Osteoarthritis (OA) is the most common joint disorder, and the main symptom is pain during movement and at rest. Standard pharmacotherapies, such as acetaminophen, nonsteroidal anti-inflammatory drugs (NSAIDs), and opioids are effective in relieving pain in some patients with OA, but not in others. However, NSAIDs and opioids increase the risk of gastrointestinal and cardiovascular complications and the risk of drug abuse, respectively. Thus, the development of new pharmacological treatments for pain in patients with OA is needed. Nociceptive and neuropathic mechanisms at both peripheral and central levels play a role in OA pain. In recent years, molecular targets involved in the mechanisms of OA pain have been identified, and new drugs based on these mechanisms have been developed. This review focuses on new findings regarding the mechanisms of OA pain and the development of pharmacotherapies based on these mechanisms.

Cancer-related pain occurs not only in the terminal stages of cancer, but is also associated with cancer treatments such as surgery, chemotherapy, and radiation therapy. Smoking temporarily relieves pain, but pain sensitivity increases in association with withdrawal symptoms. The patient has an urge to smoke when he/she feels pain, and the pain increases when the patient wants to smoke. In this situation, how can health care workers provide support to cancer patients who smoke? This paper reviews the relationship between smoking and pain, focusing on cancer-related pain, and discusses palliative smoking cessation support for cancer patients who smoke and are experiencing pain.

A 36-year-old woman in her second pregnancy with recurrent meralgia paresthetica was successfully treated by ultrasound-guided pulsed radiofrequency (PRF) at 31 weeks gestational age. During her first pregnancy, her pain had been managed by only ultrasound-guided lateral femoral cutaneous nerve (LFCN) block with local analgesics. However, the pain was exacerbated by growth of the uterus and provoked a sleep disturbance this time. Neither medication nor surgical therapy could be used in consideration of the fetus; therefore, PRF therapy was applied to the patient. A needle was inserted under the LFCN with ultrasound-guidance, and PRF ablation was performed at 2 Hz/20 ms/42℃ for 180 seconds. Since she felt only slight pain during the treatment, the effect of the therapy on pregnancy appears to be negligible. One month later, she became pain-free, except when standing for long periods. Furthermore, she experienced no complications and had a healthy gestation.

Although radial nerve compression syndrome in the proximal brachial region is rare, the author has experienced four cases of suspected radial nerve entrapment neuropathy in that region. All the patients complained of dull pain in the upper extremity region innervated by the radial nerve on flexion of their shoulder and elbow joints. They also had the following factors in common: 1) they had been treated for another neuropathy in the proximal aspect of the affected arm, 2) they had the same tender point in the axilla, where ultrasound examination revealed the radial nerve ran between the medial and lateral heads of the triceps brachii muscle, and 3) an ultrasound-guided nerve block at the tender point ameliorated the symptoms. The speculated mechanism of the nerve entrapment was that flexion of the shoulder and elbow caused traction on the radial nerve and stretching of the triceps brachii muscle, which then compressed the nerve against the humeral shaft. Additionally, the double crush syndrome was thought to be involved in the condition.

Medication overuse headache (MOH) is an aggravation of an underlying headache caused by excessive use of acute medication. The mechanism behind how chronic exposure to abortive medication leads to MOH remains unclear and no consensus for the management of these patients exists. We describe a case with history of MOH, who was able to withdraw from the overused medication after prophylactic administration of duloxetine. The patient was taking naratriptan to go to work on weekdays because he had complained of severe pain attacks in the left orbit accompanied by tearing several times a day, and chronic continuous headache with comorbid depression. Duloxetine and verapamil were administered after a diagnosis of MOH and cluster headache and the patient was able to withdraw from naratriptan without rebound headache. This case suggests that duloxetine may possibly be an option for prophylactic treatment of MOH.

We present a case of juvenile myoclonic epilepsy (JME) that occurred during pregabalin therapy for neuropathic pain. Pregabalin administration was discontinued, but a subsequent combination of levetiracetam and pregabalin suppressed epileptic seizures and, eventually, pain. A 16-year-old girl reported prolonged, intermittent pain in the area of innervation associated with trocar penetration after treatment of a spontaneous pneumothorax with a trocar catheter. Treatment with pregabalin was effective, but unintended movements of the limbs became apparent. Although the pregabalin was temporarily interrupted, electroencephalography examination revealed spikes and slow wave complexes in general; the patient was diagnosed with JME. As a result, administration of levetiracetam was initiated and pregabalin could be recovered to its previous level. One of the side effects of pregabalin is involuntary movements such as myoclonus; a similar drug, gabapentin, is known to deteriorate JME with single-agent administration. Myoclonus and epileptic seizures are similar and we had difficulty in diagnosis and treatment; however, combination therapy was able to achieve compatibility between pain management and epileptic disease treatment.

We report a case of abducens nerve palsy secondary to herpes zoster infection on the area of the face innervated by the first division of the trigeminal nerve. A 52-year-old man presenting with right facial pain and eruption was diagnosed with right trigeminal herpes zoster by a dermatologist. Two weeks later, he noticed double vision and was diagnosed as having right abducens nerve palsy by a neurosurgeon. Brain MRI was unremarkable. After the skin lesion resolved, the abducens nerve palsy and the facial pain remained. He was referred to our department and we initiated stellate ganglion block, which improved the palsy. The abducens nerve palsy may have been induced by the direct extension of inflammation, ischemia, or compression in the cavernous sinus to the ipsilateral trigeminal nerve. We herein suggest that it is important to pay attention to the eye movements of patients who have herpes zoster infection on the first division of the trigeminal nerve as herpes zoster infection of this facial region could result in abducens nerve palsy.