Grazia Devigili

Intraepidermal nerve fiber density at the distal leg: a worldwide normative reference study

The diagnostic reliability of skin biopsy in small fiber neuropathy depends on the availability of normative reference values. We performed a multicenter study to assess the normative values of intraepidermal nerve fiber (IENF) density at distal leg stratified by age deciles. Eight skin biopsy laboratories from Europe, USA, and Asia submitted eligible data. Inclusion criteria of raw data were healthy subjects 18 years or older; known age and gender; 3‐mm skin biopsy performed 10‐cm above the lateral malleolus; bright‐field immunohistochemistry protocol, and quantification of linear IENF density in three 50‐µm sections according to published guidelines. Data on height and weight were recorded, and body mass index (BMI) was calculated in subjects with both available data. Normative IENF density reference values were calculated through quantile regression analysis; influence of height, weight, or BMI was determined by regression analyses. IENF densities from 550 participants (285 women, 265 men) were pooled. We found a significant age‐dependent decrease of IENF density in both genders (women p < 0.001; men p = 0.002). Height, weight, or BMI did not influence the calculated 5th percentile IENF normative densities in both genders. Our study provides IENF density normative reference values at the distal leg to be used in clinical practice.

Intraepidermal nerve fiber density and its application in sarcoidosis

Background: Intraepidermal nerve fiber density (IENFD) is considered a good diagnostic tool for small fiber neuropathy (SFN). Objectives: To assess stratified normative values for IENFD and determine the reliability and validity of IENFD in sarcoidosis. Methods: IENFD was assessed in 188 healthy volunteers and 72 patients with sarcoidosis (n = 58 with SFN symptoms, n = 14 without SFN symptoms). Healthy controls were stratified (for age and sex), resulting in 6 age groups (20–29, 30–39, … up to ≥70 years) containing at least 15 men and 15 women. A skin biopsy was taken in each participant 10 cm above the lateral malleolus and analyzed in accordance with the international guidelines using bright-field microscopy. Interobserver/intraobserver reliability of IENFD was examined. In the patients, a symptoms inventory questionnaire (SIQ; assessing SFN symptoms) and the Vickrey Peripheral Neuropathy Quality-of-Life Instrument-97 (PNQoL-97) were assessed to examine the discriminative ability of normative IENFD values. Results: There was a significant age-dependent decrease of IENFD values in healthy controls, with lower densities in men compared with women. Good interobserver/intraobserver reliability scores were obtained (κ values ≥0.90). A total of 21 patients with sarcoidosis had a reduced IENFD score (<5th percentile; 19 [32.8%] in patients with SFN symptoms, 2 [14.3%] in patients without SFN symptoms). The validity of the normative IENFD values was demonstrated by distinguishing between the SIQ scores and various PNQoL-97 values for the different patient groups. Conclusion: This study provides clinically applicable distal intraepidermal nerve fiber density normative values, showing age- and sex-related differences.

Skin biopsy as a diagnostic tool in peripheral neuropathy

Skin biopsy is a safe, minimally invasive, painless and cheap tool for providing diagnostic information on small nerve fibers, which are invisible to routine neurophysiological tests. Biopsy can be performed in hairy skin to investigate unmyelinated and thinly myelinated fibers and in glabrous skin to examine large myelinated fibers. Morphometric analysis of skin nerves is readily accomplished through the use of immunohistochemical techniques, and has proved to be reliable, reproducible and unaffected by the severity of neuropathy. One further advantage of skin biopsy over conventional nerve biopsy is that it allows somatic nerve fibers to be distinguished from autonomic nerve fibers. Morphological changes, axonal degeneration and abnormal regeneration occur in cutaneous nerves very early in the course of peripheral neuropathies, making skin biopsy a promising tool for investigating the progression of neuropathy and the effect of neuroprotective treatments in clinical practice and trials. This article reviews the techniques that are used to investigate the innervation of human skin, the possible uses of skin biopsy in diagnosing and monitoring peripheral neuropathies, and correlations between skin biopsy findings and those of other diagnostic methods.

Skin biopsy for the diagnosis of peripheral neuropathy.

Skin biopsy has become an accepted tool for investigating small nerve fibres, which are invisible to conventional neurophysiological tests even though they are affected early on in peripheral neuropathies of varying aetiology. Morphometric analysis of epidermal and dermal nerves has proved to be reliable, reproducible and unaffected by the severity of neuropathy, making skin biopsy useful for diagnosing small fibre neuropathy (SFN) in clinical practice. The possibility of obtaining skin biopsy specimens from different sites of the body, to repeat them within the area of the same sensory nerve, to distinguish between somatic and autonomic nerves and to investigate the expression of nerve‐related proteins has widened the potential applications of this technique to clinical research. Skin biopsy performed using a minimally invasive disposable punch is a safe and painless procedure. Using specific antibodies with bright‐field immunohistochemistry or immunofluorescence technique, it is possible to investigate unmyelinated fibres innervating the epidermis of hairy and glabrous skin, large myelinated fibres supplying specialized corpuscles in glabrous skin, and autonomic fibres innervating sweat glands, blood vessels and arrector pilorum muscles. This review discusses the features of skin innervation in hairy and glabrous skin, the functional properties of skin nerve fibres and their changes in peripheral neuropathies.

Paroxysmal itch caused by gain-of-function Nav1.7 mutation

Summary A novel clinical syndrome is described, characterized by paroxysmal itch and ensuing burning pain triggered by warmth and spicy food associated with a gain‐of‐function Nav1.7 variant. ABSTRACT Itch is a common experience. It can occur in the course of systemic diseases and can be a manifestation of allergies or a consequence of diseases affecting the somatosensory pathway. We describe a kindred characterized by paroxysmal itch caused by a variant in SCN9A gene encoding for the Nav1.7 sodium channel. Patients underwent clinical and somatosensory profile assessment by quantitative sensory testing, nerve conduction study, autonomic cardiovascular reflex, and sympathetic skin response examination, skin biopsy with quantification of intraepidermal nerve fiber density, and SCN9A mutational analysis. The index patient, her mother, and a sister presented with a stereotypical clinical picture characterized by paroxysmal itch attacks involving the shoulders, upper back, and upper limbs, followed by transient burning pain, and triggered by environmental warmth, hot drinks, and spicy food. Somatosensory profile assessment demonstrated a remarkably identical pattern of increased cold and pain thresholds and paradoxical heat sensation. Autonomic tests were negative, whereas skin biopsy revealed decreased intraepidermal nerve fiber density in 2 of the 3 patients. All affected members harbored the 2215A>G I739V substitution in exon 13 of SCN9A gene. Pregabalin treatment reduced itch intensity and attack frequency in all patients. The co‐segregation of the I739V variant in the affected members of the family provides evidence, for the first time, that paroxysmal itch can be related to a mutation in sodium channel gene.

Short‐ and intermediate‐term efficacy of buprenorphine TDS in chronic painful neuropathies

Abstract  Buprenorphine is a potent opioid available as a transdermal delivery system (TDS) formulation. This open‐label study investigated its safety, tolerability, and efficacy in 30 patients with chronic painful neuropathy. Subjects with visual analogue scale (VAS) score ≥5 under stable analgesic treatment were entered. The starting dosage of 35 μg/h was increased up to 70.0 μg/h in case of unsatisfactory pain control as assessed by fortnightly visits. The primary endpoint was the number of patients achieving at least 30% pain relief at day 42 visit. Treatment was safe over the study period. Nine patients dropped out for side effects, mostly nausea and daily sleepiness. Buprenorphine TDS was well tolerated in 21 patients. Thirteen patients achieved >30% of pain relief at day 42 visit. Five patients needed to increase the dosage to 52.5 μg/h. Eight patients did not meet the primary outcome, but none allowed increasing the dosage to 70 μg/h, and four patients withdrew consent to continue the study before day 42 visit because of a ‘fear to become addicted,’ although 40% had obtained VAS reduction. In our study, which needs to be confirmed by a controlled trial, buprenorphine TDS induced clinically meaningful pain relief in about 40% of patients with chronic painful neuropathy, suggesting its use as a third‐line treatment.

Levodopa/carbidopa intestinal gel (LCIG) therapy for advanced Parkinson's Disease: An early toxic effect for small nerve fibers?

Introduction: Peripheral neuropathy related to levodopa/carbidopa intestinal gel (LCIG) therapy for advanced Parkinson disease (PD) is under investigation and is debated in the literature. The purpose of the study was to detect whether small nerve fibers are damaged during LCIG infusion. Methods: Five advanced PD patients were enrolled prior to starting LCIG infusion. Six PD patients on oral levodopa (LD) treatment and 6 PD patients naïve to LD were also enrolled. Clinical examination, the Quantitative Sensory Testing battery testing, nerve conduction studies, and intraepidermal nerve fiber density examinations were collected at baseline and at 3, 6, and 12 months after LCIG infusion was started in the study cohort. Results: After 3, 6, and 12 months, severe skin denervation and increased thermal thresholds were observed in the LCIG group. Conclusions: Significant damage to small nerve fibers was detected in PD patients soon after LCIG infusion had started, suggesting careful monitoring of small fiber impairment during LCIG is needed. Muscle Nerve, 2016 Muscle Nerve 54: 970–972, 2016

Prevalence of Neuropathic Pain in Patients with Traumatic Brachial Plexus Injury: A Multicenter Prospective Hospital-Based Study

Objective Prevalence and clinical characteristics of neuropathic pain due to traumatic brachial plexus injury. Design Observational epidemiological study. Setting Hospital-based multicenter study. Subjects One hundred seven prospectively enrolled patients with brachial plexus injury. Methods All the patients underwent clinical examination and neurophysiological testing for a definitive diagnosis of the brachial plexus lesion. The DN4 questionnaire was used to identify neuropathic pain, and the Neuropathic Pain Symptom Inventory (NPSI) to evaluate the different symptoms of neuropathic pain. The SF36 questionnaire and the Beck Depression Inventory (BDI) were used to assess quality of life and mood disturbances in patients with neuropathic pain. Results Of the 107 enrolled patients, 74 had pain (69%); neuropathic pain, as assessed by means of the DN4, was identified in 60 (56%) of these patients. According to the NPSI, the most frequent and severe pain type was the spontaneous burning pain. Clinical and neurophysiological findings showed that pain is unrelated to age but is associated with the severity of peripheral nerve damage. The SF36 questionnaire and BDI showed that neuropathic pain impairs quality of life and causes depression. Conclusions Our study provides information on the prevalence, characteristics, and variables associated with neuropathic pain due to traumatic brachial plexus injuries that might provide a basis for improving the clinical management of this condition.

Investigation on acute effects of enzyme replacement therapy and influence of clinical severity on physiological variables related to exercise tolerance in patients with late onset Pompe disease

Exercise intolerance is one of the clinical hallmarks of late-onset Pompe disease (LOPD). We studied the acute effects of ERT on the physiological variables associated with exercise tolerance in patients chronically ERT treated. Moreover, we assessed the influence of clinical severity on the investigated variables. The day before (B) and the day after (A) ERT injection, 11 LOPD patients performed on a cycle-ergometer an exercise tolerance test to voluntary exhaustion; VO2, HR, RPE, and GAA activity were determined in B and A. The disease severity was characterized by Walton scale, 6MWT, and pulmonary function tests. No significant differences in the variables related to exercise tolerance were found in A vs B, despite a significant increase in GAA activity in peripheral lymphocytes. No differences in VO2 peak were observed between patients with only skeletal muscle impairment and patients with both skeletal and respiratory muscle impairment. Distance walked at 6MWT was significantly higher than VO2 peak expressed as percentage of normal values. In conclusion, in LOPD patients the exercise tolerance test is not acutely affected by ERT administration; the peripheral muscle component seems more prominent in determining the VO2 peak decrease than the respiratory component; VO2 peak might be more sensitive than 6MWT in estimating exercise tolerance in LOPD.

45. Skin nerve α-synuclein deposits as possible new biomarker for Dementia with Lewy bodies

The object of this study is to investigate whether: (1) phosphorylated α -synuclein (p-syn) deposits in peripheral nerves might represent a useful biomarker in dementia Lewy Body (DLB) helping to differentiate DLB from other forms of dementia; (2) small fiber neuropathy (SFN) may be part of DLB pathological picture contributing to autonomic dysfunctions. 20 well-characterized DLB patients (11 of them complaining autonomic symptoms particularly orthostatic hypotension) were studied together with 23 patients with dementia of different pathogenesis (Dementia without synuclein- DWS) including 13 patients fulfilling diagnostic criteria for Alzheimer’s disease, 6 with Frontotemporal Dementia and 4 with vascular dementia. Twenty-five age-matched healthy subjects served as controls. Subjects underwent: nerve conduction velocities from the leg to evaluate large nerve fibers; skin biopsy from proximal (i.e. cervical) and distal (i.e. thigh and distal leg) sites to study small nerve fibers and deposits of phosphorylated α -synuclein, considered the pathological form of α -synuclein. P-syn was not found in any skin sample in DWS patients and controls but it was found in all DLB patients with a proximal-distal gradient with all patients positive in the cervical site. Patients complaining of autonomic symptoms showed higher widespread positivity of analyzed skin samples than patients without autonomic symptoms. Furthermore DLB patients showed a length-dependent SFN particularly important in patients complaining autonomic symptoms. Conclusions: (1) p-syn in peripheral nerves is a sensitive biomarker for DLB diagnosis helping to differentiate DLB from other forms of dementia; (2) SFN was part of DLB pathological picture contributing to induce autonomic symptoms.