1. Chronic pain Syndromes including :
a. Chest wall pain
b. Facial pain syndromes such as tic douloureux and other non-herpetic neuralgias
c. Occipital, suprascapular, ilioinguinal and other specific neuralgias
d. Facet syndrome including cervical, thoracic and lumbosacral
e. Coccydynia
f. Perineal neuropathies
g. Phantom Limb
h. Trigger points
i. Painful neuromas
J. painful superficial scars
k. Chronic low back pain with radiculopathy
I. Pituitary ablation
m. Sacral root block for sciatica pain
2 .Acute postoperative pain from thoracotomy and inguinal hernia repair
3 .Cancer pain

The use of cryoanalgesia in the management of chronic pain syndrome is gaining acceptance. It is particularly useful when other modalities of pain relief are unacceptable to patients such as surgery or device implantation, too difficult to perform, have a high incidence of complications or side effects, or has been ineffective. The techniques has been utilized in the treatment of various types of neuralgias (fascial, intercostal, postherpetic, posttraumatic), myofascial trigger point pain, post-surgical pain, cancer pain, neuroma, phantom limb pain, cervicogenic headache, cervicalgia, thoracic, lumbar and coccygeal pain. It is an outpatient procedure, readily acceptable to patients, minimal complications, and an effective alternative to pharmacologic pain Killers.

Nitrous oxide delivery system, allows safe delivery of nitrous oxide of up to 850 psi to the gas expansion orifice in the tip of the cryoprobe,uses the Joule- Thompson principle where , pressurized gas expands through a fine orifice producing a rapid drop in , temperature and freezing the probe tip and the surrounding tissue.
The freezing cycle is started by pressing the footswitch in approx 5 seconds the minimum freezing temperature of approx 60c to 75b is reached.
After release of the foots-wich the freezing cycle stops automatically and the defrost cycle starts defrosting the cryoprobe within 2-5 seconds without electric heating (non electrical).
The machine is provided with a gas pressure regulator switch and dials to record gas pressure.
Nitrous oxide is the refrigerant and is provided in a F cylinder tank .
Probe tip temperature monitoring ensure optimum freezing performance will inform operator constantly on Electronic Commond Console (E.C.C.)
1) Rapid freeze and quick defrost. Foot control provision.
2) Chargeable battery operated 6V, to prevent electrical hazard shock.
3) An alarmed timer and buzzer for the control of freezing time (mounted on E.C,C.)
4) Special insulation and isolation of the cryopencil.
5) Micro filters built into the inner exosis prevent foreign particles entering the gas line in the cryoprobe (gas scavenge system).
6) Tips (probes) may be autoclaved (uptil +134C°) and cryopencil assembly can be chemically disinfected (Cidex or Habitane) Uses N20 (600-900psi).

The basic mechanism by which pain relief results from application of freezing is the development of intracellular and extra cellular ice crystals. This creates a series of biochemical, anatomic and physiologic events in nerve tissues causing increased tonicity of intracellular and extra cellular fluids, damage to cellular proteins, cell membrane disruption caused by rapid water loss, and physical destruction of the myelin sheath and Schwann cells. Additionally, there is an associated vascular damage, allowing plasma and extra cellular fluid extravasations into the endoneurium.
Elevation of endoneural fluid pressure is highly associated with the development of Waller Ian degeneration, whereby the axon and the myeline sheath degenerate from the point of freezing distally to the nerve termination.
The size and length of nerve destruction is temperature dependent.
The intensity and duration of analgesia is dependent on the degree of nerve damage.
Nerve damage can be categorized as:
a. First degree or Neuropraxia: produces minimal damage and disrupts neural function for approximately two weeks.
b. Second degree or Axonotmesis: destruction of the axon and myeline sheath, with pain relief for several months. This is the degree of nerve injury sought by nerve cryolesoning and is a achieved by application of temperature at least 20 degrees centigrade. This results in axonal damage at the site of injury but the fibrous architecture of the nerve including the endoneurium, perineurium and epineurium is preserved. Nerve regeneration occurs almost immediately at a rate of 1-1.5 mm a day and regeneration within the intact endoneural tube occurs from the point of injury distally. Nerve histology remains normal but slower nerve conduction velocity persists up to 35 days after the new myeline sheath are fully formed. The rate and extent of cryolesioning is dependent on the proximity of the nerve to the cryoprobe, size of the cryoprobe, temperature attained by the tissue in proximity to the cryoprobe, and the rate of freezing and defrosting. The closer the probe to the nerve, the greater and more intense the neurolysis. Cryoprobes are available in various sizes. The standard freeze zones that could be created at equilibrium were 10 and 6 mm with the 14 and 16 gauge gas expansion cryoprobe, respectively. Repeated freeze-thaw cycle significantly increases the size of the lesion. Repeated cycles decrease the temperature at more distal sites from the cryoprobe and increase the freeze zone by as much as 70 percent.
c.Third to Fifth degree or Neurotmesis: destruction of both neural and stromal tissues with longer duration of analgesia. Regeneration and return of function is unpredictable. The fibrous architecture is destroyed such that neuroma formation and neuritis can develop.
The subsequent pain associated with this complication may be more intense than the original pain. Incomplete and abnormal nerve regeneration may manifest itself as anesthesia dolorosa.
Fifth degree injury is irreversible and no nerve regeneration occur, although neuroma can still form.