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The rostral part of the trigeminal sensory complex is involved in orofacial nociception
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present study, using clonidine 3 pg/kg epidurally after thoracotomy in 10 patients (compared to saline in 10 patients, in a randomized, double-blind study). did not demonstrate any decrease in need for supplementary intravenous pethidine during the first 12 postoperative hours. The side-effects of epidural clonidine were tolerable. Thus, clonidine 3 ,ug/kg epidurally seem to lack clinically important analgesic effect on severe nociceptive pain after thoracotomy. Clinical experience of long-term treatment with epidural and intrathecal opioids: a nationwide survey. S. A&r, N. Rawal and L.L. Gustafsson. Acta Anaesthesiol. Stand., 32 (1988) 2533259. Experience with spinal opioids was analyzed for the period 197991984 in a nationwide Swedish survey. 69 of 93 anesthesia departments used the method. Appr~~ximately 750 patients were treated with epidural morphine for an average duration of 124 days (3-450). Eighteen patients were treated with intrath~cal morphine for an average period of 47 days (3390). The intrathecal approach was used because of failure of the epidural route. The highest daily morphine dose was 480 mg and 50 mg for epidural and intrathecal routes, respectively. The need for increased dosage seemed to be related not only to changes in receptor sensitivity but also to changes in pain mechanisms. No case of life-threatening ventilatory depression was reported. Thirty-two departments had treated a few patients with chronic non-cancer pain conditions. Initial results were considered ‘excellent’ in 11 departments but at follow-up results were excellent in only 1 department. In addition to dislocation of the catheter, catheter occlusion or leakage, injection pain was an obstacle to successful treatment. Pruritus, urinary retention and local infections were not reported as significant probIems, but 1 case of meningitis was reported.
STOMATOLOGY SI uociceptive neurons participate in the encoding process by which monkeys perceive the intensity of noxious thermal stimulation. .--D.R. Kenshalo, Jr.. E.H. Chudler. F. Anton and R. Dubner. Brain Res.. 454 (1988) 378-382. The activity of primary somatosensory (SI) cortical nociceptive neurons was recorded while monkeys performed a behavioral task in which they detected small increases in noxious heat superimposed on noxious levels of thermal stimulation. The latency of detection of these stimuli, expressed as detection speed. was used as a measure of the perceived intensity of the stimulus. About two-thirds of the neurons that responded to noxious heat stimulation increased their discharge in response to graded increases in stimulus intensity. The remaining neurons responded to noxious heat but did not grade their response with stimulus intensity. In those neurons that encoded stimulus intensity. there was a significant correlation between neuronal discharge and detection speed. These findings suggest that SI cortical nociceptivo neurons are involved in the encoding process by which monkeys perceive the intensity of noxious thermal stimuli The rostra1 part of the trigeminal sensory complex is involved in orofacial nociception. - R. Dallel. P. Raboisson, P. Auroy and A. Woda, Brain Res., 448 (1988) 7-19. This study examined the role of the rostra1 components of the trigeminal brain-stem sensory complex in nociception by determining the effects of trigeminai tractotomy on the responses of neurons within the ventrobasal complex of the rat thalamus to noxious stimuli. The effect of tractotomy was dependent on the location of the neuron’s receptive field. Those with primarily oral fields showed minimal or no change in response after tractotomy, whereas those with facial fields were mainly suppressed by the tractotomy. These findings suggest that the rostra1 part of the trigeminal sensory complex above the obex receives nociceptive afferent fibers mainly from oral structures and is consistent with previous electrophysiological
239
and behavioral findings in cat and monkey. The findings also support the ‘onion arrangement of the trigeminal nucleus caudalis and contiguous nucleus interpolaris, structures located rostrally.
skin’ somatotopic with more medial
Sprouting of CGRP nerve fibers in response to dentin injury in rat molars. - P.E. Taylor, M.R. Byers and P.E. Redd, Brain Res., 461 (1988) 371-376. This study examined the response of calcitonin gene-related peptide (CGRP)-containing nerve fibers in the rat tooth pulp to mild tissue injury. Injury was limited to the outer dentin of molar teeth. After a 4 day survival period, there was an extensive increase in the number of CGRP-immunoreactive fibers in the tooth pulp adjacent to the injured dentin. CGRP innervation not only increased in the odontoblastic plexus and the odontoblastic layer, but also in dentinal tubules. These nerve fibers did not persist and disappeared in the 21 day postoperative group of teeth. The authors conclude that this increase in CGRP-containing fibers is due to a proliferation of CGRP-immunoreactive fibers rather than the expression of CGRP in nerve terminals that do not normally contain this peptide. They propose that the increase sprouting may be an active process by which sensory nerves enhance their effect on tissue defense and healing since CGRP is a major mediator of neurogenic in~ammation.
NEUROSURGERY Long-term efficacy of microvascular decompression ~igeminai neuralgia. - K.J. Burchiel, H. Clarke, M. Haglund and J.D. Loeser, J. Neurosurg., 69 (1988) 35-38. Forty patients were followed for an average period of 8.5 years after 44 consecutive suboccipital craniotomies for trigeminal neuralgia. Among these patients, 36 had microvascular decompression (MVD) of the nerve, 4 had repeat trigeminal rhizotomy after MVD was not successful in controlling their pain, and 4 had primary trigeminal rhizotomies. Of the 36 patients undergoing MVD, 17 (47%) experienced recurrent postoperative neuralgic pain: in 11 (31%) pain recurrence was major, and in 6 (17%) it was minor. Among the 8 patients undergoing rhizotomy, 4 (50%) had major pain recurrences and 1 (13%) had a minor recurrence, for a 63% total recurrence rate. There was a strong statistical relationship between an operative finding of arterial cross-compression of the nerve and long-term complete pain relief. Patients with other compressive pathology (related to veins or bone structures) did not on the average fare as well. Despite this, there appeared to be no point in time in the postoperative interval when the patient could be considered ‘cured.’ Major recurrences averaged 3.5% annually, and minor recurrences averaged 1.5% annually. The implications of these findings for the treatment of trigeminal neuralgia and the current understanding of the mechanism of MVD for this disorder are discussed. Glycerol rhizolysis for treatment of trigeminal neuralgia. - R.F. Young, J. Neurosurg., 69 (1988) 39-45. Percutaneous retrogasserian glycerol instillation was performed under local anesthesia for treatment of trigeminal neuralgia in 162 patients. A simplified technique that did not involve cistemography was used. Initial pain relief was achieved in 146 patients (90.1%). Recurrent pain was noted in 27 patients (18.5%) and was more frequent (50%) in patients who had undergone surgical treatments prior to glycerol injection than in those who had no previous surgical treatment (12.3%). A second glycerol injection was carried out in 9 patients and a third injection in 2 patients. The follow-up period extended from 6 to 67 months and 77.8% of patients are totally pain-free after one or more glycerol injections. Another 8.6% experienced good pain relief with the addition of small doses of pharmacological agents. Thus, 140 (86.4%) of the original 162 patients experienced satisfactory pain control following glycerol rhizolysis. Initial sensory loss on the face occurred in 117 patients (71.6%) but at the last follow-up examination
present study, using clonidine 3 pg/kg epidurally after thoracotomy in 10 patients (compared to saline in 10 patients, in a randomized, double-blind study). did not demonstrate any decrease in need for supplementary intravenous pethidine during the first 12 postoperative hours. The side-effects of epidural clonidine were tolerable. Thus, clonidine 3 ,ug/kg epidurally seem to lack clinically important analgesic effect on severe nociceptive pain after thoracotomy. Clinical experience of long-term treatment with epidural and intrathecal opioids: a nationwide survey. S. A&r, N. Rawal and L.L. Gustafsson. Acta Anaesthesiol. Stand., 32 (1988) 2533259. Experience with spinal opioids was analyzed for the period 197991984 in a nationwide Swedish survey. 69 of 93 anesthesia departments used the method. Appr~~ximately 750 patients were treated with epidural morphine for an average duration of 124 days (3-450). Eighteen patients were treated with intrath~cal morphine for an average period of 47 days (3390). The intrathecal approach was used because of failure of the epidural route. The highest daily morphine dose was 480 mg and 50 mg for epidural and intrathecal routes, respectively. The need for increased dosage seemed to be related not only to changes in receptor sensitivity but also to changes in pain mechanisms. No case of life-threatening ventilatory depression was reported. Thirty-two departments had treated a few patients with chronic non-cancer pain conditions. Initial results were considered ‘excellent’ in 11 departments but at follow-up results were excellent in only 1 department. In addition to dislocation of the catheter, catheter occlusion or leakage, injection pain was an obstacle to successful treatment. Pruritus, urinary retention and local infections were not reported as significant probIems, but 1 case of meningitis was reported.
STOMATOLOGY SI uociceptive neurons participate in the encoding process by which monkeys perceive the intensity of noxious thermal stimulation. .--D.R. Kenshalo, Jr.. E.H. Chudler. F. Anton and R. Dubner. Brain Res.. 454 (1988) 378-382. The activity of primary somatosensory (SI) cortical nociceptive neurons was recorded while monkeys performed a behavioral task in which they detected small increases in noxious heat superimposed on noxious levels of thermal stimulation. The latency of detection of these stimuli, expressed as detection speed. was used as a measure of the perceived intensity of the stimulus. About two-thirds of the neurons that responded to noxious heat stimulation increased their discharge in response to graded increases in stimulus intensity. The remaining neurons responded to noxious heat but did not grade their response with stimulus intensity. In those neurons that encoded stimulus intensity. there was a significant correlation between neuronal discharge and detection speed. These findings suggest that SI cortical nociceptivo neurons are involved in the encoding process by which monkeys perceive the intensity of noxious thermal stimuli The rostra1 part of the trigeminal sensory complex is involved in orofacial nociception. - R. Dallel. P. Raboisson, P. Auroy and A. Woda, Brain Res., 448 (1988) 7-19. This study examined the role of the rostra1 components of the trigeminal brain-stem sensory complex in nociception by determining the effects of trigeminai tractotomy on the responses of neurons within the ventrobasal complex of the rat thalamus to noxious stimuli. The effect of tractotomy was dependent on the location of the neuron’s receptive field. Those with primarily oral fields showed minimal or no change in response after tractotomy, whereas those with facial fields were mainly suppressed by the tractotomy. These findings suggest that the rostra1 part of the trigeminal sensory complex above the obex receives nociceptive afferent fibers mainly from oral structures and is consistent with previous electrophysiological
239
and behavioral findings in cat and monkey. The findings also support the ‘onion arrangement of the trigeminal nucleus caudalis and contiguous nucleus interpolaris, structures located rostrally.
skin’ somatotopic with more medial
Sprouting of CGRP nerve fibers in response to dentin injury in rat molars. - P.E. Taylor, M.R. Byers and P.E. Redd, Brain Res., 461 (1988) 371-376. This study examined the response of calcitonin gene-related peptide (CGRP)-containing nerve fibers in the rat tooth pulp to mild tissue injury. Injury was limited to the outer dentin of molar teeth. After a 4 day survival period, there was an extensive increase in the number of CGRP-immunoreactive fibers in the tooth pulp adjacent to the injured dentin. CGRP innervation not only increased in the odontoblastic plexus and the odontoblastic layer, but also in dentinal tubules. These nerve fibers did not persist and disappeared in the 21 day postoperative group of teeth. The authors conclude that this increase in CGRP-containing fibers is due to a proliferation of CGRP-immunoreactive fibers rather than the expression of CGRP in nerve terminals that do not normally contain this peptide. They propose that the increase sprouting may be an active process by which sensory nerves enhance their effect on tissue defense and healing since CGRP is a major mediator of neurogenic in~ammation.
NEUROSURGERY Long-term efficacy of microvascular decompression ~igeminai neuralgia. - K.J. Burchiel, H. Clarke, M. Haglund and J.D. Loeser, J. Neurosurg., 69 (1988) 35-38. Forty patients were followed for an average period of 8.5 years after 44 consecutive suboccipital craniotomies for trigeminal neuralgia. Among these patients, 36 had microvascular decompression (MVD) of the nerve, 4 had repeat trigeminal rhizotomy after MVD was not successful in controlling their pain, and 4 had primary trigeminal rhizotomies. Of the 36 patients undergoing MVD, 17 (47%) experienced recurrent postoperative neuralgic pain: in 11 (31%) pain recurrence was major, and in 6 (17%) it was minor. Among the 8 patients undergoing rhizotomy, 4 (50%) had major pain recurrences and 1 (13%) had a minor recurrence, for a 63% total recurrence rate. There was a strong statistical relationship between an operative finding of arterial cross-compression of the nerve and long-term complete pain relief. Patients with other compressive pathology (related to veins or bone structures) did not on the average fare as well. Despite this, there appeared to be no point in time in the postoperative interval when the patient could be considered ‘cured.’ Major recurrences averaged 3.5% annually, and minor recurrences averaged 1.5% annually. The implications of these findings for the treatment of trigeminal neuralgia and the current understanding of the mechanism of MVD for this disorder are discussed. Glycerol rhizolysis for treatment of trigeminal neuralgia. - R.F. Young, J. Neurosurg., 69 (1988) 39-45. Percutaneous retrogasserian glycerol instillation was performed under local anesthesia for treatment of trigeminal neuralgia in 162 patients. A simplified technique that did not involve cistemography was used. Initial pain relief was achieved in 146 patients (90.1%). Recurrent pain was noted in 27 patients (18.5%) and was more frequent (50%) in patients who had undergone surgical treatments prior to glycerol injection than in those who had no previous surgical treatment (12.3%). A second glycerol injection was carried out in 9 patients and a third injection in 2 patients. The follow-up period extended from 6 to 67 months and 77.8% of patients are totally pain-free after one or more glycerol injections. Another 8.6% experienced good pain relief with the addition of small doses of pharmacological agents. Thus, 140 (86.4%) of the original 162 patients experienced satisfactory pain control following glycerol rhizolysis. Initial sensory loss on the face occurred in 117 patients (71.6%) but at the last follow-up examination