Management of intractable pain with percutaneous epidural spinal cord stimulation: differences in pain-relieving effects among diseases and sites of pain

This study is a survey of the overall clinical results achieved with our pain treatment method, percutaneous epidural low-frequency (1.6-8.0 Hz) spinal cord stimulation. It examines the relationship between the effectiveness of epidural spinal cord stimulation (ESCS) and diseases or sites of pain. Continuous indwelling of the catheter electrodes in the posterior epidural space ranged from 3 to 67 days, and the duration of percutaneous ESCS varied from less than 1 wk to more than 1 yr. Complete pain relief (100%) was achieved during stimulation in 11.5% of the patients (52 of 454). Complete (100%) to partial (more than 30%) pain relief occurred in 71.1% of the patients. In six (1.3%) patients pain was aggravated by stimulation. Analgesics and/or sedatives were discontinued completely after treatment in 52 patients (11.5%) and reduced in 263 patients (57.9%). The number of patients who rated pain relief better than 50% was significantly more in carcinoma/sarcoma and causalgia (P < 0.001), and significantly less in postherpetic neuralgia and thromboangitis obliterans/arterial sclerosis obliterans (P < 0.001) than the average in all diseases. There was a significantly high responsiveness to ESCS in female patients in comparison to male patients (P < 0.05). Pain in the head/face, neck/upper extremities, and trunk responded more to ESCS than pain in the lower extremities. Alleviation of pain by ESCS was lower when the verbal pain score was high. There were no major complications in percutaneous ESCS. Thus, we have demonstrated that pain-alleviating effects of ESCS varies significantly by disease and site of pain, and that this simple percutaneous method can be used for a relatively long period.

Effects of dorsal root entry zone lesion on spinal cord potentials evoked by segmental, ascending and descending volleys

The spinal cord potentials (SCPs) were recorded from the dorsal root entry zone (DREZ) and posterior epidural space in patients before and after dorsal root entry zone lesion (DREZL) during general anaesthesia. The SCPs from the DREZ activated by segmental, ascending and descending volleys were basically the same in fundamental waveform as those recorded from the posterior epidural space. Segmentally activated slow negative (N1) wave, reflecting synchronized activities of dorsal horn neurones, and positive (P2) wave, thought to indicate primary afferent depolarization, were affected by DREZL in all 4 subjects tested, even by contralateral stimulation, suggesting that these components of the segmental SCPs in man partly reflect the activities of the contralateral dorsal horn. The spike-like potentials activated by ascending volleys were not affected by DREZL, while the subsequent slow components were decreased in the lesioned level. This may indicate that ascending spinal cord tracts are not affected by the operation, and suggests that the origin of the slow components by ascending volleys lies at least in part in the segmental dorsal horn. The slow negative and positive components, recorded at a remote segment from DREZL, in response to the descending volleys, were augmented after DREZL, suggesting that activation of ascending or descending inhibition through a feedback loop via the supraspinal structures might occur at least transiently following DREZL. All components of the SCPs activated by descending volleys were decreased or disappeared in recording from the lesioned level, as expected. Thus, intra-operative recording of the SCPs during DREZL might be beneficial for monitoring and studying human spinal cord function.

Problems related to dorsal root entry zone lesions

Several clinical problems related to the dorsal root entry zone lesions (DREZLs) in 15 patients with chronic pain are presented and discussed in terms of ratings of pain relief following surgery, development of sensory or motor weakness and postmortem histologies. Subjective pain relief exceeding 70% was achieved at around 2 weeks after the operations in most patients (13/15), and then decreased in some to 30 from 70% in the follow-up observations. Our new "objective" pain relief score was tested in these patients. A significant positive correlation between subjective pain relief and our objective pain relief scale was found, but some discrepancies between them were also found during the follow-up. Sensory loss, motor weakness, paraesthesia and a new pain were found as complications in 12, 7, 4 and 6 patients, respectively. Postmortem histological findings of the spinal cord in two patients with systemic lupus erythematosus and uterine cancer, who received bilateral DREZLs twice and bilateral DREZLs plus commissural myelotomy, respectively, indicate that care should be taken to avoid extension of the coagulation beyond the dorsal horn.

Slow positive dorsal cord potentials activated by heterosegmental stimuli

Heterosegmental slow positive waves (HSPs) and segmental spinal cord potentials were recorded from the cord dorsum in ketamine-anesthetized rats. Forepaw stimulation produced HSPs in the lumbo-sacral enlargement (lumbar HSPs), whereas hind paw stimulation evoked HSPs in the cervical cord (cervical HSP). Both the HSP and the secondary component of the slow positive wave (P2s) in the segmental spinal cord potential were highly vulnerable to anesthetics and completely disappeared after spinal cord transection at the C1/2 level, indicating that both the HSP and P2s are produced by a long feedback loop via supraspinal structures. The lumbar HSP evoked by forepaw stimulation was maximal in amplitude at the L5 level and more dominant in the ipsilateral cord dorsum than in the contralateral one, but widely distributed in the lumbo-sacral cord. A variability of onset (7-18 msec for cervical and 5-17 msec for lumbar HSPs) and peak (22-35 msec for cervical and 12-50 msec for lumbar HSPs) suggests the existence of several nuclei to form the feedback loops for descending impulses to produce the HSPs. There were no peak latency differences between the HSPs and P2s. Since there were several similar characteristics between the P2s and HSP such as a high vulnerability to anesthetic, a complete disappearance after high spinal transection and similar response curves to graded intensities of stimulation, there may be a close relationship between their feedback nuclei and the pathways mediating them. All wide dynamic range (WDR) neurons (12/12) in lamina V of Rexed responded to heterosegmental stimulation with inhibition of firing.(ABSTRACT TRUNCATED AT 250 WORDS)

Observation of spinal canal and cisternae with the newly developed small-diameter, flexible fiberscopes

Small-diameter (0.5-, 0.9-, and 1.4-mm) flexible fiberscopes were developed for visual diagnosis of spinal canal diseases. The fiberscopes were introduced via a Tuohy needle into the subarachnoid and epidural spaces of ten patients with various pain syndromes. Clear visualization of the subarachnoid space was achieved using the fiberscopes. The epidural space could be visualized only during withdrawal of the fiberscope. In five cases, the fiberscope could be advanced up to the level of the cisternae without causing the patient any discomfort. A slight headache and transient fever were noted after the examination in five and two cases, respectively, but no other complications occurred. Interestingly, preexisting pain diminished (two cases) or disappeared (one case) after the myeloscopy in three of five cases in which the myeloscopy revealed aseptic adhesive arachnoiditis. Further studies should be carried out to evaluate the usefulness of this technique.

[The effect of DREZ (dorsal root entry zone) lesions on intractable pain in patients with spinal cord injury]

Some patients with spinal cord injury complain of a severe intractable pain. This intractable pain places new hurdles on the road to return to the ordinary daily life in these patients. The effective therapy for the intractable pain has not been established. Dorsal root entry zone (DREZ) lesion was originally reported by Nashold et al to alleviate deafferented pain syndrome. Three male and one female patients with intractable pain following spinal cord injury were treated with DREZ-lesions. One month after operation, all 4 patients obtained good pain relief. However, at a follow-up period till February 1989 (ranging 11 months from 2 years and 6 months), 2 patients had subjective pain relief. When other therapies on intractable pain following spinal cord trauma are not effective, the DREZ-lesion might be considered.