Although chronic opioid therapy (COT) is effective for chronic non-cancer pain, it may cause opioid dependence or addiction. The term addiction which is characterized by compulsive opioid use and craving for opioid, includes psychological dependence but not physical dependence and tolerance. On the other hand, the term dependence includes all three factors. When the dose of opioid increases gradually in a chronic pain patient, who shows no aberrant use of opioid, the patient may display not addiction but dependence. The term addiction, however, has often been confused with dependence. Here we report how this confusion has obstructed research on addiction caused by COT. Although several guidelines of COT for preventing addiction in patients with chronic non-cancer pain were introduced recently, they include some flaws. The present report provides valuable information concerning dependence and addiction for medical associates providing COT.

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Intrathecal hyperbaric local anesthetics can cause neurologic impairment; however, there have been no studies on histopathological changes of the spinal cord after injection of local anesthetics dissolved in water or 10% glucose. We studied the effects of tetracaine dissolved in water or 10% glucose on motor function and histopathologies of the spinal cord. Rats received intrathecally different concentrations of tetracaine (0%, 0.5%, 1%, 2.5%, and 5%) dissolved in water or 10% glucose. We studied motor functions and light and electron microscopic changes of the spinal cord. Movement of the hind limbs recovered significantly faster in the 10% glucose groups than in water groups at all concentrations of tetracaine. Irreversible motor dysfunction of the hind limbs occurred only in rats injected with 5% tetracaine dissolved in water. There was no significant difference in the incidence of pathological lesions between rats receiving 5%tetracaine in water and in 10% glucose (100% vs 67%); however, significantly higher rates of pathological lesions were detected in rats receiving 2.5% tetracaine in water than in 10% glucose (71% vs 0%).
All rats that received tetracaine showed significant pathological changes in the posterior roots of the spinal cord, spreading to the posterior colums with axonal degeneration. We conclude that 10% glucose, as compared with water, lessens neurotoxicity of intrathecal tetracaine in rats.

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We retrospectively analyzed effects of trigger point injections performed at bed-side on somatic pain in seven patients (M/F, n=2/7; mean age, 69.1 years) with advanced cancer in our palliative care unit. The pain was located in the neck in three patients, lower back in 4, shoulder in 2, and buttock in 1. The painful areas were tender on palpation. The cause of pain was degenerative spondylosis in six patients, brachial plexus invasion of cancer in 1, and decubitus ulcer in 1. A total of 18 trigger point injections were done. Mean pain score decreased significantly from 3.3 preinjection to 0.9 postinjection on a face scale of 0 to 5. Trigger point injections decreased the pain of myofascial origin; however, they were not effective against neuropathic pain caused by cancer invasion, pain of decubitus ulcer, and pain of chronic pericapsulitis of the shoulder joint. There were no serious adverse events related to the trigger point injections. We conclude that trigger point injection is safe and effective for the treatment of myofascial pain in patients with advanced cancer.

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Although sleep disorders are serious complications of chronic pain, they have only been subjectively assessed on the basis of patients' complaints or questionnaires. Here, we report two neuropathic pain cases in which we objectively evaluated chronic pain-related sleep disorders with the use of actigraphy. Actigraphy is a wristwatch-typed medical instrument that can estimate participants' sleep/wake patterns. Both patients exhibited refractory pain and had severe sleeping difficulties. Having each patient wear an actigraphy, we determined the change of sleep efficiency before and after the introduction of spinal cord stimulation(SCS). We succeeded in objectively demonstrating how sleep quality improves by treating sleep disorders with SCS.

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We report a patient with ossifying ligamentum flavum whose abdominal wall and back pain decreased following repeated intercostal nerve blocks. A 62 year-old woman developed bilateral abdominal wall and back pain 11 months before she was referred to us. The patient was diagnosed as having ossifying ligamentum flavum 1 month earlier. Surgical therapy was not indicated because there were no spinal cord symptoms. Loxoprofen did not lessen the pain. The patient was referred to us. The area of pain covered the dermatomes of bilateral Th11-12. The patient had area of dysesthesia over the painful area. The pain radiated from the back to the abdominal walls. There was no obvious sensory deficit or tenderness over the paravertebral region. The muscle strength, reflex, and sensory function of the legs were normal. Computed tomography of the thoracic spine showed ossification of the ligamentum flavum at bilateral Th10/11 and Th11/12 levels. Right intercostal nerve blocks at Th11 and Th12 performed 7 days later with a local anesthetic and dexamethasone relieved the abdominal wall and back pain. The patient became able to move herself smoothly. The patient received left intercostal nerve blocks at Th11 and Th12 on the left because left-sided abdominal wall and back pain worsened. The pain on the left lessened. The pain did not recur 9 months after the last intercostal nerve blocks.

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Electrical injury is defined as muscle and neurological injuries due to electrical current through the body. It often occurs as an occupational accident. We report a patient with electrical injury who complained of exaggerated pain and restriction of movement of the injured limb. A 56-year-old man was exposed to electrical current from the left finger during welding at his workplace. The patient was admitted to our hospital on the next day. The patient complained of severe pain, muscle weakness, and restricted movement of the left upper limb and shoulder; however, he was witnessed to move the left arm freely in the ward. In addition, the patient demanded compensation of the injury. The patient was recommended to be discharged; however, he insisted on treatment in the hospital because of severe pain. The patient stayed 16 days in our hospital; thereafter, he was admitted to another hospital for 2 months. The exaggerated symptoms might have been caused so as to obtaining secondary gain.

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