Effects of Tonic Spinal Cord Stimulation on External Mechanical and Thermal Stimuli Perception Using Quantitative Sensory Testing: A Multicenter Stimulation ON-OFF Study on Chronic Pain Patients.

OBJECTIVES: Tonic spinal cord stimulation (SCS) is currently used to treat neuropathic pain. With this type of stimulation, an implantable pulse generator generates electrical paresthesias in the affected area through 1 or more epidural leads. The goal of this study was to evaluate the impact of tonic SCS on the sensory perception of chronic pain patients using quantitative sensory testing (QST). MATERIALS AND METHODS: Forty-eight patients (mean age: 57 y) with chronic leg pain due to failed back surgery syndrome or complex regional pain syndrome treated with SCS were recruited from 3 research centers. Test procedures included 2 sessions (stimulation On or Off), with measures of detection thresholds for heat, touch, vibration, and of pain thresholds for cold, heat, pressure, the assessment of dynamic mechanical allodynia, and temporal pain summation. Three different areas were examined: the most painful area of the most painful limb covered with SCS-induced paresthesias (target area), the contralateral limb, and the ipsilateral upper limb. Wilcoxon signed-rank tests were used to compare the mean difference between On and Off for each QST parameter at each area tested. P-values <0.05 were considered significant. RESULTS: Regarding the mean difference between On and Off, patients felt less touch sensation at the ipsilateral area (-0.4±0.9 g, P=0.0125) and were less sensitive at the contralateral area for temporal pain summation (-4.9±18.1 on Visual Analog Scale 0 to 100, P=0.0056) with SCS. DISCUSSION: It is not clear that the slight changes observed were clinically significant and induced any changes in patients' daily life. Globally, our results suggest that SCS does not have a significant effect on sensory perception.

Antagonismo NMDA en el tratamiento de la cefalea en racimos / NMDA antagonism in the treatment of cluster headache

El tratamiento estándar de la cefalea en racimos consiste en un tratamiento abortivo con oxígeno, triptanes, alcaloides ergóticos y/o anestésico local nasal tópico durante los episodios agudos y un tratamiento preventivo, como infiltraciones con esteroides, antagonistas de los canales del calcio y litio. Aunque la fisiopatología exacta de la cefalea en racimos no se conoce bien, se han demostrado niveles reducidos de metabolitos de quinurenina, los cuales gozan de propiedades anti-NMDA (N-metil-D-aspartato). La ketamina y el magnesio, que tienen una potente actividad antagonista NMDA, se han usado en múltiples síndromes de dolor refractario. Describimos un caso de cefalea en racimos que no respondió al tratamiento estándar y se trató de forma efectiva con infusión intravenosa de magnesio y ketamina

Standard treatment for cluster headache consists of abortive treatment with oxygen, triptans, ergot alkaloids and/or topical nasal local anesthetic during acute episodes and preventive treatment such as steroid injections, calcium channel blockers and lithium. Although the exact pathophysiology of cluster headache is not well understood, reduced serum levels of kynurenine metabolites with anti-NMDA (N-methyl-D-aspartate) properties have been demonstrated. Ketamine and magnesium, which both have potent anti-NMDA receptor activity, have been used in multiple refractory pain syndromes. We describe a case of cluster headache that was non-responsive to standard therapy and treated effectively with intravenous infusion of magnesium and ketamine