In an uncontrolled clinical trial (13), 15 adults with confirmed HSP (8 with SPG4, 1 with SPG3A, 1 with SPG8, and 5 affected by AD-HSP without an identified mutation) and symptomatic calf muscle spasticity were treated with BoNTA injections in each triceps surae (500–750 MU of Dysport®, Ipsen Biopharm Ltd., Wrexham, UK). The gene discussed is SPAST; the disease is hereditary spastic paraplegia.