WHAT IS HSP?

HSP (Hereditary Spastic Paraplegia) is not a single disease entity, but a group of rare inherited neurological conditions characterised by progressive spasticity and weakness of predominantly the lower limbs. This can cause severe gait (walking pattern) abnormalities and lead to some people being unable to walk. Some people experience difficulties with upper limb movement, continence, and fatigue.

It affects around 1 in 10,000 people and there are currently more than 30 known genetic mutations which can cause it including dominant, recessive and x-linked forms. HSP is caused by genetic mutations leading to long axonal degeneration of the upper motor neurones (the nerves in the brain and spinal cord which carry signals to the legs). Nerves in the brain's motor cortex control voluntary movement, they deliver signals via axons to lower motor neurones in the spinal cord. These spinal motor neurones transmit their impulses to the muscles. In HSP there is degeneration of the brain's motor nerves (upper motor neurones), as a result of this nerve impulses do not adequately reach the spinal motor neurone. this means that when the signal reaches the muscles in the legs it is not able to be interpreted resulting in spasticity and weakness. These symptoms increase over time as the nerve degeneration progresses.

HSP is known by a variety of names including hereditary spastic paraplegia / paraparesis, familial spastic paraplegia / paraparesis, Strumpell-Lorrain Disease, spastic spinal paralysis, diplegia spinalis progressiva and spastic paraplegia. The most commonly used terms are hereditary spastic paraplegia / paraparesis and familial spastic paraplegia / paraparesis, although HSP is arguably the more accurate of the two.