Motor Neuron Disease is any of several neurodegenerative disorders that selectively affect motor neurons, the cells that control voluntary muscles of the body. A group of related diseases of the nervous system that are characterized by steadily progressive deterioration of the motor neurons in the brain, brain stem, and spinal cord. Abbreviated MND. Motor neurons are the nerve cells along which the brain sends instructions, in the form of electrical impulses, to the muscles. The degeneration of motor neurons leads to weakness and wasting of muscles. MND usually first affects the arms or legs. Then shoulders and other muscles may be affected. Weakness and wasting in the muscles of the face and throat may cause problems with speech, chewing, and swallowing. MND does not affect touch, taste, sight, smell, or hearing, nor does it directly affect bladder, bowel, or sexual function.
Types of Motor Neuron Disease
Amyotrophic lateral sclerosis (ALS)
Primary lateral sclerosis (PLS)
Hereditary spastic paraparesis (HSP)
Progressive bulbar palsy (PBP), including hereditary forms
Spinal muscular atrophy (SMA)
X-linked spinobulbar muscular atrophy (SBMA; Kennedy disease)
Postpolio syndrome (PPS)
Progressive muscular atrophy (PMA),
progressive bulbar palsy (PBP)
|Type||UMN degeneration||LMN degeneration|
|Amyotrophic lateral sclerosis (ALS)||Yes||Yes|
|Hereditary spastic paraplegia (HSP)||Yes||No|
|Primary lateral sclerosis (PLS)||Yes||No|
|Progressive muscular atrophy (PMA)||No||Yes|
|Progressive bulbar palsy (PBP)||No||Yes, bulbar region|
|Pseudobulbar palsy||Yes, bulbar region||No|
What are the symptoms of motor neuron diseases
A brief description of the symptoms of some of the more common MNDs follows.
Amyotrophic lateral sclerosis (ALS),
It is also called Lou Gehrig’s disease or classical motor neuron disease, is a progressive, ultimately fatal disorder that disrupts signals to all voluntary muscles. Many doctors use the terms motor neuron disease and ALS interchangeably. Both upper and lower motor neurons are affected. Symptoms are usually noticed first in the arms and hands, legs, or swallowing muscles. Approximately 75 percent of people with classic ALS will develop weakness and wasting of the bulbar muscles (muscles that control speech, swallowing, and chewing). Muscle weakness and atrophy occur on both sides of the body. Affected individuals lose strength and the ability to move their arms and legs, and to hold the body upright. Other symptoms include spasticity, spasms, muscle cramps, and fasciculations. Speech can become slurred or nasal. When muscles of the diaphragm and chest wall fail to function properly, individuals lose the ability to breathe without mechanical support.
Progressive bulbar palsy,
also called progressive bulbar atrophy, involves the brain stem—the bulb-shaped region containing lower motor neurons needed for swallowing, speaking, chewing, and other functions. Symptoms include pharyngeal muscle weakness (involved with swallowing), weak jaw and facial muscles, progressive loss of speech, and tongue muscle atrophy. Limb weakness with both lower and upper motor neuron signs is almost always evident but less prominent. Individuals are at increased risk of choking and aspiration pneumonia, which is caused by the passage of liquids and food through the vocal folds and into the lower airways and lungs. Affected persons have outbursts of laughing or crying (called emotional lability). Stroke and myasthenia gravis may have certain symptoms that are similar to those of progressive bulbar palsy and must be ruled out prior to diagnosing this disorder.
which shares many symptoms of progressive bulbar palsy, is characterized by degeneration of upper motor neurons that transmit signals to the lower motor neurons in the brain stem. Affected individuals have progressive loss of the ability to speak, chew, and swallow. Progressive weakness in facial muscles leads to an expressionless face. Individuals may develop a gravelly voice and an increased gag reflex. The tongue may become immobile and unable to protrude from the mouth. Individuals may have outbursts of laughing or crying.
Primary lateral sclerosis (PLS)
It affects the upper motor neurons of the arms, legs, and face. It occurs when specific nerve cells in the motor regions of the cerebral cortex (the thin layer of cells covering the brain which is responsible for most high-level brain functions) gradually degenerate, causing the movements to be slow and effortful. The disorder often affects the legs first, followed by the body trunk, arms and hands, and, finally, the bulbar muscles. Speech may become slowed and slurred. When affected, the legs and arms become stiff, clumsy, slow and weak, leading to an inability to walk or carry out tasks requiring fine hand coordination. Difficulty with balance may lead to falls. Speech may become slow and slurred.
Progressive muscular atrophy
It is marked by slow but progressive degeneration of only the lower motor neurons. It largely affects men, with onset earlier than in other MNDs. Weakness is typically seen first in the hands and then spreads into the lower body, where it can be severe. Other symptoms may include muscle wasting, clumsy hand movements, fasciculations, and muscle cramps. The trunk muscles and respiration may become affected. Exposure to cold can worsen symptoms. The disease develops into ALS in many instances.
Spinal muscular atrophy (SMA)
It is a hereditary disease affecting the lower motor neurons. It is an autosomal recessive disorder caused by defects in the gene SMN1, which makes a protein that is important for the survival of motor neurons (SMN protein). In SMA, insufficient levels of the SMN protein lead to degeneration of the lower motor neurons, producing weakness and wasting of the skeletal muscles.
SMA type I, also called Werdnig-Hoffmann disease,
It is evident by the time a child is 6 months old. Symptoms may include hypotonia (severely reduced muscle tone), diminished limb movements, lack of tendon reflexes, fasciculations, tremors, swallowing and feeding difficulties, and impaired breathing. Some children also develop scoliosis (curvature of the spine) or other skeletal abnormalities. Affected children never sit or stand and the vast majority usually die of respiratory failure before the age of 2. However, the survival in individuals with SMA type I has increased in recent years, in relation to the growing trend toward more proactive clinical care.
Symptoms of SMA type II,
The intermediate form, usually begin between 6 and 18 months of age. Children may be able to sit but are unable to stand or walk unaided, and may have respiratory difficulties. The progression of disease is variable. Life expectancy is reduced but some individuals live into adolescence or young adulthood.
Symptoms of SMA type III (Kugelberg-Welander disease)
appear between 2 and 17 years of age and include abnormal gait; difficulty running, climbing steps, or rising from a chair; and a fine tremor of the fingers. The lower extremities are most often affected. Complications include scoliosis and joint contractures—chronic shortening of muscles or tendons around joints, caused by abnormal muscle tone and weakness, which prevents the joints from moving freely. Individuals with SMA type III may be prone to respiratory infections, but with care may have a normal lifespan.
Congenital SMA with arthrogryposis
(persistent contracture of joints with fixed abnormal posture of the limb) is a rare disorder. Manifestations include severe contractures, scoliosis, chest deformity, respiratory problems, unusually small jaws, and drooping of the upper eyelids.
Kennedy’s disease, also known as progressive spinobulbar muscular atrophy,
It is an X-linked recessive disease caused by mutations in the gene for the androgen receptor. Daughters of individuals with Kennedy’s disease are carriers and have a 50 percent chance of having a son affected with the disease. The onset of symptoms is variable and the disease may first be recognized between 15 and 60 years of age. Symptoms include weakness and atrophy of the facial, jaw, and tongue muscles, leading to problems with chewing, swallowing, and changes in speech. Early symptoms may include muscle pain and fatigue. Weakness in arm and leg muscles closest to the trunk of the body develops over time, with muscle atrophy and fasciculations.
Post-polio syndrome (PPS)
It is a condition that can strike polio survivors decades after their recovery from poliomyelitis. Polio is an acute viral disease that destroys motor neurons. Many people who are affected early in life recover and develop new symptoms many decades later. After acute polio, the surviving motor neurons expand the amount of muscle that each controls. PPS and Post-Polio Muscular Atrophy (PPMA) are thought to occur when the surviving motor neurons are lost in the aging process or through injury or illness. Many scientists believe PPS is latent weakness among muscles previously affected by poliomyelitis and not a new MND.
Symptoms of Motor Neuron Disease
You may have some or all of the symptoms listed below
- Muscle weakness, with loss of muscle mass (wasting), and movement and mobility problems
- Muscle cramps and spasms, including rippling sensations (known as fasciculation)
- Stiff joints, which may limit range of movement
- Pain or discomfort, as a result of other symptoms (not usually caused by MND directly)
- Speech and communication problems – affecting how you speak, gesture and show expression
- Swallowing difficulties – affecting how you eat and drink
- Saliva problems, where thin saliva pools in the mouth or saliva becomes thick and sticky
- Weakened coughing – which makes it harder to clear the throat
- Breathing problems – which can lead to breathlessness and fatigue
- Emotional lability – with inappropriate emotional responses, such as laughing when feeling sad
- Changes to thinking and behaviour – for about half of those diagnosed with MND.
Avobe all MND can be divided into three stages, early, middle, and advanced.
Early stage signs and symptoms
Symptoms develop slowly and can be confused with symptoms of some other unrelated neurological conditions.
- a weakening grip, making it hard to pick up and hold things
- muscle pains, cramps, and twitches
- slurred and sometimes garbled speech
- weakness in the arms and legs
- increased clumsiness and stumbling
- difficulty swallowing
- trouble breathing or shortness of breath
Middle stage signs and symptoms
As the condition progresses, symptoms become more severe.
- Muscle pain and weakness increase, and spasms and twinges worsen.
- Limbs become progressively weaker.
- Limb muscles start to shrink.
- Movement in affected limbs becomes more difficult.
- Limb muscles may become abnormally stiff.
- Joint pain grows.
- Eating, drinking, and swallowing become harder.
- Drooling occurs, due to problems controlling saliva.
- Yawning occurs, sometimes in uncontrollable bouts.
- Jaw pain may result from excessive yawning.
- Speech problems worsen, as muscles in the throat and mouth become weaker.
Eventually, the patient will be unable to move, eat, or breathe without assistance. Without supportive care, an individual will pass away. Despite the best of care currently available, complications of the respiratory system are the most common causes of death.
Diagnosis of Motor Neuron Disease
- Blood tests – These analyses can rule out other conditions and detect any rise in creatinine kinase. This is produced when muscle breaks down, and it is sometimes be found in the blood of patients with MND.
- An electroencephalogram (EEG) – small electrodes are placed on your scalp, which pick up the electrical signals from your brain and show abnormal brain activity
- Lumbar puncture (spinal tap), this helps determine via a test using the cerebral-spinal fluid, obtained from the lumbar region.
- Spinal fluid analysis – By doing a lumbar puncture (also called a spinal tap), your doctor can check the spinal fluid for an increase in white blood cells and protein. The bacteria, virus, parasite, or fungus causing the encephalitis also may be found in the spinal fluid.
- Urine analysis
- Polymerase chain reaction (PCR) testing of the cerebrospinal fluid, to detect the presence of viral DNA which is a sign of viral encephalitis.
- Blood cultures identify bacteria in the blood – Bacteria can travel from the blood to the brain. N. meningitidis and S. pneumoniae can cause both sepsis and meningitis.
- A complete blood count – with differential is a general index of health. It checks the number of red and white blood cells in your blood. White blood cells fight infection. The count is usually elevated in meningitis.
- Cerebrospinal fluid (CSF) – CSF is the fluid that surrounds your brain and spinal cord. It helps to support and protect the brain and spinal cord from trauma.
- Chest X-rays – can reveal the presence of pneumonia, tuberculosis, or fungal infections. Meningitis can occur after pneumonia.
- A CT scan – of the head may show problems like a brain abscess or sinusitis. Bacteria can spread from the sinuses to the meninges.
- MRI brain scan – This cannot detect an MND, but it can help rule out other conditions, such as stroke, brain tumor, brain circulation problems, or abnormal brain structure.
- Electromyography (EMG) and nerve conduction study (NCS) – These are often performed together. An EMG tests the amount of electrical activity within muscles, while NCS tests the speed at which electricity moves through muscles.
- Muscle biopsy – If the doctor thinks the patient may have a muscle disease, rather than MND, a muscle biopsy may be performed.
- Nerve conduction tests apply an electrical impulse through a small pad on the skin. This measures the speed at which nerves carry electrical signals.
- Transcranial Magnetic Stimulation (TMS) – measures the activity of the upper motor neurones to help diagnosis.
Treatment of Motor Neuron Disease
Management of the condition will require input from a multi-disciplinary group of health professionals that may include:
- Family doctor and medical specialists (neurology, respiratory, sleep, gastroenterology)
- Occupational therapists
- Speech and language therapists
- Nurse specialists and district nurses
- Social workers
- Palliative care specialists and hospice care
- Sleep technologists
Muscle cramps and stiffness
Baclofen, a muscle relaxer, may reduce muscle stiffness. A small pump is surgically implanted outside the body and connected to the space around the spinal cord. A regular dose of baclofen is delivered into the nervous system.
Baclofen blocks some of the nerve signals that cause spasticity. It may help with extreme yawning.
Treatment for drooling
Scopolamine, a drug for motion sickness, may help control symptoms of drooling. It is worn as a patch behind the ear.
Uncontrolled laughter or crying
Patients with speech and communication difficulties may learn some useful techniques with a qualified speech and language therapist. As the disease advances, patients often need some communication aids.
Physical and occupational therapy can help maintain mobility and function, and reduce stress.
As eating and drinking become harder, the patient may need a percutaneous endoscopic gastrostomy (PEG), a feeding tube that is placed on the abdomen, a relatively minor procedure.
A non-steroidal anti-inflammatory drug (NSAID), such as ibuprofen, will help with mild to moderate pain from muscle cramping as spasms. Drugs such as morphine can help relieve severe joint and muscle pain in the advanced stages.
Respiratory muscles usually weaken gradually, but a sudden deterioration is possible.
Mechanical ventilation can help with breathing. A machine takes in air, filters it, and pumps it into the lungs often through a tracheostomy, a surgical hole in the neck that allows for assisted breathing.
Some people use complementary therapies, including special diets that are high in vitamins. These will not cure MND, but following a healthful diet can improve overall health and wellbeing.
Stem cell transplant for ALS treatment
Stem cell research and gene therapy have shown promise for treating ALS in the future, but more studies are needed.