Painful neuropathy in subclinical hypothyroidism: clinical and neuropathological recovery after hormone replacement therapy

Impaired autonomic function and somatosensory disturbance in patients with treated autoimmune thyroiditis

Despite treatment with levothyroxine, hypothyroidism and autoimmune thyroiditis (AIT) may be associated with reduced quality of life (QoL), an enigmatic condition referred to as "syndrome T". Peripheral neuropathy, described in untreated thyroid disease, could be a contributing mechanism. We analysed autonomic and somatosensory function in 29 patients with AIT and treated hypothyroidism and 27 healthy volunteers. They underwent heart rate variability (HRV) analysis and quantitative sensory testing (n = 28), comprising 13 parameters of small and large nerve fibre function and pain thresholds. Autonomic cardiovascular function was assessed in rest, deep respiration and orthostasis. Additionally, biomarkers for autoimmunity and thyroid function were measured. Anxiety, depression and QoL were assessed using validated questionnaires. 36% of the patients showed at least one sign of somatosensory small or large fibre dysfunction. 57% presented with mild hyperalgesia to at least one stimulus. Several markers of autonomic function and some detection thresholds were related to the antibody titres. Anxiety, depression scores and QoL correlated to antibody titres and HRV measures. Autonomic and somatosensory dysfunction indicate that in treated hypothyroidism and AIT a subgroup of patients suffers from neuropathic symptoms leading to impaired QoL. Additionally, mild hyperalgesia as a possible sensitisation phenomenon should be considered a target for symptomatic treatment.

Investigation of nerve fibers in the skin by biopsy: technical aspects, indications, and contribution to diagnosis of small-fiber neuropathy

Skin biopsy with investigation of small-diameter nerve fibers in human epidermis and dermis has been proven to be a useful method for confirming small-fiber neuropathy. In medical practice, small-fiber neuropathy is increasingly recognized as a leading cause of neuropathic pain. It is a prevalent complaint in medical offices, brought by patients often as a “painful burning sensation”. The prevalence of neuropathic pain is high in small-fiber neuropathies of different etiologies, especially in the elderly; 7% of population in this age group present peripheral neuropathy. Pain and paresthesia are symptoms which might cause disability and impair quality of life of patients. The early detection of small-fiber neuropathy can contribute to reducing unhealthy lifestyles, associated to higher incidence of the disease.

Small-Fiber-Neuropathien

Die Small-Fiber-Neuropathie (SFN) ist eine Erkrankung des peripheren Nervensystems aufgrund einer isolierten oder vorwiegenden Schädigung dünn myelinisierter Aδ-Fasern und/oder unmyelinisierter C‑Fasern. Für die sichere Diagnose einer SFN ist neben der klinischen Symptomatik mit Schmerzen und Sensibilitätsstörungen, typischerweise mit distal betonter Ausbreitung, der apparative Nachweis einer Rarefizierung oder einer Funktionsstörung der dünn myelinisierten Aδ-Fasern und/oder der unmyelinisierten C‑Fasern gefordert. Im vorliegenden Beitrag wird eine Übersicht über die diagnostischen Verfahren zum Nachweis einer SFN sowie über mögliche Ursachen und Behandlungsoptionen gegeben.

Association of Thyroid Hormone Levels with Microvascular Complications in Euthyroid Type 2 Diabetes Mellitus Patients

PURPOSE

To examine the prevalence of different microvascular complications and investigate the association between thyroid hormones (THs) and these complications in euthyroid patients with type 2 diabetes mellitus (T2DM).

METHODS

A total of 248 T2DM patients were analyzed retrospectively for the study. All patients received a detailed and standard assessment to identify diabetic peripheral neuropathy (DPN), diabetic nephropathy (DN), and diabetic retinopathy (DR). Multivariate logistic regression was carried out to analyze the association between THs and diabetic microvascular complications.

RESULTS

The study found the prevalence of any microangiopathy to be 72.18% (n = 179). At the same time, the prevalence of DPN was 54.84% (n=136), while that of DN was 31.85% (n=79). Likewise, the prevalence of DR was 35.48% (n=88). The odds ratios (ORs) for free triiodothyronine (FT3) developing any microangiopathy, DPN, DN and DR were 0.200, 0.361, 0.310, and 0.588 (P<0.05), respectively. Also, the ORs for free thyroxine (FT4) developing any microangiopathy, DPN, DN and DR were 0.643, 0.800, 0.702 and 0.726 (P<0.05), respectively. Lastly, the ORs for thyroid-stimulating hormone (TSH) developing DPN was 1.57 (95% CI: 1.148-2.137, P=0.005).

CONCLUSION

The study concludes that serum FT3 and FT4 levels are negatively associated with any microangiopathy, DPN, DN and DR in euthyroid patients with T2DM, independent of traditional risk factors. However, the TSH levels are positively associated with DPN. Future larger sample-size studies are needed to confirm the relationship between thyroid hormone levels and microvascular complications in euthyroid patients with T2DM.

Contribution of Skin Biopsy in Peripheral Neuropathies

In the last three decades the study of cutaneous innervation through 3 mm-punch-biopsy has provided an important contribution to the knowledge of small fiber somatic and autonomic neuropathies but also of large fiber neuropathies. Skin biopsy is a minimally invasive technique with the advantage, compared to sural nerve biopsy, of being suitable to be applied to any site in our body, of being repeatable over time, of allowing the identification of each population of nerve fiber through its target. In patients with symptoms and signs of small fiber neuropathy the assessment of IntraEpidermal Nerve Fiber density is the gold standard to confirm the diagnosis while the quantification of sudomotor, pilomotor, and vasomotor nerve fibers allows to evaluate and characterize the autonomic involvement. All these parameters can be re-evaluated over time to monitor the disease process and to evaluate the effectiveness of the treatments. Myelinated fibers and their receptors can also be evaluated to detect a “dying back” neuropathy early when nerve conduction study is still normal. Furthermore, the morphometry of dermal myelinated fibers has provided new insight into pathophysiological mechanisms of different types of inherited and acquired large fibers neuropathies. In genetic neuropathies skin biopsy has become a surrogate for sural nerve biopsy, no longer necessary in the diagnostic process, to study genotype–phenotype correlations.

Sudomotor function testing by electrochemical skin conductance: does it really measure sudomotor function?

OBJECTIVE

Electrochemical skin conductance (ESC) is a non-invasive test of sweat function developed as a potential marker of small fiber neuropathy. Here we systematically review the evolution of this device and the data obtained from studies of ESC across different diseases.

METHODS

Electronic databases, including MEDLINE, and Google Scholar were searched through to February 2018. The search strategy included the following terms: "electrochemical skin conductance," "EZSCAN," and "Sudoscan." The data values provided by each paper were extracted, where available, and input into tabular and figure data for direct comparison.

RESULTS

Thirty-seven studies were included this systematic review. ESC did not change by age or gender, and there was significant variability in ESC values between diseases, some of which exceeded control values. Longitudinal studies of disease demonstrated changes in ESC that were not biologically plausible. Of the 37 studies assessed, 25 received support from the device manufacturer. The extracted data did not agree with other published normative values. Prior studies do not support claims that ESC is a measure of small fiber sensory function or autonomic function.

CONCLUSIONS

Although many papers report significant differences in ESC values between disease and control subjects, the compiled data assessed in this review raises questions about the technique. Many of the published results violate biologic plausibility. A single funding source with a vested interest in the study outcomes has supported most of the studies. Normative values are inconsistent across publications, and large combined data sets do not support a high sensitivity and specificity. Finally, there is insufficient evidence supporting the claim that Sudoscan tests sudomotor or sensory nerve fiber function.

Genome-wide association scan of neuropathic pain symptoms post total joint replacement highlights a variant in the protein-kinase C gene

Neuropathic pain-like joint symptoms (NP) are seen in a proportion of individuals diagnosed with osteoarthritis (OA) and post total joint replacement (TJR). In this study, we performed a genome-wide association study (GWAS) using NP as defined by the painDETECT questionnaire (score >12 indicating possible NP) in 613 post-TJR participants recruited from Nottinghamshire (UK). The prevalence of possible NP was 17.8%. The top four hits from the GWAS and two other biologically relevant single-nucleotide polymorphisms (SNPs) were replicated in individuals with OA and post TJR from an independent study in the same area (N=908) and in individuals from the Rotterdam Study (N=212). Three of these SNPs showed effect sizes in the same direction as in the GWAS results in both replication cohorts. The strongest association upon meta-analysis of a recessive model was for the variant allele in rs887797 mapping to the protein kinase C alpha (PRKCA) gene odds ratio (OR)_possNP=2.41 (95% CI 1.74-3.34, P=1.29 × 10^-7). This SNP has been found to be associated with multiple sclerosis and encodes a functional variant affecting splicing and expression of the PRKCA gene. The PRKCA gene has been associated with long-term potentiation, synaptic plasticity, chronic pain and memory in the literature, making this a biologically relevant finding.

Hypothyroidism Affects Olfactory Evoked Potentials

Background. Objective electrophysiological methods for investigations of the organ of smell consist in recordings of olfactory cortex responses to specific, time restricted odor stimuli. In hypothyroidism have impaired sense of smell. Material and Methods. Two groups: control of 31 healthy subjects and study group of 21 with hypothyroidism. The inclusion criterion for the study group was the TSH range from 3.54 to 110 μIU/mL. Aim. Assessment of the latency time of evoked responses from the olfactory nerve N1 and the trigeminal nerve N5 using two smells of mint and anise in hypothyroidism. Results. The smell perception in subjective olfactory tests was normal in 85% of the hypothyroid group. Differences were noticed in the objective tests. The detailed intergroup analysis of latency times of recorded cortical responses P_N5 and P_N1 performed by means between the groups of patients with overt clinical hypothyroidism versus subclinical hypothyroidism demonstrated a significant difference (p < 0.05) whereas no such differences were found between the control group versus subclinical hypothyroidism group (p > 0.05). Conclusion. We can conclude that registration of cortex potentials at irritation of olfactory and trigeminal nerves offers possibilities for using this method as an objective indicator of hypothyroidism severity and prognostic process factor.

[Immunohistochemical examination of skin biopsy specimens with calculation of C fibers in the diagnosis of polyneuropathy]

The paper discusses the anatomy of innervation of the skin, the epidermis and dermis in particular, which are related to pain, the markers of skin nerves and cells. It gives data on the diagnosis of fine unmyelinated fibers, by immunohistochemically examining skin biopsy specimens. The paper also describes the morphometry of skin nerves: intraepidermal nerve fibers, dermal nerve fibers, and autonomic nerve fibers. It discusses whether a skin biopsy specimen may be used to diagnose polyneuropathies of different etiology: diabetic, immune, HIV-related, and hereditary ones.

Advances in diagnostics and outcome measures in peripheral neuropathies

Peripheral neuropathies are a group of acquired and hereditary disorders presenting with different distribution and nerve fiber class involvement. The overall prevalence is 2.4%, increasing to 8% in the elderly population. However, the frequency may vary depending on the underlying pathogenesis and association with systemic diseases. Distal symmetric polyneuropathy is the most common form, though multiple mononeuropathies, non-length dependent neuropathy and small fiber neuropathy can occur and may require specific diagnostic tools. The use of uniform outcome measures in peripheral neuropathies is important to improve the quality of randomized controlled trials, enabling comparison between studies. Recent developments in defining the optimal set of outcome measures in inflammatory neuropathies may serve as an example for other conditions. Diagnostic and outcome measure advances in peripheral neuropathies will be discussed.

An update on subclinical hypothyroidism and subclinical hyperthyroidism

Subclinical thyroid dysfunction is characterized by normal levels of peripheral thyroid hormone, paired with a TSH level that is either lower than (subclinical hyperthyroidism) or higher than (subclinical hypothyroidism) the normal laboratory reference range. Slight shifts in peripheral hormone levels result in significant serum TSH changes. The exact upper limit of normal TSH and the management of subclinical hypothyroidism are still controversial. For those with TSH between high upper limit of normal and 10 mIU/L, the authors suggest selective use of thyroxine therapy. The authors agree with the general consensus in favor of therapy for those with serum TSH levels above 10 mIU/L. This recommendation is compatible with guidelines of American Thyroid Association and American Association of Clinical Endocrinologists. For subclinical hyperthyroidism persistent serum TSH <0.1 mIU/L should be treated particularly if the etiology is nodular toxic goiter. For serum TSH between 0.1 mIU/L and lower limit of normal, serum TSH co-morbidities such as cardiac risk factors and osteoporosis may favor therapy.

The physiologic effects of pain on the endocrine system

Severe pain has profound physiologic effects on the endocrine system. Serum hormone abnormalities may result and these serve as biomarkers for the presence of severe pain and the need to replace hormones to achieve pain control. Initially severe pain causes a hyperarousal of the hypothalamic-pituitary-adrenal system which results in elevated serum hormone levels such as adrenocorticotropin, cortisol, and pregnenolone. If the severe pain does not abate, however, the system cannot maintain its normal hormone production and serum levels of some hormones may drop below normal range. Some hormones are so critical to pain control that a deficiency may enhance pain and retard healing.

Pain and thyroid hormones

The role of endocrine systems in chronic pain mechanisms is slowly getting increasing experimental and clinical consideration. Many painful conditions appear to be directly and/or indirectly induced, reduced or, in some cases, modulated by hormones. We have done much work in trying to understand the relationship between hormones and pain, with particular attention to the hypothalamus-pituitary-gonadal axis. To expand our knowledge of this field, we have directed our attention to another axis, the hypothalamus-pituitary-thyroid (HPT). The literature on thyroid functions is vast but very few studies have focused on the HPT axis and pain. The few available data are considered in the present review to stimulate interest in the possible interactions between the HPT axis and pain.

The cutaneous nerve biopsy: technical aspects, indications, and contribution

Skin biopsy with a 3mm disposable circular punch is easy to perform and allows, after proper processing, the visualization of epidermal, dermal, and sweat gland nerve fibers. A technique of sampling the epidermis alone by applying a suction capsule, the "blister" technique, has also been developed. It is most common to stain immunohistochemically for the pan-axonal marker protein gene product 9.5 (PGP 9.5), an ubiquitin C-terminal hydroxylase. The sections are then observed and analyzed with bright-field microscopy or with indirect immunofluorescence with or without confocal microscopy. Most studies report quantification of intraepidermal nerve fiber density displayed in bright-field microscopy. Normative values have been established, particularly from the distal part of the leg, 10cm above the external malleolus. In diabetes mellitus early degeneration of intraepidermal nerve fibers is induced and there is slower regeneration even when there is no evidence of neuropathy. Skin biopsy is of particular value in the diagnosis of small fiber neuropathy when nerve conduction studies are normal. It may also be repeated in order to study the progressive nature of the disease and also has the potential of studying regeneration of nerve fibers and thus the effects of treatment. Inflammatory demyelinating neuropathies may also involve loss of small-diameter nerve fibers and IgM deposits in dermal myelinated nerve fibers in anti-MAG neuropathy. In some cases the presence of vasculitis in skin may indicate a nonsystemic vasculitic neuropathy and in HIV neuropathy intraepidermal nerve fiber density is reduced in a length-dependent manner. In several hereditary neuropathies intraepidermal nerve fiber density may be reduced but other abnormalities can also be demonstrated in dermal myelinated fibers. Some small swellings and varicosities may be present in the distal leg skin biopsy of healthy individuals but large axonal swellings are considered as evidence of a pathological process affecting the normal structure of nerves. The indirect immunofluorescence technique with confocal microscopy provides the opportunity to study the complex structure of sensory receptors and cutaneous myelinated fibers and the innervation of sweat glands, arrector pilorum muscles, and vessels.

Diagnosis of neuropathic pain: challenges and possibilities

Neuropathic pain complicates many diseases of the peripheral and central nervous system and is frequently encountered in clinical practice. The mechanisms underlying its occurrence and chronification remain poorly understood. As a consequence, symptomatic treatment is frequently the only available therapeutic option. An appropriate diagnostic workup is an important prelude to treatment. Moreover, identification of the site of damage in the somatosensory pathway represents a mandatory step in the process of deciding on a disease-modifying therapy for any given patient. The recent revision of the definition of neuropathic pain has introduced the concept of a nosologic-based approach to the diagnosis, which is expected to be supported by the demonstration of a relationship between the clinical picture and a lesion or disease. This underscores the need for precise diagnostic assessment of the patient. In the last decade, a number of tools including validated scales, psychophysical tests and morphometric analysis of small nerve fibers carrying thermal and nociceptive sensation have been developed; these can provide important information about the quality and intensity of the multiple features that characterize neuropathic pain. More recently, advances on the recognition of a molecular substrate for neuropathic pain, both in terms of susceptibility and novel gene mutations, have provided the potential for new diagnostic perspectives and a path toward a better comprehension of the pathogenetic mechanisms. This editorial addresses briefly the impact of these developments on the diagnosis of neuropathic pain in clinical practice.

Unmyelinated and myelinated skin nerve damage in Guillain-Barré syndrome: correlation with pain and recovery

We performed a prospective study in 32 patients with Guillain-Barré syndrome (GBS) or its variants to correlate intraepidermal nerve fiber density (IENFD) at the distal leg and lumbar region with pain, autonomic dysfunction, and outcome. In the acute phase, IENFD was reduced in 60% and 61.9% of patients at the distal leg and lumbar region, respectively. In the acute phase, 43.7% of patients complained of neuropathic pain. Their IENFD at the distal leg was significantly lower than in patients without pain (P<.001) and correlated with pain intensity (r(s)=-0.51; P=.003). Intriguingly, also patients with the pure motor variant of GBS and pain had low IENFD. At 6-month follow-up, only 3 patients complained of persisting neuropathic pain, whereas 3 patients reported late-onset pain symptoms. IENFD in the acute phase did not predict presence or intensity of pain at 6-month follow-up. IENFD in the acute phase did not correlate with clinical dysautonomia or GBS severity at nadir. However, it correlated with poorer GBS disability score at 6 months (P=.04), GBS score at nadir (P=.03), and clinically probable dysautonomia (P=.004). At 6-month follow-up, median IENFD remained significantly low both at the distal leg (P=.024) and lumbar region (P=.005). Double and triple staining confocal microscope studies showed diffuse damage of myelinated dermal nerves along with axonal degeneration, and mononuclear cell infiltration. Unmyelinated and myelinated skin nerves are diffusely affected in GBS and its variants, including the pure motor form. IENFD declines early, remains low over time, correlates with pain severity in the acute phase, and may predict long-term disability.

A case of Sheehan's syndrome that manifested as bilateral ptosis

Hypothyroidism can cause a variety of signs and symptoms of the neuromuscular system. However, ptosis in a patient with hypothyroidism is very rare. We report here on a case of central hypothyroidism that was due to Sheehan's syndrome and it manifested as bilateral ptosis in a 51-yr-old woman. She complained of exertional dyspnea and weakness. About 25-yr ago, she had a history of severe postpartum vaginal bleeding. The laboratory studies demonstrated hypopituitarism with secondary hypothyroidism. The ptosis was improved by replacement of thyroid hormone. Hypothyroidism should be considered in the differential diagnosis of patients who manifest with ptosis and that prompt replacement of hormone can lead to a complete recovery.

European Federation of Neurological Societies/Peripheral Nerve Society Guideline on the use of skin biopsy in the diagnosis of small fiber neuropathy. Report of a joint task force of the European Federation of Neurological Societies and the Peripheral Nerve Society

BACKGROUND

Revision of the guidelines on the use of skin biopsy in the diagnosis of peripheral neuropathy, published in 2005, has become appropriate owing to publication of more relevant articles. Most of the new studies focused on small fiber neuropathy (SFN), a subtype of neuropathy for which the diagnosis was first developed through skin biopsy examination. This revision focuses on the use of this technique to diagnose SFN.

METHODS

Task force members searched the Medline database from 2005, the year of the publication of the first EFNS guideline, to June 30th, 2009. All pertinent articles were rated according to the EFNS and PNS guidance. After a consensus meeting, the task force members created a manuscript that was subsequently revised by two experts (JML and JVS) in the field of peripheral neuropathy and clinical neurophysiology, who were not previously involved in the use of skin biopsy.

RESULTS AND CONCLUSIONS

Distal leg skin biopsy with quantification of the linear density of intraepidermal nerve fibers (IENF), using generally agreed upon counting rules, is a reliable and efficient technique to assess the diagnosis of SFN (Recommendation Level A). Normative reference values are available for bright-field immunohistochemistry (Recommendation Level A) but not yet for confocal immunofluorescence or the blister technique. The morphometric analysis of IENF density, either performed with bright-field or immunofluorescence microscopy, should always refer to normative values matched for age (Recommendation Level A). Newly established laboratories should undergo adequate training in a well-established skin biopsy laboratory and provide their own stratified for age and gender normative values, intra- and interobserver reliability, and interlaboratory agreement. Quality control of the procedure at all levels is mandatory (Good Practice Point). Procedures to quantify subepidermal nerve fibers and autonomic innervated structures, including erector pili muscles, and skin vessels, are under development but need to be confirmed by further studies. Sweat gland innervation can be examined using an unbiased stereologic technique recently proposed (Recommendation Level B). A reduced IENF density is associated with the risk of developing neuropathic pain (Recommendation Level B), but it does not correlate with its intensity. Serial skin biopsies might be useful for detecting early changes of IENF density, which predict the progression of neuropathy, and to assess degeneration and regeneration of IENF (Recommendation Level C). However, further studies are warranted to confirm its potential usefulness as an outcome measure in clinical practice and research. Skin biopsy has not so far been useful for identifying the etiology of SFN. Finally, we emphasize that 3-mm skin biopsy at the ankle is a safe procedure based on the experience of 10 laboratories reporting absence of serious side effects in approximately 35,000 biopsies and a mere 0.19% incidence of non-serious side effects in about 15 years of practice (Good Practice Point).