![]() ![]() Others only have lower motor neuron signs and are diagnosed with progressive muscular atrophy (PMA). Some patients have only upper motor neuron dysfunction and are said to have primary lateral sclerosis (PLS). Most ALS patients have a mixture of upper and lower motor neuron signs. In spinal onset disease, muscles that control the limbs and trunk are the first involved, and people first complain of weakness in one hand or a dropped foot that causes them to trip and fall. ![]() In ALS patients with bulbar onset, the first muscles involved are those that control speech and swallowing, and slurred speech (dysarthria) and difficulty swallowing (dysphagia) are the initial problems. When the lower motor neuron is lost, patients develop weakness, wasting (amyotrophy) and twitching (fasciculation) of muscle. When the upper motor neuron degenerates, patients experience loss of motor control, stiffness or spasticity, and abnormal or exaggerated reflexes. These two principal elements of the motor system control all voluntary movements. By definition, ALS involves two populations of “motor neurons,” the so-called upper motor neuron in the motor cortex of the brain, and the lower motor neuron in the brain stem and spinal cord, which directly connects to muscle and elicits a contraction. Diagnosing ALSĪLS is a motor neuron disorder that can present in a variety of ways in people with sporadic or familial disease. ![]() ALS-associated mutations in these same genes also occur spontaneously or de novo in individuals to cause sporadic disease. A mutation with low penetrance may actually skip a generation. These same mutations are also found in individuals with "sporadic" ALS, who have no family history-either because the family history is unknown or incomplete, or because of an issue called "penetrance,"which relates to the likelihood that a particular mutation will cause the disease. Over 30 different genes have been identified in which mutation(s) cause ALS and over 60 percent of ALS cases are caused by a mutation in one of these known ALS genes. In most cases, the cause is unknown, but in about 10 percent of patients, the disease is familial (fALS), which means that it is associated with a genetic mutation inherited from one or the other parent in a dominant manner. The combination of upper and lower motor neuron signs in the absence of sensory loss is a key finding in the clinical diagnosis of ALS. When the lower motor neuron is sick, we see muscle wasting and weakness, associated with twitching (fasciculation) and cramping. When the upper motor neuron in lost, we see exaggerated and abnormal reflexes, like the knee-jerk reflex. In the United States, approximately 5,000 people are diagnosed with ALS annually the average age at the time of diagnosis is between 55 and 65.Įssentially, two groups of motor neurons are affected, the so-called “upper” motor or corticospinal neuron in the motor cortex, and the “lower” motor neurons in the brain stem and spinal cord that directly activate the muscle. In a population of 100,000, ALS will affect approximately two people every year. Motor neuron degeneration leads to progressive muscle wasting (amyotrophy), weakness, and loss of motor control in the arms, legs, and trunk and in “bulbar” muscles that control talking, chewing, and swallowing.ĪLS is a fatal disease because it also affects respiratory muscles, including the diaphragm and accessory muscles of breathing. ALS is a neurodegenerative disease-like Alzheimer’s and Parkinson’s disease-that primarily involves the degeneration of motor neurons in the brain and spinal cord. Amyotrophic lateral sclerosis (ALS) is known as Lou Gehrig’s disease in the United States, named after the Yankee great who attended Columbia College from 1921 to 1923. ![]()
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