WHAT IS SPASTICITY?

Spasticity is a common symptom of HSP, and is an over contraction of muscles due to abnormalities in the messages to the muscles (it results from a loss of inhibition in the motor neurones leading to excess contraction in the muscles). It is often described as a stiffness, tightness or rigidity of the muscles.

Spasticity can cause movement disorders, increased muscle tone, overactive reflexes, involuntary movements (such as clonus), pain, abnormal posture, joint contratures and deformities, and decreased functional abilities. It can be treated by medications, physiotherapy, stretching, botulinum toxin injections, serial casting and the use of orthotics (splints such as AFOs).

Spasticity is not exclusive to HSP, it may also be present in cases of cerebral palsy, multiple sclerosis, stroke patients, and various dystonias among other conditions, so diagnosis is usually made based on exclusion of such conditions, although family history is taken into account and genetic testing is also used.

Spasticity can be understood using the analogy of the brain being like a radio. In a person without HSP the radio sends clear signal which are received by the muscles in the legs and interpreted fully enabling normal movement patterns. In a person with HSP the radio is not properly tuned and so transmits a lot of static. When this reaches the muscles they are unsure what to do and so go into spasm. As some of the desired signals do get through the movement can still occur, but is disrupted by the static, leading to difficulty in intentional movement. The extent to which the desired signals reach the muscles varies from person to person.