Review: small-fiber neuropathy

Validation of symptom measures in patients under investigation for postural orthostatic tachycardia syndrome (POTS): The Orthostatic Grading Scale (OGS) and the Symptom Screen for Small-fiber Polyneuropathy (SSS)

OBJECTIVES

Postural Orthostatic Tachycardia Syndrome (POTS) presents with a range of poorly delineated symptoms across several domains. There is an urgent need for standardized symptom reporting in POTS, but a lack of validated symptom burden instruments. Our aim was to evaluate the psychometric properties of two symptom burden measures: the Orthostatic Grading Scale (OGS) and the Symptom Screen for Small-Fiber Polyneuropathy (SSS), in patients under investigation for suspected POTS.

DESIGN

Psychometric validation study.

METHODS

Confirmatory factor analysis (CFA) tested the factor structure of the SSS and OGS completed by 149 patients under investigation for POTS. Scale reliability and validity were assessed. The uni-dimensionality of the SSS was assessed through principal component analysis (PCA).

RESULTS

CFA of the OGS revealed that a 1-factor structure had adequate fit. CFA of the SSS revealed that a 5-factor structure had generally appropriate fit supporting the originally proposed 5 factors (1: Gastrointestinal, 2: Somatosensory, 3: Miscellaneous, 4: Microvascular, and 5: Urological). In addition, the SSS demonstrated sufficient uni-dimensionality in the PCA, warranting use of a single total score. Omega coefficients of both measures indicated satisfactory internal reliability (0.668-0.931). Correlations with related constructs (distress (K10 score), r = 0.317-0.404, p < 0.001) and heart rate indices (with the OGS, r = 0.211-0.294, p < 0.05) suggested sound convergent and divergent validity.

CONCLUSIONS

Initial evidence suggests that the OGS and SSS have good psychometric properties for use in populations with suspected and confirmed POTS.

Remote Photoplethysmography for Evaluation of Cutaneous Sensory Nerve Fiber Function

About 2% of the world’s population suffers from small nerve fiber dysfunction, neuropathy, which can result in severe pain. This condition is caused by damage to the small nerve fibers and its assessment is challenging, due to the lack of simple and objective diagnostic techniques. The present study aimed to develop a contactless photoplethysmography system using simple instrumentation, for objective and non-invasive assessment of small cutaneous sensory nerve fiber function. The approach is based on the use of contactless photoplethysmography for the characterization of skin flowmotions and topical heating evoked vasomotor responses. The feasibility of the technique was evaluated on volunteers (n = 14) using skin topical anesthesia, which is able to produce temporary alterations of cutaneous nerve fibers function. In the treated skin region in comparison to intact skin: neurogenic and endothelial component of flowmotions decreased by ~61% and 41%, the local heating evoked flare area decreased by ~44%, vasomotor response trend peak and nadir were substantially reduced. The results indicate for the potential of the remote photoplethysmography in the assessment of the cutaneous nerve fiber function. It is believed that in the future this technique could be used in the clinics as an affordable alternative to laser Doppler imaging technique.

A capital role for the brain's insula in the diverse fibromyalgia-associated symptoms

Unexplained yet persisting general and widespread non-articular musculoskeletal pain and the associated complaints, known as fibromyalgia (FM), is a common disorder with major social and economic impact. We postulate that in FM disturbance of neurotransmitter balances at the brain's insula not only leads to aberrant pain processing but could also govern other associated symptoms. Symptoms might arise from central nervous system dysregulation mediated through an imbalance between the excitatory neurotransmitter glutamate and the inhibitory transmitter gamma-amino butyric acid. The insula could also have a leading role in the dysregulation of heart rate and blood pressure, bladder and bowel symptoms, and anxiety and sleep disturbances which are experienced by many FM patients. The presented hypothesis explains how the diverse FM-associated symptoms could be linked, and puts the brain's insula forward as a possible therapeutic target to be further explored for FM.

Sudomotor Testing of Diabetes Polyneuropathy

Objective: The performance of the Sudoscan technology for diagnosing diabetic polyneuropathy (DPN) was evaluated against the quantitative sudomotor axon reflex test (QSART). Furthermore, the association of Sudoscan with two clinical neuropathy scoring systems was evaluated. Methods: Forty-seven patients with type 2 diabetes (20 without DPN, 27 with DPN) and 16 matched controls were examined for neuropathic symptoms and for the extent of sensory deficits. Sweat latency and volume by QSART and the skin electrochemical conductance (ESC) by Sudoscan were measured. Results: The feet and hand ESC was significantly lower in patients with DPN as compared to controls. Patients with DPN had also lower hand ESC than patients without DPN. Sensitivity and specificity of feet and hand ESC for detecting DPN were 70/85% and 53/50% respectively. QSART could not differentiate between the three groups. ESC was inversely related to neuropathic symptoms and sensory impairment. ESC was significantly correlated with sensory impairment and pain. Conclusions: Sudoscan shows a good performance in detecting subjects with DPN and it correlates well with clinical signs and symptoms of neuropathy. Significance: This study provides evidence that Sudoscan has high potential to be used as screening tool for DPN and possibly also for small fiber neuropathy in diabetic patients. HIGHLIGHTS - The sudomotor function test Sudoscan shows a good performance to detect diabetes peripheral neuropathy.- Sudoscan measures significantly correlate with clinical signs and symptoms of neuropathy.- The Sudoscan technology may help to secure clinical diagnosis of small fiber neuropathy.

Tool Chest

PURPOSE

The purpose of this study was to evaluate the new indicator test for sudomotor function (Neuropad) in the diagnosis of small-fiber impairment in patients with type 2 diabetes.

METHODS

This study included 123 patients with type 2 diabetes (59 men; mean age, 64.3 +/- 8.6 years; mean diabetes duration, 12 +/- 6.1 years). Sudomotor dysfunction was assessed by means of the new indicator test. Neuropathy was diagnosed by the Neuropathy Disability Score and small-fiber impairment by temperature perception (Tiptherm device) and pain perception (Neurotip).

RESULTS

The frequency of sudomotor dysfunction was significantly (P = .001) higher in patients with neuropathy (95%) than in those without neuropathy (30.2%). Sensitivity of the indicator test for neuropathy was 95%, and specificity was 69.8%. Frequency of neuropathy was significantly (P = .018) higher with the indicator test (74.8%) than with conventional clinical examination (65.4%). Sudomotor dysfunction was significantly (P = .001) more frequent in patients with small-fiber impairment (99%) than in those without small-fiber impairment (21.7%). Sensitivity for small-fiber impairment was 99%, and specificity was 78.3%. There was no difference (P = .999) in the frequency of small-fiberimpairment as diagnosed with the indicator test (80.5%) and with clinical examination (81.3%).

CONCLUSIONS

The indicator test has a very high sensitivity and specificity for small-fiber impairment in patients with type 2 diabetes.

A model of neuropathic pain induced by sorafenib in the rat: Effect of dimiracetam

BACKGROUND

Sorafenib is a kinase inhibitor anticancer drug whose repeated administration causes the onset of a peripheral painful neuropathy. Notably, the efficacy of common analgesic drugs is not adequate and this often leads pre-mature discontinuation of anticancer therapy. The aim of this study was to establish a rat model of sorafenib-induced neuropathic pain, and to assess the effect of the new anti-neuropathic compound dimiracetam in comparison with gabapentin, pregabalin and duloxetine.

METHODS

Male Sprague-Dawley rats were treated i.v. (10 mg kg(-1)), i.p. (10 and 30 mg kg(-1)) or p.o. (80 and 160 mg kg(-1)) with sorafenib once daily for 21 days. Pain behaviour measurements (cold plate, paw pressure, electronic von Frey) were performed on days 0, 7, 14 and 21.

RESULTS

Sorafenib lowered the paw-licking threshold to non-noxious cold stimuli on day 14 of all protocols evaluated. The i.p. administration resulted in greater efficacy than the other administration routes. Sorafenib treatments did not affect paw-withdrawal responses to non-noxious or to noxious mechanical stimuli. On day 14, dimiracetam (300 mg kg(-1)), gabapentin (100 mg kg(-1)), pregabalin (30 mg kg(-1)) and duloxetine (30 mg kg(-1)) were acutely administered p.o. in sorafenib i.p.-treated rats. A single oral dose of dimiracetam induced a statistically significant increase of the pain threshold 15 min after administration. Pregabalin induced a comparable effect, whereas gabapentin and duloxetine were ineffective. Repeated twice-daily administration of dimiracetam (150 mg kg(-1) p.o.), starting on the first day of i.p sorafenib administration, significantly protected rats from sorafenib-induced decrease in the paw-licking threshold.

CONCLUSIONS

A rat model of sorafenib-induced hypersensitivity to cold stimulation has been established. Dimiracetam and pregabalin are effective in prevention of sorafenib-induced neuropathy in this model.

Acute small fiber neuropathy following Mycoplasma infection: a rare variant of Guillain-Barré syndrome

Guillain-Barré syndrome (GBS) is a well-described condition involving the peripheral nervous system. The most well-known form of this disease is acute inflammatory demyelinating polyradiculoneuropathy. Among the different variants of GBS described in the literature, the sensory variant is scantily recognized. There has been a recent attempt to classify the sensory variants of the GBS and bring more objectivity to this diagnostic paradigm. We report a rare sensory variant of GBS presenting with isolated small nerve fiber involvement peripherally in the limbs and associated facial nerve palsy in a patient who had clinical and serological evidence of a preceding Mycoplasma pneumoniae infection. The symptoms resolved gradually with intravenous immunoglobulin therapy. This case adds to the growing literature of the rare form of acute small fiber neuropathy and GBS variants.

Contact heat-evoked potential stimulation for the evaluation of small nerve fiber function

BACKGROUND

Small fiber peripheral neuropathy (SFN) is emerging as a common complication in diabetes. Currently there are few, not easily available methods of determining the integrity of small nerve fibers. This study was designed to determine the utility of a noninvasive technique, contact heat-evoked potential stimulation (CHEPS), on the identification of SFN and compare it with standardized measures of diabetic peripheral neuropathy (DPN).

SUBJECTS AND METHODS

We evaluated 31 healthy controls and 30 participants with type 2 diabetes and DPN using neurologic examination, nerve conduction studies (NCS), autonomic function tests, quantitative sensory tests (QSTs), and CHEPS. Contact heat was administered to the thenar eminence, volar and dorsal forearms, lower back, and distal lower limb. Evoked potentials were recorded from the skull vertex. Latencies and amplitudes were determined.

RESULTS

Intrapeak amplitude (IA) values were significantly reduced in the DPN group at the lower back (44.93±6.5 vs. 23.87±3.36 μV; P<0.01), lower leg (15.87±1.99 vs. 11.68±1.21 μV; P<0.05), and dorsal forearm (29.89±8.86 vs. 14.96±1.61 μV; P<0.05). Pooled data from both groups showed that IA values at different sites significantly correlated with clinical neurologic scores, NCS, QSTs, and autonomic function. Receiver operator characteristic curve analysis, used to evaluate the performance of CHEPS in detecting nerve dysfunction, was most significant for IA at the lower back (area under the curve, 0.778;±SE, 0.06; 95% confidence interval, 0.654-0.875; P<0.0001).

CONCLUSIONS

This study suggests that CHEPS is a novel, noninvasive technique able to detect impairment of small nerve fiber function from skin to cerebral cortex, providing an objective measure of C and Aδ nerve dysfunction.

Evaluation of proxy tests for SFSN: evidence for mixed small and large fiber dysfunction

Background

Though intra-epidermal nerve fiber density (IENFD) is considered the gold standard for diagnosis of small fiber sensory neuropathy (SFSN), we aimed to determine if novel threshold values derived from standard tests of small or large fiber function could serve as diagnostic alternatives.

Methods

Seventy-four consecutive patients with painful polyneuropathy and normal nerve conduction studies (NCS) were defined as SFSN cases or controls by distal IENFD <5.4 and ≥5.4 fibers/mm, respectively. Diagnostic performance of small fiber [cooling (CDT) and heat perception (HP) thresholds, axon reflex-mediated neurogenic vasodilatation] and large fiber function tests [vibration perception thresholds (VPT) and sural nerve conduction parameters] were determined by receiver operating-characteristic (ROC) curve analyses.

Results

The 26(35%) SFSN cases had mean IENFD 3.3±1.7 fibers/mm and the 48(65%) controls 9.9±2.9 fibers/mm. Male gender (p = 0.02) and older age (p = 0.02) were associated with SFSN cases compared to controls. VPT were higher and CDT lower in SFSN cases, but the largest magnitude of differences was observed for sural nerve amplitude. It had the greatest area under the ROC curve (0.75) compared to all other tests (p<0.001 for all comparisons) and the optimal threshold value of ≤12 µV defined SFSN cases with 80% sensitivity and 72% specificity.

Conclusion

In patients presenting with polyneuropathy manifestations and normal NCS, though small fiber function tests were intuitively considered the best alternative measures to predict reduced IENFD, their diagnostic performance was poor. Instead, novel threshold values within the normal range for large fiber tests should be considered as an alternative strategy to select subjects for skin biopsy in diagnostic protocols for SFSN.

Clinical manifestations of neurological involvement in primary Sjögren’s syndrome

The aim of this study was to evaluate neurological manifestations of primary Sjögren’s syndrome (pSS) and investigate the etiology and pathogenesis of peripheral and central nervous complications in pSS. Thirty-two patients with pSS were enrolled in the present study, 20 of whom had neurological involvement plus sicca symptoms. The clinical features were evaluated by neurological examinations including nerve conduction study, magnetic resonance imaging, cerebrospinal fluid, and electroencephalogram. The frequency of fever was significantly higher (P = 0.006) in pSS with neurological involvement than in pSS without neurological involvement. There was no statistical significance in other factors between the two groups. Peripheral nervous system (PNS), central nervous system (CNS), and both PNS and CNS involvements were revealed in 14, 3, and 3 patients, respectively. Optic neuritis and trigeminal neuralgia were revealed frequently in cranial neuropathy. Anti-aquaporin 4 antibody was detected in one patient with optic neuritis. Of the nine patients with polyneuropathy, eight patients presented pure sensory neuropathy including small fiber neuropathy (SFN). pSS with SFN appeared to have no clinically abnormal features, including muscle weakness and decreasing deep tendon reflex. Skin biopsy revealed epidermal nerve fiber degenerated in one pSS patient with pure sensory neuropathy who was diagnosed as having SFN. Our observations suggest that a number of mechanisms can be attributed to neurological involvements in pSS rather than just the mechanisms previously described (i.e., vasculitis and ganglioneuronitis). Presumably, specific autoantibodies may directly induce injury of the nervous system.

Neuropathy in prediabetes: does the clock start ticking early?

Between 25% and 62% of patients with idiopathic peripheral neuropathy are reported to have prediabetes, and among individuals with prediabetes 11-25% are thought to have peripheral neuropathy, and 13-21% have neuropathic pain. Population-based studies suggest a gradient for the prevalence of neuropathy, being highest in patients with manifest diabetes mellitus, followed by individuals with impaired glucose tolerance then impaired fasting glucose and least in those with normoglycemia. The most sensitive test to assess glucose metabolism status is the oral glucose tolerance test. Pathogenesis involves hyperglycemia, microvascular abnormalities, dyslipidemia and the metabolic syndrome. Individuals with prediabetes have less severe neuropathy than those with manifest diabetes mellitus. Sensory modalities are more frequently affected than motor modalities, but impairment of small nerve fibers could be the earliest detectable sign. Diagnosis should rely on careful clinical examination, with emphasis on the evaluation of small fibers. An oral glucose tolerance test should be performed in patients with idiopathic neuropathy. The only treatment with any efficacy is lifestyle modification to improve control of hyperglycemia and cardiovascular risk factors, but long-term efficacy of this approach has not been established. This Review summarizes the current evidence on the association between prediabetes and neuropathy.

Quality of life and objective measures of diabetic neuropathy in a prospective placebo-controlled trial of ruboxistaurin and topiramate

BACKGROUND

The Norfolk Quality of Life Questionnaire-Diabetic Neuropathy (Norfolk QOL-DN) is a validated comprehensive questionnaire designed to capture the entire spectrum of DN related to large fiber, small fiber, and autonomic neuropathy not captured in existing instruments. We aimed to determine if the Norfolk QOL-DN could be used to capture changes in QOL that correlate with nerve fiber-specific objective measures in a placebo-controlled trial of two agents that affect different nerve fibers.

METHODS

Sixty patients with DN were allocated to treatment on ruboxistaurin (RBX) (n = 18), topiramate (TPX) (n = 18), or placebo (n = 18). QOL-DN was administered and objective measures of nerve function were performed at entry and end of the study period.

RESULTS

Total QOL scores improved significantly in the active treatment groups (RBX -9.56 ± 4.13; TPX -12.22 ± 2.76) but not in placebo (-5.56 ± 3.49). There were differences in nerve function improvement between treatments. Neurological symptom scores (NSS) improved with TPX from 5.5 (2.3) to 4.3 (0.65) (p = .007), sensory scores improved with TPX from 15.5 (1.79) to 8.3 (1.19) (p < .001), motor scores did not change, and sensory and motor impairment scores improved with TPX from 18.8 (2.15) to 12.1 (1.71) (p = .003). Total neuropathy scores (TNS) improved with TPX from 24.35 (2.61) to 16.35 (2.02) (p = .001). Neuropathy total symptom score-6 (NTSS-6) changes were significant for both treatments: RBX 4.38 (0.75) to 1.49 (0.38) (p < .001) and TPX 7.57 (1.3) to 4.26 (0.95) (p = .036). Changes in QOL-DN large fiber subscores correlated (Spearman's rank) significantly with changes in NTSS-6 (r = 0.55; p < .0001), NSS (r = 0.31; p < .04), neuropathy impairment score (NIS) (r = 0.35; p < .02), and TNS (r = 0.48; p < .0006). Changes in QOL-DN small fiber subscores correlated significantly with changes in NTSS-6 total scores (r = 0.40; p < .005) and intraepidermal nerve fiber density (IENFD) (r = -0.29; p < .05).

CONCLUSION

Ruboxistaurin produced significant improvement in large fiber measures while TPX produced significant changes in small fiber measures. The Norfolk QOL-DN tool differentiated between these changes captured in the fiber-specific domains. Correlations were found between objective measures of neuropathy and total QOL, but those with nerve fiber domain scores were modest and reinforce the need to quantify QOL as an endpoint in neuropathy independent of other measures.

Assessment of symptomatic diabetic patients with normal nerve conduction studies: utility of cutaneous silent periods and autonomic tests

Established electrophysiological methods have limited clinical utility in the diagnosis of small-fiber neuropathy (SFN). In this study, diabetic patients with clinically diagnosed SFN were evaluated with autonomic tests and cutaneous silent periods (CSPs). Thirty-one diabetic patients with clinically suspected SFN and normal nerve conduction studies were compared with 30 controls. In the upper extremities (UE), the CSP parameters did not differ statistically between the patient and control groups, whereas, in the lower extremities (LE), patients had prolonged CSP latencies (P = 0.018) and shortened CSP durations (P < 0.001). The sensitivity of the CSP duration was 32.6%, and the specificity was 96.7%. The expiration-to-inspiration ratios and amplitudes of the sympathetic skin responses in the lower extremities were also reduced. Our findings indicate that the diagnostic utility of CSPs was higher than that of the autonomic tests to support the clinically suspected diagnosis of SFN.

New diagnostic tests for diabetic distal symmetric polyneuropathy

Neuropathy needs to be diagnosed early to prevent complications, such as neuropathic pain or the diabetic foot. It is obvious that diagnosis of neuropathy needs to be improved. New peripheral nerve function tests that appear to facilitate diagnosis are now emerging. This review outlines the new tests that have been proposed for the diagnosis of diabetic distal symmetric polyneuropathy, the commonest form of neuropathy in diabetes. New tests are classified into those mainly assessing large-fiber function (tactile circumferential discriminator, steel ball-bearing, and automated nerve conduction study) and those mainly assessing small-fiber function (NeuroQuick and Neuropad). Emerging tests are promising but must be evaluated in prospective studies. Moreover, their cost-effectiveness needs more careful appraisal. The clinician should, therefore, still rely on established modalities to diagnose neuropathy, but wider use of the new tests is expected in the near future.

Primary Raynaud phenomenon and small-fiber neuropathy: is there a connection? A pilot neurophysiologic study

The pathophysiologic factors of primary Raynaud phenomenon (RP) are unknown. Preliminary evidence from skin biopsy suggests small-fiber neuropathy (SFN) in primary RP. We aimed to quantitatively assess SFN in participants with primary RP. Consecutive patients with an a priori diagnosis of primary RP presenting to our outpatient rheumatology clinic over a 6-month period were invited to participate. Cases of secondary RP were excluded. All participants were required to have normal results on nailfold capillary microscopy. Assessment for SFN was accomplished with autonomic reflex screening, which includes quantitative sudomotor axonal reflex test (QSART), and cardiovagal and adrenergic function testing, thermoregulatory sweat test (TST), and quantitative sensory test (QST) for vibratory, cooling, and heat-pain sensory thresholds. Nine female participants with a median age of 38 years (range 21-46 years) and a median symptom duration of 9 years (range 5 months-31 years) were assessed. Three participants had abnormal results on QSART, indicating peripheral sudomotor autonomic dysfunction. Two participants had evidence of large-fiber involvement with heat-pain thresholds on QST. Heart rate and blood pressure responses to deep breathing, Valsalva maneuver, and 70° tilt were normal for all participants. Also, all participants had normal TST results. In total, three of the nine participants had evidence of SFN. The presence of SFN raises the possibility that a subset of patients with primary RP have an underlying, subclinical small-fiber dysfunction. These data open new avenues of research and therapeutics for this common condition.

Pharmacogenetics of nucleoside reverse-transcriptase inhibitor-associated peripheral neuropathy

Peripheral neuropathy is an important complication of antiretroviral therapy. Nucleoside reverse-transcriptase inhibitor (NRTI)-associated mitochondrial dysfunction, inflammation and nutritional factors are implicated in its pathogenesis. Pharmacogenetic and genomic studies investigating NRTI neurotoxicity have only recently become possible via the linkage of HIV clinical studies to large DNA repositories. Preliminary case-control studies using these resources suggest that host mitochondrial DNA haplogroup polymorphisms in the hemochromatosis gene and proinflammatory cytokine genes may influence the risk of peripheral neuropathy during antiretroviral therapy. These putative risk factors await confirmation in other HIV-infected populations but they have strong biological plausibility. Work to identify underlying mechanisms for these associations is ongoing. Large-scale studies incorporating clearly defined and validated methods of neuropathy assessment and the use of novel laboratory models of NRTI-associated neuropathy to clarify its pathophysiology are now needed. Such investigations may facilitate the development of more effective strategies to predict, prevent and ameliorate this debilitating treatment toxicity in diverse clinical settings.

Extreme efficacy of intravenous immunoglobulin therapy for severe burning pain in a patient with small fiber neuropathy associated with primary Sjögren's syndrome

Neurological involvement occurs in approximately 20% of patients with primary Sjögren's syndrome. Although neurological symptoms can affect the peripheral nervous system and the central nervous system, the most frequent symptom is polyneuropathy. Small fiber neuropathy (SFN) is a form of painful peripheral polyneuropathy that is common in patients with diabetic neuropathy, but may also occur in toxic, infectious, or immune-mediated neuropathy. We show here a patient with Sjögren's syndrome who developed SFN and was treated with intravenous immunoglobulin (IVIG) therapy, which was immediately and extremely effective. Because of the efficacy of IVIG therapy, we propose that direct immune-mediated mechanisms may be involved in the pathogenesis of SFN complicated by Sjögren's syndrome.

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.

A 6-month, randomized, double-masked, placebo-controlled study evaluating the effects of the protein kinase C-beta inhibitor ruboxistaurin on skin microvascular blood flow and other measures of diabetic peripheral neuropathy

OBJECTIVE

Diabetes leads to protein kinase C (PKC)-beta overactivation and microvascular dysfunction, possibly resulting in disordered skin microvascular blood flow (SkBF) and other changes observed in diabetic peripheral neuropathy (DPN) patients. We investigate the effects of the isoform-selective PKC-beta inhibitor ruboxistaurin mesylate on neurovascular function and other measures of DPN.

RESEARCH DESIGN AND METHODS

Endothelium-dependent and C fiber-mediated SkBF, sensory symptoms, neurological deficits, nerve fiber morphometry, quantitative sensory and autonomic function testing, nerve conduction studies, quality of life (using the Norfolk Quality-of-Life Questionnaire for Diabetic Neuropathy [QOL-DN]), and adverse events were evaluated for 20 placebo- and 20 ruboxistaurin-treated (32 mg/day) DPN patients (aged > or =18 years; with type 1 or type 2 diabetes and A1C < or =11%) during a randomized, double-masked, single-site, 6-month study.

RESULTS

Endothelium-dependent (+78.2%, P < 0.03) and C fiber-mediated (+56.4%, P < 0.03) SkBF at the distal calf increased from baseline to end point. Significant improvements from baseline within the ruboxistaurin group were also observed for the Neuropathy Total Symptom Score-6 (NTSS-6) (3 months -48.3%, P = 0.01; end point -66.0%, P < 0.0006) and the Norfolk QOL-DN symptom subscore and total score (end point -41.2%, P = 0.01, and -41.0, P = 0.04, respectively). Between-group differences in baseline-to-end point change were observed for NTSS-6 total score (placebo -13.1%; ruboxistaurin -66.0%, P < 0.03) and the Norfolk QOL-DN symptom subscore (placebo -4.0%; ruboxistaurin -41.2%, P = 0.041). No significant ruboxistaurin effects were demonstrated for the remaining efficacy measures. Adverse events were consistent with those observed in previous ruboxistaurin studies.

CONCLUSIONS

In this cohort of DPN patients, ruboxistaurin enhanced SkBF at the distal calf, reduced sensory symptoms (NTSS-6), improved measures of Norfolk QOL-DN, and was well tolerated.

Cardiopulmonary Rehabilitation and Cancer Rehabilitation. 3. Cancer Rehabilitation

This self-directed learning module highlights the treatment and rehabilitation of patients with cancer. It is part of the study guide on cardiac, pulmonary, and cancer rehabilitation in the Self-Directed Physiatric Education Program for practitioners and trainees in physical medicine and rehabilitation. This article reviews medical and rehabilitation issues in patients with various types of cancer. Cases were selected to allow discussion of problems seen in both younger and older patient populations. Identification of common sequelae of cancer and cancer treatments, associated rehabilitation challenges, and appropriate interventions are included.

OVERALL ARTICLE OBJECTIVE

To summarize the medical and rehabilitation issues in patients with various types of cancer.

Small-Fiber Neuropathy Associated with Capecitabine (Xeloda)-induced Hand-foot Syndrome: A Case Report

Hand-foot syndrome commonly results from treatment with capecitabine and is associated with pain, dysesthesias, paresthesias, and temperature intolerance. The cause of these symptoms in hand-foot syndrome has not been determined. We present the clinical, electrophysiologic, and biopsy data from a patient with capecitabine-induced hand-foot syndrome as supporting evidence implicating small-fiber neuropathy as the cause of these neuropathic symptoms. A patient with stage 4 breast cancer who develops capecitabine-induced hand-foot syndrome is referred for clinical and electrophysiologic testing. Intraepidermal nerve fiber density is assessed. Clinical evaluation demonstrates markedly decreased pain and temperature sensation with preserved strength, proprioception, and light touch. Standard electrodiagnostic testing is normal. The assessment of epidermal nerve fiber density demonstrates marked small-fiber loss both proximally and distally. In conclusion, small-fiber neuropathy is a likely cause of the neuropathic symptoms encountered in capecitabine-induced hand-foot syndrome. Similar clinical, electrophysiologic, and pathologic assessments are needed to confirm this finding in larger populations.

Small fibre neuropathies

PURPOSE OF REVIEW

To summarize the recent advances in aetiology, diagnostic assessment, and treatment of small fibre neuropathies.

RECENT FINDINGS

New causes of small fibre neuropathy have been recognized and advances in neurophysiologic and neuropathologic techniques for investigating small fibres have been made, increasing the interest in this field. In particular, skin biopsy proved to be a sensitive method to diagnose small fibre neuropathy. It allows the detection of subclinical abnormalities of peripheral nerve function in patients with diabetes and tongue denervation in patients with burning mouth syndrome. This technique has also been used to demonstrate the neuroprotective effect of erythropoietin in experimental models of neuropathy. Among nonconventional neurophysiologic techniques for investigating small fibres, laser-evoked potential and contact heat-evoked potential stimulators have been developed and deserve particular interest. Several trials on neuropathic pain that is a typical feature of small fibre neuropathies have been performed and guidelines have recently been published.

SUMMARY

Detection of small fibre impairment allows earlier diagnosis of neuropathy and could be used as an outcome measure in future regenerative neuropathy trials. Standardization of skin biopsy can have an important impact on clinical practice and research. Further studies are needed to assess the reliability of current neurophysiologic techniques for testing small fibre function in peripheral neuropathies and the correlation with well established neuropathologic examination.

Treatment of painful polyneuropathies

The treatment of painful polyneuropathies has begun to improve over the past several years. This is based on an evolving understanding of the pathogenesis related to the development of diabetic neuropathy and other diseases that may lead to peripheral nerve injury. Consensus on evaluation strategies for patients presenting with pain has furthered our ability to define neuropathic pain and accompanying signs and symptoms that may respond to particular therapeutic approaches. Recent therapeutic advances in medical management have demonstrated improved outcomes in pain relief. This, along with lower side effect-related issues, has led to improved compliance and patient satisfaction. The assessment and treatment of comorbid conditions, which include sleep, anxiety, and depression, have further advanced the management of painful polyneuropathies in patients. New antiepileptics, antidepressants, and topical therapies have contributed to improved patient outcomes.

Small fiber neuropathy: a common and important clinical disorder

Small fiber neuropathy (SFN) is a neuropathy selectively involving small diameter myelinated and unmyelinated nerve fibers. Interest in this disorder has considerably increased during the past few years. It is often idiopathic and typically presents with peripheral pain and/or symptoms of autonomic dysfunction. Diagnosis is made on the basis of the clinical features, normal nerve conduction studies (NCS) and abnormal specialized tests of small nerve fibers. Among others, these tests include assessment of epidermal nerve fiber density, temperature sensation tests for sensory fibers and sudomotor and cardiovagal testing (QSART) for autonomic fibers. Unless an underlying disease is identified, treatment is usually symptomatic and directed towards alleviation of neuropathic pain.