Evolution of Technology

Botox Chemical Denervation

Botox, aka Onabotulinumtoxin A, is an example of a chemical compound used in selective denervation. It is isolated from the naturally occurring neurotoxin Clostridium botulinum. The mechanism of its action is via prevention of the release of the neurotransmitter acetylcholine at the presynaptic nerve terminal. In this way it effectively blocks neurotransmission from nerve to muscle or gland. This state can last for months, until certain components of the nerve are able to regenerate and again release acetylcholine at the presynaptic terminal.

Evolution of Procedure

Selective Denervation

Selective denervation refers to the providers ability to select which neuron they would like to deem non functional. This may be done in cases of facial muscle asymmetry after facial paralysis, or more commonly with Botox injections for facial “wrinkles”, or rhytids. Two ways of performing selective denervation are with mechanical, or “cold knife” excision, and chemically with injectable material. Cold knife denervation consists of a surgeon isolating a nerve (commonly with the innervated muscle) and selectively severing it without damaging surrounding structures. This should deem the innervated muscle paralyzed.

Evolution of Diagnosis

Frey Syndrome

Frey syndrome, also knowing gustatory sweating, is classically described in patients after parotidectomy surgery. It occurs as a result of aberrant reinnervation of the superficial skin sweat glands by the deeper parotid parasympathetic neurons. Generally, there is a proportional increase in occurrence and severity of gustatory sweating with increases in extent of parotid tissue excised. The result of this phenomenon is that the patient may sweat from the cheek when encountering certain foods or flavors.