KIF1A and Alzheimer disease: SPG4, related toSPASTgene mutation, is the most common SPG and may rarely present with cerebellar atrophy.63Other AD SPG may also present with ataxia, including SPG6, SPG10, SPG27, SPG30 and SPG31.61Moreover, another AD neurologic disorder that manifests either as isolated spastic paraplegia or the combination of ataxia, spastic paraplegia, and mental retardation, was described in 2002 and named as spastic paraplegia, ataxia and mental retardation (SPAR).64