquired nystagmus may develop later in life, and requires exploration for its cause. Some examples of causes include:
  • External factors: alcohol, drugs (especially sedatives), head injury
  • Inner ear pathologies: labyrinthitis, Meniere's disease, vestibular neuritis, BPPV
  • Deficiencies: thiamine deficiency, vitamin B12 deficiency
  • Central nervous system pathologies affecting the brain's control of the eyes: a tumor, multiple sclerosis

Clinical Presentation

Symptoms may include:

• Blurred or jumpy vision
  • Oscillopsia: the illusory sensation that with head movement the stationary visual world is moving
• Dizziness
  • Vertigo: a type of dizziness that is often described as feeling that you are spinning or that the world is spinning around you
• Loss of balance
• Abnormal head posture -Some people find that their eye movements reduce in certain positions, and they may move their head to maintain this position. This can result in neck and shoulder problems.

Diagnosis

• When nystagmus is a new symptom and occurs with new dizziness or vertigo, the patient should get prompt medical attention.

• People experiencing pendular nystagmus for the first time should see a neurologist or neuro-ophthalmologist. Although it is not typically an emergency, pendular nystagmus should be assessed promptly.
• Depending on associated symptoms, the medical practitioner may:
  • Order tests such as a brain MRI or blood tests to rule out a potentially dangerous cause e.g. stroke
  • Perform an ocular exam
  • Perform a vestibular exam
• The type and direction of the nystagmus may be indicative of the cause and help to diagnose individuals

Treatment

• Canalith Repositioning Maneuvers - if testing is positive for BPPV, repositioning maneuvers for the affected canal can be used by a trained practitioner to treat nystagmus and vertigo
• Vestibular Rehabilitation Therapy (VRT) - if testing is positive for vestibulopathy or inner ear pathology, VRT may be used to help restore balance and vision through central compensation
• Surgery - In rare cases eye muscle surgery can be performed which reduces the extent of the eye movement
• Null point training - Vision may be improved through null point training, where an eye care professional works with the person to train their eyes in the direction where vision is the clearest
• Magnifier - the use of a magnifier will enlarge print which can make it easier to read.
• Postural - changes can be made to allow for viewing positions that reduce the nystagmus. e.g. bringing reading material closer.
• Medications - various drugs are being used to manage the condition. Botulinum toxin injections have been shown to help some people with the acquired form of nystagmus (not usually effective in people with congenital nystagmus). The drugs gabapentin, baclofen and memantine have also proved to have some success at reducing the effects of acquired nystagmus in some people and they are also being trialed for people with congenital nystagmus. They do not work for everyone and can have unpleasant side effects.
• Various alternative therapies have been tried by people with nystagmus and, although there is no robust clinical or scientific evidence that they work, some people say they have led to improved vision.
  • These include vision therapy, acupuncture, cranial osteopathy, and Alexander Technique.
  • Relaxation techniques, meditation, Yoga, Pilates, and/or Tai Chi can help indirectly by reducing stress and helping people to stay calm. It has been found that, with both congenital and acquired nystagmus, the calmer and more rested a person is, the less the impact of their nystagmus on their sight and general well-being. People with acquired nystagmus also find that the worst effects of oscillopsia are alleviated if they are free from anxiety, fatigue and stress.