| Prevalence | 1.2–9.6 per 100,000 depending on population and ascertainment methods. Estimated global incidence rate of 3.6 per 100,000. |
| Autosomal dominant (AD-HSP) | 75–80% of registered cases in European populations |
| Autosomal recessive (AR-HSP) | More common in consanguineous populations (North Africa, Middle East, South Asia) |
| X-linked | Rare (<5%) |
| De novo mutations | Increasingly recognized with expanded genetic-testing |
| Age at onset | Highly variable — from infancy to the 7th decade. Bimodal distribution with peaks in the 1st decade (childhood-onset forms) and 3rd–4th decades (adult-onset forms). |
| Most common subtypes | SPG4 (40–45% of AD-HSP), SPG3A (~10% of AD-HSP), SPG11 (18% globally, most common AR-HSP). |
| Pure HSP | Most commonly associated with SPG4, SPG3A, SPG31, SPG6 |
| Complex HSP with thin corpus callosum | SPG11, SPG15, SPG47-50 |
| HSP with cerebellar ataxia | SPG7, SPG46 |
| HSP with peripheral neuropathy | SPG3A, SPG10, SPG30 |
| HSP with cognitive impairment | SPG11, SPG15, SPG21, SPG47-50 |
| Databases | OMIMOrphanetClinicalTrialsPubMed |