Conditions 

Motor neuron disease

Motor neuron disease (MND) is an uncommon condition that affects the brain and nerves. It causes weakness that gets worse over time.

There’s no cure for MND, but there are treatments to help reduce the impact it has on a person’s daily life. Some people live with the condition for many years.

MND can significantly shorten life expectancy and, unfortunately, eventually leads to death.

Motor neurons in the brain and spinal cord send electrical messages from the brain to the muscles to move the arms, legs, trunk, neck, and head. As motor neurons degenerate, the muscles do not work properly and gradually weaken and waste away. This muscle weakness and wasting affects speech, swallowing, movement, and breathing.

There are different forms of motor neuron disease. The three main forms are amyotrophic lateral sclerosis (ALS), progressive muscular atrophy (PMA), and progressive bulbar palsy (PBP). Each form is named according to the pattern of symptoms it presents. The most common form is ALS (also known as Lou Gehrig’s disease). A fourth form of the disease, primary lateral sclerosis (PLS), is rare and often only provisionally diagnosed.

Most cases of motor neuron disease occur randomly, with no known cause. However, 5–10% of people will have a family history of the disease, suggesting a genetic link in those cases.

Motor neuron disease is most commonly diagnosed in those over the age of 40 years, occurring mainly in those aged between 50 and 70 years. In some cases, though, symptoms can first appear in a person’s 20s.  Usually the onset of motor neuron disease is gradual but younger patients may show a more rapid progression. The average life expectancy is 2–4 years from diagnosis but some people succumb within a matter of months, while others live up to 20 years or (in rare cases) beyond.

Symptoms

Symptoms of motor neuron disease happen gradually and may not be obvious at first.

Early symptoms can include:

• weakness in your ankle or leg – you might trip, or find it harder to climb stairs
• slurred speech, which may develop into difficulty swallowing some foods
• a weak grip – you might drop things, or find it hard to open jars or do up buttons
• muscle cramps and twitches
• weight loss – your arms or leg muscles may have become thinner over time
• difficulty stopping yourself from crying or laughing in inappropriate situations

As the condition progresses, motor neuron disease sufferers may not be able to:

• Walk
• Use their hands and arms
• Speak clearly, or at all
• Swallow
• Hold up their head

Weakness of the respiratory muscles makes breathing and coughing difficult. Difficulty swallowing makes it more likely that food or saliva will be inhaled into the lungs. This increases the risk of infection in the lungs, which is often the cause of death for people with motor neuron disease.

Pain may be experienced. Musculoskeletal pain, pressure associated with immobility and muscle cramps are the most common causes of pain.  Motor neuron disease does not affect touch, sight, smell, hearing, or intellect.

Diagnosis

There is no specific test for motor neuron disease and it may be difficult to diagnose in the early stages.  Diagnosis relies on a complete medical history and physical examination, as well diagnostic tests.

A common test used in the diagnostic process is an electromyogram (EMG) which is an electrical test of muscle function. Another common test is a nerve conduction study (NCS) which assesses a nerve’s ability to send a signal.  Other tests that may be used to assist with the diagnosis and rule out other causes for the symptoms include blood tests and magnetic resonance imaging (MRI) scans