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| CASE REPORT |
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| Year : 2021 | Volume
: 7
| Issue : 2 | Page : 42-45 |
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Ultrasound-guided percutaneous cryoneurolysis of mental nerve: A preferred technique of cryoneurolysis
Smruti Rekha Hota, Gautam Das
Daradia Pain Hospital, Kolkata, West Bengal, India
| Date of Submission | 01-Feb-2022 |
| Date of Acceptance | 25-Sep-2022 |
| Date of Web Publication | 08-Mar-2023 |
Correspondence Address:
Smruti Rekha Hota
Flat No. 204, City Pride Apartment, Khetrajpur, Sambalpur - 768 003, Odisha
India
 Source of Support: None, Conflict of Interest: None
DOI: 10.4103/jrap.jrap_1_22
Mental neuralgia is a chronic debilitating neuropathic pain condition that is persistent, severe, and substantially interferes both with quality of life and recreational and daily activities. Pain is excruciating, often described as an electric shock-like sensation by the patient. We are reporting a case in which ultrasound-guided percutaneous cryoneurolysis is described and demonstrated in a patient with mental neuralgia where multiple other modalities of treatments failed. The current pharmacologic therapy is inadequate and intolerable with side effects such as somnolence and nausea. Cryoneurolysis is an alternative method that utilizes extremely cold temperatures with freezing and then simultaneously defrosting to reversibly ablate peripheral nerves and is potentially a novel method for chronic pain management.
Keywords: Cryoneurolysis, mental neuralgia, neuropathic pain
How to cite this article:
Hota SR, Das G. Ultrasound-guided percutaneous cryoneurolysis of mental nerve: A preferred technique of cryoneurolysis. J Recent Adv Pain 2021;7:42-5 |
How to cite this URL:
Hota SR, Das G. Ultrasound-guided percutaneous cryoneurolysis of mental nerve: A preferred technique of cryoneurolysis. J Recent Adv Pain [serial online] 2021 [cited 2023 Mar 31];7:42-5. Available from: http://www.jorapain.com/text.asp?2021/7/2/42/371247 |
| Introduction | |  |
Cryoneurolysis is a safe, minimally invasive therapeutic method based on temporary interruption of transmission of sensory functions in selected structures of the nervous system by application of very low temperature. This method is slowly gaining popularity and is especially recommended when traditional methods were proven to be unsatisfactory.
The mental foramen, which lies inferior to the outer lip below the second premolar, midway between the upper and lower borders of the mandible, is localized using transverse scanning in a cephalad direction from the inferior border of the mandible.[1],[2] The mental nerve is a branch of the inferior alveolar nerve which is a branch of the posterior division of the mandibular nerve. It comes out through the mental foramen and supplies the skin over the chin, skin and the mucous membrane of the lower lip, and the labial aspect of the gums of canines and incisors. Mental neuralgia is one of the painful chronic neuropathic pain that is persistent, severe, and substantially interferes both with quality of life and recreational and daily activities. Pain is excruciating, often described as an electric shock-like sensation by the patients.
We present the case of a 67-year-old man with mental neuralgia complaining of left jaw pain and sharp and shooting in nature, which was refractory to initial treatment attempts. The patient ultimately responded to cryoneurolysis targeted along the mental foramen anatomically. Despite multiple failed prior treatment attempts, the patient demonstrated sustained analgesia after the cryoneurolysis of the mental nerve. It is a novel technique of treatment of mental neuralgia where the patient was successfully treated.
Other traditional methods for the treatment of mental neuralgia include blind local and steroid injections and blind alcohol neurolysis but there is a high risk of systemic toxicity; reported complications of blind injections for the treatment of mental neuralgia include soreness, infection, swelling, dysesthesia, and headache along with the cross talk.[3] Hence, complications related to mental nerve blocks can be reduced by US assistance. Other treatment options include pulsed radiofrequency of the mental nerve at the mental foramen, where pain relief was not immediate, was lasted for 6 months.[4] Radiofrequency of the Gasserian ganglion has a long list of complications as it is a more invasive technique, radiofrequency ablation (RFA) of the peripheral nerve cannot be done due to high failure chances, damage to motor fibers may lead to weakness and paralysis, and damage to touch fibers leads to numbness, neuritis, deafferentation pain due to ectopic signal generation and cross talk.
| Case Report | | |
A 67-year-old man with a past medical history of diabetes mellitus and hypertension presented to our pain clinic with the chief complaints of persistent sharp shooting electric shock-like left jaw pain. The pain started, approximately, 7 years before the initial presentation, when he was diagnosed with mental neuralgia. The pain was severely impaired the patient's quality of life and ability to participate in activities of daily living.
The patient further described his pain as constant, severe sharpshooting, and electric shock-like sensation over his left jaw. Average pain severity was reported on an NRS scale of 9/10. The patient's history and the physical examination revealed his pain was mainly located over the left jaw.
Initially, the patient's pain was treated with a course of carbamazepine but he experienced drowsiness. He underwent failed attempts of RFA and glycerol injections. Although he was initially relieved of pain, it reoccurred after a period of 6 months to 1 year. A majority of his pain along with the dermatomal distribution of a mental nerve, the decision was made to specifically target the mental nerve for cryoneurolysis, for greater sustained pain relief.
| Methods | | |
Informed procedural consent was obtained from the patient as per ISSP format. In the supine position, the area was cleaned with betadine. The procedure was done under USG guidance. We used a hockey stick probe with a frequency of 18 MHz for the procedure. During transverse scanning over the inferior portion of the mandible at the level of the second premolar and scanning in the cephalad direction until a hypoechoic cleft within the hyperechoic line of the periosteum of the mandible is visible indicating the mental foramen [Figure 1].[1] We confirmed pulsating artery over there [Figure 2]. About 2 ml of 1% lignocaine is infiltrated targeting the mental foramen [Figure 3]. We used a cryoprobe of 20 gauge which forms a spherical lesion of 5 mm [Figure 4] and [Figure 5]. After adequate anesthesia was obtained, cryoneurolysis was performed using the cryoprobe. As cryoprobe insertion is angle independent, we introduced the cryoprobe under USG guidance in-plane technique along the foramen [Figure 6] so that tip of the cryoprobe was placed in the mental foramen to cover the length and depth of the mental nerve [Figure 7]. Cryoneurolysis which is a process of freezing and defrosting started at a temperature of −78°C for 180 s, the tip of the probe achieved a cooling temperature of a maximum of −78°C. There is the formation of an ice ball as a posterior acoustic shadow under USG [Figure 8] afterward defrosting for 40 s. The same cycle was repeated once again by advancing the needle by 2 mm. We used the patient to tolerate the procedure well, without any complications reported. The patient had more than 70% pain relief (NRS 3 on the NRS scale) in the mental nerve distribution. | Figure 1: The mental foramen is identified as a hypoechoic cleft within the hyperechoic line of the periosteum of the mandible
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 | Figure 2: Color Doppler showing the pulsatile flow of the mental artery in the mental foramen
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 | Figure 3: One percent lignocaine is infiltrated around the mental foramen
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 | Figure 6: Cryoprobe insertion into the mental foramen under USG guidance
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 | Figure 7: Final position of a cryoprobe in mental foramen covering the length and breadth of the mental nerve
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 | Figure 8: Posterior acoustic shadow is seen suggesting ice ball formation
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| Discussion | | |
Mental neuralgia is a severe neuropathic pain that is characterized by sharp, shooting pain or electric shock-like sensations. The pain often limits daily activities, prevents sleep, and may be associated with depression. Currently, the usual treatment approach is multimodal.
Overall cryoneurolysis is the safest technique among the techniques practiced currently. This simple and minimally invasive percutaneous procedure usually performed under USG or fluoroscopy guidance can be repeated as many times as required which is safe and suitable for mixed nerves. It is mostly painless and a longer duration of pain relief is achieved without any scar tissue formation. This procedure is even suitable for patients having pacemakers or stimulators.
Cryoneurolysis is an established treatment modality for chronic pain conditions that include neuropathic pain.[5] Recently, cryoneurolysis has been applied to acute and perioperative pain conditions.[6],[7] The concept behind cryoneurolysis involves inducing cold temperature in the proximity of a peripheral nerve by creating an ice ball that causes reversible axonal degeneration which is also known as Wallerian degeneration.[8],[9] A modern cryoneurolysis machine includes a cryoprobe that creates extremely cold temperatures by passing gas down the shaft at high pressure and through a small opening into a closed tip to low pressure, resulting in the absorption of heat by the Joule–Thompson effect. The gas is evacuated through an internal tube within the shaft so that no gas makes contact with the patient. An ice ball forms at the tip of the probe, inducing Wallerian degeneration distal to the point of ablation. The basic physics is when high-pressure compressed gas in the device (nitrous oxide or carbon dioxide) is released through a tiny opening and expands and the tip goes below −70° centigrade, there is the production of extremely cold temperature.[8] There may be a conduction block, activation of descending inhibitory pathway, decrease in excitatory neurotransmission, generalized sodium channel blockage, and probably a combination of all of the above.[9]
There are many advantages of cryoneurolysis over any other neurolytic techniques including surgical, thermal, and chemical ablation (like alcohol neurolysis). In cryoneurolysis, the epineurium, perineurium, and endoneurium are generally intact.[6],[7],[8],[9] We can directly visualize the ablation zone under USG guidance. We can use multiple probes simultaneously to increase the size of the lesion. As it is second-degree nerve damage, so the nerve is regenerated in 6–24 months, and the motor fiber recovers quickly. This allows for nerve regeneration and reduced risk of neuroma formation as compared to other neurolytic modalities.[5] Neuroma formation can significantly worsen preexisting pain.
In addition, many of the surrounding structures, such as the connective tissues of the nerves and blood vessels, as well as the bone, have been found to resist cold injury.[8] The result is that the extracellular matrix and scaffold structure of the nerves and vessels remain intact, allowing the affected axon/myelin sheath or vascular cells to regenerate and repair the injury site. In comparison, heat lesions have been found to not only destroy cells but also disrupt the structural matrix, resulting in a narrower therapeutic window.[9],[10],[11]
The adverse effects and contraindications of cryoneurolysis include bleeding, bruising, redness and infections. As expected, the treatment area will likely become insensate. In our case, these risks were deemed to be exceedingly minimal due to the superficial nature of the cryoablation and probe used. The contraindications to cryoablation, specifically, include patients who have a history of cryoglobulinemia, Raynaud's syndrome, or cold urticaria.[8] Our patient had none of these features.
Given the severity of mental neuralgia and disabling pain to patients, cryoablation offers a technique that is minimally invasive, with less risk compared to other forms of neurolysis. Probe technology advances have enabled percutaneous insertion and its use in treating chronic nerve pain increased subsequently. Again, the advent of USG guidance now enables an extremely precise application to any peripheral nerves. Duration of effect lasts for 6 months to 2 years.
Pulsed radiofrequency of the mental nerve is also done under USG guidance, after cleaning and draping, a 22 G needle is inserted perpendicularly just medial to the mental foramen until there is contact with bone. The location of the nerve is confirmed when the patient experiences reproducible paresthesia in the chin by sensory stimulation with 50 Hz, 0.5 V. Subsequently, a pulsed radiofrequency current of 45 V lasting for 120 s is administered with no preceding local anesthetic. The maximum temperature should not exceed 42°C, but if this occurs the output should be reduced. RFA of the mental nerve may lead to deafferentation pain which is due to ectopic signal generation and cross talk.
Another technique is blind injections of alcohol but it includes soreness, infection, swelling, dysesthesia, and headache. The alcohol block technique was used in a patient who does not respond appropriately to the medical therapies. With alcohol block, only short-term pain relief is obtained. The inflammation and fibrosis were observed in numerous patients with alcohol ablation.[3]
| Conclusion | | |
Cryoneurolysis of the mental nerve is an effective technique to provide significant analgesia for mental neuralgia. The effect is reversible, relatively painless, and not associated with neuroma formation. It has been performed successfully in about 20 patients having mental neuralgia with satisfactory results in our center. It is found to be technically superior compared to other methods but has to be tested in a larger group of patients.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8]
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