Duncan D. Atherton

Use of the novel contact heat evoked potential stimulator (CHEPS) for the assessment of small fibre neuropathy: correlations with skin flare responses and intra-epidermal nerve fibre counts

BackgroundThe Contact Heat Evoked Potential Stimulator (CHEPS) rapidly stimulates cutaneous small nerve fibres, and resulting evoked potentials can be recorded from the scalp. We have studied patients with symptoms of sensory neuropathy and controls using CHEPS, and validated the findings using other objective measures of small nerve fibres i.e. the histamine-induced skin flare response and intra-epidermal fibres (IEF), and also quantitative sensory testing (QST), a subjective measure.MethodsIn patients with symptoms of sensory neuropathy (n = 41) and healthy controls (n = 9) we performed clinical examination, QST (monofilament, vibration and thermal perception thresholds), nerve conduction studies, histamine-induced skin flares and CHEPS. Skin punch biopsies were immunostained using standard ABC immunoperoxidase for the nerve marker PGP 9.5 or the heat and capsaicin receptor TRPV1. Immunoreactive IEF were counted per length of tissue section and epidermal thickness recorded.ResultsAmplitudes of Aδ evoked potentials (μV) following face, arm or leg stimulation were reduced in patients (e.g. for the leg: mean ± SEM – controls 11.7 ± 1.95, patients 3.63 ± 0.85, p = 0.0032). Patients showed reduced leg skin flare responses, which correlated with Aδ amplitudes (rs = 0.40, p = 0.010). In patient leg skin biopsies, PGP 9.5- and TRPV1-immunoreactive IEF were reduced and correlated with Aδ amplitudes (PGP 9.5, rs = 0.51, p = 0.0006; TRPV1, rs = 0.48, p = 0.0012).ConclusionCHEPS appears a sensitive measure, with abnormalities observed in some symptomatic patients who did not have significant IEF loss and/or QST abnormalities. Some of the latter patients may have early small fibre dysfunction or ion channelopathy. CHEPS provides a clinically practical, non-invasive and objective measure, and can be a useful additional tool for the assessment of sensory small fibre neuropathy. Although further evaluation is required, the technique shows potential clinical utility to differentiate neuropathy from other chronic pain states, and provide a biomarker for analgesic development.

Contact heat evoked potentials using simultaneous EEG and fMRI and their correlation with evoked pain

BackgroundThe Contact Heat Evoked Potential Stimulator (CHEPS) utilises rapidly delivered heat pulses with adjustable peak temperatures to stimulate the differential warm/heat thresholds of receptors expressed by Aδ and C fibres. The resulting evoked potentials can be recorded and measured, providing a useful clinical tool for the study of thermal and nociceptive pathways. Concurrent recording of contact heat evoked potentials using electroencephalogram (EEG) and functional magnetic resonance imaging (fMRI) has not previously been reported with CHEPS. Developing simultaneous EEG and fMRI with CHEPS is highly desirable, as it provides an opportunity to exploit the high temporal resolution of EEG and the high spatial resolution of fMRI to study the reaction of the human brain to thermal and nociceptive stimuli.MethodsIn this study we have recorded evoked potentials stimulated by 51°C contact heat pulses from CHEPS using EEG, under normal conditions (baseline), and during continuous and simultaneous acquisition of fMRI images in ten healthy volunteers, during two sessions. The pain evoked by CHEPS was recorded on a Visual Analogue Scale (VAS).ResultsAnalysis of EEG data revealed that the latencies and amplitudes of evoked potentials recorded during continuous fMRI did not differ significantly from baseline recordings. fMRI results were consistent with previous thermal pain studies, and showed Blood Oxygen Level Dependent (BOLD) changes in the insula, post-central gyrus, supplementary motor area (SMA), middle cingulate cortex and pre-central gyrus. There was a significant positive correlation between the evoked potential amplitude (EEG) and the psychophysical perception of pain on the VAS.ConclusionThe results of this study demonstrate the feasibility of recording contact heat evoked potentials with EEG during continuous and simultaneous fMRI. The combined use of the two methods can lead to identification of distinct patterns of brain activity indicative of pain and pro-nociceptive sensitisation in healthy subjects and chronic pain patients. Further studies are required for the technique to progress as a useful tool in clinical trials of novel analgesics.

Relocation of Painful End Neuromas and Scarred Nerves from the Zone II Territory of the Hand

This paper reports the results of treatment by proximal relocation of 46 painful end-neuromas or scarred nerves in 33 patients from the pre-defined Zone II of the hand. The relocated nerves included four palmar cutaneous branches of the median nerve, 17 dorsal branches of the ulnar nerves and 25 digital nerves. If no pain at the original site and no pain or only mild pain at the relocation site are considered an adequate treatment of these difficult problems, these relocation procedures achieve complete control of spontaneous baseline pain, complete control of spontaneous spikes of pain, 93% control of direct pressure pain, complete control of movement pain (excluding the extremes of movement of the wrist into extension, supination and, less frequently, pronation) and 96% control of hypersensitivity of the overlying skin.

Relocation of Painful Neuromas in Zone III of the Hand and Forearm

Painful nerves are a difficult and complex clinical problem. We describe the result of treatment by proximal relocation of 51 painful end neuromas and scarred nerves of the forearm in 33 patients. The relocated nerves included 29 superficial radial nerves, 16 lateral antebrachial cutaneous nerves, two medial cutaneous nerves and four posterior cutaneous nerves. These relocations achieved no, or only mild, pain in 100% of nerves at the original site and 94% of nerves at the relocation site. It also achieved no, or only mild, hypersensitivity in 96% of nerves at the original site and 98% of nerves at the relocation site. The technical difficulties encountered in this region, in particular on the radial aspect of the wrist, are discussed.

Age-dependent development of chronic neuropathic pain, allodynia and sensory recovery after upper limb nerve injury in children.

Forty-nine children with distal upper limb nerve injury were studied at a mean follow-up of 2 years 3 months. Patients who were aged 5 years or younger at the time of nerve injury (15/49) had no chronic neuropathic pain symptoms or allodynia. Patients with allodynia on quantitative sensory testing but no spontaneous pain (8/49) were all older than 5 years and those reporting spontaneous chronic neuropathic pain (5/49) were all older than 12 years at the time of injury. Previous studies of adults with similar nerve injuries report chronic hyperaesthesia in up to 40% of cases. Semmes–Weinstein monofilament testing showed a positive correlation between age at injury and abnormal sensory threshold (r = 0.60, P<0.0001). These findings indicate that young children show better sensory recovery and are less likely to develop long-term chronic neuropathic pain syndromes than adults following nerve injury.

A randomised controlled trial of a double layer of Allevyn™ compared to Jellonet and proflavin as a tie-over dressing for small skin grafts

INTRODUCTION The tie-over dressing is used to encourage skin graft take by minimising dead space, reducing seroma and haematoma formation and by graft immobilisation. Various materials have been proposed, however we have compared one of the most popular, Jellonet with a bolster of proflavin-soaked cotton wool, to a newer dressing, Allevyn foam. PATIENTS AND METHODS Sixty patients were recruited and randomised into either group. Any patient requiring surgery involving a split or full thickness graft due to be carried out in the outpatient department on any site was invited to participate. Outcome measures included percentage take, pain on dressing removal (visual analogue scale) and infection. Ethical approval was obtained from the North and Mid Essex Local Research Ethics Committee. RESULTS There was no statistical difference in graft take between the two groups at day 5 (P=0.963). The Allevyn dressing was statistically more comfortable (P=0.0182). DISCUSSION We propose that Allevyn foam provides an effective and comfortable method for securing small split and full thickness skin grafts. While offering equal levels of graft take, improved levels of comfort may lend itself to use in sensitive areas such as the nose, ear and around the eye.

Relocation of neuromas of the lateral antebrachial cutaneous nerve of the forearm into the brachialis muscle.

Painful neuromas following injury to the radial side of the wrist can be treated by relocation away from the zone of injury and implantation into muscle. Relocation to the brachialis muscle is useful for isolated neuromas of the lateral antebrachial cutaneous nerve and involves a shorter dissection than relocation to the brachioradialis. It is also useful in patients undergoing multiple procedures to avoid disturbing previous relocations to the brachioradialis. This paper describes the successful relocation of painful neuromas of the lateral antebrachial cutaneous nerve to the brachialis muscle in seven patients.

Practical management of the burnt patient with epidermolysis bullosa

Epidermolysis bullosa (EB) is a group of inherited bullous disorders characterised by blister formation in response to mechanical trauma. Care of burns patients with this disease can be difficult, in particular with respect to healing of the skin graft donor sites. A number of techniques, such as laying of the sheared epidermis as a graft, can help speed up healing time. There are three major categories of EB; the commonest is EB simplex which is characterised by intraepidermal skin separation. Other subtypes include junctional EB (characterised by skin separation in the lamina lucida), and dystrophic EB (sublamina densa separation); which is the form our patient suffered from. The integrity of the skin and resistance against external shearing forces is provided by the dermal–epidermal junction (DEJZ), a highly specialized basement membrane zone which attaches the epidermis to the dermis. In addition to the basement membrane molecules, this zone contains the anchoring complexes which strengthen the adhesion of epithelial cells to the extracellular matrix of the dermis. Fibrils extend from the lamina densa of the epidermal basement membrane into the dermal connective tissue. Mutations in the gene coding for collagen VII causes a defect in these fibrils which in turn causes the disruption in the DEJZ seen in dystrophic EB [1]. A further form, hemidesmosomal bullosa is also recognised which is characterised by blistering at the hemidesmosomal level in the superior aspect of the basement membrane. It addition to the skin,

Salvage of the lower limb after a full thickness burn with loss of the knee extensor mechanism: a case report.

We report on a 79-year-old woman who underwent salvage of the knee and lower leg using a Whichita Fusion Nail for knee arthrodesis, combined with a medial gastrocnemius muscle flap for a 3% contact burn that resulted in loss of the extensor mechanism. This provided an alternative to above-knee amputation when extensor mechanism reconstruction was not feasible.

Gastric acid burns from binge drinking

Figure 1 Superficial partial thickness and mid dermal burn to breasts and upper abdomen secondary to vomiting as a consequence of excess alcohol intake. A nineteen-year-old female presented to the Chelsea and Westminster Hospital Burns unit with a partial thickness burn to the anterior chest. Two days previously she had consumed a large amount of alcohol at a party and had been found semi-conscious, presumed secondary alcohol intoxication, having vomited onto the front of her T-shirt. It was estimated that she had been in this state for 3e4 h. The patient’s cloths were changed but she did not shower until 12 h later, thereby potentially increasing the contact time between skin and the stomach contents. On examination there was a 2% superficial partial thickness and mid dermal burn to the breasts and upper abdomen (Figure 1). Litmus testing of the burn wound was neutral. Thorough cleansing and debridement of the blistered skin was performed. Due to an associated flare, the patient was dressed in Bactroban (GSK, UK) and Mepetil (M} olnlycke Health Care, UK) and an oral course of Augmentin (co-amoxiclav) was started. The flare had resolved on review at 24 h and by 72 h most of the periphery of the burn was already beginning to reepithelialise. The wound continued to be dressed in Mepetil until healed. The pH of stomach acid is on average around two, but can be lower. As well as the skin, other tissues are at risk from the stomach contents; for example the teeth in bulimia and gastro oesophageal reflux disease, the lung in aspiration injury and the lining of the stomach itself. Partial thickness burns secondary to contact with gastric contents have been reported previously in patients with disconnected percutaneous endoscopic gastrostomy (PEG) feeding apparatus. However we believe this to be the first time in the literature that such an injury has been described secondary to vomiting, in this case triggered by excess alcohol consumption. As with any chemical burn, the severity of the injury is related in particular to the pH of the chemical and the duration of contact with the agent. Interestingly the patient burnt after contact with their leaked PEG feed was also thought to have the same contact time of approximately 3e4 h.