The role of skin biopsy in differentiating small-fiber neuropathy from ganglionopathy.

BACKGROUND AND PURPOSE: We aimed to test the clinical utility of the leg:thigh intraepidermal nerve-fiber (IENF) density ratio as a parameter to discriminate between length-dependent small-fiber neuropathy (SFN) and small-fiber sensory ganglionopathy (SFSG) in subjects with signs and symptoms of small-fiber pathology. METHODS: We retrospectively evaluated thigh and leg IENF density in 314 subjects with small-fiber pathology (173 with distal symmetrical length-dependent SFN and 141 with non-length-dependent SFSG). A group of 288 healthy subjects was included as a control group. The leg:thigh IENF density ratio was calculated for all subjects. We used receiver operating characteristic curve analyses to assess the ability of this parameter to discriminate between length-dependent SFN and SFSG, and the decision curve analysis to estimate its net clinical benefit. RESULTS: In patients with neuropathy, the mean IENF density was 14.8 ± 6.8/mm at the thigh (14.0 ± 6.9/mm in length-dependent SFN and 15.9 ± 6.7/mm in patients with SFSG) and 7.5 ± 4.5/mm at the distal leg (5.4 ± 3.2/mm in patients with length-dependent SFN and 10.1 ± 4.6/mm in patients with SFSG). The leg:thigh IENF density ratio was significantly (P < 0.01) lower in patients with length-dependent SFN (0.44 ± 0.23) compared with patients with SFSG (0.68 ± 0.28). The area under the curve of the receiver operating characteristic analysis to discriminate between patients with length-dependent SFN and SFSG was 0.79. The decision curve analysis demonstrated the clinical utility of this parameter. CONCLUSIONS: The leg:thigh IENF ratio represents a valuable tool in the differential diagnosis between SFSG and length-dependent SFN.

A multi-center, multinational age- and gender-adjusted normative dataset for immunofluorescent intraepidermal nerve fiber density at the distal leg.

BACKGROUND AND PURPOSE: Quantification of intraepidermal nerve fibers (IENFs) in skin biopsies is now the tool of choice to diagnose small fiber neuropathies. An adequate normative dataset, necessary to assess normality cutoffs, is available for brightfield microscopy but not for immunofluorescence. METHODS: Intraepidermal nerve fiber density data in distal leg skin samples processed with immunofluorescence were collected from 528 healthy individuals from four experienced laboratories worldwide. In all laboratories skin samples were collected, processed and analyzed according to standard procedures. Quantile regression analysis was employed to tailor the fit of the 5° percentile as the normal cutoff value and to test and measure the effect of age, gender, body mass index, race, biopsy site (lateral distal lower leg or medial posterior mid-calf) and participating laboratory as possible influential variables. RESULTS: Age, gender and biopsy site showed an independent linear correlation with IENF density. For each decade the 5° quantile IENF cutoff showed a 0.54 fibers/mm decrease, whilst females exhibited a 1.0 fiber/mm cutoff greater than males. Compared to the lateral distal lower leg, biopsies from the calf showed a 3.4 fibers/mm lower 5° percentile cutoff, documenting a variation linked by site. CONCLUSIONS: An age- and gender-adjusted normative dataset for IENF density at the lateral distal lower leg obtained with indirect immunofluorescence is presented for the first time by sharing data from four experienced laboratories worldwide. This dataset can be used as reference for laboratories processing skin biopsies with this technique.

Anabolic-androgenic steroids and brain reward.

Anabolic-androgenic steroid (AAS) effects on brain reward were investigated in male rats with electrodes implanted in the lateral hypothalamus using the rate-frequency curve shift paradigm of brain stimulation reward. In the first experiment, treatment for 2 weeks with the AAS methandrostenolone had no effect on either the reward or performance components of intracranial self-stimulation. In the second experiment, treatment for 15 weeks with an AAS "cocktail" consisting of testosterone cypionate, nandrolone decanoate, and boldenone undecylenate did not alter brain reward but did produce a slight but significant change in bar press rate. In addition to the AAS treatment, animals in the second study were administered a single injection of d-amphetamine before and after 15 weeks of AAS exposure. The rate-frequency curve shift observed in response to a systemic injection of amphetamine was significantly greater in animals after 15 weeks of treatment with the AAS cocktail. Although AAS do not appear to alter the rewarding properties of brain stimulation, AAS may influence the sensitivity of brain reward systems.

Ghrelin and obestatin concentrations during puberty: relationships with adiposity, nutrition and physical activity.

Ghrelin and obestatin are two peptides associated with appetite control and the regulation of energy balance in adults. It is intuitive that they have an important role in growth and development during puberty. Therefore, it is acknowledged that these peptides, in addition to others, form part of the substrate underlying energy homeostasis which in turn will contribute to body weight regulation and could explain changes in energy balance during puberty. Both peptides originate from the stomach; hence, it is intuitive that they are involved in generating signals from tissue stores which influence food intake. This could be manifested via alterations in the drive to eat (i.e. hunger), eating behaviors and appetite regulation. Furthermore, there is some evidence that these peptides might also be associated with physical activity behaviors and metabolism. Anecdotally, children and adolescents experience behavioral and metabolic changes during growth and development which will be associated with physiological changes.

Autoimmune autonomic ganglionopathy: IgG effects on ganglionic acetylcholine receptor current.

BACKGROUND: Autoimmune autonomic ganglionopathy (AAG) is an acquired immune-mediated form of diffuse autonomic failure. Many patients have serum antibodies that bind to the ganglionic acetylcholine receptors (AChRs) that mediate fast synaptic transmission in autonomic ganglia. Previous clinical studies and observations in animal models suggest that AAG is an antibody-mediated neurologic disorder. METHODS: Using whole-cell patch clamp techniques, we recorded ganglionic AChR currents in cultured human IMR-32 cells and examined the effects of bath application of IgG derived from patients with AAG. RESULTS: IgG from seven patients with AAG all produced a progressive decline in whole-cell ganglionic AChR current, whereas IgG from control subjects had no effect. The effect was abolished at low temperature. Fab antibody fragments had no effect unless a secondary antibody was added concurrently. IgG from one patient also produced a more immediate reduction of ganglionic AChR current. CONCLUSIONS: The characteristics of antibody-mediated inhibition of ganglionic acetylcholine receptor (AChR) current are consistent with modulation and blocking of the membrane AChR, analogous to the effects of muscle AChR antibodies in myasthenia gravis. Our observations demonstrate that antibodies in patients with autoimmune autonomic ganglionopathy (AAG) cause physiologic changes in ganglionic AChR function and confirm that AAG is an antibody-mediated disorder.

The utility of skin biopsy for prediction of progression in suspected small fiber neuropathy.

Twenty-eight patients with sensory complaints of unknown etiology had repeated skin biopsies. Patients with large nerve fiber swellings on initial biopsy showed a decline in epidermal nerve fiber density on repeated biopsies (p < 0.05 within group; p < 0.05 vs those without swellings). Patients without nerve fiber swellings did not have changes in nerve fiber density between biopsies. Patients with large nerve fiber swellings were most likely to present clinically with paresthesias (p < 0.05).

Autonomic neuropathy and coeliac disease.

Coeliac disease is associated with numerous neurological manifestations including cerebellar ataxia, myelopathy, myopathy, and peripheral neuropathy. This report describes four patients who presented subacutely with presyncope and postural nausea. All four patients had biopsy proven coeliac disease with dysautonomia present on autonomic evaluation. These four patients comprised 2.4% of patients referred for autonomic testing in one year. Thus the frequency of coeliac disease is similar to that reported in idiopathic peripheral neuropathy.