Hereditary Spastic Paraparesis (HSP), also known as familial spastic paraplegia, comprises a group of inherited disorders that primarily affect the lower extremities. The main clinical features involve progressive spasticity and weakness of the legs due to degeneration of the axonal tracts of the corticospinal pathway in the spinal cord.

Epidemiology

HSP affects approximately 1 in 11,000 people. The disorder can be inherited in autosomal dominant, autosomal recessive, or X-linked patterns, leading to varied presentations and onset across patients.

Aetiology

The aetiology of HSP involves genetic mutations leading to axonal degeneration, primarily of the corticospinal tracts, but also potentially of the dorsal column pathways. These changes are most pronounced in corticospinal tracts leading to the lower limbs and the fasciculus gracilis fibres (part of the dorsal column) from the lower limbs. As a result, the lower limbs are usually more affected than the upper limbs.

PC

Key diagnostic criteria for HSP include:

• A family history of the condition
• Progressive gait disturbance
• Spasticity of lower limbs
• Hyper-reflexia of lower limbs
• Extensor plantar responses

Typically, the power in lower limb muscles is normal or only mildly reduced.

Differential Diagnosis

The main conditions to consider in the differential diagnosis of HSP include:

• Multiple Sclerosis (MS): This condition can present with lower limb spasticity and hyper-reflexia. However, MS typically has episodic symptoms, sensory deficits, and optic neuritis which are not seen in HSP.
• Amyotrophic Lateral Sclerosis (ALS): While ALS can cause spasticity and hyper-reflexia, it also leads to progressive muscle weakness, atrophy, and bulbar signs which distinguish it from HSP.
• Cerebral Palsy (CP): CP may present with similar symptoms to HSP but typically has an early onset (infancy to early childhood) and is non-progressive.