Peripheral nerve stimulation in intractable neuropathic pain.

Peripheral nerve stimulation (PNS) is a neurostimulation analgesic technique. PNS is utilized to treat peripheral neuropathic pain. It is highly sophisticated and a specialized technique used where other forms of treatment have failed. This paper describes the PNS procedure, its therapeutic principles, indications, and the comprehensive care for patients after the PNS implant. First, we summarize our experience using this type of invasive treatment. In the second part, a case of intractable neuropathic pain following repeated surgery to the ulnar nerve is reported. Prior to PNS, the patient underwent multiple types of antineuralgic treatment with no significant result. Only after the PNS application, was a significant analgesic effect achieved.

Functional magnetic resonance imaging of cerebral activation during spinal cord stimulation in failed back surgery syndrome patients.

Spinal cord stimulation (SCS) consisting of electrical stimulation of the dorsal spinal cord using epidural electrodes has been shown to relieve chronic neuropathic pain. To analyze the cerebral activation patterns related to SCS, and to evaluate the effects of SCS on the processing of acute experimental pain, we performed functional magnetic resonance imaging (fMRI) on eight patients suffering from failed back surgery syndrome who were also being treated with SCS for severe pain in their legs and lower back. Three types of stimulation were used, each lasting 36s: (i) SCS, (ii) heat pain (HP) applied to the leg affected by neuropathic pain, and (iii) simultaneous HP and SCS. During SCS, we found increased activation of the medial primary sensorimotor cortex somatotopically corresponding to the foot and/or perineal region, contralateral posterior insula, and the ipsilateral secondary somatosensory cortex (S2). Decreased activation was seen in the bilateral primary motor cortices and the ipsilateral primary somatosensory cortex corresponding to the shoulder, elbow and hand. Compared to separately presented HP and SCS, simultaneous HP and SCS showed statistically significant activation of the bilateral inferior temporal cortex and the ipsilateral cerebellar cortex. The activation of the primary motor cortex, insula and S2 during SCS may directly interfere with the processing of neuropathic pain. When SCS is associated with heat pain, the paralimbic association cortex and cerebellum show activation exceeding the sum of activations resulting from separate SCS and heat pain stimulation. The explanation of this could possibly rest with the continuous comparisons of simultaneous pain and somatosensory sensations occurring in a single dermatome.

Effects of spinal cord stimulation on the cortical somatosensory evoked potentials in failed back surgery syndrome patients.

OBJECTIVE: To evaluate the functional activation of the somatosensory cortical regions in neuropathic pain patients during therapeutic spinal cord stimulation (SCS). METHODS: In nine failed back surgery syndrome patients, the left tibial and the left sural nerves were stimulated in two sessions with intensities at motor and pain thresholds, respectively. The cortical somatosensory evoked potentials were analyzed using source dipole analysis based on 111 EEG signals. RESULTS: The short-latency components of the source located in the right primary somatosensory cortex (SI: 43, 54 and 65ms) after tibial nerve stimulation, the mid-latency SI component (87ms) after sural nerve stimulation, and the mid-latency components in the right (approximately 161ms) and left (approximately 168ms) secondary somatosensory cortices (SII) were smaller in the presence of SCS than in absence of SCS. The long-latency source component arising from the mid-cingulate cortex (approximately 313ms) was smaller for tibial and larger for sural nerve stimuli during SCS periods compared to periods without SCS. CONCLUSIONS: SCS attenuates the somatosensory processing in the SI and SII. In the mid-cingulate cortex, the effect of SCS depends on the type of stimulation and nerve fibers involved. SIGNIFICANCE: Results suggest that the effects of SCS on cortical somatosensory processing may contribute to a reduction of allodynia during SCS.