Primary progressive multiple sclerosis (PPMS) is one of the rarest of the four forms of multiple sclerosis (MS), making up approximately 10 percent to 20 percent of MS cases worldwide. Like other forms of multiple sclerosis, PPMS is an autoimmune disorder that affects the brain, spinal cord, and optic nerve — also known as the central nervous system. Specifically, PPMS causes damage to the neurons (nerve cells) and their protective covering, a substance called myelin. Ultimately, immune system attacks leave the nerves of the central nervous system unable to function properly.

Two key traits differentiate PPMS from other types of MS. First, PPMS has no periods of remission (when symptoms improve or clear up). Second, imaging shows more areas of damage, or lesions, on the spine than in the brain for people with PPMS.

Although PPMS and secondary progressive MS (SPMS) are both progressive forms of MS, SPMS develops in people who have had relapsing MS. People with PPMS experience progressive MS from the beginning, without a period of relapse and remission first. Unlike other types of MS, which tend to disproportionately affect women, PPMS occurs at the same frequency in both men and women.

What Are the Symptoms of PPMS?

People with PPMS tend to experience a greater impact on their motor functions than those with other forms of MS. This is because PPMS causes more spinal cord lesions than it does brain lesions.

Not all people with PPMS will experience all of the symptoms below. Although some symptoms of PPMS are caused directly by the disease itself, others may develop as a result of other symptoms.

Fatigue

Fatigue is one of the most common symptoms of PPMS. Fatigue affects almost 80 percent of people with MS. Fatigue is defined as extreme tiredness or exhaustion not caused by sleeplessness. Chronic, persistent fatigue can cause secondary symptoms, like impaired walking. It can have dire impacts on a person's quality of life as well, such as limiting their ability to work or socialize.

Decreased Mobility

Mobility is a person’s ability to independently move from place to place. Muscle weakness, particularly leg weakness, is often an early symptom of PPMS. Muscle spasms or spasticity, gait problems, and impaired coordination further contribute to difficulty walking. In about 9 percent of PPMS cases, areas in the brain that control balance, movement, and posture are affected.

Limited mobility can further weaken muscles and increase disability. This loss of independence can be stressful and exacerbate mood problems, such as depression, for people living with PPMS.

Cognitive Challenges

Cognition refers to high-level mental functions, such as learning, reasoning, and remembering. Forgetfulness is a symptom people with PPMS sometimes notice early on. Other cognitive changes associated with PPMS include difficulty concentrating, focusing, or thinking clearly. Some people describe these symptoms as brain fog.

Sensory Issues

Vision problems like blurriness and poor contrast are rare but can occur in people with PPMS. Other sensory symptoms of PPMS can include numbness, tingling, and pain.

Mood Changes

Mood changes and depression can occur with PPMS. Depression disproportionately affects people with MS. In fact, depression is one of the most common symptoms of MS. Almost half of those living with MS experience at least one episode of clinical depression. Depression can either be a primary symptom of PPMS or a natural response to being diagnosed with a chronic, progressive condition that currently does not have a cure.

Other PPMS Symptoms

PPMS can also cause symptoms including:

• Bowel problems
• Bladder issues
• Sexual dysfunction

How Does PPMS Progress?

MS is classified by levels of disease activity and the way the condition progresses. MS progression is measured by the extent of disability it causes, with steps known as disability milestones. PPMS symptoms worsen progressively over time. There may be periods when the course of PPMS quickens, slows, or stops for a time, but the symptoms never resolve or improve. This progressive course sets PPMS apart from other forms of MS that involve periods of relapse and remission.

A case of PPMS can be described in one of four ways:

• Inactive without progression — Symptoms aren’t getting worse, and there is no advancement in disability milestones.
• Inactive with progression — No increase in symptom intensity and no new symptoms or lesions (seen on MRI scans), but disability is progressing.
• Active without progression — Symptoms may get worse, or new symptoms may develop, but there is no disability progression.
• Active with progression — There are new or worsening symptoms, or scans show new lesions, and disability has increased over the past 12 months.

What Is the Prognosis for People With PPMS?

MS is an unpredictable disease. Some doctors believe two factors can help predict the prognosis of someone with PPMS: the age you were when PPMS symptoms began and which symptoms you had at that time.

Age at Onset

Those who are younger when PPMS symptoms begin may have a slower disease progression and a longer time until disability. Some data suggests that age is the only consistent predictor of disease course. Early diagnosis and prompt treatment are also shown to improve treatment outcome and prognosis.

Symptoms at Onset

Which symptoms occur first may provide insight into how quickly a person’s symptoms will progress. According to some studies, those who have sensory symptoms only when PPMS begins may progress more slowly than those who have a combination of sensory symptoms with other issues, such as muscle weakness and balance problems.

Individuals with PPMS are often thought to have a poorer prognosis than those with other forms of MS. Nerve damage in people living with PPMS tends to accumulate and cause disability sooner than it does for those with RRMS, the most common type of MS. The good news is that MS progresses quite slowly in most cases. Less than 25 percent of people with PPMS had reached disability milestones by their fifth year after diagnosis. Your health care provider can help you create a plan to slow down disease progression and improve outcomes.