Circadian pain patterns in human pain conditions - A systematic review.

BACKGROUND: Chronobiology is the science of how physiological processes in the body follow a pattern of time. Pain has been shown to follow a circadian rhythm, with different types of pain having variable expression along this rhythm. OBJECTIVE: This article reviews the nature of diurnal variations in pain along with a discussion of the mechanisms of circadian rhythm of pain. EVIDENCE REVIEW: We conducted a literature search on the PubMed and Google Scholar electronic databases, through April 2022. Publications were screened for English language, full-text availability, and human subjects. Randomized controlled trials and observational trials were included. Data were extracted from studies on patients with acute or chronic pain phenotypes, which provide pain severity data and corresponding diurnal time points. FINDINGS: The literature search led to the inclusion of 39 studies. A circadian pattern of pain was found to be present in nociceptive, neuropathic, central, and mixed pain states. Postoperative pain, fibromyalgia, trigeminal neuralgia, and migraines were associated with higher pain scores in the morning. Temporomandibular joint pain, neuropathic pain, labor pain, biliary colic, and cluster headaches increased throughout the day to reach a peak in the evening or night. Arthritis and cancer pain were not associated with any circadian rhythmicity. Furthermore, the circadian rhythm of pain was not found to be altered in patients on analgesics. CONCLUSION: The results of this review suggest that an understanding of diurnal variation may help improve therapeutic strategies in pain management, for instance through analgesic titration.

Transforaminal epidural steroid injection can result in further neurological injury in a patient with severe foraminal stenosis and nerve impingement.

BACKGROUND: Chronic low back pain (LBP) is highly prevalent and costly in our society. The use of epidural steroid injections (ESIs) for the treatment of radicular LBP is very widespread and continues to rise. The most popular injection is the lumbar/sacral transforaminal epidural steroid injection (TFESI). Here, we present a serious neurological complication resulting from such a TFESI that was only reversed by timely neurosurgical intervention. CASE DESCRIPTION: A 49-year-old male presented with a 5-year history of progressive neurogenic claudication and right lower extremity pain/radiculopathy. He had previously received multiple lumbar ESIs and other conservative therapy. Due to a recent exacerbation of his radiculopathy associated with MRI-documented lumbosacral spondylosis, he underwent a right L5/S1 TFESI under fluoroscopic guidance. This resulted in acute right lower extremity weakness accompanied by a right-sided foot drop and sphincter dysfunction. Although the follow-up MRI was noncontributory, the EMG showed L5/S1 denervation, and the patient underwent an L4-5, L5-S1 laminectomy with discectomies at the L4-5 and L5-S1 levels. Immediately after the surgery, the patient's weakness and sensory deficits improved. Two years later, the patient continued to do well without evidence of recurrence of signs or symptoms of lumbosacral radiculopathy. CONCLUSION: Patients should be counseled about the risk and benefits of TFESI. Surgical treatment may be warranted in patients who develop acutely progressive worsening following these non-FDA (Food/Drug Administration) approved injections.