Peter Hauer

Bio: Peter Hauer is an academic researcher from Johns Hopkins University. The author has contributed to research in topics: Nerve fiber & Peripheral neuropathy. The author has an hindex of 26, co-authored 38 publications receiving 4393 citations. Previous affiliations of Peter Hauer include Johns Hopkins University School of Medicine & University of Utah.

Epidermal Nerve Fiber Density Normative Reference Range and Diagnostic Efficiency

Abstract: Background The sensitivity of neuron-specific antibodies permit the identification of the small unmyelinated nerve fibers within the skin. Objectives To develop a reference range of epidermal nerve fiber density in humans, and to evaluate their diagnostic efficiency for sensory neuropathies. Methods Ninety-eight normal controls (age range, 13-82 years) were examined with both directed neurologic examinations and quantitative sensory testing. The diagnostic utility was examined in 20 patients with sensory neuropathies. Each subject had 2 punch biopsies performed at each site in the thigh and distal part of the leg (total of 392 biopsies). After formalin fixation, 50-µm-thick free-floating sections were stained with a polyclonal antibody to neuron-specific ubiquitin hydrolase, anti–protein gene product 9.5. We enumerated intraepidermal nerve fibers per millimeter to derive a "linear density." The linear density technique was validated against a stereological technique that used the fractionator to measure the total length of intraepidermal nerve fibers per 3-mm punch. Results The biopsy technique was well tolerated, with no notable complications. The linear density quantitation was rapid and had high intraobserver and interobserver reliability. We determined that the density of intraepidermal fibers in normal controls was 21.1±10.4 per millimeter (mean±SD) in the thigh (fifth percentile, 5.2 per millimeter), and was 13.8±6.7 per millimeter at the distal part of the leg (fifth percentile, 3.8 per millimeter). Significantly higher intraepidermal fiber densities were seen in the youngest group ( P =.004), and we observed no significant effect of race, sex, height, or weight. The density at the thigh was significantly correlated with that at the distal part of the leg ( P =.01) and was consistently higher by about 60%, a reflection of the normal proximal-distal gradient. The results obtained with stereology and the linear density correlated significantly ( P =.001), providing internal validation for the technique. Epidermal nerve fiber density was significantly reduced ( P =.001) in patients with sensory neuropathies. With a cutoff derived from the fifth percentile of the normative range for the distal part of the leg, the technique had a positive predictive value of 75%, a negative predictive value of 90%, and a diagnostic efficiency of 88%. Conclusions We have established a reference range for intraepidermal nerve fiber density in normal humans by means of a simple quantitation method based on enumeration of individual intraepidermal nerve fibers on vertical sections of punch skin biopsy specimens stained with the sensitive panaxonal marker anti–protein gene product 9.5. The utility of the density measurement was confirmed for sensory neuropathy with a diagnostic efficiency of 88%. Skin biopsies may be useful to assess the spatial distribution of involvement in peripheral nerve disease and the response to neurotrophic and other restorative therapies.

Cutaneous innervation in sensory neuropathies: Evaluation by skin biopsy

Abstract: Objective: To use punch skin biopsies to evaluate the loss of intra-epidermal nerve fibers in sensory neuropathies. Background: Previous assessments of epidermal nerve fibers have been constrained by relatively insensitive staining techniques and variability in quantification. Methods: Punch skin biopsies were performed on the heel and leg of HIV-seronegative controls, HIV-seropositive individuals without neuropathy, and patients with sensory neuropathies, including HIV-seronegative and HIV-positive individuals. After formalin fixation, 50-micro meter free-floating sections were stained with a monoclonal antibody to neuron-specific ubiquitin hydrolase, PGP9.5. The number of intraepidermal fibers/mm in at least three sections from each patient was counted by one observer blinded to site and clinical status. Results: Dermal and epidermal nerve fibers were readily identified and quantified. The immunostaining technique reliably demonstrated a dermal plexus of myelinated and unmyelinated fibers parallel to the surface of the skin. In the epidermis, unmyelinated fibers ascended vertically between the keratinocytes to reach the stratum corneum. The number of intra-epidermal fibers/mm in the distal leg (mean plus minus SEM) was 17.84 plus minus 3.03 in seven HIV-seronegative controls. Epidermal fiber number was significantly reduced (p equals 0.01) in five HIV-infected patients with sensory neuropathies associated with didanosine or zalcitabine therapy (1.07 plus minus 0.40) and in eight HIV-seronegative patients with sensory neuropathies (3.1 plus minus 3.1). Four of five neurologically normal HIV-seropositive subjects had reduced numbers of epidermal fibers, suggesting a subclinical neuropathy. Serial biopsies in one individual demonstrated the evolution of degenerating epidermal fibers after development of zalcitabine-induced sensory neuropathy. Conclusion: Skin biopsies stained with the sensitive panaxonal marker anti-PGP9.5 demonstrated significant reduction in intraepidermal fibers in sensory neuropathies. This simple and repeatable technique is a reliable method for quantitation of small cutaneous sensory fibers. In addition, skin biopsies may be useful in assessing the course and spatial distribution of involvement in peripheral nerve disease. NEUROLOGY 1995;45: 1848-1855

The time course of epidermal nerve fibre regeneration: studies in normal controls and in people with diabetes, with and without neuropathy.

Abstract: Summary We sought to develop and validate a standardized cutaneous nerve regeneration model and to define the rate of epidermal nerve fibre (ENF) regeneration first in healthy control subjects and then in neuropathic and neuropathy-free subjects with diabetes. Next, we assessed the effect of different factors on the rate of nerve fibre regeneration and investigated whether such an approach might offer insight into novel trial designs and outcome measures. All subjects had a standardized topical capsaicin dressing applied to the distal lateral thigh. ENF densities derived from skin biopsies were determined at baseline, after capsaicin treatment and at reinnervation time points. For each subject, the best fit line from post-denervation data was determined and the slope was used as the rate of regeneration. In healthy control subjects, regeneration was correlated with psychophysical sensory testing, electron microscopy studies and immunohistochemistry with alternative axonal membrane markers. Topical capsaicin application produced complete or nearly complete denervation of the epidermis in both control subjects and people with diabetes. The rate of regeneration was associated with the baseline ENF density (P < 0.001), but not age (P = 0.75), gender (P = 0.18), epidermal thickness (P = 0.4) or post-capsaicin treatment density (P = 0.7). ENF regeneration, as determined by recovery of ENF density, occurred at a rate of 0.177 6 0.075 fibres/mm/ day in healthy control subjects and was significantly reduced in subjects with diabetes (0.074 6 0.064, P < 0.001) after adjusting for changes in baseline ENF density. Among subjects with diabetes, the presence of neuropathy was associated with a further reduction in regenerative rate (0.10 6 0.07 versus 0.04 6 0.03, P = 0.03), though diabetes type (P = 0.7), duration of diabetes (P = 0.3) or baseline glycated haemoglobin (P = 0.6) were not significant. These results have several implications. First, topical capsaicin application can produce a uniform epidermal nerve fibre injury that is safe and well tolerated, and offers an efficient strategy to measure and study nerve regeneration in man. Secondly, using our techniques, reduced rates of nerve regeneration were found in people with diabetes without evidence of neuropathy and indicate that abnormalities in peripheral nerve function are present early in diabetes, before signs or symptoms develop. These results suggest that regenerative neuropathy trials could include non-neuropathic subjects and that trial duration can be dramatically shortened.

Small-fiber sensory neuropathies: Clinical course and neuropathology of idiopathic cases

Abstract: We describe the clinical features, natural history, and neuropathology of 32 patients presenting with “burning feet”, for whom no specific cause was identified. All had neuropathic pain in the feet and morphological abnormalities of cutaneous innervation in skin obtained using punch biopsy. Most (29) had an abnormal sensory examination. All had normal strength, proprioception, tendon reflexes, and nerve conductions. Two clinical patterns were apparent, based on natural history and spatial distribution of cutaneous denervation. Most (28) patients presented with neuropathic pain initially restricted to the feet and toes but extending more proximally to involve the legs and hands with time. Intraepidermal nerve fiber (IENF) density was most severely reduced distally, with more normal IENF densities in skin from proximal sites. In contrast, a minority (4) presented with the abrupt onset of generalized cutaneous burning pain and hyperesthesia. In these patients, IENF densities were reduced in skin from both proximal and distal sites. Absolute IENF densities in calf skin were reduced below the lower limit of normal (5th percentile) in 26 (81%). Of the 6 who underwent sural nerve biopsy, 4 had selective loss of small myelinated and/or unmyelinated axons and 2 had normal histology and fiber densities despite reduced IENF densities in skin biopsy specimens. Punch skin biopsy from proximal and distal sites is a useful means of assessing these distinctive patients and may provide further insight into pathophysiology.

Intraepidermal nerve fiber density in patients with painful sensory neuropathy

Abstract: Despite prominent symptoms of neuropathic pain, patients with small-fiber sensory neuropathies have few objective abnormalities on clinical examination and routine electrodiagnostic studies. We quantified intraepidermal nerve fiber (IENF) density in sections of skin obtained by punch skin biopsy, and found it to be significantly reduced in patients with painful sensory neuropathies compared with age-matched control subjects. In addition, IENF density correlated with clinical estimates of neuropathy severity, as judged by the extent of clinically identifiable sensory abnormalities. IENF density at the calf was lower than that obtained from skin at more proximal sites, indicating the length dependency of small-fiber loss in these neuropathies.

Recommendations for the Pharmacological Management of Neuropathic Pain: An Overview and Literature Update

Abstract: The Neuropathic Pain Special Interest Group of the International Association for the Study of Pain recently sponsored the development of evidence-based guidelines for the pharmacological treatment of neuropathic pain. Tricyclic antidepressants, dual reuptake inhibitors of serotonin and norepinephrine, calcium channel α2-δ ligands (ie, gabapentin and pregabalin), and topical lidocaine were recommended as first-line treatment options on the basis of the results of randomized clinical trials. Opioid analgesics and tramadol were recommended as second-line treatments that can be considered for first-line use in certain clinical circumstances. Results of several recent clinical trials have become available since the development of these guidelines. These studies have examined botulinum toxin, high-concentration capsaicin patch, lacosamide, selective serotonin reuptake inhibitors, and combination therapies in various neuropathic pain conditions. The increasing number of negative clinical trials of pharmacological treatments for neuropathic pain and ambiguities in the interpretation of these negative trials must also be considered in developing treatment guidelines. The objectives of the current article are to review the Neuropathic Pain Special Interest Group guidelines for the pharmacological management of neuropathic pain and to provide a brief overview of these recent studies.

Diabetic Somatic Neuropathies

Abstract: ropathic pain (7–10), and this and other putative mechanisms will be discussed The clinical features, diagnosis, and management of the focal and multifocal neuropathies will be described A major portion of this review will discuss the clinical features, assessment, and management of the patient with the most common form of DN, diabetic distal sensory polyneuropathy (DPN) The late sequelae of DPN and their prevention will also be described Finally, practical guidelines for the screening of DPN in clinical practice will be provided For further details on this topic, please refer to recent reviews (11– 18)