Primary Lateral Sclerosis
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Primary lateral sclerosis (PLS) is a form of motor neuron disease that primarily affects the nerve cells in the brain responsible for controlling voluntary movements. In PLS, the degeneration of these nerve cells leads to muscle weakness in areas such as the legs, arms, and tongue.
The initial symptoms often involve difficulty with balance, leading to slow and clumsy movements. As the disease progresses, individuals may experience increasing difficulties with hand and arm coordination, followed by challenges in chewing, swallowing, and speaking. In some cases, the disease may start with issues related to speech and swallowing.
PLS can occur at any age but is most commonly diagnosed between the ages of 40 and 60. It tends to be more prevalent in men than in women. A rare form of the disease, known as juvenile primary lateral sclerosis, can begin in early childhood and is linked to a genetic mutation inherited from both parents.
Often confused with amyotrophic lateral sclerosis (ALS), another type of motor neuron disease, PLS progresses more slowly and is generally not life-threatening. Although related to ALS, PLS and ALS differ significantly in their impact and progression rates.
Symptoms
Symptoms of primary lateral sclerosis (PLS) generally develop slowly and worsen over time, often beginning in the legs. In rare cases, symptoms may start with weakness in the tongue or hands before progressing to the legs. Symptoms can vary significantly between individuals, but commonly include:
- Spasticity: This involves stiffness, weakness, and muscle spasms in the legs. Spasticity may initially affect only one leg and can eventually spread to the arms, hands, tongue, and jaw.
- Movement issues: Movement may become slower, and individuals might experience tripping, clumsiness, and balance problems.
- Hand coordination: Difficulty with fine motor skills and general clumsiness of the hands may occur.
- Speech and swallowing difficulties: Symptoms can include a hoarse voice, slowed or slurred speech, drooling, and problems with chewing and swallowing.
- Emotional changes: Some individuals may experience frequent, rapid, and intense emotional shifts.
- Other late symptoms: Rarely, breathing and bladder problems may develop in the later stages of the disease.
Consult a healthcare professional when:
- Adults: Consult a healthcare professional if you have persistent leg or arm stiffness or weakness, or if you encounter difficulties with swallowing or speaking.
- Children: Take your child to a healthcare provider if they develop muscle spasms or seem to lose balance more frequently than usual.
Causes
Primary lateral sclerosis (PLS) is defined by the progressive degeneration of the brain’s motor nerve cells responsible for controlling movement.
Most cases of primary lateral sclerosis has no known cause.
- Adult-onset primary lateral sclerosis: This condition is typically not inherited. The reason behind its onset remains unclear.
- Juvenile primary lateral sclerosis: PLS in children is a hereditary autosomal recessive condition. This implies that for a gene to be passed on to a kid, both parents must be carriers. Mutations in the ALS2 gene are the cause of juvenile PLS.
The ALS2 gene provides instructions for making a protein known as alsin, which is found in motor neuron cells. In individuals with juvenile primary lateral sclerosis, alterations in these instructions result in unstable alsin protein that does not function correctly. This instability affects muscle function. However, experts are uncertain on how this particular gene leads to PLS.
Risk factors
Primary lateral sclerosis can occur in individuals of any age, although the average age of diagnosis is around 50 years old, with cases reported in both younger and older individuals, including children. It is also observed to be more prevalent in males. Additionally, there are no known environmental factors that have been definitively linked to the development of PLS.
Diagnosis
In some cases, it can take three to four years to diagnose PLS because in the beginning, ALS symptoms may resemble those of PLS until additional symptoms emerge later on.
Tests that may be ordered include:
- Physical examination: The diagnosis of PLS involves a series of assessments including physical and neurological examinations, review of personal and family medical history, along with specific testing. The healthcare providers will carefully evaluate the symptoms to differentiate PLS from similar conditions such as ALS or multiple sclerosis.
- Blood tests: Possible reasons for the weakness of muscles or infections can be identified through this test.
- Magnetic resonance imaging (MRI): Causes of symptoms, such as spinal cord tumors, multiple sclerosis, or structural issues, can be shown by an MRI. Generally, imaging tests like MRI may show evidence of damaged nerve cells in the brain or spine.
- Nerve conduction studies: The nerves’ ability to convey impulses to muscles in different parts of the body is measured by a small amount of electrical current. Existing nerve damage can be identified during this procedure.
- Spinal tap: During the procedure, small samples of cerebrospinal fluid are taken using a thin, hollow needle that is placed into the spinal canal. This liquid envelops the spinal cord and brain. Also referred to as lumbar puncture, this procedure can assist in ruling out infections, multiple sclerosis, and other abnormalities specific to neuromuscular conditions.
- Electromyogram (EMG): In this test, a needle electrode is inserted through the skin into various muscles to measure their electrical signals. This can assist in distinguishing between ALS, which affects both upper and lower motor neurons, and PLS, an illness of the upper motor neurons.
EMG measures the electrical activity in the muscles during both rest and contraction. Multiple EMGs may be required over a few years to confirm a diagnosis of PLS accurately. - Genetic testing: This may be recommended in suspected cases of juvenile primary lateral sclerosis.
Treatment
Treatment for primary lateral sclerosis (PLS) primarily centers on managing symptoms and may encompass a range of strategies. Given that PLS cannot be halted, prevented, or reversed, the objectives revolve around preserving function and alleviating symptoms.
Treatment options include:
- Medication: Common medications used to address PLS symptoms include baclofen, clonazepam, and tizanidine for muscle stiffness, quinine for muscle cramps, and diazepam to promote muscle relaxation. If oral medications fail to control muscle spasms effectively, surgery may be recommended to implant a medication pump that delivers baclofen directly into the spinal fluid, providing targeted relief. Drooling in PLS can be improved with medications like amitriptyline, while severe and frequent mood swings may be managed with antidepressants if necessary.
- Physical and occupational therapies: This address muscle weakness and improve flexibility and joint mobility. Maintaining muscle strength, flexibility, and range of motion can be facilitated by strengthening and stretching activities.
- Speech and language therapy: If PLS affects the facial muscles, speech therapy may be able to aid with swallowing and communicating.
- Nutrition support: Special feeding techniques may be recommended to help maintain body weight despite difficulties eating caused by symptoms. Specific diet and nutritional supplements may also be prescribed.
- Assistive devices: Specialized devices may be employed to assist with speaking difficulties. Devices such as canes, walkers, or wheelchairs may also be recommended to enhance independence and mobility.
