Cryoneurolysis

Dr .Moallemy

Historical Considerations

Cryoanalgesia is a technique in which cold is applied to produce pain relief.

The analgesic effect of cold has been known to humans for more than 2 millennia. Hippocrates (460–377 bc) provided the first written record of the use of ice and snow packs applied before surgery as a local pain-relieving technique.

Early physicians, such as Avicenna of Persia (980–1070 ad) and Severino of Naples (1580–1656) recorded using cold for preoperative analgesia.

In 1812, Napoleon's surgeon general, Baron Dominique Jean Larrey, recognized that the limbs of soldiers frozen in the Prussian snow could be amputated relatively painlessly.

Contemporary interest in cryoanalgesia was sparked in 1961, after Cooper described a cryotherapy unit in which liquid nitrogen was circulated through a hollow metal probe that was vacuum insulated except at the tip.

The coldest temperature used today is approximately −70°C.

Physics of Cryoanalgesia The working principle of a cryoprobe is that compressed gas

(nitrous oxide or carbon dioxide) expands. The cryoprobe consists of an outer tube and a smaller inner

tube that terminates in a fine nozzle High-pressure gas (650 to 800 psi) is passed between the two tubes and is released through a small orifice into a chamber at the tip of the probe. In the chamber, the gas expands, and the substantial reduction in pressure (80 to 100 psi) results in a rapid decrease in temperature and cooling of the probe tip.

Absorption of heat from surrounding tissues accompanies expansion of any gas, according to the principles of the general gas law; this is the adiabatic principle of gas cooling and heat extraction, also known as the Joule-Thomson effect.

The sealed construction of the cryoprobe ensures that no gas escapes from the probe tip, handle, or hose.

The rapid cooling of the cryoprobe produces a tip surface temperature of approximately −70°C (–94°F)

Tissue in contact with the tip cools rapidly and forms an ice ball. The ice ball varies in size, depending on probe size, freeze time, tissue permeability to water, and the presence of vascular structures (heat sink). The ice ball typically measures 3.5 to 5.5 mm in diameter.

Precise levels of gas flow through the cryoprobe are essential for maximum efficiency. Inadequate gas flow does not freeze tissue. Excessive gas flow results in freezing down the stem of the probe and the associated risk of cold skin burns.

The application of cold to peripheral nerves, whether by direct cooling of localized segments or complete immersion of tissue in a cold medium, induces reversible conduction block. The extent and duration of the effect depend on the temperature attained in the tissues and the duration of exposure.

In practice, a freeze of 2 to 3 minutes' duration produces a good result.

Histologically, the axons and myelin sheaths degenerate after cryolesioning (wallerian degeneration), but the epineurium and perineurium remain intact, thus allowing subsequent nerve regeneration. The duration of the block is a function of the rate of axonal regeneration after cryolesioning, which is reported to be 1 to 3 mm/day

The absence of external damage to the nerve and the minimal inflammatory reaction to freezing ensure that regeneration is exact. The regenerating axons are unlikely to form painful neuromas. (Surgical and thermal lesions interrupt perineurium and epineurium.) Other neurolytic techniques (alcohol, phenol) potentially can produce painful neuromas because the epineurium and perineurium are disrupted.

Clinically, a cryoblock lasts weeks to months. The analgesia often lasts longer than the time required for

axons to regenerate. The reasons are still a matter of speculation, but it is obvious that cryoanalgesia is more than just a temporary disruption of axons. Possibly, sustained blockade of afferent input to the central nervous system (CNS) has an effect on CNS windup.

One report suggested that cryolesions release sequestered tissue protein or facilitate changes in protein antigenic properties.

Perhaps immune mechanisms play a role in the analgesic response after cryoablation.

Indications and Contraindications

Cryoanalgesia is best suited for clinical situations when analgesia is required for weeks or months. Permanent blockade does not usually occur because the cryoinjured axons regenerate .

Cryoanalgesia is suited for painful conditions that originate from small, well-localized lesions of peripheral nerves (e.g., neuromas, entrapment neuropathies, and postoperative pain).

Cryoablative procedures can be open or closed (percutaneous), depending on the clinical setting. Most often, open procedures are performed as part of postoperative analgesia.

The cryoprobe is withdrawn only after the tissue thaws because removing it earlier can tear tissue.

Percutaneous (closed) cryoablation is the technique of choice for outpatient chronic pain management.

Patients should be fully aware that a cryoanalgesia procedure usually is not a permanent solution. It can ameliorate symptoms, however, and can allow the patient to participate in physical therapy more fully.

Cryoanalgesia for chronic pain syndromes always should be preceded by diagnostic or prognostic local anesthetic injections.

After a test block with local anesthetic, the examiner should inquire about the patient's tolerance to the numbness and the extent of pain reduction.

If the patient's response to the test injections is inadequate, the patient will not have a good response to cryodenervation. Patients also should be aware that numbness can replace pain, and small areas of skin depigmentation can occur if the ice ball frosts skin because the probe is not deep enough or is inadequately insulated from tissues.

All procedures are performed with appropriate sterile preparation. As a general rule, infected areas are avoided.

TECHNIQE The cryolesion is attempted only after successful temporary reduction of symptoms by a diagnostic block . Localization is facilitated with stimulation between 50 and

100 Hz at less than 0.5 V for sensory nerves or at 2 to 5 Hz for motor nerves.

Two or three 2-minute cycles are usually sufficient.

During the freezing, care is taken to prevent frostbite if the probe comes in direct contact with the skin. Continuous irrigation with 0.9% saline solution at room temperature reduces the possibility of skin injury.

Clinical Pearls and Tricks of theTrade1.Postoperative Pain Management

At many institutions, cryoanalgesia is reserved for patients with special analgesia needs and patients at high risk who cannot receive standard postoperative treatment

Cryoanalgesia procedures are provided intra-operatively by surgeons who have access to involved peripheral nerve and pain management specialists participating in the operative procedure.

At times, pain specialists are called on to provide cryoanalgesia postoperatively, in which case they must decide whether some other alternative is more suitable than open or closed cryodenervation.

Popular Cryodenervation Techniques for Postoperative Pain Management

Post-thoracotomy pain: Post-thoracotomy cryoanalgesia is most effective for treating

incisional pain, but it is ineffective for pain from visceral pleura supplied by autonomic fibers or for ligament pain of the chest secondary to rib retraction. Post-thoracotomy cryoanalgesia often has little effect on chest tube pain, for

the same reasons. For effective intra-operative cryoneurolysis, intercostal

nerves on each side of the thoracotomy incision are lesioned. If a rib is removed, that intercostal nerve also undergoes cryolesioning. The intercostal nerves are best cryoablated just lateral to the transverse process, before the collateral intercostal nerve branches

A comparison of epidural analgesia and intercostal nerve cryoanalgesia for post-thoracotomy pain as part of a randomized control study cast some doubt on the long-term utility of cryoanalgesia for post-thoracotomy pain.

Both thoracic epidural analgesia and intercostal nerve cryoanalgesia produced satisfactory analgesia for post-thoracotomy acute pain. The incidence of post-thoracotomy chronic pain is high. Cryoanalgesia may be a factor that increases the incidence of neuropathic pain.

Postherniorrhaphy pain: A cryolesion of the ilioinguinal nerve reduced analgesic

requirements during the postoperative period. After repair of the internal ring, posterior wall of the

inguinal canal, and internal oblique muscle, the ilioinguinal nerve on the surface of the muscle is identified and mobilized. The surgeon elevates the nerve above the muscle, and an assistant performs the cryoablation.

the technique is not widely used. Given its effectiveness and freedom from side effects, it

is ideal for ambulatory surgery.

Chronic Pain Management

For management of chronic pain, open cryoablation is avoided whenever the procedure can be performed effectively percutaneously.

Before committing to cryoablation, the provider must perform a series of test blocks to determine presence of a consistent analgesic response. A favorable response before cryoablation occurs when the local anesthetic injection decreases pain, and the numbness that replaces the pain is tolerated by the patient.

Care always must be taken to ensure correct positioning of the needles. When necessary, fluoroscopic guidance should be used.

Many patients with chronic pain have suffered for a long time and are hopeful that the next procedure is going to be the long-awaited successful treatment. These patients are responsive to suggestion and placebo effect. To identify such effects, the first test injection is done with lidocaine and the second with bupivacaine.

For patients who do not have the desired response to bupivacaine or lidocaine, further testing is necessary, including differential blockade with local anesthetics and normal saline solution and consideration of consultation with a clinical psychologist.

Bending the probe during percutaneous introduction can distort the lumen of the low-pressure outer tube, increase the resistance pressure to the expanding nitrous oxide gas, and convert a low-pressure exhaust system to one of higher pressure.

To maintain the integrity of the cryoprobe, the probe should be placed through an introducer.

The operator always should check to see that the cryoprobe fits through the lumen of the catheter.

Careful palpation with a small blunt instrument, such as a felt-tipped pen, can help to localize a soft tissue neuroma or another palpable pain generator.

An image intensifier (fluoroscopy) can identify bony landmarks.

Contrast medium improves definition of tissue planes, capsules, and spaces. (Nonionic contrast medium should be used in areas close to neural tissue.)

The nerve stimulator at the tip of the cryoprobe is used to produce a muscle twitch in a mixed nerve.

The operator freezes the nerve for 2 to 3 minutes.

Often, the patient has discomfort initially as cooling begins, but it should dissipate quickly. If significant pain persists beyond 30 seconds, the operator should investigate whether the ice ball is in the proper position.

In general, with closed procedures, two freeze cycles of 2 minutes each, followed by thaw cycles, are sufficient. In areas with a large vascular heat sink, longer periods of cryotherapy are necessary. Pain relief should be immediate and should be assessed subjectively and by physical examination while the patient is on the procedure table .

Intercostal neuralgia Percutaneous cryolesions of the intercostal nerves can

be offered for various pain syndromes, including post-thoracotomy pain, traumatic intercostal neuralgia, rib fracture pain, and occasionally postherpetic neuropathy.

For each of these conditions, a meticulous series of local anesthetic blocks is performed before consideration is given to cryoablation.

The volume of local anesthetic should be kept to less than 3 to 4 mL to prevent tracking back into the epidural space. In addition, only two or three levels should be injected at any one time because systemic absorption could confound interpretation of the patient's response.

Because the intercostal nerve runs with a large arterial and venous heat source, the use of two 4-minute cryolesions at each level is suggested.

After the procedure, a chest film is obtained to check for pneumothorax.

Effective blockade in some patients with postherpetic neuropathy suggests that this pain is sometimes related to peripheral afferent input, as opposed to being strictly a central neuropathy.

Neuromas

Typically, painful neuromas are associated with lancinating or shooting pain that is aggravated by movement or deformation of nearby soft tissues.

First-line therapy should include empirical trials of anticonvulsants, tricyclic antidepressants, steroids, and local anesthetics, including a topical local anesthetic cream or patch.

Cryoablation seems most effective when the volume of local anesthetic necessary to produce analgesia is 1 mL or less. After the block with lidocaine, the patient's response and its duration are recorded. If initial blockade is successful in decreasing the patient's symptoms, it should be followed by at least one more injection with bupivacaine.

Iliac crest bone harvest

The pain associated with the harvest of iliac crest bone for fusion often responds to cryoablation when more conservative therapies have failed.

Such pain often is associated with deep, lancinating pain and often is attributed to periosteal neuromas.

Cryoablation of an anterior iliac crest bone harvest site. (From Waldman SD: Cryoneurolysis in clinical practice. In Interventional pain management, ed 2, Philadelphia, 2001, Saunders.)

Biomechanical spine pain Cryolesions have been used effectively for cervical and

lumbar facet syndromes and for pain from the interspinous ligaments

For biomechanical pain of lumbar facet origin, the patient typically has pain that is exacerbated by hyperextension of the lumbar spine .

A fluoroscopically guided diagnostic intra-articular facet block can be performed in patients who fulfill the aforementioned criteria.

The levels chosen for injection are determined by bone scan, computed tomography, plain films, and, most important, physical examination findings.

To confirm a facet pain generator, repeat blockade of the facet nerves can be done next. If the result is similar, it is reasonable to consider ablation.

In patients who continue to be responsive, improvement is observed on physical examination, especially with lumbar hyperextension. For these patients, a cryoablative procedure can be considered

A 12-gauge introducer catheter is introduced to the junction of the transverse process and the pedicle, the Scottie dog's eye. At this point, the cryoprobe is inserted into the introducer catheter.

The nerve stimulator is used to locate the sensory branch. When pain is reproduced or the patient feels dysesthesia overlapping the region of the pain, motor testing is in order to ensure that the ice ball is not near a motor nerve.

Two cryolesions are made, each of 2 minutes' duration. The patient is expected to have some postprocedure discomfort,

but should notice improvement.

In the recovery room, ice can be applied to the operative site for 30 minutes for local postoperative irritation and swelling. Application of ice may decrease swelling and facilitate mobilization

The patient should continue with outpatient lumbar strengthening programs. If the musculature is significantly deconditioned, it may be better to restart the program in water. After muscle condition improves, the patient should begin a supervised industrial rehabilitation program that offers vocational retraining and job placement.

One publication demonstrated that the evidence-based information available for cryodenervation in facet denervation is indeterminate.

Cervical facet syndrome Patients with cervical facet syndrome typically present with

severe posterior neck pain and muscle spasm. If these patients fail to respond to conservative therapy, a

diagnostic series of injections with fluoroscopic guidance is considered. To patients who respond to local anesthetic injections with reduction in pain, cryodenervations can be offered as an adjunct to comprehensive physical therapy and rehabilitation.

One study concluded that with intra-articular facet joint injections, the evidence for short- and long-term pain relief is limited for cervical pain and moderate for lumbar pain. For medial branch blocks, the evidence is moderate for short- and long-term pain relief. For medial branch neurotomy, the evidence is moderate for short- and long-term pain relief.

Interspinous ligament pain

Interspinous ligament pain is common after a spine operation (lumbar, thoracic, or cervical). Pain impulses from interspinous ligaments are carried by the medial branch of the posterior ramus Patients report severe movement-related spine pain, identified to the midline, which is worsened with hyperextension and relieved by small volumes of local anesthetic injected into the intraspinous ligament.

Cryodenervation can be considered in local anesthetic–responsive patients

Coccygodynia

When coccygodynia has failed to respond to conservative therapy, including the patient's use of a donut pillow, NSAIDs, and local steroid injections, consideration can be given to coccygeal neural blockade as the coccygeal nerve exits from the sacral canal at the level of the cornu

Perineal pain

Pain over the dorsal surface of the scrotum, perineum, and anus that has not responded to conservative management at times can be managed effectively with cryodenervation from inside the sacral canal with bilateral S4 lesions. Test local anesthetic injections should produce a positive response before cryoablations are performed bilaterally at S4.

Ilioinguinal, iliohypogastric, and genitofemoral neuropathies

Ilioinguinal, iliohypogastric, and genitofemoral neuropathies often complicate herniorrhaphy, general abdominal surgery, and cesarean section. Patients present with sharp, lancinating to dull pain radiating into the lower abdomen or groin.

The pain is exacerbated by lifting and defecating. If the patient is responsive to a series of low-volume test

injections, consideration can be given to cryodenervation of the appropriate nerve. Significant care and time must be spent localizing the nerve with the sensory nerve stimulator.

The patient may help to localize the pain generator by

pointing with one finger to the point of maximum tenderness

Lower Extremity Pain Neuralgia resulting from irritation of the infrapatellar

branch of the saphenous nerve develops weeks to years after blunt injury to the tibial plateau or after knee replacement

Neuralgia secondary to irritation of the deep and superficial peroneal and intermediate dorsal cutaneous nerves can be seen weeks to years after injury to the foot and ankle.

Neuralgia resulting from irritation of the superior gluteal branch of the sciatic nerve is common after injury to the lower back and hip sustained while lifting.

The clinical presentation consists of sharp pain in the lower back, dull pain in the buttock, and vague pain to the popliteal fossa

Craniofacial Pain

Craniofacial nerves can be cryolesioned with a percutaneous or open technique.

Entrapment neuropathies and neuromas are more responsive to local anesthetic and cryodenervations than are neuropathies of medical causes. Meticulous diagnostic injection ensures the best outcome with cryoablation

A nerve stimulator is used to localize the nerve. Because these areas are relatively densely vascular, injecting a few milliliters of saline solution containing 1:100,000 epinephrine is recommended before inserting the cryoprobe introducer cannula. A postprocedural ice pack applied for 30 minutes reduces pain and swelling.

Irritative neuropathy of the supraorbital nerve often occurs at the supraorbital notch.Vulnerable to blunt trauma, this nerve often is injured by deceleration against an automobile windshield. Commonly confused with migraine and frontal sinusitis, the pain of supraorbital neuralgia often manifests as a throbbing frontal headache

This neuralgia often worsens over time, perhaps owing to scar formation around the nerve.

Neuropathic pain in the distribution of the supraorbital nerve can be addressed with an open or closed cryoablative procedure as long as appropriate conservative therapy has failed and the pain responds to a series of test local anesthetic injections

The infraorbital nerve (see Fig. 179.12) is the termination of the second division of the trigeminal nerve. Irritative neuropathy can occur at the infraorbital foramen secondary to blunt trauma or fracture of the zygoma with entrapment of the nerve in the bony callus .

Cryoablation can be accomplished by an open or closed technique. The closed technique can be performed from inside the mouth through the superior buccolabial fold. In both operations, the probe is advanced until it lies over the infraorbital foramen

The mandibular nerve can be irritated at many locations along its path.

Injury to the mental nerve, the terminal portion of the mandibular nerve, frequently occurs in edentulous patients. Pain can be reproduced easily with palpation

The auriculotemporal nerve can be irritated at many sites Patients often present with temporal pain associated with

retro-orbital pain. Pain often is referred to the teeth. Posterior auricular neuralgia often follows blunt injury to

the mastoid area. It is common in abused women and usually involves the left side owing to the preponderance of right-handed abusers. The clinical presentation consists of pain in the ear associated with a feeling of “fullness” and tenderness. This syndrome often is misdiagnosed as a chronic ear infection. The posterior auricular

nerve runs along the posterior border of the sternocleidomastoid muscle, superficially and immediately posterior to the mastoid.

The glossopharyngeal nerve lies immediately subjacent to the tonsillar fossa

Many other common peripheral nerve injuries are amenable to cryodenervation, including most cutaneous branches and the occipital, suprascapular, superficial radial, and anterior penetrating branches of the intercostal nerves.