Dorsal root ganglia, posterior roots and peripheral nerves are not directly affected.HSP affects several pathways in motor neurons. Many genes were identified and linked to HSP. It remains a challenge to accurately define the key players in each of the affected pathways, mainly because many genes have multiple functions and are involved in more than one pathway. Axon pathfinding
Pathfinding is important for axon growth to the right destination (e.g. another nerve cell or a muscle). Significant for this mechanism is the L1CAM gene, a cell surface glycoprotein of the immunoglobulin superfamily. Mutations leading to a loss-of-function in L1CAM are also found in other X-linked syndromes. All of these disorders display corticospinal tract impairment (a hallmark feature of HSP). L1CAM participates in a set of interactions, binding other L1CAM molecules as well as extracellular cell adhesion molecules, integrins, and proteoglycans or intracellular proteins like ankyrins.The pathfinding defect occurs via the association of L1CAM with neuropilin-1. Neuropilin-1 interacts with Plexin-A proteins to form the Semaphorin-3A receptor complex. Semaphorin-a3A is then released in the ventral spinal cord to steer corticospinal neurons away from the midline spinal cord / medullary junction. If L1CAM does not work correctly due to a mutation, the cortiocospinal neurons are not directed to the correct position and the impairment occurs. Lipid metabolism
Axons in the central and peripheral nervous system are coated with an insulation, the myelin layer, to increase the speed of action potential propagation. Abnormal myelination in the CNS is detected in some forms of hsp HSP.
Available therapies mainly consist of symptomatic medical management and promoting physical and emotional well-being. Therapeutics offered to HSP patients include:

Baclofen – a voluntary muscle relaxant to relax muscles and reduce tone. This can be administered orally or intrathecally. (Studies in HSP )
Tizanidine – to treat nocturnal or intermittent spasms (studies available )
Diazepam and clonazepam – to decrease intensity of spasms
Oxybutynin chloride – an involuntary muscle relaxant and spasmolytic agent, used to reduce spasticity of the bladder in patients with bladder control problems
Tolterodine tartrate – an involuntary muscle relaxant and spasmolytic agent, used to reduce spasticity of the bladder in patients with bladder control problems
Cro System – to reduce muscle overactivity (existing studies for spasticity )
Botulinum toxin – to reduce muscle overactivity (existing studies for HSP patients)
Antidepressants (such as selective serotonin re-uptake inhibitors, tricyclic antidepressants and monoamine oxidase inhibitors) – for patients experiencing clinical depression
Physical therapy – to restore and maintain the ability to move; to reduce muscle tone; to maintain or improve range of motion and mobility; to increase strength and coordination; to prevent complications, such as frozen joints, contractures, or bedsores. Prognosis
Although HSP is a progressive condition, the prognosis for individuals with HSP varies greatly. It primarily affects the legs although there can be some upperbody involvement in some individuals. Some cases are seriously disabling while others are less disabling and are compatible with a productive and full life. The majority of individuals with HSP have a normal life expectancy.