Primary Lateral Sclerosis

Primary lateral sclerosis (PLS) is a rare neuromuscular condition that affects cells in your brain and spinal cord that manage movement. It causes worsening muscle stiffness and coordination issues.

Symptoms usually affect your legs first. Over time, stiffness and mild weakness spread to other muscles throughout your body.

PLS is often mistaken for a more common condition called amyotrophic lateral sclerosis (ALS). These two conditions may be related, but they’re different. PLS gets worse more slowly than ALS and typically isn’t fatal.

There isn’t a cure for primary lateral sclerosis. But treatment can help manage your symptoms. Supports like a walker or cane can help with your mobility.

Symptoms of PLS

Primary lateral sclerosis symptoms develop slowly over many years. Some of the first symptoms you may notice include:

• Muscle stiffness and/or weakness in your legs (spasticity)
• Difficulty walking or maintaining your balance
• Muscle spasms or painful cramps

As the condition progresses, you may have:

• Muscle stiffness and weakness in your fingers, hands and arms
• Difficulty controlling your bladder (urinary urgency and incontinence)
• Pain in your neck and lower back

Other symptoms may include:

• Difficulty swallowing
• Slurred speech
• Executive dysfunction
• Memory issues
• Outbursts of inappropriate laughing or crying (pseudobulbar affect)

Primary lateral sclerosis causes

Researchers don’t know the cause of most PLS cases. But they think it may happen due to certain gene changes. The condition isn’t hereditary — it doesn’t pass down in your biological family. Cases usually happen randomly. There’s nothing you can do to prevent it.

PLS is a type of motor neuron disease (MND). Motor neurons are cells that control skeletal muscle activity, like walking and breathing.

PLS slowly breaks down upper motor neurons. As a result, your muscles don’t get the messages they need to move as expected.

Risk factors

Age and sex are the main risk factors for primary lateral sclerosis.

On average, PLS begins around age 50. But it can develop at any point. It affects males more than females.

Complications

As PLS progresses, you may have trouble walking without assistance. You might need to use a cane, walker or wheelchair.

You may also be at greater risk of falls, which could cause injuries.

Because PLS is a long-term, worsening condition, it can impact your quality of life. This may take a toll on your mental health and lead to depression.

How doctors diagnose primary lateral sclerosis

Your healthcare provider will diagnose PLS after a physical exam, a neurological exam and testing. They’ll review your symptoms to rule out more common, look-alike conditions, such as ALS or multiple sclerosis.

Diagnostic testing may include:

• Blood tests
• Nerve conduction study and electromyography (EMG) to check how well your nerves and muscles work
• MRI of your brain and spinal cord
• A cerebrospinal fluid (CSF) analysis after a lumbar puncture (spinal tap) to look for issues specific to certain conditions

It may take a while to get an accurate diagnosis. If possible, see a neurologist who specializes in motor neuron diseases.

Can PLS turn into ALS?

PLS and ALS are two distinct conditions. But you may get misdiagnosed with PLS and actually have ALS. That’s because early signs of ALS, especially upper motor neuron-predominant ALS, can look like PLS,

PLS only affects your upper motor neurons (UMNs). ALS affects both your upper and lower motor neurons (LMNs).

You may receive a PLS diagnosis first if you only have UMN symptoms. If LMN symptoms develop later, your provider may change your diagnosis to ALS.

How is it treated?

There’s no direct treatment for primary lateral sclerosis. But certain therapies can help manage the symptoms. Options include:

• Medications to reduce muscle stiffness and spasms
• Medications to help with pseudobulbar affect
• Physical therapy to build muscle and improve flexibility and range of motion
• Devices to assist with independence and mobility, like a cane, walker or wheelchair
• Speech therapy for speaking or swallowing issues

You’ll likely work with a team of medical specialists. They’ll tailor a care plan to your health needs and goals.

What can I expect if I have primary lateral sclerosis?

PLS is a long-term condition that gets worse over time. How fast your symptoms appear and worsen varies. The progression is generally slow, changing over seven to 14.5 years, on average.

If you notice a sudden worsening of symptoms, contact your healthcare provider.

Medications are effective in decreasing symptoms and helping you go about your day. For your safety, you may want to consider using a cane, walker or wheelchair to give you more independence and confidence when you move. These devices can also help prevent falls.

Primary lateral sclerosis doesn’t directly lower your life expectancy. But the condition may lead to falls, which can cause serious injuries.