Functional Characterization of At-Level Hypersensitivity in Patients With Spinal Cord Injury.

At-level and above-level hypersensitivity was assessed in patients with chronic complete thoracic spinal cord injury (SCI). Patients were classified using somatosensory mapping (brush, cold, pinprick) and assigned into 2 groups (ie, patients with at-level hypersensitivity [SCIHs, n = 8] and without at-level hypersensitivity [SCINHs, n = 7]). Gender and age-matched healthy subjects served as controls. Quantitative sensory testing (QST), electrically- and histamine-induced pain and itch, laser Doppler imaging, and laser-evoked potentials (LEP) were recorded at-level and above-level in SCI-patients. Six of 8 SCIHs, but 0 of 7 SCINHs patients suffered from neuropathic below-level pain. Clinical sensory mapping revealed spreading of hypersensitivity to more cranial areas (above-level) in 3 SCIHs. Cold pain threshold measures confirmed clinical hypersensitivity at-level in SCIHs. At-level and above-level hypersensitivity to electrical stimulation did not differ significantly between SCIHs and SCINHs. Mechanical allodynia, cold, and pin-prick hypersensitivity did not relate to impaired sensory function (QST), axon reflex flare, or LEPs. Clinically assessed at-level hypersensitivity was linked to below-level neuropathic pain, suggesting neuronal hyperexcitability contributes to the development of neuropathic pain. However, electrically evoked pain was not significantly different between SCI patients. Thus, SCI-induced enhanced excitability of nociceptive processing does not necessarily lead to neuropathic pain. QST and LEP revealed no crucial role of deafferentation for hypersensitivity development after SCI. PERSPECTIVE: At-level hypersensitivity after complete thoracic SCI is associated with neuropathic below-level pain if evoked by clinical sensory stimuli. QST, LEP, and electrically-induced axon reflex flare sizes did not indicate somatosensory deafferentation in SCIHs.

Nondermatomal somatosensory deficits in chronic pain are associated with cerebral grey matter changes.

OBJECTIVES: Widespread sensory deficits occur in 20-40% of chronic pain patients on the side of pain, independent of pain aetiology, and are known as nondermatomal sensory deficits (NDSDs). NDSDs can occur in absence of central or peripheral nervous system lesions. We hypothesised that NDSDs were associated with cerebral grey matter changes in the sensory system and in pain processing regions, detectable with voxel-based morphometry. METHODS: Twenty-five patients with NDSDs, 23 patients without NDSDs ("pain-only"), and 29 healthy controls were studied with high resolution structural MRI of the brain. A comprehensive clinical and psychiatric evaluation based on Diagnostic and Statistical Manual was performed in all patients. RESULTS: Patients with NDSDs and "pain-only" did not differ concerning demographic data and psychiatric diagnoses, although anxiety scores (HADS-A) were higher in patients with NDSDs. In patients with NDSDs, grey matter increases were found in the right primary sensory cortex, thalamus, and bilaterally in lateral temporal regions and the hippocampus/fusiform gyrus. "Pain-only" patients showed a bilateral grey matter increase in the posterior insula and less pronounced changes in sensorimotor cortex. CONCLUSIONS: Dysfunctional sensory processing in patients with NDSDs is associated with complex changes in grey matter volume, involving the somatosensory system and temporal regions.

Bilateral Sensory Changes and High Burden of Disease in Patients With Chronic Pain and Unilateral Nondermatomal Somatosensory Deficits: A Quantitative Sensory Testing and Clinical Study.

OBJECTIVES: Widespread sensory deficits resembling hemihypoesthesia occur in 20% to 40% of chronic pain patients on the side of pain, independent of pain etiology, and have been termed nondermatomal sensory deficits (NDSDs). Sensory profiles have rarely been investigated in NDSDs. MATERIALS AND METHODS: Quantitative sensory testing according to the protocol of the German Research Network on Neuropathic Pain (DFNS) was performed in the face, hand, and foot of the painful body side and in contralateral regions in chronic pain patients. Twenty-five patients with NDSDs and 23 without NDSDs (termed the pain-only group) were included after exclusion of neuropathic pain. Comprehensive clinical and psychiatric evaluations were carried out. RESULTS: NDSD in chronic pain was associated with high burden of disease and more widespread pain. Only in the NDSD group were significantly higher thresholds for mechanical and painful stimuli found in at least 2 of 3 regions ipsilateral to pain. In addition, we found a bilateral loss of function for temperature and vibration detection, and a gain of function for pressure pain in certain regions in patients with NDSD. Sensory loss and gain of function for pressure pain correlated with pain intensity in several regions. DISCUSSION: This may indicate a distinct sensory profile in chronic non-neuropathic pain and NDSD, probably attributable to altered central pain processing and sensitization. The presence of NDSD in chronic non-neuropathic pain may be regarded as a marker for higher burden of pain disease.

Tetrahydrocannabinol (Delta 9-THC) Treatment in Chronic Central Neuropathic Pain and Fibromyalgia Patients: Results of a Multicenter Survey.

Central neuropathic pain is difficult to treat, but delta 9-Tetrahydrocannabinol (delta 9-THC) may be a promising therapeutic agent. We administered in 172 patients on average 7.5 mg delta 9-THC over 7 months. Of these, 48 patients prematurely withdrew due to side effects, insufficient analgesia, or expense of therapy. Thus, 124 patients were assessed retrospectively in a multicenter telephone survey. Reported changes in pain intensity, recorded on a numeric rating scale (NRS), Pain Disability Index (PDI), Medical Outcomes Short-Form (SF-12), Quality of Life Impairment by Pain (QLIP), Hospital Anxiety Depression Scale (HADS), and amount of concomitant pain medication were recorded. Psychometric parameters (PDI, SF-12, QLIP, HADS) and pain intensity improved significantly during delta 9-THC treatment. Opioid doses were reduced and patients perceived THC therapy as effective with tolerable side effects. About 25% of the patients, however, did not tolerate the treatment. Therapy success and tolerance can be assessed by a transient delta 9-THC titration and its maintained administration for several weeks. The present survey demonstrates its ameliorating potential for the treatment of chronic pain in central neuropathy and fibromyalgia. A supplemental delta 9-THC treatment as part of a broader pain management plan therefore may represent a promising coanalgesic therapeutic option.

Pulsed radiofrequency treatment of the lumbar medial branch for facet pain: a retrospective analysis.

BACKGROUND: The use of pulsed radiofrequency (PRF) for treatment of the medial branch is controversial. STUDY DESIGN: A retrospective study of the results of PRF treatment of the medial branch in 48 patients with chronic low back pain was carried out. Patients who did not respond were offered treatment with conventional radiofrequency heat lesions. PATIENT MATERIAL: Patients were included who had low back pain and >50% pain relief following a diagnostic medial branch block. The mean age was 53.1 +/- 13.5 years, the mean duration of pain was 11.4 +/- 10.9 years (range 2-50). Nineteen patients had undergone surgery. METHODS: Pain scores on a numeric rating scale of 1-10 were noted before and after the diagnostic nerve block, before the procedure, and at 1-month and 4-month follow-up. PRF was applied for 2 minutes at a setting of 2 x 20 ms/s and 45 V at a minimum of two levels using a 22G electrode with a 5 mm active tip. Heat lesions were made at 80 degrees C for 1 minute. OUTCOME DEFINITION: A successful outcome was defined as a >60% improvement on the numeric rating scale at 4-month follow-up. RESULTS: In 21/29 nonoperated patients and 5/19 operated patients, the outcome was successful. In the unsuccessful patients who were subsequently treated with heat lesions, the success rate was 1/6. CONCLUSION: The setup of our study does not permit a comparison with the results of continuous radiofrequency (CRF) for the same procedure, other than the detection of an obvious trend. When comparing our results with various studies on CRF of the medial branch such a trend could not be found. Based on these retrospective data, prospective and randomized trials, for example, radiofrequency vs PRF are justified.