Authored by MCN Neurologists
Amyotrophic Lateral Sclerosis (ALS), also known as “Lou Gehrig’s disease,” is a neurodegenerative disease of motor neurons in the brain and the spinal cord. The disorder is characterized by progressive muscle weakness, atrophy, fasciculation (muscle twitching), spasticity, speech difficulty, swallowing difficulty and respiratory failure. Sensory functions and autonomic functions (functions that are subconscious and mostly involuntary, such as heart rate, breathing and perspiration) are usually unaffected. The annual incidence of ALS is about 1-3 cases per 100,000. The peak age of onset is around 60 to 70 years. Men tend to be affected more commonly than women. About 10% of ALS patients have a family history.
Causes of ALS
The cause of ALS is not entirely clear and is an active area of research. Genetic mutations have recently been found in some of the familial ALS patients (e.g., SOD1 gene mutation account for 20% of familial cases). Most ALS cases are, however, sporadic and not associated with any known genetic mutation. No known environmental factors have been consistently shown to cause ALS, nor have trauma, physical activity or alcohol consumption.
Symptoms of ALS
Initial clinical presentation of ALS varies according to the segments of motor neurons affected.
Limb muscles presentation (80% of ALS cases)
Upper motor neurons (located in the brain): Resultant symptoms include muscle spasticity and hyper-reflexive reaction.
Lower motor neurons (located in the spinal cord): Resultant symptoms are characterized by muscle weakness, atrophy (muscle wasting) and fasciculations. Initial limb weakness tends to be asymmetric.
Bulbar muscles presentation (20% of ALS cases)
Patients will present with speech difficulty and chewing and swallowing difficulty. Tongue muscle wasting and fasciculation may also be noticeable.
After the initial symptoms arise, the condition will gradually spread out to other segments of the body. Some patients may have a more mixed pattern of initial symptom presentation and others may have a faster speed of progression. Eventually, however, all patients will develop swallowing difficulty and life-threatening respiratory failure.
ALS Examination and Tests
ALS is diagnosed based on clinical symptoms and careful neurological examination. From the initial presentation to the final establishment of an ALS diagnosis, the assessment process can take many months to complete. Your neurologist will take a detailed history about the onset, duration and progression of your symptoms. A general physical examination and a detailed neurological assessment will be performed to identify the degree and the segments of the body affected. As the symptoms and signs are progressively identified, the diagnosis of ALS can be placed into one of the three possible categories: Possible ALS,Probable ALS and Definite ALS. Only through serial follow-up examinations and laboratory-based EMG testing can a definite diagnosis finally be made.
1. Blood tests may be performed to rule out common infection, inflammation or metabolic disorders as the underlying etiology.
2. Brain and spinal cord MRI studies may be performed to rule out brain and spinal cord structural lesions as the cause of the motor neuron signs.
3. Most patients will need EMG and nerve conduction studies to rule out other peripheral nerves lesions. EMG tests can sometimes detect ALS cases early (before their clinical manifestation is obvious).
4. Testing for SOD1 mutations is now commercially available. Note, however, that this type of mutation is present only in a small portion of familial ALS cases.
Treatment of ALS
Medication – The only medication currently approved by the FDA for treating ALS is Riluzole. Clinical trials have shown that Riluzole has a modest effect on ALS and can increase the median duration of survival by about 60 days.
ALS Specialty Clinic – ALS patients are often referred to an ALS Clinic where multidisciplinary supportive care is utilized to prolong survival and improve patients’ quality of life. The treatment team may include many members, such as a neurologist who has experience in neuromuscular disease, registered nurses, speech pathologists, physical therapists, occupational therapists, respiratory therapists, neuropsychologists, social workers and research coordinators.
For further information about ALS, click on the following links:
www.ninds.nih.gov/disorders/amyotrophiclateralsclerosis/detail_amyotrophiclateralsclerosis.htm (National Institute of Health)
www.alsa.org (ALS Association)