Motor Neurone Diseases (MND)
- Article
- 2021-03-21
Motor neuron diseases (MNDs) are a group of progressive neurological disorders that destroy cells that control essential muscle activity, such as speaking, walking, breathing, and swallowing. Normally, messages from nerve cells in the brain (called the upper motor neurons) are transferred to nerve cells in the brain stem and spinal cord (called the lower motor neurons) and from them to certain muscles. When these signals are disrupted, it can result in gradual muscle weakening, withering away, and uncontrollable twitching (called fasciculations). Ultimately, the ability to control voluntary movement can be lost. MNDs can be inherited or acquired, and they occur in all age groups. MND is more common in men than women, and symptoms can appear after the age of 40. In children, especially in hereditary or familial forms of the disease, symptoms may be present at birth or appear before the child learns to walk.
The causes of sporadic (non-hereditary) MNDs are unknown, but ecological, toxic, viral, or genetic factors may be involved. Common MNDs include amyotrophic lateral sclerosis (ALS), progressive bulbar palsy, primary lateral sclerosis, and progressive muscle atrophy. Other MNDs include the many hereditary forms of spinal muscle atrophy and post-polio syndrome, a condition that can affect polio survivors decades after recovering from poliomyelitis.
Therapy
There is no cure or standard treatment for the MNDs. Symptomatic and supportive treatment can help patients feel more comfortable while maintaining their quality of life. The drug riluzole (Rilutek®), which is approved by the United States Food and Drug Administration (FDA) to treat ALS, extends lifespan by 2-3 months, but does not relieve symptoms. The FDA has also approved the use of edarvarone to reduce clinical deterioration in ALS. Other drugs that can help reduce symptoms include muscle relaxants such as baclofen, tizanidine and the benzodiazepines for spasticity; glycopyrrolate and atropine to treat excessive saliva; and anticonvulsants and non-steroidal anti-inflammatory drugs to relieve pain. Panic attacks can be treated with benzodiazepines.
The FDA has approved nusinersen (Spinraza ™) as the first drug approved for the treatment of children and adults with spinal muscle atrophy. The drug is administered by intrathecal injection into the fluid surrounding the spinal cord. It is designed to increase the production of the full-length SMN protein, which is crucial for motor neuron maintenance.
Physical therapy and speech therapy, occupational therapy and rehabilitation can help improve posture, prevent joint arrest, slow muscle weakness and atrophy, and cope with swallowing difficulties. Applying heat can relieve muscle pain. Aids such as supports or braces, orthoses, speech synthesizers and wheelchairs help some patients to remain independent. Proper nutrition and a balanced diet are essential to maintain weight and strength.
Prognosis
Prognosis varies depending on the type of MND and age of onset. Some MNDs, such as primary lateral sclerosis and Kennedy disease, are not fatal and are slow to progress. Patients with spinal muscle atrophy may appear stable for long periods, but improvement is not expected. Some MNDs, such as ALS and some forms of spinal muscle atrophy, are deadly.
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