Motor Neuron Disease
Causes for Motor Neuron Disease
There are multiple 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) which affects about 75% of all motor neurone disease sufferers. A fourth form of the disease, primary lateral sclerosis (PLS), is rare and often only provisionally diagnosed.Most cases of motor neurone disease occur randomly, with no known causes for motor neuron disease. However, 5 – 10% 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, and has its highest incidence in those aged between 50 and 70 years. In some cases, though, symptoms of motor neuron disease can first appear in a person’s 20s.
Usually the onset is gradual but younger patients may show a more rapid progression. The average life expectancy is two to four years from diagnosis but some people succumb within a matter of months, while others live up to 20 years.
Signs and Symptoms of Motor Neuron Disease
Initial symptoms will depend on the form of the condition. However, the most common early sign is weakness in the arms and legs. This is often more pronounced on one side than the other. Other early signs of the condition include:
- Muscle twitching
- Muscle wasting
- An increasingly stiff, clumsy walk
- General fatigue
- Difficulty with chewing, swallowing and speech
Motor neuron disease can affect the upper motor neurons in the brain (causing generalised muscle spasms and exaggerated reflexes), or the lower motor neurons in the brain stem and spinal cord (causing a progressive wasting and weakness of muscles responsible for speech, chewing and swallowing). Because motor neuron disease is a progressive disease, both the upper and lower motor neurons are eventually affected.
As the condition progresses, motor neuron disease sufferers may not be able to:
- Use their hands and arms
- Speak clearly, or at all
- Hold up their head
Motor Neuron Disease 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. If motor neurone disease is suspected, a referral to a neurologist (a doctor who specialises in the treatment of diseases of the nervous system) will be recommended.
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 and urine tests
- Computerised tomography (CT) or magnetic resonance imaging (MRI) scans
- Muscle biopsy – to determine the health of the muscle tissue
Treatment of Motor Neuron Disease
A disease-modifying drug called riluzole (Rilutek), which has the potential to modestly prolong survival in some patients, is available in New Zealand.
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
Together, and in conjunction with the patient and family, they will work to maintain mobility and make maximum use of the affected person’s abilities. A wide variety of equipment to help overcome practical difficulties and communication problems are available.The progressive nature of the condition means that most people will eventually require full time nursing care. When breathing becomes too difficult, a mechanical ventilator may be required to maintain breathing. While the use of a ventilator can prolong life and improve sleep, it will not alter the course of the condition, and many people with motor neuron disease therefore choose not to use ventilators for lengthy periods.
Motor Neuron Disease Support and information
22 Chelford Road