Definition

Motor neuron disease (MND) is a rare disease that attacks the brain and motor nerves. This disease causes progressive weakness of the limbs over time. Motor neurons play a role in transmitting signal messages between the brain, spinal cord, and muscles.

When we walk, talk to a friend, or chew food, the nervous system is the system working behind these activities. Therefore, like other parts of the body, the nervous system can also be damaged.

There are many types of motor neuron diseases. The most well-known is Amyotrophic Lateral Sclerosis (ALS), made famous by the renowned scientist Stephen Hawking. Other types of motor neuron diseases include:

• Primary Lateral Sclerosis (PLS)

          A rare form of motor neuron disease primarily causes weakness and stiffness in the body.

• Progressive Bulbar Palsy (PBP)

Muscle weakness due to lower motor neuron disorders, mainly affecting the facial, throat, and tongue muscles.

• Pseudobulbar Palsy

Similar to PBP but occurs due to upper motor neuron disorders.

• Progressive Muscular Atrophy

Progressive muscle weakness causes muscle loss and shrinkage.

• Spinal Muscular Atrophy

A congenital disease affecting the lower motor neurons.

• Kennedy's Disease

A rare condition that increases muscle weakness and causes hormonal changes.

All types of MND can significantly reduce life expectancy and can be life-threatening. Symptoms affect patients to varying degrees and speeds, making the disease progression difficult to predict. There is currently no cure for MND. Therapy aims to reduce the impact of the disease on the patient's daily life.

Causes

Motor neuron disease is caused by the degeneration of motor neurons in the brain and spinal cord, which can affect the functioning of other nerve cells.

The exact cause of motor neuron disease is not yet known. It is believed that lifestyle, environment, and genetics contribute to the disease. Once the neurons are affected, they gradually stop functioning properly over time.

Risk factor

Motor neuron disease is a rare condition that primarily affects individuals in their 60s and 70s. However, it can also affect adults at any age.

If you have close relatives with motor neuron disease or related conditions such as frontotemporal dementia (dementia due to damage to the front and side of the brain), you have a risk factor for developing motor neuron disease. However, in most cases, motor neuron disease is not inherited genetically.

Symptoms

The symptoms of motor neuron disease appear gradually and may not be clear at the onset. The disease affects patients differently, with varying sequences of muscle weakness and speeds of symptom progression. The complaints that arise also depend on the type of disease.

Early symptoms may include:

• Weakness in the heel or foot, causing stumbling or difficulty climbing stairs.
• Slurred speech and facial expressions.
• Difficulty swallowing food and saliva.
• Weak grip, causing difficulty holding objects, opening bottle caps, or buttoning clothes.
• Muscle cramps and tingling.
• Weight loss, with arm and leg muscles becoming small and thin over time.
• Breathing difficulties, causing shortness of breath and weakness.
• Difficulty controlling laughter or crying in inappropriate situations.

Diagnosis

A neurologist will conduct interviews, physical examinations, and supporting tests to diagnose this disease. No single test can definitively diagnose motor neuron disease due to its degenerative and slow-progressing nature.

Medical Interview

The interview will include:

• The patient's main complaint.
• Accompanying complaints, if any.
• The duration of the complaint.
• Family history of motor neuron disease.
• History of other illnesses.
• Occupational history.
• Lifestyle.
• Medication history.

Physical Examination

The doctor will conduct a physical examination starting with the general condition of the patient to check for walking disorders, consciousness disorders, blood pressure, respiratory rate, pulse, and body temperature.

Then, the doctor will conduct a more specific neurological examination, including:

• Balance examination.
• Motor function examination to evaluate muscle tone and strength, body position and coordination, and any uncontrolled muscle movements.
• Sensory function examination, including pain, temperature, touch, position, or vibration sensations.
• Facial nerve examination.

Supporting Examinations

Supporting examinations may include blood tests to check for ongoing infections and CT scans or MRIs of the brain and spinal cord.

Additionally, electromyography (EMG) can be performed to examine the electrical activity in muscles and nerves. A lumbar puncture may also be conducted if necessary, where spinal fluid is taken with a needle inserted through the spine.

Management

No medication has been proven to cure motor neuron disease. The treatment aims to improve the patient's quality of life and reduce the effects of the symptoms. The therapy is expected to reduce the pain experienced by the patient.

The management that can be done includes:

• Occupational therapy to help patients with daily activities.
• Physiotherapy to train muscle strength and movement.
• Speech therapy to help patients speak clearly.
• Nutritional therapy to support proper nutrition intake despite having motor neuron disease.
• Medication provided and supervised by a neurologist to slow the disease progression, relieve muscle stiffness, and improve saliva conditions.
• Emotional and psychological support.

Complications

Motor neuron disease will worsen over time. Moving, swallowing, and breathing will become more difficult due to the progressive muscle weakness. As time goes by, patients may need feeding tubes or oxygen tubes to assist with basic functions (breathing and eating).

Patients can become paralyzed and experience breathing difficulties, leading to death. The duration from diagnosis to death varies among patients.

For example, many people live for years, even up to a decade, with motor neuron disease. Therefore, regular consultations with the treating doctor are necessary for the patient's survival.

Prevention

The exact cause of the disease is still unknown, although it is believed to be related to lifestyle factors, genetic mutations, and environmental factors. Therefore, there is no sure way to prevent motor neuron disease.

However, you can take the following steps to reduce the likelihood of developing motor neuron disease:

• Avoid smoking.
• Maintain a balanced diet, increasing vitamin E and antioxidant intake.
• Avoid obesity.
• Avoid exposure to toxins and pollutants in the workplace, always use personal protective equipment, especially if you work in industries with exposure to pesticides and heavy metals like lead, iron, and manganese.
• Engage in physical activity at least 3 times a week for 30 minutes to keep the body fit.

When to see a doctor?

You should see a doctor if there are early symptoms of motor neuron disease as described above. The likelihood of developing motor neuron disease is very low as it is a very rare disease, but early diagnosis is crucial for timely treatment.

You should also see a doctor if you have close relatives with motor neuron disease or related conditions such as frontotemporal dementia. The doctor may recommend genetic counseling if necessary.

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