Stroke And Motor Neuron Disease: Is There A Link?

Motor neuron disease (MND) is a group of rare neurodegenerative diseases that affect the motor neurons in the spine and brain, causing a loss of function over time. While the exact causes are unclear, it is known that MND can be caused by genetic, toxic, viral, and other environmental factors. MND typically affects movement, with early signs including weakness and slurred speech. But can a stroke cause motor neuron disease?

Upper and lower motor neurons

Motor neurons are nerve cells that send electrical signals to the muscles, allowing us to move, speak, swallow and breathe. They are divided into upper and lower motor neurons, which form a two-neuron circuit.

Upper Motor Neurons

Upper motor neurons originate in the cerebral cortex of the brain and travel down to the brain stem or spinal cord. They use glutamate as a neurotransmitter. Upper motor neurons are involved in voluntary motor responses, as these actions are backed by thoughts.

On a neurological examination, typical signs of an upper motor neuron lesion include:

• Minimal disuse atrophy or contractures
• Increased tone (spasticity or rigidity) +/- ankle clonus
• Pyramidal pattern of weakness (extensors weaker than flexors in arms, and vice versa in legs)
• Upgoing plantars (Babinski sign)

Lower Motor Neurons

Lower motor neurons begin in the spinal cord and innervate muscles and glands throughout the body. They use acetylcholine as a neurotransmitter. When complex motor operations are required, lower motor neurons consult upper motor neurons, and they work in union to provide a meaningful response.

On a neurological examination, typical signs of a lower motor neuron lesion include:

• Variable patterns of weakness
• Reduced or absent reflexes
• Downgoing plantars or absent response

Upper vs Lower Motor Neuron Lesions

Upper motor neuron lesions present with hypertonia and spastic paralysis, whereas lower motor neuron lesions are associated with hypotonia and flaccid paralysis. This is due to the impaired ability of motor neurons to regulate descending signals, resulting in disordered spinal reflexes.

Symptoms of motor neuron disease

Motor neuron disease (MND) is a rare condition that progressively damages parts of the nervous system, leading to muscle weakness and muscle wasting. While the symptoms of MND vary depending on the type and the area of the body it affects, there are some common symptoms that are seen across the different types.

Early-Stage Symptoms

In the early stages of MND, symptoms develop slowly and can often be mistaken for other health conditions. Some common early-stage symptoms include:

• Weak grip, making it hard to pick up and hold things
• Muscle pains, cramps, and twitches
• Weakness in the arms and legs
• Clumsiness and stumbling
• Difficulty swallowing
• Trouble breathing or shortness of breath
• Inappropriate emotional responses, such as laughing or crying
• Weight loss, as muscles lose their mass

Middle-Stage Symptoms

As the condition progresses, the early symptoms become more severe. People may also experience:

• Drooling due to problems with swallowing
• Uncontrollable yawning, which can lead to jaw pain
• Changes in personality and emotional states
• Difficulty breathing

Advanced-Stage Symptoms

In the advanced stages of MND, the disease can become life-threatening. Some common advanced-stage symptoms include:

• Needing help with moving, eating, and breathing
• Breathing problems, which are the most common cause of death in MND
• Increased physical disability, with many people developing generalised paralysis
• Loss of speech and difficulty swallowing
• Mild cognitive and behavioural changes

Other Symptoms

Other symptoms of MND that may occur at any stage include:

• Slurred speech
• Muscle wasting and weight loss
• Emotional lability, such as exaggerated responses to slight upsets
• Cognitive changes, including changes in thought processes
• Respiratory changes

Types of motor neuron disease

Motor neuron disease (MND) refers to a group of rare neurodegenerative diseases that affect motor nerves in the spine and brain, causing a loss of function over time. MND can appear at any age but usually affects people over 50 and is more common in males. While the exact causes are unclear, the National Institute of Neurological Diseases and Stroke reports that genetic, toxic, viral, and other environmental factors may play a role.

There are several types of MND, including:

Amyotrophic Lateral Sclerosis (ALS)

Also known as Lou Gehrig's disease, ALS is the most common type of MND. It affects both the upper and lower motor neurons, causing a rapid loss of muscle control and eventual paralysis. Most cases of ALS are sporadic, meaning anyone can get it, but around 5-10% of cases in the United States are hereditary. On average, people with ALS live for 3-5 years after diagnosis, but some can live for 10 years or longer with supportive care.

Primary Lateral Sclerosis (PLS)

PLS is similar to ALS but only affects the upper motor neurons. It causes weakness and stiffness in the arms and legs, slowed movement, and problems with balance and speech. PLS is more common in men and usually develops between the ages of 40 and 60. It is not fatal, but there is no cure, and extensive testing is required for diagnosis.

Progressive Bulbar Palsy (PBP)

PBP is a form of ALS that damages motor neurons in the brain stem, which controls functions such as swallowing, speaking, and chewing. People with PBP may have trouble chewing and swallowing, slur their words, and experience uncontrollable laughter or crying. Many people with PBP eventually develop ALS.

Progressive Muscular Atrophy (PMA)

PMA is a less common form of MND that mainly affects the lower motor neurons. Weakness usually starts in the hands and then spreads to other parts of the body. It can be inherited or sporadic. PMA is an uncommon subtype of ALS and tends to develop later in life.

Spinal Muscular Atrophy (SMA)

SMA is an inherited condition that affects the lower motor neurons. It is caused by a defect in the SMN1 gene, which normally produces a protein that protects motor neurons. SMA has several types, classified based on when symptoms first appear and the severity of those symptoms. Type 1, also called Werdnig-Hoffmann disease, starts around 6 months of age, while Type 2 starts between 6 and 12 months. Type 3, or Kugelberg-Welander disease, starts between ages 2 and 17, and Type 4 usually starts after age 30. SMA is always hereditary, and while some types are stable or mild, others are severe and can reduce life expectancy.

Diagnosis of motor neuron disease

Motor neuron disease (MND) is challenging to diagnose in the early stages as its symptoms can resemble those of other conditions, such as multiple sclerosis, peripheral neuropathy, or a stroke. If a doctor suspects MND, they will refer the patient to a neurologist for further evaluation.

The neurologist will typically perform a thorough medical history evaluation, a physical examination, and an extensive neurological exam to assess motor and sensory function, hearing and speech, vision, coordination and balance, thinking, and changes in mood or behaviour.

To aid in the diagnosis, the neurologist may also request the following tests:

• Blood and urine tests: These can help rule out other conditions and detect any rise in creatinine kinase, a substance that muscles produce when they break down.
• MRI brain scan: While it cannot detect MND, an MRI can help exclude other conditions, such as a stroke, brain tumour, or unusual brain structures.
• Electromyography (EMG) and nerve conduction study (NCS): EMG measures electrical activity in the muscles, while NCS measures the speed of electrical conduction through the muscles.
• Spinal tap or lumbar puncture: This involves taking a sample of cerebrospinal fluid to analyse and rule out other conditions.
• Muscle biopsy: This can help detect or exclude a muscle disease, although it is an invasive procedure and not always deemed necessary for diagnosis.

Even with these tests, diagnosing MND can be challenging, and neurologists may need to monitor the patient over time to confirm the diagnosis.

Treatment of motor neuron disease

Motor neuron disease (MND) is a rare condition that progressively damages parts of the nervous system, causing muscle weakness and often visible wasting. While there is no cure for MND, there are treatments available to help relieve the symptoms and improve quality of life. Here is a detailed overview of the treatment options for MND:

Medications

Several medications have been approved to treat MND and slow its progression. For example, riluzole (the only licensed medication in the UK that has shown a survival benefit for people with MND) slows down the damage to motor neuron cells by reducing their sensitivity to the nerve transmitter glutamate. Edaravone (Radicava) is used for ALS, while nusinersen (Spinraza) and onasemnogene abeparvovec (Zolgensma) are used to treat SMA. Muscle relaxers can be prescribed to reduce muscle stiffness and help with muscle spasms. Botulinum toxin injections can also be used to treat muscle stiffness by weakening overactive muscles. Additionally, medications such as amitriptyline, glycopyrrolate, and atropine can be used to treat excessive saliva production and drooling.

Physical and Occupational Therapy

Physical and occupational therapy play a crucial role in helping individuals with MND improve their posture, prevent joint immobility, and slow muscle weakness and atrophy. Stretching and strengthening exercises can help reduce stiffness, improve range of motion, and increase circulation. Physiotherapy can also help with muscle cramps, and in some cases, a medication called quinine can be prescribed to treat them.

Speech and Language Therapy

Speech and language therapy is beneficial for those with MND who experience communication and swallowing difficulties. Therapists can teach techniques to improve speech clarity and provide assistance with swallowing and chewing.

Dietary Advice

Dietitians or dieticians support individuals with MND to ensure they maintain a balanced diet and proper nutrition, which is crucial for maintaining weight and strength.

Palliative Care

As MND advances, palliative care may be required to manage pain, provide comfort, and improve quality of life.

Assistive Devices

Mobility and communication devices can help individuals with MND maintain their independence. Feeding tubes and breathing assistance, such as ventilators, may be needed as the condition progresses.

Frequently asked questions