Leigh Syndrome—Degenerative Nerve Diseases

Also called: Neurodegenerative diseases

Degenerative nerve diseases affect many of your body’s activities, such as balance, movement, talking, breathing, and heart function. Many of these diseases are genetic. Sometimes the cause is a medical condition such as alcoholism, a tumor, or a stroke. Other causes may include toxins, chemicals, and viruses. Sometimes the cause is not known.

Degenerative nerve diseases include

• Alzheimer’s disease
• Amyotrophic lateral sclerosis
• Friedreich’s ataxia
• Huntington’s disease
• Lewy body disease
• Parkinson’s disease
• Spinal muscular atrophy

Degenerative nerve diseases can be serious or life-threatening. It depends on the type. Most of them have no cure. Treatments may help improve symptoms, relieve pain, and increase mobility.

• Multiple system atrophy (Medical Encyclopedia)
• Progressive multifocal leukoencephalopathy (Medical Encyclopedia)

Leigh syndrome is a severe neurological disorder that usually becomes apparent in the first year of life. This condition is characterized by progressive loss of mental and movement abilities (psychomotor regression) and typically results in death within two to three years, usually due to respiratory failure. A small number of individuals do not develop symptoms until adulthood or have symptoms that worsen more slowly.The first signs of Leigh syndrome seen in infancy are usually vomiting, diarrhea, and difficulty swallowing (dysphagia), which disrupts eating. These problems often result in an inability to grow and gain weight at the expected rate (failure to thrive). Severe muscle and movement problems are common in Leigh syndrome. Affected individuals may develop weak muscle tone (hypotonia), involuntary muscle contractions (dystonia), and problems with movement and balance (ataxia). Loss of sensation and weakness in the limbs (peripheral neuropathy), common in people with Leigh syndrome, may also make movement difficult.Several other features may occur in people with Leigh syndrome. Many individuals with this condition develop weakness or paralysis of the muscles that move the eyes (ophthalmoparesis); rapid, involuntary eye movements (nystagmus); or degeneration of the nerves that carry information from the eyes to the brain (optic atrophy). Severe breathing problems are common, and these problems can worsen until they cause acute respiratory failure. Some affected individuals develop hypertrophic cardiomyopathy, which is a thickening of the heart muscle that forces the heart to work harder to pump blood. In addition, a substance called lactate can build up in the body, and excessive amounts are often found in the blood, urine, or the fluid that surrounds and protects the brain and spinal cord (cerebrospinal fluid) of people with Leigh syndrome.The signs and symptoms of Leigh syndrome are caused in part by patches of damaged tissue (lesions) that develop in the brains of people with this condition. A medical procedure called magnetic resonance imaging (MRI) reveals characteristic lesions in certain regions of the brain. These regions include the basal ganglia, which help control movement; the cerebellum, which controls the ability to balance and coordinates movement; and the brainstem, which connects the brain to the spinal cord and controls functions such as swallowing and breathing. The brain lesions are often accompanied by loss of the myelin coating around nerves (demyelination), which reduces the ability of the nerves to activate muscles used for movement or relay sensory information from the rest of the body back to the brain.