Motor Neuron Disease

A group of debilitating disorders involving progressive degeneration of the nerves (motor neurons) that control muscle movement.  This causes loss of voluntary muscle control, stiffness, paralysis, and muscle wasting.  Some forms run in families or are caused by gene mutations.  In 90% of cases, the cause is unknown.  There are 4 basic types of MND, divided according to which motor neurons are involved in the degeneration process.  The most common form is Amyotrophic Lateral Sclerosis (ALS) also known as Lou Gherig’s disease.  It is a fatal neurological disease with rapid regression of function that involves the loss of both upper (brain) and lower (spinal cord) motor neurons.  The limb muscles are usually affected first, and then the facial, speech, and swallowing muscles.  Bulbar palsy, which strikes mostly older women, is the second type of MND that involves both types of motor neurons.   The motor neurons in the brain stem are the most vulnerable, though sometimes only upper motor neurons are affected.    The first symptom is weakness in the muscles of swallowing and speech.  The third type is progressive muscular atrophy (PMA), a less common form which affects only lower motor neurons.  The fourth type is primary lateral sclerosis (PLS), a rare form which affects only the upper motor neurons and progresses slowly.  MND usually appears about midlife, between the ages of 50-70, though there is a rare juvenile form.  Symptoms include fatigue, weakened grip, twitching, clumsiness, and cramping in limb muscles.  The disease continues on to affect the person’s abilities to carry out everyday activities, such as walking, talking, swallowing, and speaking.  Eventually, respiratory muscles are affected, and the person may succumb to pneumonia or respiratory failure.  There is currently no cure, and treatment aims to ease symptoms and aid with activities of daily life.