We present a case of a 34-year-old right-handed Caucasian male with chronic occipital neuralgia refractory to medical therapies and minimally invasive pain procedures who underwent surgical cervical dorsal root ganglionectomy which completely relieved his headaches. The histopathological and immunohistochemical findings of the resected cervical dorsal root ganglia were consistent with active herpes simplex virus type 1 (HSV-1) infection causing ganglionitis. To the best of our knowledge, this case represents the first histopathologically proven HSV-1 cervical dorsal root ganglionitis in humans. This case provides an insight into a possible etiology of occipital neuralgia.

We conducted this experiment to determine the role of glutamate in the mechanism of sleep apnoeas by administering riluzole, a glutamate release inhibitor, to freely moving rats in which sleep-related apnoeas are physiological phenomena. Adult Sprague-Dawley rats were implanted with electrodes for electroencephalogram (EEG) and electromyogram (EMG) recording to monitor sleep and were placed inside a single-chamber plethysmograph to monitor respiration. Sleep and respiration were recorded for 6 h following intraperitoneal administration of 0.5, 5.0 and 10.0 mg kg(-1) riluzole. Riluzole dose-dependently suppressed post-sigh apnoeas during rapid eye movement (REM) sleep but had no effect on sleep-related spontaneous apnoeas. The drug (5.0 and 10.0 mg kg(-1)) also dose-dependently reduced wakefulness and increased sleep. It appears that glutamate, an excitatory neurotransmitter, plays a role in the genesis of the post-sigh apnoeas during REM sleep.

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OPIOIDS ARE POTENT analgesics and the mainstay of treatment for moderate to severe postoperative pain. The most commonly used intravenous (IV) opioids in the postanesthesia care unit are morphine, fentanyl, and hydromorphone. All of these agents are potent agonists at the mu-opioid receptor and, when administered in comparable doses, analgesic and adverse effects are similar. Clinicians are quite aware of variability in patient response to what is considered an appropriate dose of an IV opioid. If adequate analgesia is not achieved, increasing the dose and/or frequency of administration (to increase the plasma level) of the opioid does not always improve pain relief and could increase adverse effects. 1 Furthermore, the relationship between opioid dose and pain intensity (using the visual analog scale) is not linear. 2 Opioids have a narrow therapeutic index, necessitating patient-specific opioid therapy with frequent and responsive nurse monitoring to prevent serious events.Many factors contribute to variability in opioid response, including individual differences in mu-opioid receptor binding and receptor response. One muopioid receptor gene generates many different muopioid receptor subtypes. Although the binding pocket for the opioid is the same, genetic variations away from the binding site may influence the efficacy of the opioid. 3 There is also a polymorphism of the mu-opioid receptor that alters a patient's sensitivity to analgesia, but not to respiratory depression, from the opioid. 4 The literature is conflicting regarding gender differences in analgesic response to an opioid. 5,6 There appears to be a greater risk of opioidinduced respiratory depression in women (possibly because the volume of distribution of morphine is smaller in women, making morphine more potent in women than men). 5,7 Elderly patients may require less or comparable 8 amounts of opioid than younger adults to achieve pain relief in the immediate postoperative period, but age-related decreases in volume of distribution and clearance substantially influence opioid requirements over time. One study reported a nearly two-fold difference between 20-and 70-year-olds in the expected first 24-hour patientcontrolled analgesia (PCA) morphine requirements for an "average" subject (45 mg/day for 70-year-olds vs 85 mg/day for 20-year-olds). 9 Factors such as age are better predictors of opioid requirements, whereas factors such as genetic polymorphisms are unpredictable and unknown.It has been demonstrated that one 10-mg intramuscular injection of morphine provides at least 50% pain relief in only one of every three adult postoperative patients. 10 With individualization of opioid dosing immediately after surgery, pain relief can be achieved in a greater percentage of patients. 2 If one is titrating an opioid dose (eg, 1 mg IV morphine every 10 minutes), when the opioid dose is near (eg, within one bolus of) the dose ultimately required to provide analgesia, the patient's reduction in pain intensity is substantial. 11 To determine an appropriat...

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