Cryoablation

Cryoablation is a process that uses extreme cold to destroy tissue. Cryoablation is performed using hollow needles (cryoprobes) through which cooled, thermally conductive fluids are circulated. Cryoprobes are positioned adjacent to the target in such a way that the freezing process will destroy the diseased tissue. Once the probes are in place, the attached cryogenic freezing unit removes heat from ("cools") the tip of the probe and by extension from the surrounding tissues.

Ablation occurs in tissue that has been frozen by at least three mechanisms:

1. formation of ice crystals within cells thereby disrupting membranes, and interrupting cellular metabolism among other processes;
2. coagulation of blood thereby interrupting bloodflow to the tissue in turn causing ischemia and cell death; and
3. induction of apoptosis, the so-called programmed cell death cascade.

The most common application of cryoablation is to ablate solid tumors found in the lung, liver, breast, kidney and prostate. The use in prostate and renal cryoablation are the most common. Although sometimes applied in cryosurgery through laparoscopic or open surgical approaches, most often cryoablation is performed percutaneously (through the skin and into the target tissue containing the tumor) by a medical specialist, such as an interventional radiologist. The term is from cryo- + ablation.

This offers distinct advantages and disadvantages when compared to other pain management modalities. Unlike chemical neurolysis (e.g., alcohol or phenol), cryoanalgesia is non-neurolytic and maintains the nerve's architectural integrity, facilitating regeneration and reducing the risk of deafferentation pain. Compared to radiofrequency ablation (RFA), cryoanalgesia often results in a less painful procedure and a lower incidence of neuroma formation. However, RFA may offer longer-lasting pain relief in some cases. Traditional local anesthetic nerve blocks provide immediate but short-lived relief, whereas cryoanalgesia provides extended pain control without permanent nerve destruction

The equipment for cryoanalgesia typically consists of a cryoanalgesia unit (console) and specialized cryoprobes. The console regulates the flow of a cryogen (e.g., nitrous oxide or carbon dioxide gas) to the tip of the cryoprobe. Cryoprobes vary in size and design, featuring a small, insulated shaft and a uninsulated tip that forms an ice ball upon activation. Different probe sizes are chosen based on the target nerve's diameter and location.

Cryoanalgesia is indicated for a wide range of chronic pain conditions where a temporary but prolonged nerve block is desired. Common indications include post-thoracotomy pain syndrome, intercostal neuralgia, trigeminal neuralgia (peripheral branches), occipital neuralgia, neuropathic pain following surgery or trauma, phantom limb pain, and pain associated with spasticity. It is also used for managing acute pain in certain surgical procedures, such as rib fractures or sternotomy.