Thalamic stimulation and recording in patients with deafferentation and central pain

Thalamic exploration was carried out in 39 patients with central or deafferentation pain. Several patients were explored more than once or bilaterally; therefore, 52 explorations were carried out. In 16 cases, microelectrode recording and microstimulation were employed. In the deafferented thalamus, a phenomenon of central allodynia was identified, in which patients with hyperpathia experience pain on stimulation rather than the usual sensations. With microrecording, a distinct unit firing in bursts can be identified and classified into three types. In several patients, the thalamic somatotopic map is found to be altered, and this reorganization can be classified into four types.     

Spontaneous neuronal hyperactivity in the medial and intralaminar thalamic nuclei of patients with deafferentation pain

Electrical activity was recorded from single cells in the thalamus of 10 patients with chronic pain associated with deafferentation. Under local anesthesia, these patients underwent either electrode implantation or thalamotomy for treatment of their pain. In eight of the 10 patients, single units were identified as discharging spontaneously in high-frequency, often rhythmic, bursts. The discharges were of two types: short bursts comprised of two to six spikes with a burst frequency of one to four per second; and long trains of 30 to 80 spikes of similar frequency. Reconstruction of electrode trajectories indicated that recordings were made from the region corresponding to the lateral aspect of the mediodorsal thalamic nucleus, the central lateral nucleus, a small part of the central median nucleus, and the parafascicular nucleus. In the eight patients in whom spontaneous neuronal burst activity was exhibited, it was impossible to study activity evoked by natural cutaneous stimulation due to the continuous spontaneous neuronal discharges. Both animal and human studies have suggested that pain related to deafferentation is accompanied by spontaneous hyperactivity in the dorsal horn of the spinal cord and in the ventral posterior thalamic nuclei. The authors present evidence of spontaneous neuronal hyperactivity in the intralaminar thalamic nuclei of patients with pain related to deafferentation. The findings suggest that spontaneous neuronal discharge in patients with pain related to deafferentation is more widespread in the central nervous system than has been previously appreciated. The results have important implications for the surgical treatment of chronic pain.     

Motor cortex stimulation for central and peripheral deafferentation pain. Report of eight cases

The authors tested a modified motor cortex stimulation protocol for treatment of central and peripheral types of deafferentation pain. Four patients with thalamic pain and four with peripheral deafferentation pain were studied. Preoperative pharmacological tests of pain relief were performed using phentolamine, lidocaine, ketamine, thiopental, and placebo. In five patients we placed a 20- or 40-electrode grid in the subdural space to determine the best stimulation point for pain relief for a few weeks before definitive placement of a four-electrode array. In three patients, the four-electrode array was implanted in the interhemispheric fissure as a one-stage procedure to treat lower-extremity pain. In two patients with pain extending from the extremity to the trunk or hip, dual devices were implanted to drive two electrodes. Six of eight patients experienced pain reduction (two each with excellent, good, and fair relief) from motor cortex stimulation. No correlation was apparent between pharmacological test results and the effectiveness of motor cortex stimulation. Patients with peripheral deafferentation pain, including two with phantom-limb pain and two with brachial plexus injury, attained pain relief from motor cortex stimulation, with excellent results in two cases. Testing performed with a subdural multiple-electrode grid was helpful in locating the best stimulation point for pain relief. Motor cortex stimulation may be effective for treating peripheral as well as central deafferentation pain.     

Motor cortex stimulation in patients with deafferentation pain: activation of the posterior insula and thalamus

OBJECT: The mechanisms underlying deafferentation pain are not well understood. Motor cortex stimulation (MCS) is useful in the treatment of this kind of chronic pain, but the detailed mechanisms underlying its effects are unknown. METHODS: Six patients with intractable deafferentation pain in the left hand were included in this study. All were righthanded and had a subdural electrode placed over the right precentral gyrus. The pain was associated with brainstem injury in one patient, cervical spine injury in one patient, thalamic hemorrhage in one patient, and brachial plexus avulsion in three patients. Treatment with MCS reduced pain; visual analog scale (VAS) values for pain were 82 +/- 20 before MCS and 39 +/- 20 after MCS (mean +/- standard error). Regional cerebral blood flow (rCBF) was measured by positron emission tomography with H2(15)O before and after MCS. The obtained images were analyzed with statistical parametric mapping software (SPM99). RESULTS: Significant rCBF increases were identified after MCS in the left posterior thalamus and left insula. In the early post-MCS phase, the left posterior insula and right orbitofrontal cortex showed significant rCBF increases, and the right precentral gyrus showed an rCBF decrease. In the late post-MCS phase, a significant rCBF increase was detected in the left caudal part of the anterior cingulate cortex (ACC). CONCLUSIONS: These results suggest that MCS modulates the pathways from the posterior insula and orbitofrontal cortex to the posterior thalamus to upregulate the pain threshold and pathways from the posterior insula to the caudal ACC to control emotional perception. This modulation results in decreased VAS scores for deafferentation pain.     

Assessment of sexual activity in patients with back pain compared with patients with neck pain

Recent research has shown significant adverse effects of chronic low back pain on sexual activity in 46% of patients. To establish whether and how chronic low back pain adversely affects sexual activity, a questionnaire-based study was conducted on a patient group (low back pain) and a comparison group (neck pain). Patients were administered a visual analog scale, a series of conventional questionnaires, and a specifically designed sexual activity questionnaire covering frequency of intercourse before and since onset of pain, discomfort during intercourse, satisfaction with sexual life, and comfortable and uncomfortable basic coital positions. Patients with low back pain reported more interference than did patients with neck pain, and women with low back pain were more affected than men. Compared with the other groups, women with low back pain had greater reduction in frequency of intercourse, more marked discomfort during intercourse, and more interference with their sexual lives. The most pain generating position was prone for both genders, and the most comfortable one was supine. Sexual impairment, more marked in women, seems to be related to the triggering of pain by intercourse and to psychologic factors.     

Microsurgical DREZ-lesion in the treatment of deafferentation pain

The lesion of the dorsal root entry zone (DREZL) of the spinal cord, recently introduced by Nashold and performed with radiofrequency or with laser, may be carried out with a microsurgical technique. Since 1978 up 1982 we have treated a series of 12 patients suffering from Pancoast's syndrome with a C8-T2 selective posterior rhizotomy (SPR). It has been observed that every deafferentative aspect of the pain was completely relieved. Such effect on the deafferentative aspect of the pain was most probably due to a lesion on the perforating vessels feeding the posterior grey horn. The lesion of this structure was therefore ischemic and this operation had to be indicate for the treatment of such pain. A series of 8 patients, suffering from cancer pain projected to anaesthetic areas, and 2 patients with benign post-thoracotomy pain, underwent to microsurgical DREZ lesion. The relief from pain was complete and no complications concerning pyramidal or posterior pathways involvement was observed. Preliminary good results suggest that a more selective lesion is possible with the microsurgical DREZ. It should be interesting a comparison between more large series of microsurgical DREZL and the more tested radiofrequency lesion.     

Image-guided motor cortex stimulation in patients with central pain.

According to recent clinical data, motor cortex stimulation (MCS) is an alternative treatment for central pain syndromes. We present our minimally invasive technique of image guidance for the placement of the motor cortex-stimulating electrode and assess the clinical usefulness of both neuronavigation and vacuum headrest. Five patients suffering from central pain underwent MCS with the guidance of a frameless stereotactic system (BrainLab AG, Munich, Germany). The neuronavigation was used for identification of the precentral gyrus and accurate planning of the single burr hole. The exact location was reconfirmed by an intraoperative stimulation test. Postoperative clinical and neuroradiological evaluations were performed in each patient. The navigation system worked properly in all 5 neurosurgical cases. Determination of the placement of stimulating electrode was possible in every case. All patients obtained postoperative pain relief. No surgical complication occurred, and the postoperative course was uneventful in all patients. This preliminary experience may confirm image guidance as a useful tool for the surgery of MCS. Additionally, minimal and safe exposure can be achieved using a single burr hole and vacuum headrest.     

Correlation between salivary alpha-amylase activity and pain scale in patients with chronic pain

BACKGROUND AND OBJECTIVES: The visual analog scale (VAS) is commonly used to assess pain intensity. However, the VAS is of limited value if patients fail to reliably report. Objective assessments are therefore clearly preferable. Previous reports suggest that elevated salivary alpha-amylase may reflect increased physical stress. There is a close association between salivary alpha-amylase and plasma norepinephrine under stressful physical conditions. In this study, we have determined the usefulness of a portable salivary alpha-amylase analyzer as an objective biomarker of stress. METHODS: Thirty patients (male/female = 15/15, age: 60.5 +/- 15.3 years) with chronic low back or leg pain (pain (+) group) and 20 pain-free control patients undergoing elective surgery under general anesthesia with epidural analgesia (pain (-) group) were recruited. Patients received epidural block with 5 to 10 mL 1% lidocaine. VAS, blood pressure, and heart rates were assessed before and 30 and 45 minutes after the epidural block. Salivary alpha-amylase was simultaneously measured using a portable analyzer. The relationship between the VAS and salivary alpha-amylase in chronic pain patients was assessed. RESULTS: After the epidural block both heart rate and systolic blood pressure decreased by approximately 8%. In the pain (+) group, the epidural block markedly decreased the VAS pain scale and salivary alpha-amylase from 56 +/- 22 to 19 +/- 16 mm (P < .01) and from 82 +/- 48 to 45 +/- 28 U/mL (P < .01), respectively, with a significant correlation between the 2 measures (r = 0.561, P < .01). In contrast, salivary alpha-amylase did not change significantly in the pain (-) group. CONCLUSIONS: Because there was a significant correlation between VAS pain scale and salivary alpha-amylase, we suggest that this biomarker may be a good index for the objective assessment of pain intensity. In addition, a simple to use portable analyzer may be useful for such assessment.     

Stereotactic rostral mesencephalotomy in cancer pain and deafferentation pain. A series of 40 cases with follow-up results

Stereotactic rostral mesencephalotomy was performed in two groups of patients to investigate the long-term results in regard to pain relief. A standardized technique of target localization with ventriculography was used. Group A consisted of 33 patients with otherwise intractable pain due to cancer. Group B consisted of seven patients with deafferentation pain. Long-term pain relief was good (57%) for Group A and nonexistent for Group B patients. It is concluded that stereotactic rostral mesencepthalotomy is a valuable means for treating nociceptive cancer pain in lateral syndromes, but is of no value in neuropathic pain. Anatomical correlates for the results obtained are discussed and a hypothesis on the plasticity of the neo- and paleospinal afferent systems is formulated.     

经PICC测中心静脉压异常患者的护理

目的 探讨经PICC测中心静脉压(CVP)异常患者的护理方法。方法对72例经PICC置管的危重患者共进行318次CVP测量,其中11例68例次测得CVP＜5 cmH2O,对伴低血压者予以大量补液（24 h补液量＞4 500 ml）,对血压正常者24 h补液量3 500～4 500 ml;15例84例次测得CVP＞12 ...     

Dorsal root entry zone lesions for the control of deafferentation pain: experiences in ten patients

Experiences with radiofrequency lesions of the dorsal root entry zone in 10 patients are reported. All of these patients suffered from central (deafferentation) pain. The early postoperative results were poor in the 2 patients with traumatic paraplegia and good in all 8 patients with pain in the cervical segments. Two patients treated with cervical DREZ lesions died. In 2 of the remaining 6 patients with cervical lesions, pain recurred. Four had a good result up to 30 months after operation.     

Diagnosis and management of patients with overactive bladder syndrome and abnormal detrusor activity

Overactive bladder syndrome (OABS) is a widely recognized syndrome with symptoms that can include urinary urgency, frequency, nocturia, and incontinence. Although there may be several causative factors for OABS, detrusor overactivity is the most common. In addition, urinary incontinence can also be due to a distinct but equally bothersome condition underactive bladder syndrome, or detrusor underactivity. The incomplete bladder emptying that characterizes detrusor underactivity often arises from impaired contractile function of the detrusor muscle. The variations in etiologies of the two syndromes necessitate patient evaluations tailored to individual symptom presentation. Increased awareness of the differences between the manifestations of OABS and underactive bladder syndrome call for specific approaches to the management of bladder dysfunction.     

Antinociceptive effects of phenobarbital in "tail-flick" test and deafferentation pain.

Deafferentation pain has been related to abnormal electrical hyperactivity in the neurons of the sensory relays in the central nervous system. This electrical activity resembles the epileptoid pattern observed in experimental epileptoid foci. With the aim of preventing this hyperactivity, rats were given long-term treatment with phenobarbital after sciatic transection and dorsal cervical rhizotomy. Daily intramuscular injections of saline solution or 5 and 10 mg/kg of phenobarbital were administered for 20 days, starting 10 days before surgery. Larger doses of phenobarbital delayed the onset and reduced the severity of autotomy. In a test of acute pain, the effect of intraperitoneal (1-16 mg) and intrathecal (100-500 micrograms) phenobarbital was studied by measuring the "tail-flick" response latency. Intraperitoneal phenobarbital did not modify acute pain, but 500 micrograms of intrathecal phenobarbital increased the threshold of pain. These results indicate that (a) phenobarbital, a drug with anticonvulsant activity, reduces deafferentation behavior in rats, and (b) intrathecal phenobarbital has an antinociceptive action in acute experimental pain.     

Microsurgical junctional DREZ coagulation for treatment of deafferentation pain syndromes

BACKGROUND: In the treatment of intractable deafferentation pain, different procedures in the DREZ have proved most effective. For most of the spot-like techniques special equipment is mandatory. In this study the technique and the results of junctional DREZ coagulation for treatment of different pain syndromes with the help of bipolar forceps is presented. METHODS: In 40 patients with intractable deafferentation pain syndromes a junctional DREZ coagulation lesion along the entire dorsolateral fissure of the involved spinal cord segments was made using bipolar forceps. Etiologies of the pain included avulsion of the brachial plexus (21 cases), postherpetic pain (4 cases), phantom pain (3 cases), peripheral nerve injury (3 cases), reflex sympathetic dystrophy (2 cases), spinal cord transsection (1 case), and syringomyelia (6 cases). RESULTS: Of 21 patients who underwent junctional DREZ surgery for pain because of brachial plexus avulsion 10 (47.6%) had complete, 7 (33.3%) excellent, 3 (14.3%) good, and 1 (4.7%) fair pain relief (follow-up 20 to 120 months). In the group of 19 patients (follow-up 6 to 84 months) with pain syndromes other than postavulsion pain we achieved excellent results in 10 cases (52.6%), good in 8 (42.1%) and no pain relief in 1 case (5.3%). Transient sensory neurological disturbances lasting up to 8 weeks were observed in 6 (15%) cases; permanent sensory and motor deficit in 1 (2.5%) case. CONCLUSIONS: Clinical results of junctional coagulation DREZ lesion for the treatment of deafferentation pain syndromes are promising. There is no need for special equipment for creating DREZ lesions. The lesions are precisely placed with only a bipolar electrode. Postoperative complications are rare and transient. We believe that the junctional coagulation includes the entire dorsolateral sulcus and DREZ structures important for deafferentation pain.     

Patterns of muscular activity during movement in patients with chronic low-back pain

Bilateral paraspinal electromyogram (EMG) at levels L1-L2 and L4-L5, and abdominal EMG of a group of 20 low-back pain patients were compared to those of a group of 20 pain-free controls during flexion, extension, lateral bending to right and left, and rotation to right and left. The results showed no significant left-right differences in paraspinal EMG levels between low-back pain patients and pain-free controls during any of the movements. However, patterns of paraspinal and abdominal EMG were found to be different for low-back pain patients compared to pain-free controls during flexion only.     

Partial cortical deafferentation promotes development of paroxysmal activity

This study tested the hypothesis that early functional alterations in neuronal synchrony in the partially deafferented cortex may lead to spontaneously occurring electrographic seizures. In vivo experiments with partial deafferentation of cat suprasylvian gyrus after extensive undercut of the white matter were conducted using multi-site EEG, extracellular unit and intracellular recordings. The amplitudes of EEG waves were much higher in the areas surrounding deafferented cortical fields as compared with control and with undercut cortex. In 40% of animals with undercut cortex, paroxysmal activity occurred 2-3 h after the undercut and was initiated in the relatively intact cortex, adjacent to the more disconnected one. The seizures that followed the undercut consisted of spike-wave/polyspike-wave complexes and fast runs, resembling the electrographic patterns of some clinical epileptic syndromes. An increased local synchrony in the relatively intact cortex evolved into paroxysmal activity that ultimately spread to the deafferented cortex. The electrographic seizures were found only in animals that showed a propagation of the slow sleep-like oscillation in control conditions. The increase of long-range synchrony within a given seizure was associated with seizure termination. These results indicate that alterations in neuronal synchrony following neuronal trauma can be a critical factor triggering electrographic seizures.     

Ultrasonic lesion of the trigeminal nucleus caudalis for deafferentation facial pain

Summary The deafferentation facial pain syndrome, caused by physical, herpetic or tumourous lesions of the trigeminal sensory root, was successfully managed with ultrasonic trigeminal nucleotomy. The article presents this new surgical technique and its results in 14 patients suffering from severe facial pain and dysaesthesias.