SPG11 and Global developmental delay: The most common form of autosomal dominant disease, SPG4 (spastin, 30–40% of autosomal dominant families) is typically associated with ‘uncomplicated’ forms of disease while others such as SPG11 (spatacsin, autosomal recessive, 50% of recessive families) are frequently associated with cognitive delays and characteristic neuroimaging findings (i.e., thin corpus callosum) [6,38,39].