Such neurosurgical targeting has proven effective in aromatic L-amino acid decarboxylase (AADC) deficiency, where a recombinant AAV cassette containing a working copy of defective enzyme L-dopa decarboxylase is stereotactically injected into bilateral putamina or substantia nigra pars compacta [10, 116]. Here, DDC is linked to aromatic L-amino acid decarboxylase deficiency.