[Treatment and indication of botulinum toxin type A for limb spasticity - can we break the 6 months barrier?]

It is common knowledge that recovery of motor function is limited at 6 months after the onset of stroke. But there are some reports that motor functions are improved with using botulinum toxin type A for limb spasticity in the maintenance stage of stroke. Though it has been thought that botulinum toxin type A works in the peripheral nerves so far, Caleo showed botulinum toxin can affect the central nervous system. We suspected botulinum toxin type A affected the spinal cord directly following retrograde transynaptic transport from our experiments and his reports. So, we deduce the abnormal stretch reflex is made a modification by affecting the spinal cord, not only the injected muscle is relaxed, but also motor function is improved. Botulinum toxin type A shows sustained activity up to only 3 months, so we think we should use sufficient dose of botulinum toxin which may cause weakness. Rehabilitation with injected muscles contractions is important soon after botulinum toxin treatment, because botulinum toxin has a specific affinity to cleave certain proteins involved in the mechanism of acetylcholine exocytosis. The new botuslinum toxins type A which decrease the risk of production of antibodies and diffusion of noninjected muscles are under development.