Various embodiments may include methods of manufacture of a retrofitted neural injection system. Various embodiments may include acquiring an injection needle comprising a hollow cannula with an open distal end. Then, forming at least one side port in the hollow cannula proximate to the distal end. Then, sealing the open distal end of the hollow cannula with a biocompatible sealant so as to eliminate fluid communication between an inside and an outside of the hollow cannula via the distal end. In some embodiments, the biocompatible sealant may be comprised of a thermosetting material. In some embodiments, the biocompatible sealant may be comprised of a cured epoxy resin. In some embodiments, the biocompatible sealant may be comprised of an aliphatic polymer. In some embodiments, the biocompatible sealant may be comprised of a polyfluorocarbon.