Motor Neuron Disease (MND)

Motor neuron disease (MND) is a group of neurological disorders that gradually destroy your motor neurons. Your motor neurons are nerve cells that control muscle movement involved in activities like breathing, speaking, swallowing and walking.

Messages from neurons in your brain (upper motor neurons) are usually transmitted to neurons in your spinal cord (lower motor neurons). From there, they move to the muscles in your body. Your upper motor neurons tell your lower motor neurons to produce muscle movements.

When your muscles can’t receive these messages from your lower motor neurons, they begin to weaken and shrink in size (muscle atrophy). When your lower motor neurons can’t receive signals from your upper motor neurons, it can cause muscle stiffness and overactive reflexes (hyperreflexia). This can make voluntary movements difficult and slow. Over time, you may lose the ability to walk and control other movements.

There’s no cure for motor neuron diseases. They’re progressive diseases that get worse over time. But there are treatments available that can help reduce the impact the condition has on your life.

Motor neuron disease types

Healthcare providers classify MNDs by whether they affect your upper motor neurons, lower motor neurons or both. MND disease types include:

Amyotrophic lateral sclerosis (ALS)

Amyotrophic lateral sclerosis (ALS) is the most common MND. It affects both your upper and lower motor neurons. Also known as Lou Gehrig’s disease, ALS causes rapid loss of muscle control and eventually paralysis. Many healthcare providers use the terms ALS and motor neuron disease interchangeably.

Progressive bulbar palsy (PBP)

Progressive bulbar palsy (PBP) attacks the lower motor neurons connected to your brainstem. Your brainstem (bulbar region) controls the muscles you need for speaking, chewing, swallowing and other functions. Another name for PBP is progressive bulbar atrophy.

Primary lateral sclerosis (PLS)

Primary lateral sclerosis (PLS) affects only your upper motor neurons. The disorder frequently affects your legs first. Then, it affects your arms, hands and torso. Finally, it affects the muscles you use for speaking, swallowing and chewing.

Progressive muscular atrophy (PMA)

Progressive muscular atrophy (PMA) only affects your lower motor neurons. The condition mostly affects males, and typically at a younger age than most other adult-onset MNDs. Weakness in your hands is usually the first symptom, and then it spreads to your lower body. It can also affect your torso and breathing.

Spinal muscular atrophy (SMA)

Spinal muscular atrophy (SMA) is an inherited condition that affects your lower motor neurons. It’s the most common genetic cause of infant death. Changes in the SMN1 gene cause a loss of the SMN protein. This loss slowly destroys the lower motor neurons, producing muscle wasting and weakness that eventually leads to death.

Kennedy’s disease

Kennedy’s disease is related to a gene on the X chromosome in males. Changes in the gene for the androgen receptor cause the disease. Over time, people develop weakness in their arms and legs, often starting in their pelvic or shoulder regions. They may also develop pain and numbness in their hands and feet.

Post-polio syndrome (PPS)

Post-polio syndrome (PPS) affects polio survivors up to four decades after they’ve recovered from their initial illness, which can cause major damage to motor neurons. Symptoms include muscle and joint weakness, fatigue, pain that gradually gets worse over time, muscle twitches and atrophy, and intolerance to cold.

Motor neuron disease symptoms

MND symptoms occur gradually and may not be obvious at first. Early MND symptoms may include:

• Weakness in your legs or ankles that makes it harder to climb up stairs, or causes you to trip often
• Slurred speech (dysarthria)
• Difficulty swallowing
• Weakened grip that makes it hard to button a shirt or open a jar, or you may drop things easily
• Muscle twitches and cramps
• Weight loss due to your arms and legs getting thinner over time
• Trouble stopping yourself from laughing or crying in inappropriate situations (pseudobulbar affect)

Other MND symptoms may include:

• Breathlessness
• Trouble breathing that occurs when lying down
• Repeated (recurrent) chest infections
• Disturbed sleep
• Poor concentration and/or memory
• Confusion
• Morning headaches
• Fatigue

Causes of MND

Problems with your motor neurons cause motor neuron diseases. These cells slowly stop functioning properly over time. Researchers don’t know why this occurs.

Some cases of MND are inherited, meaning they’re passed on through biological families. In these cases, a single genetic change causes the condition. They’re usually inherited in one of several ways:

• Autosomal dominant means that you only need one copy of a changed gene from one biological parent with the disorder to be at risk of the disease.
• Autosomal recessive means that you must inherit one copy of the changed gene from each parent to be at risk of the disease.
• X-linked inheritance means a female parent carries the gene on one X chromosome and passes the disorder along to male children.

In non-inherited cases, different factors may play a role in the development of MND. These include viral, toxic, genetic and/or environmental factors.

Risk factors

MND most commonly affects people in their 60s and 70s, but it may also affect children and adults of all ages. You’re more likely to develop an MND if you have a close relative with the condition or a close relative with a related condition called frontotemporal dementia.

How doctors diagnose MND

An MND diagnosis can be difficult to make in the early stages. There’s no single test for the conditions. Your healthcare provider may suspect MND if you have progressive muscle weakness without pain or loss of sensation. They may ask you questions, like:

• Which body parts are affected?
• When did your symptoms start?
• Which symptoms appeared first?
• Have the symptoms changed over time?

Your provider may request several tests to help make a diagnosis. These may include:

• Electromyography (EMG). Electromyography records electrical activity in your muscles. It can help determine if the problem is in your muscles, nerves or neuromuscular junction.
• Nerve conduction studies. Nerve conduction studies measure how fast nerves transmit impulses.
• Magnetic resonance imaging (MRI) scan. A brain MRI and sometimes spinal cord MRI can check for abnormalities that may cause similar symptoms.

To help rule out other conditions, your healthcare provider may request additional tests, including:

• Blood tests
• Urine tests
• Spinal tap (lumbar puncture)
• Genetic tests

Over time, MND causes symptoms that are so characteristic that the diagnosis is obvious without any testing.

How is motor neuron disease treated?

There’s no specific cure or treatment for motor neuron disease. But researchers continue to study safe and effective options to treat the condition.

You may work with a team of healthcare providers to help you manage the symptoms of the disease. Motor neuron disease treatment may include physical therapy to help you maintain your muscle strength and keep your joints flexible.

If you have swallowing difficulties, you may receive nutrition through a tube inserted through your abdominal wall into your stomach (gastrostomy tube).

Many people with MND find relief from their symptoms by taking certain medications, including:

• Baclofen, to help make muscles less tight and reduce muscle spasms
• Phenytoin or quinine, to help decrease muscle cramps
• Glycopyrrolate, to reduce drooling
• Antidepressants, to help with depression
• Benzodiazepines, to help with pain as the disease progresses

In people with ALS, a couple of medications can help prolong life and slow the decline in function, including riluzole and edaravone.

Many people also participate in clinical trials.

When should I see my healthcare provider?

You should see a healthcare provider if you have possible early signs of MND, like muscle weakness. You may not have MND, but it’s important to get a correct diagnosis as early as possible to help get you the care and support you need.

You may also want to see a provider if you have a close relative with MND or frontotemporal dementia and you’re worried you may be at risk of the disease. Your provider may refer you to a genetic counselor to talk about your risk.

What can I expect if I have this condition?

Motor neuron diseases are progressive diseases that get worse over time. It’s important that you find a healthcare provider who fully understands your condition. They can help you find appropriate treatment to help you manage your disease.

It’s also important to have a support system in place. As your condition progresses, you’ll find that you need help with more and more tasks that become difficult to do. Reach out to friends or loved ones, or ask your provider if they can provide resources for you to get support from your community. Remember, you’re not alone.

What is the life expectancy of a person with motor neuron disease?

Unfortunately, motor neuron diseases significantly shorten your life expectancy. They’re progressive diseases that’ll eventually lead to death. But how long it takes to reach that stage varies. Some people live for a few years or even decades before passing away from the effects of the diseases. Your healthcare provider can help you better understand the specifics of your prognosis (outlook).