Constant Current vs. Constant Voltage Systems for Temporal Spinal Cord Stimulation for Intractable Pain.

Although spinal cord stimulation (SCS) is a useful treatment for chronic intractable pain, the optimal method of stimulation has not yet been established. In this prospective, crossover study, we compared the efficacy of using a constant current (CC) system with that of a constant voltage (CV) system for temporal SCS. Twenty patients were enrolled and divided into two groups. For 10 patients, a CV system was applied on Days 1-5, followed by the use of a CC system on Days 6-10. For the other 10 patients, a CC system was applied for the first five days, followed by a CV system for the subsequent five days. We evaluated the alteration of pain intensity using a visual analogue scale (VAS), the area of stimulation, the stability of effect, and patient satisfaction regarding treatment. The pain scores decreased significantly after the start of the SCS. There was no significant difference in the change in VAS between the two systems. The stimulation method used for temporal SCS did not affect the reduction of pain intensity. Patients felt a wider stimulation area by the CC system compared to the CV system.

Multiple P2Y subtypes in spinal microglia are involved in neuropathic pain after peripheral nerve injury.

A prominent signaling pathway in the development of neuropathic pain involves ATP acting on microglial purinergic receptors. Among the P2Y metabotropic receptors, we reported before that the P2Y12 receptor is upregulated in microglia following nerve injury and involved in the phosphorylation of p38 MAPK, and in the development of pain behavior. In this study, we examined the expression of P2Y6, P2Y13, and P2Y14 receptors in the spinal cord and whether these receptors are involved in the pathogenesis of neuropathic pain following peripheral nerve injury. We found that spared nerve injury induced a dramatic increase of not only P2Y12, but also P2Y6, 13, and 14 receptor mRNA expression in spinal microglia. The increase continued for at least 2 weeks after injury. To determine whether p38 MAPK can induce the expression of P2Y receptors, we administered intrathecally the p38 MAPK inhibitor SB203580 and found that it significantly suppressed P2Y6, P2Y13, and P2Y14 but not P2Y12 mRNAs. Intrathecal injection of the specific P2Y6 antagonist MRS2578, specific P2Y13 antagonist MRS2211 or P2Y14 antisense LNA, attenuated mechanical pain hypersensitivity. The mixture of three antagonists for P2Y6, 12, and 13 showed a longer suppressive effect on pain behavior than the individual treatments. Our data demonstrate that ATP and other nucleotides may stimulate activated microglia with the upregulation of P2Y6, P2Y12, P2Y13, and P2Y14 receptors following nerve injury and these receptors are involved in the development of neuropathic pain.

The effects of temporary spinal cord stimulation (or spinal nerve root stimulation) on the management of early postherpetic neuralgia from one to six months of its onset.

OBJECTIVE: We examined the efficacy of temporary spinal cord stimulation involving the insertion of only a needle and quadripolar lead into the epidural space and applied using an extracorporeal stimulation generator for a few weeks of early postherpetic neuralgia from one to six months of its onset. MATERIALS AND METHODS: Temporary spinal cord stimulation was applied in 33 patients with postherpetic neuralgia and in whom epidural block was effective. Temporary spinal cord stimulation was applied over seven days, and analgesic effects was evaluated based on visual analog scale (VAS) values before and after one, three, and six months following treatment. An analgesic effect was defined as a decrease of over 50% in the VAS value compared with before treatment. RESULTS: VAS values decreased significantly from 68.1 mm (standard deviation [SD]± 15.2) before treatment to 37.5 mm (SD ± 20.4) after one month, to 38.0 mm (SD ± 18.7) after three months, and to 35.0 mm (SD ± 21.3) after six months. In 21/33 (63.6%) cases, an analgesic effect, defined as a decrease in the VAS value of greater than 50%, was observed one month after treatment, in 20/33 (60.6%) cases such an effect was observed three months after treatment, and in 21/33 (63.6%) cases the effect was still observed six months after treatment. CONCLUSIONS: Temporary spinal cord stimulation is an effective analgesic method for early postherpetic neuralgia from one to six months of its onset.

[Measurement of clinical pain intensity: quantitative sensory testing].

Pain is a private internal event, the degree of which can not be evaluated directly by others. The measurement of the nociceptive pain threshold may apply to the evaluation of the degree of the pain. The instruments using mechanical and electrical stimulation are available for the clinical application. Thermotest allows the testing of quantitative evaluation of thermal thresholds such as heat, cold, and heat and cold pain sensation. A machine for the thermotest using radiant heat and contact heat is available in Japan. There is an instrument using puncturing stimulus and pressure stimulus for a mechanical stimulation. A puncturing stimulus is suitable for the clinical use with a handy instrument such as von Frey filaments and needle type algometry. In clinical practice, the pressure algometry is usually applied over a bony surface or over the muscle. The method seems to be well suited for the evaluation of pain in musculoskeletal disorders. The electrical stimulation test provides a quantitative measure of pain tolerance to a transcutaneous stimulation, neuroselective for large and small myelinated and unmyelinated nerve fibers. There are characteristics including advantages and faults in each method, and the method of measurement corresponding to the purpose and application is important.

[Report of a case: the anesthetic management for fetal tracheal intubation with intact uteroplacental circulation during cesarean section].

We experienced a case of cesarean section in a patient with a fetus having a prenatally diagnosed huge cervical mass, which could cause airway obstruction immediately after delivery. The fetal cervical mass was confirmed at 19 gestational weeks, and amniocentesis was performed at 33 weeks. At 35 weeks, MRI showed the large mass that could disturb the airway patency after birth, and elective cesarean section was scheduled at 37 weeks. In the anesthetic management, anesthesia was maintained with isoflurane in oxygen, and ritodorine and nitroglycerin were used for obtaining uterine relaxation and keeping uteroplacental circulation. Fetal head was exposed from the uterine incision site and tracheal intubation was successfully performed. After confirming the neonatal oxygenation under manual ventilation, the baby was delivered. After delivery, the mass was diagnosed as cystic hygroma and he was maintained under mechanical ventilation in NICU. Five months later subtotal excision of the cervical cystic hygroma and tracheostomy were performed.