BackgroundThe guidelines on trigeminal neuralgia management that have been agreed and jointly published by the American Academy of Neurology and the European Federation of Neurological Societies recommend carbamazepine (CBZ) and oxcarbazepine (OXC) as the first-choice medical treatments in patients with trigeminal neuralgia (TN). The aim of this retrospective study was to analyze the natural history of classical trigeminal neuralgia in a large cohort of patients, focusing on drug responsiveness, side effects related to CBZ and OXC, and changes in pain characteristics during the course of disease.FindingsWe selected the last 100 consecutive patients with typical TN who began treatment with CBZ and the last 100 with OXC. All had MRI scans and a complete neurophysiological study of trigeminal reflexes. Among them, 22 were excluded on the basis of neuroradiological or neurophysiological investigations, to avoid the inclusion of patients with possible secondary TN. The initial number of responders was 98% with CBZ with a median dose of 600 mg (range 200–1200), and of 94% with OXC, with a median dose of 1200 mg (range 600–1800). In a mean period of 8.6 months, 27% of responders to CBZ incurred in undesired effects to a level that caused interruption of treatment or a dosage reduction to an unsatisfactory level. In a mean period of 13 months, the same occurred to 18% of responders to OXC. Among patients who had a good initial response, only 3 patients with CBZ and 2 with OXC developed late resistance. During the course of disease, paroxysms worsened in intensity in 3% of patients, and paroxysms duration increased in 2%. We did not observe the onset of a clinically manifest sensory deficit at any time in any patient.ConclusionsUnlike common notion, in our large patient sample the worsening of pain with time and the development of late resistance only occurred in a very small minority of patients. CBZ and OXC were confirmed to be efficacious in a large majority of patients, but the side effects caused withdrawal from treatment in an important percentage of patients. These results suggest the opportunity to develop a better tolerated drug.

Despite concerted efforts from pharmacologic research into neuropathic pain, many patients fail to achieve sufficient pain relief with medication alone. For this reason, increasing interest centres on neurostimulation techniques. We assessed whether transcutaneous spinal direct current stimulation (tsDCS) modulates conduction in ascending nociceptive spinal pathways. We measured changes induced by anodal and cathodal tsDCS over the thoracic spinal cord on face- and foot-laser evoked potentials (LEPs) and foot-cold pressor test responses in 20 healthy subjects. Whereas anodal tsDCS reduced the amplitude of the N1 and N2 components of foot-LEPs (P<0.05) neither anodal nor cathodal tsDCS changed LEPs evoked by face stimulation. Pain tolerance to the cold pressor test was significantly higher after anodal than after cathodal tsDCS (P<0.05). Conversely, no difference was found in the pain threshold or pain ratings to the cold pressor test between the two polarity conditions. Our data suggest that anodal tsDCS over the thoracic spinal cord might impair conduction in the ascending nociceptive spinal pathways, thus modulating LEPs and increasing pain tolerance in healthy subjects.

While the lack of somatosensory nervous system damage is incompatible with neuropathic pain as the mechanism underlying pain in JHS/EDS-HT, the lowered cold and heat pain thresholds and increased wind-up ratio imply that pain in JHS/EDS-HT might arise through central sensitization. Hence, this connective tissue disorder and fibromyalgia share similar pain mechanisms. WHAT DOES THIS STUDY ADD?: In patients with JHS/EDS-HT, the persistent nociceptive input due to joint abnormalities probably triggers central sensitization in the dorsal horn neurons and causes widespread pain.

In this clinical and neurophysiological study, we examined the clinical characteristics and underlying mechanisms of neuropathic pain related to multiple sclerosis. A total of 302 consecutive patients with multiple sclerosis were screened for neuropathic pain by clinical examination and the DN4 tool. In patients selected for having ongoing extremity pain or Lhermitte's phenomenon, we recorded somatosensory evoked potentials, mediated by Aβ non-nociceptive fibres, and laser evoked potentials, mediated by Aδ nociceptive fibres. Of the 302 patients, 92 had pain (30%), and 42 (14%) neuropathic pain. Patients with neuropathic pain had more severe multiple sclerosis, as assessed by the expanded disability severity score, than those without pain. Whereas, in patients with ongoing neuropathic pain, laser evoked potentials were more frequently abnormal than somatosensory evoked potentials, we found the opposite in patients with Lhermitte's phenomenon. Our data underline the clinical importance of pain in multiple sclerosis and indicate that a more severe disease is associated with a higher risk of developing neuropathic pain. The prevalence of pain that we found, which was lower than that reported in previous studies, may reflect the lesser disease severity in our patients. Neurophysiological data show that whereas ongoing extremity pain is associated with spinothalamic pathway damage, Lhermitte's phenomenon is related to damage of non-nociceptive pathways. These findings may be useful in designing a new therapeutic approach to neuropathic pain related to multiple sclerosis.

We aimed at seeking more precise diagnostic information on the sensory nervous system involvement described in patients with amyotrophic lateral sclerosis (ALS). We investigated large myelinated nerve fibres with nerve conduction study and small-nerve fibres with Quantitative Sensory Testing (QST) (assessing thermal-pain perceptive thresholds) and skin biopsy (assessing intraepidermal nerve fibre density) in 24 consecutive patients with ALS, 11 with bulbar-onset and 13 with spinal-onset. In 23 of the 24 patients, regardless of ALS onset, nerve conduction study invariably showed large myelinated fibre sparing. In patients with bulbar-onset ALS, QST found normal thermal-pain perceptive thresholds and skin biopsy disclosed normal intraepidermal nerve fibre density. Conversely, in patients with spinal-onset, thermal-pain thresholds were abnormal and distal intraepidermal nerve fibre density was reduced. Sensory nervous system involvement in ALS differs according to disease onset. Patients with spinal-onset but not those with bulbar-onset ALS have concomitant distal small-fibre neuropathy. Neurologists should therefore seek this ALS-related non-motor feature to improve its diagnosis and treatment.