Paola Penza

The diagnostic criteria for small fibre neuropathy: from symptoms to neuropathology

Small fibre neuropathy (SFN), a condition dominated by neuropathic pain, is frequently encountered in clinical practise either as prevalent manifestation of more diffuse neuropathy or distinct nosologic entity. Aetiology of SFN includes pre-diabetes status and immune-mediated diseases, though it remains frequently unknown. Due to their physiologic characteristics, small nerve fibres cannot be investigated by routine electrophysiological tests, making the diagnosis particularly difficult. Quantitative sensory testing (QST) to assess the psychophysical thresholds for cold and warm sensations and skin biopsy with quantification of somatic intraepidermal nerve fibres (IENF) have been used to determine the damage to small nerve fibres. Nevertheless, the diagnostic criteria for SFN have not been defined yet and a ‘gold standard’ for clinical practise and research is not available. We screened 486 patients referred to our institutions and collected 124 patients with sensory neuropathy. Among them, we identified 67 patients with pure SFN using a new diagnostic ‘gold standard’, based on the presence of at least two abnormal results at clinical, QST and skin biopsy examination. The diagnosis of SFN was achieved by abnormal clinical and skin biopsy findings in 43.3% of patients, abnormal skin biopsy and QST findings in 37.3% of patients, abnormal clinical and QST findings in 11.9% of patients, whereas 7.5% patients had abnormal results at all the examinations. Skin biopsy showed a diagnostic efficiency of 88.4%, clinical examination of 54.6% and QST of 46.9%. Receiver operating characteristic curve analysis confirmed the significantly higher performance of skin biopsy comparing with QST. However, we found a significant inverse correlation between IENF density and both cold and warm thresholds at the leg. Clinical examination revealed pinprick and thermal hypoesthesia in about 50% patients, and signs of peripheral vascular autonomic dysfunction in about 70% of patients. Spontaneous pain dominated the clinical picture in most SFN patients. Neuropathic pain intensity was more severe in patients with SFN than in patients with large or mixed fibre neuropathy, but there was no significant correlation with IENF density. The aetiology of SFN was initially unknown in 41.8% of patients and at 2-year follow-up a potential cause could be determined in 25% of them. Over the same period, 13% of SFN patients showed the involvement of large nerve fibres, whereas in 45.6% of them the clinical picture did not change. Spontaneous remission of neuropathic pain occurred in 10.9% of SFN patients, while it worsened in 30.4% of them.

Trigeminal small-fiber sensory neuropathy causes burning mouth syndrome

&NA; Burning mouth syndrome is a common disorder that frequently affects women in the 5th–7th decade. It is characterized by persisting painful symptoms mainly involving the anterior two‐thirds of the tongue. For several years it has been attributed to psychological causes. We investigated the innervation of the epithelium of the tongue to assess whether damage of peripheral nerve fibers underlies the pathogenesis of the disease. We examined 12 patients with clinically definite burning mouth syndrome for at least 6 months. We obtained superficial biopsies of the lateral aspect of the anterior two‐thirds of the tongue from all patients and nine healthy controls. Immunohistochemical and confocal microscope co‐localization studies were performed with cytoplasmatic, cytoskeletric, Schwann cell, and myelin markers for pathological changes. The density of epithelial nerve fibers was quantified. Patients showed a significantly lower density of epithelial nerve fibers than controls, with a trend toward correlation with the duration of symptoms. Epithelial and sub‐papillary nerve fibers showed diffuse morphological changes reflecting axonal degeneration. Our study demonstrates that burning mouth syndrome is caused by a trigeminal small‐fiber sensory neuropathy and that superficial biopsy of the tongue can be helpful in assessing the diagnosis. These findings shed light into the pathogenesis of this common disorder and could contribute to evaluate targeted therapies in patients.

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.

Intraepidermal nerve fiber density in rat foot pad: neuropathologic–neurophysiologic correlation

Abstract  Quantification of cutaneous innervation in rat footpad is a useful tool to investigate sensory small‐diameter nerve fibers, which are affected early in peripheral neuropathies. The aim of this work was to provide normative reference data on the density of intraepidermal nerve fibers (IENFs) and Langerhans cells in the hindpaw footpad of Sprague–Dawley and Wistar rats. We also evaluated the sensibility of IENF density by comparing neuropathologic findings with neurophysiologic examination and the presence of peripheral neuropathy in two well‐characterized animal models of neuropathy. IENF density was quantified in 22 Sprague–Dawley rats and 13 Wistar rats and compared with 19 age‐matched Sprague–Dawley rats with streptozotocin‐induced diabetic neuropathy and 30 age‐matched Wistar rats with cisplatin‐ or paclitaxel‐induced neuropathy. Antidromic tail sensory nerve conduction velocity (SNCV) was assessed in all animals. IENF and Langerhans cell densities were constant in healthy Sprague–Dawley rats at any age, and they were similar to those observed in healthy Wistar rats. In neuropathic rats, both SNCV and IENF density were significantly reduced with respect to controls. Quantification of IENF density was significantly correlated with changes in conduction velocity. Diabetic neuropathy rats alone showed a significantly higher density of Langerhans cells compared with controls. Our study demonstrated that IENF density quantification correlates with SNCV changes and suggests that this might represent a useful outcome measurement in experimental neuropathies.

Protective Effect of Erythropoietin and Its Carbamylated Derivative in Experimental Cisplatin Peripheral Neurotoxicity

Purpose: Antineoplastic drugs, such as cisplatin (CDDP), are severely neurotoxic, causing disabling peripheral neuropathies with clinical signs known as chemotherapy-induced peripheral neurotoxicity. Cotreatment with neuroprotective agents and CDDP has been proposed for preventing or reversing the neuropathy. Erythropoietin given systemically has a wide range of neuroprotective actions in animal models of central and peripheral nervous system damage. However, the erythropoietic action is a potential cause of side effects if erythropoietin is used for neuroprotection. We have successfully identified derivatives of erythropoietin, including carbamylated erythropoietin, which do not raise the hematocrit but retain the neuroprotective action exerted by erythropoietin. Experimental Design: We have developed previously an experimental chemotherapy-induced peripheral neurotoxicity that closely resembles CDDP neurotoxicity in humans. The present study compared the effects of erythropoietin and carbamylated erythropoietin (50 μg/kg/d thrice weekly) on CDDP (2 mg/kg/d i.p. twice weekly for 4 weeks) neurotoxicity in vivo. Results: CDDP given to Wistar rats significantly lowered their growth rate (P < 0.05), with slower sensory nerve conduction velocity (P < 0.001) and reduced intraepidermal nerve fibers density (P < 0.001 versus controls). Coadministration of CDDP and erythropoietin or carbamylated erythropoietin partially but significantly prevented the sensory nerve conduction velocity reduction. Both molecules preserved intraepidermal nerve fiber density, thus confirming their neuroprotective effect at the pathologic level. The protective effects were not associated with any difference in platinum concentration in dorsal root ganglia, sciatic nerve, or kidney specimens. Conclusions: These results widen the spectrum of possible use of erythropoietin and carbamylated erythropoietin as neuroprotectant drugs, strongly supporting their effectiveness.

Effects of Manidipine and Delapril in Hypertensive Patients With Type 2 Diabetes Mellitus The Delapril and Manidipine for Nephroprotection in Diabetes (DEMAND) Randomized Clinical Trial

To assess whether angiotensin-converting enzyme inhibitors and third-generation dihydropyridine calcium channel blockers ameliorate diabetic complications, we compared glomerular filtration rate (GFR; primary outcome), cardiovascular events, retinopathy, and neuropathy in 380 hypertensive type 2 diabetics with albuminuria <200 mg/min included in a multicenter, double-blind, placebo-controlled trial (DEMAND [Delapril and Manidipine for Nephroprotection in Diabetes]) and randomized to 3-year treatment with manidipine/delapril combination (10/30 mg/d; n=126), delapril (30 mg/d; n=127), or placebo (n=127). GFR was centrally measured by iohexol plasma clearance. Median monthly GFR decline (interquartile range [IQR]) was 0.32 mL/min per 1.73 m2 (IQR: 0.16–0.50 mL/min per 1.73 m2) on combined therapy, 0.36 mL/min per 1.73 m2 (IQR: 0.18–0.53 mL/min per 1.73 m2) on delapril, and 0.30 mL/min per 1.73 m2 (IQR: 0.12–0.50 mL/min per 1.73 m2) on placebo (P=0.87 and P=0.53 versus combined therapy or delapril, respectively). Similar findings were observed when baseline GFR values were not considered for slope analyses. Albuminuria was stable in the 3 treatment groups. The hazard ratio (95% CI) for major cardiovascular events between combined therapy and placebo was 0.17 (0.04–0.78; P=0.023). Among 192 subjects without retinopathy at inclusion, the hazard ratio for developing retinopathy between combined therapy and placebo was 0.27 (0.07–0.99; P=0.048). Among 200 subjects with centralized neurological evaluation, the odds ratios for peripheral neuropathy at 3 years between combined therapy or delapril and placebo were 0.45 (0.24–0.87; P=0.017) and 0.52 (0.27–0.99; P=0.048), respectively. Glucose disposal rate decreased from 5.8±2.4 to 5.3±1.9 mg/kg per min on placebo (P=0.03) but did not change on combined or delapril therapy. Treatment was well tolerated. In hypertensive type 2 diabetic patients, combined manidipine and delapril therapy failed to slow GFR decline but safely ameliorated cardiovascular disease, retinopathy, and neuropathy and stabilized insulin sensitivity.

Morphometry of dermal nerve fibers in human skin

Objective: We aimed to assess the innervation density of dermal nerves in human skin biopsies by bright-field immunohistochemistry. Methods: The size of dermal area where nerve length was quantified was validated in 30 skin biopsy sections (5 controls and 5 patients with small-fiber neuropathy [SFN]). It was obtained dividing an area of 200-μm depth from the dermal-epidermal junction into 4 equal portions. The length of dermal nerves (DNFL) was measured into 150 sections (25 controls and 25 patients with SFN) and values per millimeter of epidermis (DNFL/mm) and dermal area (DNFL/mm2) were obtained. Age- and gender-matched normative values of intraepidermal nerve fiber (IENF) density were used as gold standard to calculate the performance of dermal nerve morphometry. Results: Patients showed significantly lower DNFL (1.96 mm ± 0.96 SD), DNFL/mm (0.65 ± 0.29 SD), and DNFL/mm2 (3.75 ± 1.7 SD) than controls (DNFL 3.52 mm ± 1.31 SD, 5th percentile 2.05; DNFL/mm 1.25 ± 0.39, 5th percentile 0.71; DNFL/mm2 7.07 ± 2.41 SD, 5th percentile 3.95). Sensitivity, specificity, and percentage of individuals correctly classified were 75.8%, 73.9%, and 74.8% for DNFL, 75%, 80%, and 77.7% for DNFL/mm, and 75.8%, 80.2%, and 78.1% for DNFL/mm2. Receiver operator characteristic area analysis confirmed the excellent discrimination (0.8–0.9) between patients and controls. Dermal nerve morphometry significantly correlated with IENF density. Spearman rank correlation demonstrated good agreement for interobserver analysis (0.87–0.89), and between DNFL and IENF densities (0.71–0.73; p < 0.0001). Conclusions: We provided a reliable method to quantify the innervation density of dermal nerves that might improve the diagnostic yield of skin biopsy.

Erythropoietin in amyotrophic lateral sclerosis: A pilot, randomized, double-blind, placebo-controlled study of safety and tolerability

Preclinical studies demonstrated that erythropoietin is neuroprotective in different models of peripheral and central nervous system diseases. We investigated safety and tolerability of recombinant human erythropoietin (rhEPO) in amyotrophic lateral sclerosis (ALS). We performed a phase II double-blind, randomized, placebo-controlled study. After screening, 23 patients were randomly assigned to rhEPO or placebo arm. Patients were examined during a six-month lead-in period, and then they received fortnightly either 40,000 units of rhEPO or placebo for 24 months. Primary outcomes were adverse events, safety, and death or tracheotomy. Treatment was safe and well tolerated. One patient in the rhEPO arm dropped out for a superficial phlebitis. Median values of haematocrit, haemoglobin, red cells, and reticulocytes were non-significantly higher in rhEPO than placebo arm. Haemoglobin did not increase >1 g/dl between subsequent doses. Anti-rhEPO antibodies were not detected. Survival and slope of ALSFRS-R curves did not significantly differ between treatment groups. RhEPO treatment was safe and well tolerated in ALS patients. Our results suggest that larger studies are warranted to confirm safety of treatment and to investigate different dose schedule and efficacy.

Burning Tongue and Burning Tip : The Diagnostic Challenge of the Burning Mouth Syndrome

ObjectiveTo investigate the clinical features of burning mouth syndrome (BMS) in a large cohort of patients and to correlate them with the results of tongue biopsy. MethodsWe screened 98 patients complaining of oral burning pain for at least 6 months. Forty-two patients were excluded after screening for contact sensitivity to dental materials, food allergies, tongue injuries, malignancies, connective tissue and metabolic disorders, oral infectious diseases, vitamin deficiencies, and other systemic diseases known to cause neuropathy. Fifty-six patients underwent neurologic examination and assessment of pain intensity, depression, anxiety, quality of sleep, and quality of life. Tongue biopsy with the quantification of epithelial nerve fibers (ENF) was performed in 51 patients. ResultsCompared with 9 healthy participants (4.13±1.85 SD), epithelial innervation density was significantly reduced in 38 patients (1.35±1.46 SD; P<0.0001) and normal in 13 patients (6.1±2.19 SD). The clinical features differed in the two groups: patients with reduced ENF density complained of pain in the whole tongue, lips, hard palate, and alveolar ridges, reported dysgeusia and xerostomia in 29% of cases (P<0.001), and 24% of them were depressed. Patients with normal innervation complained of pain on the tip of the tongue, reported dysgeusia and xerostomia in 7.7% of cases, and 54% of them were depressed (P<0.017). DiscussionThe diagnostic criteria for BMS are not defined yet and the relationship with depression and anxiety is debated. We proposed a biopsy-supported approach for the diagnosis. Our study shows that BMS can present with two distinct clinical pictures and that tongue biopsy can contribute to the assessment of the diagnosis. Mood disorders occur frequently and should be considered when approaching patients and treatment options. These observations could help physicians in identifying patients with BMS and addressing them with the appropriate diagnostic work-up and treatment.