Peripheral Nerve Entrapments in Cancer Pain.

Peripheral nerve entrapments can occur anywhere in the head and body and can cause significant pain. Cancer pain can be caused by these entrapments, triggered by a variety of etiologies, including tumor invasion, surgical trauma, chemotherapy, or scarring. Knowing the cause of pain can help the physician treat the problem effectively, and will decrease unnecessary and potentially worsening surgeries and high dose opioid therapies, as well as unnecessary pain. A knowledgeable interventional pain physician can diagnose and treat these nerves entrapments in the most effective manner, providing improved pain relief and quality of life.Key points Nerve entrapments can occur throughout the body in cancer patients due to multiple etiologies such as tumor invasion, surgical trauma, or cancer therapy. The problem of nerve entrapments in cancer pain is under-recognized. Patients with nerve entrapment syndromes frequently complain of a burning tingling sensation and other paresthesias in the nerve distribution which can progress to a complete loss of sensory and motor function. Diagnostic tools include history and physical exam, imaging, nerve conduction studies as well as diagnostic nerve injections/blocks. Treatment of nerve entrapments can range from neuropathic pain medications to nerve blocks and nerve ablations to surgical decompression.

Ultrasound-Guided Regional Anesthesia Using a Head-Mounted Video Display: A Randomized Clinical Study.

BACKGROUND: Ultrasonography is increasingly being used in every field of medicine, especially regional anesthesia. To successfully perform the procedure, a knowledge of anatomy and ultrasonoanatomy as well as technical 3D hand-eye coordination skills are required. Medical practitioners who use ultrasound devices to perform regional blocks have to correlate the position of the ultrasound probe on the patient, needle position, and ultrasound picture. To achieve that, the practitioner has to intermittently look between the patient and the ultrasonography screen. This requires extra head rotations, increasing the time and complexity of the procedure. Newer technologies are available that can alleviate the need for these extra head movements, such as head-mounted displays (HMDs), which are connected to the ultrasonography machine and project the ultrasonography picture onto the HMD goggles so that the provider can see the monitor without unnecessary head rotations. OBJECTIVE: Our theory was that the use of the HMD goggles would decrease the overall procedure duration as well as provider head rotations. STUDY DESIGN: This was a randomized clinical study. SETTING: The research was conducted at an academic medical center at the University of Texas Medical Branch, Galveston, TX. METHODS: We secured Institutional Review Board (IRB) approval to perform the study. We chose an HMD, which can be mounted on the head like regular goggles. By connecting the HMD with the ultrasonography machine, the ultrasound picture can be projected directly in front of the physician's eyes. Twenty-four patients were randomized to receive a regional anesthetic performed by anesthesiology residents using a conventional ultrasound-guided approach or using the HMD in addition. We measured the number of attempts, head rotations, and time needed to obtain a satisfactory nerve stimulation in addition to outcomes and adverse effects. Our data were interpreted by our statistician with P < .05 indicating statistical significance. RESULTS: Regional anesthetics performed with the HMD were significantly faster (59.08 vs 175.08 seconds) with significantly fewer head movements (0.83 vs 4.75) and attempts (1 vs 1.42). There were no significant differences in patient demographics, type of regional anesthetic, level of resident training, or outcomes. No complications were noted. LIMITATIONS: A limitation of our research is that neither observers nor providers were blinded to the way blocks were performed. This would have been practically impossible because participants had to wear an HMD. CONCLUSIONS: The HMD could provide advantages in regional anesthesia by decreasing the time and attempts and improving ergonomics. These findings can be easily translated into other ultrasound- or optic/camera-guided procedures outside of regional anesthesia, such as vascular access or laparoscopic surgery.IRB: UTMB IRB #12-143.

Incidence of Cervicogenic Headache Following Lower Cervical Radiofrequency Neurotomy.

BACKGROUND: The facet joints contribute to chronic cervical spine pain in an estimated 55% of chronic neck pain cases and can be treated with percutaneous radiofrequency neurotomy (PRN). Damage to surrounding structures during treatment or successful treatment of the primary pain source leading to unmasking could lead to new onset of pain, including cervicogenic headache (CGH). In this study, we aimed to define the incidence of headache in patients who have been previously treated with PRN for lower cervical facet pain. SETTING: All patients treated at a single academic institution's pain management clinic from 2014 to 2016 with cervical PRN were reviewed. METHODS: All patients treated at a single institution's pain management clinic from 2014 to 2016 were reviewed. Those treated with lower cervical PRN were identified, and incidence of CGH was described as a percentage of the study population. Patient age and pain scores between those with and without headaches following treatment were compared by unpaired T-tests. Gender, presence of comorbid disease and levels involved, quality of pain, exacerbating and alleviating factors, location of referred pain, and previous treatments between those with and without headaches following treatment were compared using chi-square tests. RESULTS: Among the 88 patients in the study group, 12 were found to have only moderate relief of their pretreatment pain as well as a new onset headache meeting the diagnostic criteria for cervicogenic headache. Compared to those without a headache after treatment, those diagnosed with cervicogenic headache were more likely to be female (P = 0.041), report a higher maximum pain level on presentation (P = 0.015), have a diagnosis of diabetes prior to presentation (P = 0.011), and have had the procedure performed at levels which included C3 (P = 0.013) (Table 1). LIMITATIONS: The limitations of this study include its single-center design, as this cohort may not be truly representative of the population of patients receiving cervical PRN as a whole, and as a result, these results may not be generalizable. Due to the small size of the cohort, more subtle differences in presenting signs and symptoms between those with and without headaches may not be detectable. Finally, as previously mentioned, the lack of data on some of the patients who presented with headache may have led to underdiagnosis of the true incidence of cervicogenic headache. Future work should look to re-examine the incidence of CGH in a larger cohort to validate the findings here and further define risk factors for post-procedural CGH. CONCLUSIONS: This retrospective review of all patients seen over 2 years in an academic pain clinic found a 13.6% incidence of cervicogenic headache following cervical radiofrequency neurotomy at levels C3-C7. This supports the possibility of the unmasking phenomenon following the procedure, though contributing mechanisms underlying this phenomenon may be multifactorial and require further study.IRB: This study was approved by the institution's Institutional Review Board (IRB2010601795). KEY WORDS: Cervical spine, facetogenic pain, percutaneous radiofrequency neurotomy, cervicogenic headache, chronic pain, zygapophysial joints, innervation convergence, retrospective chart review.