Initial findings using high-resolution magnetic resonance imaging for visualisation of the sural nerve and surrounding anatomy in healthy volunteers at 7 Tesla.

Background And Aims: Histopathological diagnosis is the gold standard in many acquired inflammatory, infiltrative and amyloid based peripheral nerve diseases and a sensory nerve biopsy of sural or superficial peroneal nerve is favoured where a biopsy is deemed necessary. The ability to determine nerve pathology by high-resolution imaging techniques resolving anatomy and imaging characteristics might improve diagnosis and obviate the need for biopsy in some. The sural nerve is anatomically variable and occasionally adjacent vessels can be sent for analysis in error.

Intravenous immunoglobulin and intravenous methylprednisolone as optimal induction treatment in chronic inflammatory demyelinating polyradiculoneuropathy: protocol of an international, randomised, double-blind, placebo-controlled trial (OPTIC).

Background: International guidelines recommend either intravenous immunoglobulin (IVIg) or corticosteroids as first-line treatment for chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). IVIg treatment usually leads to rapid improvement and is generally safe, but does not seem to lead to long-term remissions. Corticosteroids act more slowly and are associated with more side effects, but may induce long-term remissions.

Characterisation and mechanisms of bradykinin-evoked pain in man using iontophoresis.

Bradykinin (BK) is an inflammatory mediator that can evoke oedema and vasodilatation, and is a potent algogen signalling via the B1 and B2 G-protein coupled receptors. In naïve skin, BK is effective via constitutively expressed B2 receptors (B2R), while B1 receptors (B1R) are purported to be upregulated by inflammation. The aim of this investigation was to optimise BK delivery to investigate the algesic effects of BK and how these are modulated by inflammation.

Multiple somatotopic representations of heat and mechanical pain in the operculo-insular cortex: a high-resolution fMRI study.

Whereas studies of somatotopic representation of touch have been useful to distinguish multiple somatosensory areas within primary (SI) and secondary (SII) somatosensory cortex regions, no such analysis exists for the representation of pain across nociceptive modalities. Here we investigated somatotopy in the operculo-insular cortex with noxious heat and pinprick stimuli in 11 healthy subjects using high-resolution (2 × 2 × 4 mm) 3T functional magnetic resonance imaging (fMRI). Heat stimuli (delivered using a laser) and pinprick stimuli (delivered using a punctate probe) were directed to the dorsum of the right hand and foot in a balanced design.

Identifying brain activity specifically related to the maintenance and perceptual consequence of central sensitization in humans.

Central sensitization (CS) refers to an increase in the excitability of spinal dorsal horn neurons that results from, and far outlasts the initiating nociceptive input. Here, functional magnetic resonance imaging was used to examine whether supraspinal activity might contribute to the maintenance of CS in humans. A crossover parametric design was used to distinguish and control for brain activity that is related to the consequence of increased pain experienced during CS.

Similar nociceptive afferents mediate psychophysical and electrophysiological responses to heat stimulation of glabrous and hairy skin in humans.

The ability to perceive and withdraw rapidly from noxious environmental stimuli is crucial for survival. When heat stimuli are applied to primate hairy skin, first pain sensation is mediated by type-II A-fibre nociceptors (II-AMHs). In contrast, the reported absence of first pain and II-AMH microneurographical responses when heat stimuli are applied to the hand palm has led to the notion that II-AMHs are lacking in this primate glabrous skin.

Pharmacological modulation of pain-related brain activity during normal and central sensitization states in humans.

Abnormal processing of somatosensory inputs in the central nervous system (central sensitization) is the mechanism accounting for the enhanced pain sensitivity in the skin surrounding tissue injury (secondary hyperalgesia). Secondary hyperalgesia shares clinical characteristics with neurogenic hyperalgesia in patients with neuropathic pain. Abnormal brain responses to somatosensory stimuli have been found in patients with hyperalgesia as well as in normal subjects during experimental central sensitization.

Simultaneous recording of laser-evoked brain potentials and continuous, high-field functional magnetic resonance imaging in humans.

Simultaneous recording of event-related electroencephalographic (EEG) and functional magnetic resonance imaging (fMRI) responses has the potential to provide information on how the human brain reacts to an external stimulus with unique spatial and temporal resolution. However, in most studies combining the two techniques, the acquisition of functional MR images has been interleaved with the recording of evoked potentials. In this study we investigated the feasibility of recording pain-related evoked potentials during continuous and simultaneous collection of blood oxygen level-dependent (BOLD) functional MR images at 3 T.

Somatotopic organisation of the human insula to painful heat studied with high resolution functional imaging.

Pain perception is a multidimensional phenomenon, derived from sensory, affective, cognitive-evaluative and homeostatic information. Neuroimaging studies of pain perception have investigated the role of primary somatosensory cortex (SI); however, they have typically failed to demonstrate the expected somatotopy. An alternative network for the sensory component of pain has been proposed, involving a temperature and pain-specific nucleus of the thalamus (VMpo) and its projections to dorsal posterior insula (dpIns).

A role for the brainstem in central sensitisation in humans. Evidence from functional magnetic resonance imaging.

Animal studies have established a role for the brainstem reticular formation, in particular the rostral ventromedial medulla (RVM), in the development and maintenance of central sensitisation and its clinical manifestation, secondary hyperalgesia. Similar evidence in humans is lacking, as neuroimaging studies have mainly focused on cortical changes. To fully characterise the supraspinal contributions to central sensitisation in humans, we used whole-brain functional magnetic resonance imaging at 3T, to record brain responses to punctate mechanical stimulation in an area of secondary hyperalgesia.

Operculoinsular cortex encodes pain intensity at the earliest stages of cortical processing as indicated by amplitude of laser-evoked potentials in humans.

Converging evidence from different functional imaging studies indicates that the intensity of activation of different nociceptive areas (including the operculoinsular cortex, the primary somatosensory cortex, and the anterior cingulate gyrus) correlates with perceived pain intensity in the human brain. Brief radiant laser pulses excite selectively Adelta and C nociceptors in the superficial skin layers, provide a purely nociceptive input, and evoke brain potentials (laser-evoked potentials, LEPs) that are commonly used to assess nociceptive pathways in physiological and clinical studies. Adelta-related LEPs are constituted of different components.

Adelta nociceptor response to laser stimuli: selective effect of stimulus duration on skin temperature, brain potentials and pain perception.

Objective: To disclose a possible effect of duration of pulsed laser heat stimuli on Adelta nociceptor responses, skin temperature profiles, brain evoked potentials and pain perception.

Methods: We used a laser stimulator which works in the millisecond range and allows us to change the duration of the pulse while keeping the total energy of the stimulus constant. In 10 healthy volunteers, we measured the intensity of perceived pain with a 0-10 scale and the latency and amplitude of the early N1 and late N2 components of the scalp potentials evoked by laser pulses of equal energy and three different stimulus durations (2, 10, and 20 ms).