Paraparesis occurs when you’re partially unable to move your legs. The condition can also refer to weakness in your hips and legs. Paraparesis is different from paraplegia, which refers to a complete inability to move your legs.

This partial loss of function can be caused by injury, genetic disorders, or viral infection. Keep reading to learn more about why this happens, how it can present, as well as treatment options and more.

Paraparesis results from degeneration or damage to your nerve pathways. This article will cover the two main types of paraparesis — genetic and infectious.

Hereditary spastic paraparesis (HSP)

HSP is a group of nervous system disorders that cause weakness and stiffness (spasticity) of the legs that get worse over time. This group of diseases is also known as familial spastic paraplegia and Strumpell-Lorrain syndrome. This genetic type is inherited from one or both of your parents.

It’s estimated that 10,000 to 20,000 people in the United States have HSP. Symptoms may begin at any age, but for most people they’re first noticed between the ages of 10 and 40 years.

Forms of HSP are lumped into two different categories: pure and complicated.

Pure HSP: Pure HSP has the following symptoms:

  • gradual weakening and stiffening of the legs
  • balance difficulties
  • muscle cramps in the legs
  • high foot arches
  • change in sensation in the feet
  • urinary problems, including urgency and frequency
  • erectile dysfunction

Complicated HSP: About 10 percent of people with HSP have complicated HSP. In this form, symptoms include those of pure HSP plus any of the following symptoms:

  • lack of muscle control
  • seizures
  • cognitive impairment
  • dementia
  • vision or hearing problems
  • movement disorders
  • peripheral neuropathy, which can cause weakness, numbness, and pain, usually in the hands and feet
  • ichthyosis, which results in dry, thick, and scaling skin

Tropical spastic paraparesis (TSP)

TSP is a disease of the nervous system that causes weakness, stiffness, and muscle spasms of the legs. It’s caused by the human T-cell lymphotrophic virus type 1 (HTLV-1). TSP is also known as HTLV-1 associated myelopathy (HAM).

It typically occurs in people in areas close to the equator, such as:

  • the Caribbean
  • equatorial Africa
  • southern Japan
  • South America

An estimated 10 to 20 million people worldwide carry the HTLV-1 virus, and less than 3 percent of them will go on to develop TSP. TSP affects women more than men. It may occur at any age, though the average age is 40 to 50 years.

Symptoms include:

  • gradual weakening and stiffening of the legs
  • back pain that may radiate down the legs
  • paresthesia, or burning or prickling feelings
  • urinary or bowel function problems
  • erectile dysfunction
  • inflammatory skin conditions, such as dermatitis or psoriasis

In rare cases, TSP can cause:

  • eye inflammation
  • arthritis
  • lung inflammation
  • muscle inflammation
  • persistent dry eye

Causes of HSP

HSP is a genetic disorder, meaning it’s passed from parents to children. There are more than 30 genetic types and subtypes of HSP. The genes can be passed on with dominant, recessive, or X-linked modes of inheritance.

Not all children in a family will develop symptoms, although they may be carriers of the abnormal gene.

About 30 percent of people with HSP don’t have any family history of the disease. In these cases, the disease starts randomly as a new genetic change that wasn’t inherited from either parent.

Causes of TSP

TSP is caused by HTLV-1. The virus can be passed from one person to another through:

  • breastfeeding
  • sharing infected needles during intravenous drug use
  • sexual activity
  • blood transfusions

You can’t spread HTLV-1 through casual contact, like shaking hands, hugging, or sharing a bathroom.

Less than 3 percent of people who have contracted the HTLV-1 virus develop TSP.

Diagnosing HSP

To diagnose HSP, your doctor will examine you, ask about your family history, and rule out other possible causes of your symptoms.

Your doctor may order diagnostic tests, including:

The results of these tests will help your doctor differentiate between HSP and other possible causes of your symptoms. Genetic testing for some types of HSP is also available.

Diagnosing TSP

TSP is usually diagnosed based on your symptoms and the likelihood that you were exposed to HTLV-1. Your doctor may ask you about your sexual history and whether you’ve used intravenous drugs before.

They may also order an MRI of your spinal cord or a spinal tap to collect a sample of cerebrospinal fluid. Your spinal fluid and blood will both be tested for the virus or antibodies to the virus.

Treatment for HSP and TSP is focused on symptom relief through physical therapy, exercise, and the use of assistive devices.

Physical therapy can help you maintain and improve your muscle strength and range of motion. It can also help you avoid pressure sores. As the disease progresses, you may use an ankle-foot brace, cane, walker, or wheelchair to help you get around.

Medications can help reduce pain, muscle stiffness, and spasticity. Medications can also help control urinary problems and bladder infections.

Corticosteroids, like prednisone (Rayos), may reduce inflammation of the spinal cord in TSP. However, they won’t change the long-term outcome of the disease.

Research on the use of antiviral and interferon medications is being done for TSP, but the drugs aren’t in regular use.

Your individual outlook will vary depending on the type of paraparesis you have and its severity. Your doctor is your best resource for information about the condition and its potential impact on your quality of life.

With HSP

Some people who have HSP may experience mild symptoms, while others may develop disability over time. Most people with pure HSP have a typical life expectancy.

Possible complications of HSP include:

  • calf tightness
  • cold feet
  • fatigue
  • back and knee pain
  • stress and depression

With TSP

TSP typically worsens over time, but it’s rarely fatal. Most people live for several decades after diagnosis. Preventing urinary tract infections and skin sores will help improve the length and quality of your life.

A serious complication of HTLV-1 infection is the development of adult T-cell leukemia or lymphoma. Although less than 5 percent of people with the viral infection develop adult T-cell leukemia, you should be aware of the possibility. Be sure your doctor checks for it.