Primary lateral sclerosis (PLS) is a rare, neuromuscular disorder that affects the central motor neurons and is characterized by painless but progressive weakness and stiffness of the muscles of the legs. Such weakness may progress to affect the arms and the muscles at the base of the brain (bulbar muscles). Less frequently, the muscles of the face are affected. In most cases, the disorder affects adults during midlife. The exact cause of primary lateral sclerosis is unknown.
Primary lateral sclerosis is a rare disorder affecting the nerve cells that control voluntary muscles. In most cases, the muscles of the legs are involved first. However, in some cases, the disorder may begin in the muscles of the hands or tongue.
In many cases, the initial symptom of primary lateral sclerosis is progressive muscle weakness and stiffness of the voluntary muscles of legs. The disorder usually affects one leg and then progresses to the other. Affected individuals experience involuntary muscle spasms (spasticity) that result in slow, stiff movements of the legs. As a result, affected individuals may have difficulty walking and maintaining balance, may experience cramping of affected muscles, and may appear clumsy. As the disorder progresses, affected individuals may have increasing difficulties walking and may eventually require a cane or similar device to assist in walking.
Although primary lateral sclerosis begins in the legs, it progresses to affect the muscles of the hands and at the base of the brain. As a result, affected individuals may also exhibit difficulty forming words (dysarthria) and difficulty swallowing (dysphagia). In some cases, these symptoms may precede the development of muscle weakness in the legs. Some affected individuals may experience loss of bladder control late in the course of primary lateral sclerosis.
The specific course of primary lateral sclerosis varies from case to case. The disorder may progress rapidly within a few years or slowly over a few decades.
The exact cause of primary lateral sclerosis is not known. Most cases seem to occur randomly, for no apparent reason (sporadically). Primary lateral sclerosis is one of a group of disorders known as motor neuron diseases. Motor neuron diseases are characterized by malfunction of the nerve cells (motor neurons) within the brain and spinal cord that carry instructions from the brain to the muscles.
Primary lateral sclerosis is a rare disorder that affects males and females in equal numbers. In most cases, the disorder occurs during the fifth decade. However, according to the medical literature a familial form may exist that affects children. The exact prevalence of primary lateral sclerosis and motor neuron diseases is unknown.
Treatment of primary lateral sclerosis involves the use of drugs to help control specific symptoms. Baclofen and tizanidine may be prescribed for spasticity, quinine for cramps, and diazepam, a drug that relaxes muscles, for muscular contractions. Additional treatments may include physical therapy to prevent stiffness of joints, and speech therapy may be needed to aid affected individuals whose ability to speak has been impaired by muscle weakness. Other treatment is symptomatic and supportive.
In the Neuromuscular Disorders Program at Northwestern University Medical School, a study of the cause(s) of sporadic (non-inherited) diseases of the motor neurons, such as primary lateral sclerosis, is in progress. The research team hopes to determine whether genetic factors may predispose an individual to a disease such as PLS and whether sporadic motor-neuron diseases may be the result of not one but several genetic factors.
Blood samples from patients and their living parents, brothers, and sisters are needed for this study. Two tablespoons of blood are needed from each participant. The research team will supply tubes and instructions. Samples may be drawn near the patient’s home.
For information, contact:
Nailah Siddique, RN, MSN, Clinical Nurse Specialist
Scientists are conducting extensive ongoing research on motor neuron diseases in the areas of nerve growth factors, axonal transport, androgen receptor in motor neurons, and DNA/RNA changes.
A clinical trial is underway to study whether the part of the brain that controls movement (motor cortex) works properly in individuals with primary lateral sclerosis. For more information, contact:
National Institute of Neurological Disorders and Stroke (NINDS)
9000 Rockville Pike
Bethesda, Maryland 20892
Patient Recruitment and Public Liaison Office
Information on current clinical trials is also posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government web site.
For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:
Tollfree: (800) 411-1222
TTY: (866) 411-1010
For information about clinical trials sponsored by private sources, contact:
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eMedicine-Primary Lateral Sclerosis: Article by Carmel Armon, MD, MHS