In Reply Ramirez-Zamora and Okun suggested that the conditions of spastic paraplegia type 7 (SPG7) and adult-onset Alexander disease should have been included in the discussion of the differential diagnoses.
Hereditary spastic paraplegias are a diverse group of conditions, many of which have onset in adulthood.1 Most of these disorders are heralded by spasticity as a prominent feature. Spastic paraplegia type 7 can often present with ataxia.1 However, symptom onset in most of these cases is in the mid- to late-30s, which is later than symptom onset in the presented patient.2 Clinical features, such as proximal weakness leading to waddling gait, ophthalmoplegia, and cognitive impairment associated with SPG7 mutation, were not present in our case. Additionally, many SPG7 cases are associated with moderate to severe cerebellar atrophy on magnetic resonance imaging, which was not present in the case discussed.3
Remster E, Dubey D. Considering Spastic Paraplegia Type 7 and Adult-Onset Alexander Disease—Reply. JAMA Neurol. Published online May 01, 2017. doi:10.1001/jamaneurol.2017.0433