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Background: We aimed at evaluating the differential involvement of large myelinated Aβ‐, small myelinated Aδ‐, and unmyelinated C‐fibers in patients with diabetic polyneuropathy and how they contribute to neuropathic pain. Methods: We collected clinical and diagnostic test variables in 133 consecutive patients with diabetic polyneuropathy. All patients underwent Aβ‐fiber mediated nerve conduction study, Aδ‐fiber mediated laser‐evoked potentials and skin biopsy mainly assessing unmyelinated C‐fibers. Results: Pure large‐fiber and small‐fiber polyneuropathy were relatively uncommon; conversely mixed‐fiber polyneuropathy was the most common type of diabetic polyneuropathy (74%). The frequency of neuropathic pain was similar in the three different polyneuropathies. Ongoing burning pain and dynamic mechanical allodynia were similarly associated with specific small‐fiber related variables. Conclusions: Diabetic polyneuropathy mainly manifests as a mixed‐fiber polyneuropathy, simultaneously involving Aβ‐, Aδ‐, and C‐fibers. In most patients, neuropathic pain is distinctly associated with small‐fiber damage. The evidence that the frequency of neuropathic pain does not differ across pure large‐, pure small‐, and mixed‐fiber polyneuropathy, raises the possibility that in patients with pure large‐fiber polyneuropathy nociceptive nerve terminal involvement might be undetected by standard diagnostic techniques. [ABSTRACT FROM AUTHOR]

Objectives: We aimed to investigate the conduction velocity of the cold spinal pathway in healthy humans. Methods: Using a cold stimulator consisting of micro‐Peltier elements that was able to produce steep cooling ramps up to −300°C/s, we recorded cold‐evoked potentials after stimulation of the dorsal midline at C5, T2, T6 and T10 vertebral levels and calculated the conduction velocity of the cold spinal pathway. In all participants, we used laser stimulation to deliver painful heat (Aδ‐fibres–mediated) and warm (C‐fibres–mediated) stimuli to the same sites in order to compare the conduction velocity of the cold spinal pathway with that of the nociceptive and warm spinal pathways. Results: Cold stimulation evoked large‐amplitude vertex potentials from all stimulation sites. The mean conduction velocity of the cold spinal pathway was 12.0 m/s, which did not differ from that of the nociceptive spinal pathway (10.5 m/s). The mean conduction velocity of the warm spinal pathway was 2.0 m/s. Discussion: This study provides previously unreported findings regarding cold spinal pathway conduction velocity in humans that may be useful in the assessment of spinal cord lesions as well as in intraoperative monitoring during spinal surgery. Significance: This neurophysiological study provides previously unreported findings on cold spinal pathway conduction velocity in healthy humans. Cold‐evoked potentials may represent an alternative to laser‐evoked potential recording, useful to assess spinothalamic tract in patients with spinal cord lesions and monitor patients during spinal surgery. [ABSTRACT FROM AUTHOR]

Background: In this neurophysiological study, we aimed at verifying the nociceptive selectivity of the new, micropatterned electrode (150IDE), recently designed to generate an electric field limited to the intraepidermal free nerve endings.Methods: Using the new 150IDE, we recorded evoked potentials after stimulation of the face and hand dorsum in 22 healthy participants and in patients with exemplary conditions selectively affecting the nociceptive system. We also measured the peripheral conduction velocity at the upper arm and verified the nociceptive selectivity of 150IDE assessing the effect of a selective block of nociceptive nerve fibres of radial nerve with local anaesthetic infiltration. In healthy participants and in patients, we have also compared the 150IDE-evoked potentials with laser-evoked potentials.Results: In healthy participants, the 150IDE-evoked pinprick sensation and reproducible scalp potentials, with latency similar to laser-evoked potentials. The mean peripheral conduction velocity, estimated at the upper arm, was 12 m/s. The selective nociceptive fibre block of the radial nerve abolished the scalp potentials elicited by the 150IDE stimulation. In patients, the 150IDE-evoked potentials reliably detected the selective damage of the nociceptive system.Conclusions: Our neurophysiological study shows that this new 150IDE provides selective information on nociceptive system.Significance: 150IDE is a promising new tool for investigating nociceptive system in patients with neuropathic pain. [ABSTRACT FROM AUTHOR]

Background Patients presenting with bilateral trigeminal hypoesthesia may go on to have trigeminal isolated sensory neuropathy, a benign, purely trigeminal neuropathy, or facial-onset sensory motor neuronopathy (FOSMN), a malignant life-threatening condition. No diagnostic criteria can yet differentiate the two conditions at their onset. Nor is it clear whether the two diseases are distinct entities or share common pathophysiological mechanisms. Methods Seeking pathophysiological and diagnostic information to distinguish these two conditions at their onset, in this neurophysiological and morphometric study we neurophysiologically assessed function in myelinated and unmyelinated fibres and histologically examined supraorbital nerve biopsy specimens with optic and electron microscopy in 13 consecutive patients with recent onset trigeminal hypoesthesia and pain. Results The disease course distinctly differed in the 13 patients. During a mean 10 year follow-up whereas in eight patients the disease remained relatively stable, in the other five it progressed to possibly life-threatening motor disturbances and extra-trigeminal spread. From two to six years elapsed between the first sensory symptoms and the onset of motor disorders. In patients with trigeminal isolated sensory neuropathy (TISN) and in those with FOSMN neurophysiological and histological examination documented a neuronopathy manifesting with trigeminal nerve damage selectively affecting myelinated fibres, but sparing the Ia-fibre-mediated proprioceptive reflex. Conclusions Although no clinical diagnostic criteria can distinguish the two conditions at onset, neurophysiological and nerve-biopsy findings specify that in both disorders trigeminal nerve damage manifests as a dissociated neuronopathy affecting myelinated and sparing unmyelinated fibres, thus suggesting similar pathophysiological mechanisms. [ABSTRACT FROM AUTHOR]

Background: The 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. Findings: We 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. Conclusions: Unlike 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. [ABSTRACT FROM AUTHOR]

Neuropathic pain, i.e. pain arising as a direct consequence of a lesion or disease of the somatosensory system, affects about the 7 % of the general population. In this short review, we describe the most reliable laboratory tools for assessing neuropathic pain, such as quantitative sensory testing, laser-evoked potential recordings and skin biopsy, procedures that selectively assess nociceptive pathways. [ABSTRACT FROM AUTHOR]