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  • Reduced C-afferent fibre density affects perceived pleasantness and empathy for touch.

    13 June 2018

    We examined patients with a heritable disorder associated with a mutation affecting the nerve growth factor beta gene. Their condition has been classified as hereditary sensory and autonomic neuropathy type V. Carriers of the mutation show a reduction in density of thin and unmyelinated nerve fibres, including C afferents. A distinct type of unmyelinated, low-threshold mechanoreceptive C fibre, the C-tactile afferent, is present in hairy but not glabrous skin of humans and other mammals. They have been implicated in the coding of pleasant, hedonic touch of the kind that occurs in affiliative social interactions. We addressed the relationship between C fibre function and pleasant touch perception in 10 individuals from a unique population of mutation carriers in Sweden. We also investigated the effect of reduced C-fibre density on patients' evaluation of observed interpersonal touch (empathy). Results showed that patients perceived gentle, slow arm stroking, optimal for eliciting C-tactile afferent responses (1-10  cm/s), as less pleasant than did matched controls and also differed in their rating patterns across stimulation velocities. Further, patients' blood-oxygen-level-dependent responses in posterior insular cortex--a target for C afferents--were not modulated by stimulation optimal for activating C-tactile afferents. Hence, perception of the hedonic aspect of dynamic touch likely depends on C-tactile afferent density. Closely similar patterns between individuals' ratings of felt and seen touch suggest that appraisal of others' touch is anchored in one's own perceptual experience, whether typical or atypical.

  • Somatotopic organization of gentle touch processing in the posterior insular cortex.

    18 June 2018

    A network of thin (C and A delta) afferents relays various signals related to the physiological condition of the body, including sensations of gentle touch, pain, and temperature changes. Such afferents project to the insular cortex, where a somatotopic organization of responses to noxious and cooling stimuli was recently observed. To explore the possibility of a corresponding body-map topography in relation to gentle touch mediated through C tactile (CT) fibers, we applied soft brush stimuli to the right forearm and thigh of a patient (GL) lacking A beta afferents, and six healthy subjects during functional magnetic resonance imaging (fMRI). For improved fMRI analysis, we used a highly sensitive multivariate voxel clustering approach. A somatotopic organization of the left (contralateral) posterior insular cortex was consistently demonstrated in all subjects, including GL, with forearm projecting anterior to thigh stimulation. Also, despite denying any sense of touch in daily life, GL correctly localized 97% of the stimuli to the forearm or thigh in a forced-choice paradigm. The consistency in activation patterns across GL and the healthy subjects suggests that the identified organization reflects the central projection of CT fibers. Moreover, substantial similarities of the presently observed insular activation with that described for noxious and cooling stimuli solidify the hypothesized sensory-affective role of the CT system in the maintenance of physical well-being as part of a thin-afferent homeostatic network.

  • Pleasantness of touch in human glabrous and hairy skin: order effects on affective ratings.

    30 April 2018

    The tactile sense comprises pathways for both discriminative and affective touch. Low threshold unmyelinated mechanoafferents (C tactile, CT) in the human hairy skin have recently been linked to pleasant touch sensation. Here, we investigated how perception of the hedonic aspect of tactile stimulation differs between the hairy skin of the arm, and the glabrous skin of the palm, which is not innervated by CT afferents. Three groups of naïve, healthy subjects (total n=28) rated pleasantness on a visual analogue scale (VAS) when we stroked with a soft brush with speeds from 0.1 to 30cm/s on the palm or forearm. We used two different experimental approaches: in experiments 1 and 2, stimuli were delivered successively on the palm and arm (or arm and palm) in temporally separate sequential blocks. In experiment 3, stimuli were delivered alternately on arm and palm. We found that the order of stimulus presentation, palm/arm or arm/palm, has an effect on pleasantness ratings of gentle brush stroking with varying velocity. Notably, the perception of pleasantness for palm stimulation was affected by previous stimulation of the arm, but not vice versa. Thus, assessment of valence of touch may be influenced by affective reactions elicited by activation of the CT afferent pathway.

  • Acute foramen magnum syndrome from acquired Chiari I malformation relieved by ventriculoperitoneal shunt revision.

    12 December 2017

    An adult case of shunt malfunction presenting with acute quadriparesis as a manifestation of foramen magnum syndrome with acquired Chiari type I malformation is described in this study. The corticospinal function was restored after shunt revision. MRI showing considerable ascent of cerebellar tonsils after surgery is shown. Theories regarding the formation of acquired Chiari I malformations, alongside the possible synergistic roles of intracranial pathologies and cerebrospinal fluid drainage in the development of this entity are discussed.

  • Disseminated intravascular coagulation after isolated mild head injury.

    26 April 2018

    A rare case is described of acute disseminated intravascular coagulation (DIC) following isolated mild head injury with acute subdural haematoma, coagulopathy onset preceding craniotomy. Surgical treatment of the cause followed by swift diagnosis and treatment soon after surgery enabled a good outcome. Post-operative recollection of subdural and extadural blood was treated by further surgery. DIC following isolated mild head injury without axonal damage is rare, but fatal if missed. Thrombocytopaenia in head injured patients should be investigated expediently. Post-operative interim imaging (if not standard practice) should also be considered to exclude haemorrhagic recollection requiring further surgery.

  • The changing face of paediatric hydrocephalus: a decade's experience.

    8 December 2017

    All 253 children receiving neurosurgical intervention for hydrocephalus (HCP) at a single British Neurosurgical Unit over a decade were investigated by retrospective case note review. Referral rates and mean age at presentation remained stable throughout, as did proportions of children presenting due to myelomeningocoele or meningitis. Comparing the first and second halves of the decade, the predominant aetiologies (intraventricular haemorrhage [IVH] at <1 year and brain tumour at 1-16 years) reduced from comprising half (70/129) of all cases to just over one-third (43/124). Other significant changes included a 45% reduction in neonatal IVH and a 179% increase in rare miscellaneous disorders. Outcome after 4 years of follow-up for all patients showed 44.4% without deficit, 11.9% with non-cognitive neurological deficits only, 11.5% with cognitive impairment only, 13.5% with both cognitive and neurological impairments, and 15.5% mortality.

  • Identification of neurocircuitry controlling cardiovascular function in humans using functional neurosurgery: implications for exercise control.

    14 May 2018

    The neurocircuitry underlying human cardiovascular control during exercise has yet to be fully elucidated. Functional imaging studies and animal studies have so far identified potential circuits that might be involved in the cardiovascular response to exercise, so-called 'central command'. This brief review highlights neurocircuits that may have functional significance as judged from direct recordings of electrical activity during exercise in patients with implanted deep brain stimulating electrodes. Of particular interest is the periaqueductal grey area (PAG), where electrodes are implanted in humans to treat chronic pain. This area is known to be important in the exercise pressor reflex in animals. Our studies have shown that changes occur in this region during anticipation of exercise, indicating a possible role in the central command of cardiovascular variables before and during exercise. This leads us to suggest that the PAG may be an 'integrating area' between the feedback signals from muscle and the feedforward signals from higher centres. The role of the PAG in cardiovascular control in humans, with reference to electrical stimulation experiments, is also described.

  • Cerebral venous sinus thrombosis complicating traumatic head injury.

    8 June 2018

    Cerebral venous sinus thrombosis (CVST) is a rare complication of traumatic head injury. Here we present a patient with traumatic extradural haematoma successfully evacuated with good clinical recovery. However, the patient then deteriorated and died. The cause, at post mortem, was a propagating CVST, sustained at the time of head injury. CVST, although rare, is therefore an important cause of deterioration in traumatic head injury. This patient with CVST is unique in that CVST was not considered as a diagnosis in the face of more obvious pathology and was responsible for late deterioration. We discuss the potential difficulties in both the detection and management of such a complication, particularly in association with extradural haematoma.

  • Straight sinus stenosis as a proposed cause of perimesencephalic non-aneurysmal haemorrhage.

    31 May 2018

    Perimesencephalic nonaneurysmal haemorrhage (PMNH), a term first coined in 1985, is a diagnosis of exclusion. It is considered a benign form of subarachnoid haemorrhage with a good prognosis and a low risk of rebleeding. Its precise aetiology has not yet been determined. Haemorrhage of venous origin has been proposed as a cause, and has been demonstrated to be associated with venous abnormalities of the basal vein of Rosenthal. We present a patient with PMNH in whom an 80% stenosis at the union of the vein of Galen with the straight sinus is demonstrated. We thus propose hypertensive venous rupture secondary to venous sinus stenosis as an alternative cause for PMNH.

  • A torque-based method demonstrates increased rigidity in Parkinson's disease during low-frequency stimulation

    26 April 2018

    Low-frequency oscillations in the basal ganglia are prominent in patients with Parkinson's disease off medication. Correlative and more recent interventional studies potentially implicate these rhythms in the pathophysiology of Parkinson's disease. However, effect sizes have generally been small and limited to bradykinesia. In this study, we investigate whether these effects extend to rigidity and are maintained in the on-medication state. We studied 24 sides in 12 patients on levodopa during bilateral stimulation of the STN at 5, 10, 20, 50, 130 Hz and in the off-stimulation state. Passive rigidity at the wrist was assessed clinically and with a torque-based mechanical device. Low-frequency stimulation at < 20 Hz increased rigidity by 24 % overall (p - 0.035), whereas high-frequency stimulation (130 Hz) reduced rigidity by 18 % (p - 0.033). The effects of low-frequency stimulation (5, 10 and 20 Hz) were well correlated with each other for both flexion and extension (r - 0.725 ± SEM 0.016 and 0.568 ± 0.009, respectively). Clinical assessments were unable to show an effect of low-frequency stimulation but did show a significant effect at 130 Hz (p - 0.002). This study provides evidence consistent with a mechanistic link between oscillatory activity at low frequency and Parkinsonian rigid ity and, in addition, validates a new method for rigidity quantification at the wrist. © The Author(s) 2012. This article is published with open access at Springerlink.com.