No abstract

The aim was to compare the analgesic effectiveness and adverse effect incidence of oral dextromethorphan (DM) with placebo in patients with neuropathic pain. The first 10-day treatment period was a multiple-dose double-blind randomised controlled cross-over comparison of 13.5 mg of DM 3 times a day (t.d.s.) with placebo t.d.s.: 5 treatment pairs, each pair 1 day DM and 1 day placebo. The second 10-day treatment period used 27 mg of DM t.d.s. vs. placebo, with the same design. The study incorporated a 5 pair n-of-1 design for each of the 2 doses of DM. Patients took the study medication in addition to any pre-existing analgesic regime. Patients who reported benefit could continue with DM after the study. Nineteen patients with chronic neuropathic pain were studied over two 10-day treatment periods. Outcome measures were pain intensity, pain relief, adverse effects, mood, sleep and global rating of treatment. These were recorded by daily patient diaries and by clinic assessments before and after each treatment period. There were no significant differences between DM and placebo on any of the clinic assessment outcome measures. Two patients had significantly better analgesia on more than one outcome measure on within-patient testing. One had better analgesia with DM. The other had better analgesia with placebo. Ten patients had no adverse effects on either dose of DM. Two patients withdrew during the first treatment period because of adverse effects (which included increased pain intensity), and 5 during the second period. Five patients continued with DM after the study for 1-3 months. No long-term clinical benefit was apparent in those who continued with open DM. Dextromethorphan at either 40.5 or 81 mg daily did not relieve neuropathic pain.

Cognitive-behavioural approaches to treatment have become an important part of the clinical management of chronic pain. More recent developments in cognitive-behavioural theory, based on recent developments in the understanding and treatment of health anxiety, have emphasized the importance of catastrophizing appraisals, which drive both attentional processes and behavioural responses, which in turn are believed to be crucial for the maintenance of chronic pain. The experiment conducted here investigated the responses of pain patients (n=39) and controls (n=71) to a behavioural task (prolonged squeezing a dynamometer). Subsequently, the impact of a cognitive task, which fully engaged participants' attention (dichotic listening) was examined. Participants were asked, firstly, to sustain an isometric muscle contraction task (squeezing); secondly, to learn an attentional demanding task (dichotic listening); thirdly, to recall the discomfort experienced in the squeezing task and lastly, to perform both squeezing and dichotic listening at the same time. The squeezing tasks were experimentally manipulated by attaching a more or less negative label ("pain tolerance test" vs. "muscle stamina and strength test"). Patients were found to be less able to sustain prolonged muscle tension than controls, but the effect was not evident once the distracting task was introduced; similar effects were found for discomfort. All participants subsequently recalled the squeezing task as being longer and associated with less discomfort than they had actually recorded it at the time. In the dichotic listening tasks, although patients detected the same number of words overall as controls did, they were less able to focus on the target channel (i.e. they detected more of the words included as distractors on the unattended channel).

Summary: Cryoanalgesia, the local application of extreme cold to nerves to produce analgesia, has been used to treat patients with intractable perineal pain. The cryoprobe was inserted percutaneously through the sacral hiatus into the sacral canal to produce anaesthesia of the lower sacral nerve roots. Forty patients received a total of 70 treatments: 31 patients (78%) were helped by the procedure and the median duration of improvement was 30 days. The treatment was more successful in relieving symptoms in patients suffering from pelvic cancer and coccydynia. The best results were obtained in those patients who received numerous freeze applications or prolonged freezing.

We recommend that patients be managed in a regional pain clinic, where a multidisciplinary approach promotes self-management of pain. Patients who were able to accept conservative treatment, and taper or withdraw opiate analgesia, had a better prognosis.