The Injection of Botox to reduce facial lines and wrinkles has long been assumed to be purely cosmetic in nature. Hollywood’s rush to it has normalized the procedure and even given it an air of frivolity.
New research, however, has revealed an unintentional and rather dramatic consequence: Botox injections in the forehead rearrange the brain’s sensory map of the hands. The scary part is that clients typically come back for regular injections, because the paralysis the toxin induces lasts only two to three months. The unanswered question is whether repeated treatments over a period of years results in permanent changes to one’s brain.
Botox is the brand name for botulinum toxin–a, one of the most lethal poisons known. The neurotoxin is produced by the bacterium Clostridium, a spore commonly found in plants, soil, water, and animals. The clinical syndrome of botulism, which is often lethal, typically occurs from either a wound infection or eating undercooked or improperly canned food. The toxin paralyzes muscles by blocking the release of acetylcholine, the principal neurotransmitter at the nerve–muscle junction.
For a long time we have known that the brain is plastic, meaning that it circuits and microscopic anatomy are malleable. They can physically change in response to a number of factors. For example, in violinists the brain map devoted to the non-bowing fingers is much larger than the same finger region in non-violinists. In newly-blind individuals learning braille, the cortical area devoted to the “reading finger” greatly expands into the suddenly unused visual cortex.
The brain maps of the hand and face territories lie next to one another in the sensory cortex. After hand amputations, tactile inputs from the face routinely widen and shift into the territory newly deprived of sensory input from the hand. Likewise, patients with facial paralysis due to Bell’s palsy or stroke have enhanced metabolic activity in the hand region of the sensory cortex. The principle is well established that the cortical representation of one body part widens in response to injury affecting another body part.
Based on this knowledge one would expect hand maps to increase after a patient’s face is paralyzed by Botox injections. And yet exactly the opposite happens. This suggests that the cortical reorganization to a limited Botox facial paralysis is intrinsically different from that observed after functional loss from amputations, facial nerve injury, or stroke.
The tentative explanation for this surprising observation is that the limited paralysis caused by Botox deprives the brain of sensory inputs normally generated by forehead movement. Even more unexpected is that both hands suffer a loss of cortical brain activity following a relatively small loss of facial movements.
The current studies did not investigate whether cortical remapping was limited only to the hands, or whether other body parts also suffered. But it is a question that all who elect this procedure should ponder. If This topic strikes a note, drop me a line.