Modulation of practice-dependent plasticity in human motor cortex.
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Motor practice may lead to expansion of trained representations in the motor cortex, but it is unknown whether this practice-dependent plasticity can be purposefully enhanced or depressed. Evidence, mainly based on animal experiments, indicates that the activity of GABA-related cortical inhibition is important in controlling the extent to which plasticity may occur. We tested the role of GABA in modulating practice-dependent plasticity in the human motor cortex. A decrease in GABA-related cortical inhibition was achieved by ischaemic nerve block (INB) in the hand by deafferentation/deefferentation and an increase was achieved by administration of the GABA(A) receptor agonist lorazepam. In Experiment 1, healthy subjects performed motor practice (MP), consisting of repeated ballistic contractions of the biceps muscle in the absence (MP alone) or presence of INB (MP+INB). Changes in the biceps motor cortex representation were assessed by transcranial magnetic stimulation (TMS). MP+INB resulted in a dramatic increase in the size of the motor evoked potential (MEP) and in paired-pulse excitability compared with mild or no changes in the MP-alone and INB-alone conditions. In Experiment 2, this dramatic increase in biceps representation induced by MP+INB was replicated when subjects were pretreated with placebo, but this increase was prevented or even switched to a decrease when subjects were pretreated with lorazepam. These findings indicate that a decrease in GABA-related inhibition facilitates practice-dependent plasticity in the human motor cortex, whereas an increase depresses it. In Experiment 3, practice-dependent plasticity (assessed by TMS, as in the first two experiments) was also tested at the behavioural level. The dramatic increase in biceps MEP size induced by MP+INB was paralleled by an increase in peak acceleration of the fastest elbow flexion movements. Similarly, the lack of change in MEP size in the MP-alone condition was paralleled by a lack of change in peak acceleration. We propose that changes in GABA activity may be instrumented to modulate plasticity purposefully; for instance, to enhance plastic change and recovery of function after a lesion in neurological patients. (+info)
Celiac plexus block: injectate spread and pain relief in patients with regional anatomic distortions.
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BACKGROUND: The success of the neurolytic celiac plexus block, despite different approaches and methods used, depends on adequate spread of the injectate in the celiac area. This retrospective study was conducted to evaluate the patterns of alcohol spread and pain relief in patients with cancer or therapy-related anatomic distortion of the celiac area. METHODS: From 177 cancer patients who underwent computed tomography (CT)-guided single-needle neurolytic celiac plexus block via an anterior approach, a radiologist, blind to the aim of the study, retrospectively selected 105 patients with abnormal anatomy of the celiac area as judged by CT images obtained before the block. To evaluate CT patterns of neurolytic (mixed with contrast) spread, the celiac area was divided on the frontal plane into four quadrants: upper right and left and lower right and left, as related to the celiac artery. Results were expressed as the number of quadrants into which contrast spread, ie., four, three, two, or one quadrants with contrast. The patterns of contrast spread according to the number of quadrants with anatomic distortion were analyzed. Patient assessment by visual analog scale was reviewed to evaluate the degree of pain relief. Pain relief 30 days after block was considered long-lasting. Pain relief at 30 days after block was analyzed according to the number of quadrants with contrast. RESULTS: Overall, four, three, two, and one quadrants with contrast were observed in 9 (8%), 21 (20%), 49 (47%), and 26 (25%) patients, respectively. An inverse correlation was observed between the number of quadrants with anatomic distortion and the number of quadrants with contrast (P < 0.001). Long-lasting pain relief was noticed in nine of nine patients (100%; 95% confidence interval, 66-100) with contrast in four-quadrants, and in 10 of 21 patients (48%; 95% confidence interval, 26-70) with contrast in 3 quadrants (P < 0.01). None of the 75 patients with contrast in two quadrants or one quadrant experienced long-lasting pain relief. CONCLUSIONS: These findings suggest that, using the single-needle anterior approach, the neurolytic spread in the celiac area is highly hampered by the regional anatomic alterations. It also appears that only a complete (four quadrants) neurolytic spread in the celiac area can guarantee long-lasting analgesia, and that this picture may be obtained in a very limited fraction of patients with regional anatomic alterations. (+info)
Therapeutic efficacy of selective nerve root blocks in the treatment of lumbar radicular leg pain.
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The objective of this study was to investigate the clinical effectiveness of nerve root blocks (i.e., periradicular injection of bupivacaine and triamcinolone) for lumbar monoradiculopathy in patients with a mild neurological deficit. We have retrospectively analysed 30 patients (29-82 years) with a minor sensory/motor deficit and an unequivocal MRI finding (20 disc herniations, 10 foraminal stenoses) treated with a selective nerve root block. Based on the clinical and imaging findings, surgery (decompression of the nerve root) was justifiable in all cases. Twenty-six patients (87%) had rapid (1-4 days) and substantial regression of pain, five required a repeat injection. 60% of the patients with disc herniation or foraminal stenosis had permanent resolution of pain, so that an operation was avoided over an average of 16 months (6-23 months) follow-up. Nerve root blocks are very effective in the non-operative treatment of minor monoradiculopathy and should be recommended as the initial treatment of choice for this condition. (+info)
Inhibition of electromyographic activity in human triceps surae muscles during sinusoidal rotation of the foot.
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Torque and electromyographic (EMG) responses to sinusoidal rotations of the foot were measured. The frequency range of the movements was 0.5 Hz to 15 Hz at amplitudes ranging between 1 and 10 degrees. At frequencies above 7 Hz, the EMG activity did not follow individual foot rotation cycles. The EMG activity was inhibited whenever the peak torque was large with respect to the first cycle peak torque. Dantrolene sodium reduced the torque developed in triceps surae, allowing the EMG activity to follow individual stretch cycles. As the drug was metabolized, the EMG activity returned to the character seen in the pre-drug control--that is, inhibition on alternate stretch cycles. It is concluded that the EMG inhibition phenomenon can be attributed in part to force receptors in muscle but that these receptors are not the sole contributors to the inhibition. (+info)
Preemptive effects of a combination of preoperative diclofenac, butorphanol, and lidocaine on postoperative pain management following orthognathic surgery.
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The aim of the study was to investigate whether preemptive multimodal analgesia (diclofenac, butorphanol, and lidocaine) was obtained during sagittal split ramus osteotomy (SSRO). Following institutional approval and informed consent, 82 healthy patients (ASA-I) undergoing SSRO were randomly assigned to 1 of 2 groups, the preemptive multimodal analgesia group (group P, n = 41) and the control group (group C, n = 41). This study was conducted in a double-blind manner. Patients in group P received 50 mg rectal diclofenac sodium, 10 micrograms/kg intravenous 0.1% butorphanol tartrate, and 1% lidocaine solution containing 10 micrograms/mL epinephrine for regional anesthesia and for bilateral inferior alveolar nerve blocks before the start of surgery. Postoperative pain intensity at rest (POPI) was assessed on a numerical rating score (NRS) in the postanesthesia care unit (PACU) and on a visual analogue scale (VAS) at the first water intake (FWI) and at 24, 48, and 72 hours after extubation. POPI in the PACU was significantly lower in group P than in group C, whereas there were no significant differences at FWI, 24, 48, and 72 hours after extubation in both groups. Preemptive multimodal analgesia was not observed in this study. (+info)
Clinical evaluation of inferior alveolar nerve block by injection into the pterygomandibular space anterior to the mandibular foramen.
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The conventional inferior alveolar nerve block (conventional technique) has potential risks of neural and vascular injuries. We studied a method of inferior alveolar nerve block by injecting a local anesthetic solution into the pterygomandibular space anterior to the mandibular foramen (anterior technique) with the purpose of avoiding such complications. The insertion angle of the anterior technique and the estimation of anesthesia in the anterior technique were examined. The predicted insertion angle measured on computed tomographic images was 60.1 +/- 7.1 degrees from the median, with the syringe end lying on the contralateral mandibular first molar, and the insertion depth was approximately 10 mm. We applied the anterior technique to 100 patients for mandibular molar extraction and assessed the anesthetic effects. A success rate of 74% was obtained. This is similar to that reported for the conventional technique but without the accompanying risks for inferior alveolar neural and vascular complications. (+info)
Inferior alveolar nerve block by injection into the pterygomandibular space anterior to the mandibular foramen: radiographic study of local anesthetic spread in the pterygomandibular space.
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We studied the spread of local anesthetic solution in the inferior alveolar nerve block by the injection of local anesthetic solution into the pterygomandibular space anterior to the mandibular foramen (anterior technique). Seventeen volunteers were injected with 1.8 mL of a mixture containing lidocaine and contrast medium utilizing the anterior technique. The course of spread was traced by fluoroscopy in the sagittal plane, and the distribution area was evaluated by lateral cephalograms and horizontal computed tomography. The results indicate that the contrast medium mixture spreads rapidly in the pterygomandibular space to the inferior alveolar nerve in the subjects who exhibited inferior alveolar nerve block effect. We concluded that the anesthetic effect due to the anterior technique was produced by the rapid distribution of anesthetic solution in the pterygomandibular space toward the mandibular foramen, and individual differences in the time of onset of analgesia may be due to differences in the histologic perineural tissues. (+info)
Adverse reactions triggered by dental local anesthetics: a clinical survey.
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One hundred and seventy-nine patients completed a questionnaire focusing on adverse reactions to dental local anesthetics as manifested by 16 signs and symptoms. Twenty-six percent of the participants reported having at least 1 adverse reaction. It was found that most of the adverse reactions occurred within the first 2 hours following the injection of local anesthetics. Pallor, palpitations, diaphoresis, and dizziness were the most common adverse reactions reported in the study. The results pointed to a significant relationship between anxiety, gender, injection technique, and procedure with a higher incidence of adverse reactions. (+info)