Pharmacological classification of central post-stroke pain: comparison with the results of chronic motor cortex stimulation therapy

Abstract

In an attempt to clarify the neurochemical background of central post-stroke pain and to undertake a pharmacological analysis, the basic pharmacological characteristics of this intractable pain syndrome were investigated by the morphine, thiamylal and ketamine tests. In addition, the correlation between the pharmacological characteristics and the effects of chronic motor cortex stimulation therapy was examined. The study employed 39 central post-stroke pain patients who had intractable hemibody pain associated with dysesthesias, and radiologically demonstrated lesions in the thalamic area (thalamic pain, n = 25) or suprathalamic area (suprathalamic pain, n = 14). The pharmacological evaluations showed that definite pain reduction occurred in eight of the 39 cases (20.5%) by the morphine test, in 22 of the 39 cases (56.4%) by the thiamylal test, and in 11 of 23 cases (47.8%) by the ketamine test. Based on these pharmacological assessments, there was no obvious difference between thalamic and suprathalamic pain. A comparison of the long-term follow-up results of chronic motor cortex stimulation therapy revealed that thiamylal and ketamine-sensitive and morphine-resistant cases displayed long-lasting pain reduction with chronic motor cortex stimulation therapy, whereas the remaining cases did not show good results. We conclude that pharmacological classification of central post-stroke pain by the morphine, thiamylal and ketamine tests could be useful for predicting the effects of chronic motor cortex stimulation therapy. It has recently been suggested that excitatory amino acids may be involved in the development of central post-stroke pain. However, the fact that only 23 of the present 39 cases (59.0%) of thalamic and suprathalamic pain were sensitive to the thiamylal or ketamine test reflects the complex pharmacological background and the difficulties associated with treating central post-stroke pain.

Types and effectiveness of treatments used by people with chronic pain associated with spinal cord injuries: influence of pain and psychosocial characteristics

“…For example, several investigators 24,50 have suggested that specific neurological subgroups of neuropathic pains may respond to opioids. Thus, it is possible that 'opioid responsive' neuropathic pain subgroups may also exist in the SCI chronic pain population.…”

Motor cortex stimulation for neuropathic pain

“…Barbiturate sensitivity and opioid insensitivity have been suggested as possible predictors of response. 1,22,24 Transcranial magnetic stimulation may be another useful predictor of response.1,14 Another possible predictor in patients with poststroke pain could be the level of muscle strength demonstrated in the painful area.10 Results of such preoperative testing, however, are no guarantee of a successful outcome, as not all patients who respond to propofol respond to MCS and, equally, morphine-insensitive patients have been shown to respond to stimulation. 1 We have not, therefore, routinely performed any specific investigations other than head computerized tomography and magnetic resonance imaging, preoperative chest radiography, electrocardiography and blood count, clotting screen, and serum chemistry.…”

Recording of Corticospinal Evoked Potential for Optimum Placement of Motor Cortex Stimulation Electrodes in the Treatment of Post-stroke Pain -Two Case Reports-

“…Therefore, both hand and foot areas were stimulated together, since it is important to induce muscle contraction or muscle twitch in the painful area for the motor cortex stimulation therapy. 10,[19][20][21][22] Our previous experience with patients with MMT of 4 suggested that the threshold intensity to induce muscle contraction under stimulation conditions of 25 Hz with 0.2 msec duration is 5.8 ± 0.9 V (n ＝ 10). In the present patients, muscle contraction was induced at 2.9 V in Case 1 and 3.3 V in Case 2.…”

“…[2][3][4]7,8,[11][12][13]16,17,22) In the large series, the long-term success rate for pain alleviation was about 50%. The pain control provided by motor cortex depends on stimulation of neuronal circuits mediated by corticospinal tract neurons originating from the motor cortex.…”