User:Morgan Merritt/sandbox

=Cryoneurolysis=

Introduction
Cryoneurolysis, also referred to as Cryoanalgesia or Cryoneuroablation, is a procedure used to treat nerve pain. It is performed by inserting a small probe to locate and freeze the nerve. The procedure decreases the conductivity of the nerve and has similar effects to removing insulation from a wire. Other treatments for neuralgia including medications, alcohol injections, or surgery often fail or lead to returning nerve pain. Cryoneurolysis is minimally invasive and has significantly reduced pain in patients with many different conditions. The procedure allows for regeneration of the damaged nerve, as well as function of the nerve. Cryoneurolysis has been used to treat disorders such as phantom limb pain, pain associated with intercostal nerves, foot neuromas, ilioinguinal nerves, occipital neuralgia, and many others. The procedure can be used on almost any tissue in the body, and is able to provide pain relief with controlled tissue destruction.

Equipment
Cryoneurolysis is performed by using a probe, called a cryoprobe, which is a hollow tube with a smaller inner tube. Pressurized Carbon dioxide or Nitrous oxide is released into the tube and expands into the tip. The gas causes heat to be extracted from the probe and the temperature reaches as low as -89 degrees Celsius. Once the temperature has dropped, an ice ball forms at the tip of the probe. The ice ball ranges in temperature from -50 degrees to -70 degrees Celsius.

Technique
In order for the procedure to be effective, it is necessary for the target nerve to be precisely located. The first step in locating the correct nerve is palpation. Then, when necessary, fluoroscopic localization is used. The cryoprobe also has a nerve-stimulator in order to precisely locate the nerve. to Once the nerve is located, a local anesthetic is injected into the skin. It is important for the patient to not be sedated, unless necessary, so that they may respond to stimulation. To begin the Cryoneurolysis, a needle is inserted into the skin and the area is flushed with saline. A catheter is then inserted, through which the cryoprobe may pass. The cryoprobe is inserted into the catheter and the catheter is withdrawn to expose the tip of the probe. Once the nerve is correctly located with the probe, sensory stimulation begins. Once it is confirmed that the nerve is not too close to motor nerves, the gas flow is turned on. Upon initiation of gas flow, the patient will experience a burning sensation lasting for only about 30 seconds. After the first initial 30 seconds, the patient should not feel any pain. One cycle of Cryonurolysis consists of two-to-three minutes of freezing with 30 seconds of defrosting time following.

Physiology
All nerves cease conduction at -20 degrees Celsius, while myelinated nerves cease conduction at -10 degrees Celsius. When cold is applied to nerves, it creates a block in conduction. Cryoneurolysis works by damaging the vasa nervorum. The ice balls cause vascular damage to this structure. Wallerian degeneration is created, but the myelin sheath is not damaged. The structure for regeneration is provided by the Schwann cell basal lamina, which is not damages by Cryoneurolysis.

Treatment of Disorders
There are 5 categories of nerve injury:
 * first degree (neurapraxia)
 * second degree (axonotmesis)
 * third, fourth, and fifth (neurotmesis)

Cryoneurolysis can be used to treat conditions in any of the five categories. Some conditions which Cryoneurolysis has shown to effectively treat include Phantom limb pain, second trimester genetic amniocentesis, post-thoracotomy pain, and zygapophyseal joint pain.

Phantom Limb Pain
Phantom Limb Pain is understood to be caused by interactions between the central nervous system and the peripheral nervous system. It can cause anywhere from mild to severe pain. In a study done with five patients reportedly suffering from limb pain, 2.5 years after the Cryoneurolysis procedure, 60% of patients reported excellent results, 20% reported acceptable results, and 20% reported only a slight decrease in pain.

Second Trimester Genetic Amniocentesis
Second Trimester Genetic Amniocentesis is done in order to test a fetus for certain conditions, such as Down Syndrome and Spina Bifida. The procedure is very common, and also painful. In one study, 372 pregnant women were randomized to receive or not receive Cryoneurolysis prior to the Amniocentesis procedure. 184 received Cryoneurolysis and 188 did not. The study showed that the women who received Cryoneurolysis perceived less pain than those who did not, which concludes that Cryoneurolysis is effective in decreasing the pain of Second Trimester Genetic Amniocentesis.

Post-Thoracotomy Pain
Post-Thoracotomy Pain is often due to injury of the intercostal nerves. In a clinical study, 200 patients were randomized into Cryoneurolysis and non-Cryoneurolysis groups and their pain was assessed after a thoracotomy. In the Cryoneurolysis group, the nerve and function were completely restored after 6 months following the procedure. This study concluded that Cryoneurolysis provided long-term pain relief for post-thoracotomy pain.

Zygapophyseal Joint Pain
In 15%-54% of people with low-back pain, the cause is Lumbar facet joint syndrome. In a study, 91 patients underwent Cryoneurolysis over a 4-year period. This study showed a significant decrease in pain and concluded that Cryoneurolysis can lead to sustained pain relief.

Effectiveness
While it has been shown that Cryoneurolysis is effective in treating nerve pain, the ideal combination of temperature and duration of freezing is still debated. Cryoneurolysis performed at -20 degrees Celsius or higher has not shown any significant results, while treatment at -60 degrees Celsius or lower has. More severe nerve damage is caused by lower temperatures, and more severe damage leads to longer recovery time. Since Cryoneurolysis damages nerves without forming neuromas or causing neuritis, it can be performed repeatedly. Repeated Cryoneurolysis has not been shown to significantly decrease pain; however, since loss of nerve function is temporary, it may be necessary to perform the procedure again.

History
The use of cold for pain relief has been known since Hippocrates's (460-377 B.C) first written records. Since Hippocrates, there have been numerous accounts of ice as pain relief by Ancient Egyptians, Avicenna of Persia (A.D.982–1070) and many others. In 1812, half-frozen soldiers from the Moscow battle were noted to have been able to tolerate amputations with little pain. In 1851, Ice and Salt mixtures were promoted by Arnott for nerve pain. It was noted by Trendelenberg that nerve damage resulted from freezing, as well as nerve function. He also noted that nerves were able to regenerate. In 1961, Cooper et al. created an early cryoprobe, which reached a temperature of -190 degrees Celsius using liquid Nitrogen. Following this, in 1967 an Ophthalmic Surgeon named Amoils further developed the cryoprobe using carbon dioxide and nitrous oxide. His device reached a temperature of -70 degrees Celsius. The term "Cryoanalgesia" was coined by Lloyd and his coworkers.