Can Botox in my face cause numbness in my thumb?

A motor nerve is a nerve that stimulates muscle contractions. A sensory nerve is a nerve that transmits sensations (temperature, pressure, pain etc). The motor nerve communicates with its corresponding muscle at what is called the neuromuscular junction. To initiate a muscle contraction, a signal is sent down the nerve cell. When that signal reaches the end of the nerve cell (the nerve terminal), a chemical (neurotransmitter) is released from the nerve terminal. This neurotransmitter stimulates the muscle cells to contract.



Botox works by interrupting the communication between the motor nerve and muscle, thereby reducing or eliminating the muscle contraction. The Botox molecule binds to a specific receptor at the very end of the nerve cell (the nerve terminal). The Botox molecule is taken up by the nerve cell, and through a series of actions Botox blocks the release of the neurotransmitter (acetylcholine) from the nerve terminal. When the neurotransmitter is not released, the nerve cannot cause the muscle to contract, and as a result the muscle relaxes.





The binding of Botox is irreversible, so the effect of Botox disappears as the Botox molecule degrades.





Botox works only on motor nerves that stimulate the contraction of muscles. Botox does not work on sensory nerves, so it does not cause numbness or other sensory changes.





When used as recommended for the treatment of facial lines and wrinkles, Botox  is administered in small doses and small volumes - so it acts very locally.





So, rest assured that Botox injections for your facial lines and wrinkles did not cause numbness in your thumb. That numbness is likely cause by some nerve compression in either your neck, arm, or wrist. Best wishes

Hello,

Botox can't cause any numbness in your thumbs. Its mechanism of action just doesn't work this way.  Please consult your neurologist for other possibilities such as carpal tunnel syndrome.

Best regards.

Edward Fruitman M.D.

Trifecta Med Spa. NYC

Botox in the forehead does not cause numbness on the extremities. The numbness in your thumb, may be from other reasons. The most common will be some pressure over the median nerve, this from a repetitive action on your wrist or forearm, also can be from sleeping over the arm or forearm during the night, etc. Check with a neurologist for a better evaluation.