Hereditary Spastic Paraplegia (HSP)

How HSP affects the body

Movement signals travel from the brain's motor cortex down long nerve fibers (the corticospinal tracts) in the spinal cord. These are among the longest nerve fibers in the body, and in HSP their far ends gradually deteriorate. The fibers to the legs are longest, so the legs are affected first and most. The result is an "upper motor neuron" pattern: stiffness, brisk reflexes and weakness, rather than muscle wasting.

Types of HSP

By symptoms

• Pure (uncomplicated) HSP: leg spasticity and weakness, often with bladder urgency and mild loss of vibration sense in the feet. Most common.
• Complicated (complex) HSP: additional problems such as ataxia, peripheral neuropathy, intellectual disability, seizures, vision or hearing problems, or a thin corpus callosum on MRI.

By inheritance

• Autosomal dominant: one copy of the faulty gene causes HSP, and each child of an affected parent has a 50 percent chance of inheriting it. SPG4 (SPAST gene) is the most common form overall.
• Autosomal recessive: two faulty copies are needed. These forms are more often complicated.
• X-linked and mitochondrial forms are rare.

Different genetic types are named SPG followed by a number.

Symptoms

• Stiff legs, especially the calves and thighs
• Difficulty walking, tripping and dragging the toes
• A stiff-legged, scissoring walk, or walking on tiptoes
• Weakness in the hips and legs
• Muscle spasms and cramps
• High arches and curled toes over time
• Bladder urgency, frequency or incontinence
• Reduced vibration sense in the feet
• Fatigue and back pain from altered posture

Onset varies widely, even within one family. Progression is usually slow over years to decades. Some childhood-onset forms progress little after adolescence.

Diagnosis

HSP is a diagnosis made after other causes of leg spasticity are excluded.

• Neurological examination: spasticity, weakness, brisk reflexes and upgoing toes (Babinski sign) in the legs.
• Family history of similar walking problems.
• MRI of the brain and spine to rule out spinal cord compression, multiple sclerosis, tumors and other structural causes.
• Blood tests: vitamin B12, copper, HIV, HTLV-1, syphilis and other causes of spinal cord disease.
• Genetic testing: a gene panel or exome sequencing identifies the type in many people, though not all.

Conditions that can look similar

Treatment

There is no treatment that stops nerve degeneration yet. Care focuses on maintaining mobility, comfort and independence:

• Physical therapy: daily stretching, strengthening, aerobic exercise and balance training. Regular exercise is the cornerstone of care.
• Spasticity medicines: oral baclofen, tizanidine or gabapentin. Intrathecal baclofen pumps for severe spasticity.
• Botulinum toxin injections into specific tight muscles.
• Orthotics: ankle-foot orthoses, braces and supportive footwear.
• Mobility aids: canes, walkers, and wheelchairs for longer distances.
• Bladder management: medicines for urgency, pelvic floor therapy, and checks for incomplete emptying.
• Occupational therapy for home and work adaptations.
• Surgery for contractures or tendon tightness in some cases.
• Genetic counseling for affected families.

Outlook

Life expectancy is usually normal in pure HSP. The degree of disability varies: some people have only mild stiffness, while others eventually need a wheelchair. Complicated forms may have a more serious course depending on the type. Research into gene-targeted therapies is ongoing.

Frequently asked questions

What is hereditary spastic paraplegia?

Hereditary spastic paraplegia is a group of inherited conditions in which the nerve fibers carrying movement signals to the legs slowly degenerate. This causes increasing stiffness and weakness of the legs and difficulty walking. It can start at any age.

Is hereditary spastic paraplegia fatal?

Pure HSP does not usually shorten life expectancy. It mainly affects walking and mobility. Some complicated forms with additional neurological problems may have a more serious course. Physical therapy and spasticity treatment help maintain function.

How is HSP inherited?

Most commonly autosomal dominant, meaning a parent with HSP has a 50 percent chance of passing it to each child. Some types are autosomal recessive, where both parents carry a gene change, and rare types are X-linked. Genetic testing and counseling can clarify the pattern in a family.

Can hereditary spastic paraplegia be treated?

There is no cure, but treatment helps. Daily stretching, exercise and physical therapy maintain mobility. Medicines such as baclofen and tizanidine, botulinum toxin injections and orthotics reduce stiffness. Bladder symptoms can also be treated.