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Genetic and Rare Diseases Information Center (GARD)

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Primary lateral sclerosis


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Your Question

My husband was diagnosed with multiple sclerosis (MS) in 1999, and now with a second opinion he was diagnosed with possible primary lateral sclerosis (PLS). How does MS differ from PLS? How are MS and PLS diagnosed?

Our Answer

We have identified the following information that we hope you find helpful. If you still have questions, please contact us.

What are the signs and symptoms of multiple sclerosis?

The peak age of onset is between ages 20 and 40, although it may develop in children and has also been identified in individuals over 60 years of age. The most common signs and symptoms include sensory disturbance of the limbs; partial or complete visual loss; acute and subacute motor dysfunction of the limbs; diplopia (double vision); and gait dysfunction. These signs and symptoms may occur alone or in combination, and have to be present for a minimum of 24 hours to be considered a "clinical attack." The signs and symptoms in individuals with MS are extremely variable, even among affected relatives within families.[1] Symptoms vary because the location and severity of each attack can be different. Episodes can last for days, weeks, or months. These episodes alternate with periods of reduced or no symptoms (remissions). While it is common for the disease to return (relapse), the disease may continue to get worse without periods of remission. Because nerves in any part of the brain or spinal cord may be damaged, patients with multiple sclerosis can have symptoms in many parts of the body.[2]

Muscle symptoms may include loss of balance, muscle spasms, numbness or abnormal sensation in any area, problems moving arms or legs, problems walking, problems with coordination and making small movements, and tremor or weakness in one or more arms or legs. Bowel and bladder symptoms may include constipation and stool leakage, difficulty beginning to urinate, frequent need or strong urge to urinate, and incontinence. Eye symptoms may include double vision, eye discomfort, uncontrollable rapid eye movements, and vision loss. There may be numbness, tingling, or pain in the face, muscles, arms or legs. Other brain and nerve symptoms may include decreased attention span, poor judgment, and memory loss; difficulty reasoning and solving problems; depression or feelings of sadness; dizziness and balance problems; and hearing loss. Individuals may also have slurred or difficult-to-understand speech, trouble chewing and swallowing, and sexual symptoms such as problems with erections or vaginal lubrication.[2]
Last updated: 3/30/2011

What are the signs and symptoms of primary lateral sclerosis?

Primary lateral sclerosis (PLS) causes weakness in the voluntary muscles, such as those used to control the legs, arms and tongue. PLS can happen at any age, but it is more common after age 40. A subtype of PLS, known as juvenile primary lateral sclerosis, begins in early childhood. PLS is often mistaken for another, more common motor neuron disease called amyotrophic lateral sclerosis (ALS). However, primary lateral sclerosis progresses more slowly than ALS, and in most cases is not considered fatal.[3]

Signs and symptoms of PLS typically take years to progress.[3] The hallmark of PLS is progressive weakness and spasticity of voluntary muscles. The first symptoms are often tripping or difficulty lifting the legs. Other people may be the first to notice a change in the affected person's gait. Occasionally, speaking (dysarthria) and swallowing (dysphasia) difficulties, or arm weakness are the first symptoms. Speech problems can begin with hoarseness, a reduced rate of speaking, excessive clearing of the throat, or slurred speech when a person is tired. In some cases, speech becomes so slurred that others cannot understand it. Drooling can be a problem as well due to weakened bulbar muscles.[4] Many people report painful muscle spasms and other pain. Other common symptoms may include hyperactive reflexes and Babinkski's sign. Wherever symptoms originate, the legs, arms, hands, and speech and swallowing muscles are eventually affected. As the disease progresses, assistive devices such as canes, walkers or wheelchairs are typically needed.[4]
Last updated: 3/30/2011

How is multiple sclerosis diagnosed?

Symptoms of MS may mimic those of many other nervous system disorders. The disease is a clinical diagnosis,[1] and is typically diagnosed by ruling out other conditions. A health care provider may suspect MS if there are decreases in the function of two different parts of the central nervous system (such as abnormal reflexes) at two different times (referred to as dissemination in time and space).[1][2] Dissemination in time and space is commonly used criteria for diagnosing relapsing-remitting MS (RR-MS). Dissemination in time means that there are at least two clinical attacks, each lasting at least 24 hours, separated by at least one month, or a slow, stepwise progressive course for at least six months. Dissemination in space means that there are lesions in more than one area or functional system of the brain or spinal cord white matter. For primary progressive MS (PP-MS), there are currently no diagnostic criteria that are universally accepted.[1]

Physicians may perform a variety of tests to evaluate an individual suspected of having MS. A neurological exam may show reduced nerve function in one area of the body, or spread over many parts of the body. This may include abnormal nerve reflexes, decreased ability to move a part of the body, decreased or abnormal sensation, and other loss of nervous system functions. An eye examination may show abnormal pupil responses, changes in the visual fields or eye movements, decreased visual acuity, problems with the inside parts of the eye, and rapid eye movements triggered when the eye moves. Other specific tests to diagnose multiple sclerosis may include lumbar puncture (spinal tap) for cerebrospinal fluid tests; MRI scan of the brain and MRI scan of the spine; nerve function study; and a variety of blood tests.[2]
Last updated: 3/30/2011

How is primary lateral sclerosis diagnosed?

There is no single test that confirms a diagnosis of primary lateral sclerosis (PLS). Because the disease can mimic signs and symptoms of other neurological diseases such as multiple sclerosis and amyotrophic lateral sclerosis (ALS), several tests are done to rule out other diseases. After taking a careful record of an individual's medical history and performing a complete neurological examination, a doctor may order the following tests:
  • Blood work. Blood tests are done to check for infections or other possible causes of muscle weakness.
  • Magnetic resonance imaging (MRI) of the brain and spine. An MRI or other imaging tests may reveal signs of nerve cell degeneration and look for other causes of symptoms, such as structural abnormalities, spinal cord compression, multiple sclerosis and spinal cord tumors.
  • Motor and sensory nerve conduction studies. These tests use a low amount of electrical current to test how quickly the nerves carry impulses through the body, and can indicate damage to nerve cells.
  • Electromyogram (EMG). During this test, the doctor inserts a needle electrode through the skin into various muscles. The electrical activity of the muscles is evaluated when they contract and when they're at rest. This test can measure the involvement of lower motor neurons, which can help to differentiate between PLS and ALS.
  • Cerebrospinal fluid (CSF) analysis. An analysis of the CSF, which is taken during a lumbar puncture in the lower back, can help to rule out multiple sclerosis and other causes of spasticity.[3]
After other diseases are ruled out, a doctor may make a preliminary diagnosis of PLS. Sometimes doctors wait three to four years before being sure of the diagnosis, because early ALS can look just like PLS until additional symptoms surface a few years later.[3]
Last updated: 6/6/2011

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