In early stages, the progressive muscle disease amyotrophic lateral sclerosis, or ALS, also known as Lou Gehrig's disease, causes weakness, slurred speech, muscle cramps and twitching. As the disease progresses and muscles waste away, movement, speech, swallowing and breathing become difficult. Within three to five years of the onset of symptoms, most people with ALS die from respiratory failure. Many conditions mimic certain aspects of ALS and doctors must perform several tests to arrive at the correct diagnosis.
Motor Neuron Diseases
The National Institute of Neurological Disorders and Stroke classifies ALS and some similar conditions as motor neuron diseases because the fundamental problem underlying the conditions lies in the inability of nerve cells (neurons) to correctly signal to the muscles. The lack of communication causes muscle weakness, wasting and twitching.
In ALS, both the upper and lower motor neurons are affected while other motor neuron diseases affect only one set of neurons. Upper motor neurons originate in the brain and control the lower motor neurons in the brain stem and spinal cord. The lower motor neurons in turn stimulate the muscles, telling them when to contract and when to relax.
Primary lateral sclerosis (PLS) affects only the upper motor neurons but symptoms are quite similar to ALS; however PLS progresses much more slowly. PLS can develop into ALS. Spinal muscular atrophy affects only the lower motor neurons. It is hereditary and generally affects younger people whereas ALS most commonly affects people from 40 to 60 years old. Other motor neuron diseases include progressive bulbar palsy, progressive muscular atrophy and post-polio syndrome.
Multiple Sclerosis
Multiple sclerosis (MS) occurs when the immune system malfunctions and attacks the protective sheath covering nerve fibers. It produces symptoms similar to ALS such as numbness, weakness and lack of coordination, particularly in the legs, feet and ankles that can make patients very clumsy when walking. With MS, however, especially in the early stages, the symptoms come and go in discrete episodes rather than progressively worsening, according to the Mayo Clinic.
Parkinson's Disease
Parkinson's disease develops when brain cells fail to make enough of the neurotransmitter dopamine. Early symptoms of Parkinson's disease include muscle tremors, poor balance and a shuffling walk. Those symptoms and others such as slurred speech and a lack of facial expression occur in ALS as well. In later stages of both ALS and Parkinson's, dementia and depression can develop. Parkinson's disease generally progresses much more slowly than ALS.
