A Simplified Screening Protocol Predicts Pathological Electroneurographic Results in Patients with Suspected Polyneuropathy

Toward a Useful and Cost-Effective Workup in Chronic Polyneuropathy: The EXPRESS Study Protocol

BACKGROUND

Knowledge gaps exist about the usefulness and extent of blood tests and nerve conduction studies in the workup of polyneuropathy. We hypothesize that a limited workup improves costs spent on diagnostics without loss of diagnostic reliability or disadvantageous effect on treatment choice in many patients with a clinical diagnosis of chronic polyneuropathy. We aim to determine which investigations are necessary in the workup of patients with suspected chronic polyneuropathy clinically diagnosed by neurologists in an outpatient clinic and will perform an early health technology assessment.

METHODS

This is a prospective multicenter quality in healthcare evaluation. We compare two diagnostic strategies, both performed on all participants: the standard care by each patient's neurologist and the proposed (limited) workup by the study panel members consisting of neurologists with experience in neuromuscular diseases.

RESULTS

The primary outcome is the effectiveness of a limited workup expressed as concordance between the patient's neurologist diagnosis and the panel diagnosis. This will be related to differences in costs and impact on treatment or patient management otherwise. Other outcomes are burden/gain for the patient in terms of number of investigations, time to diagnosis, hospital visits, sick leave, loss of productivity, expenses, experienced quality of care.

CONCLUSION

This multicenter prospective observational study on quality in health care will provide improved evidence about the components of a cost-effective workup for patients with chronic polyneuropathy.

Investigation of Inter- and Intra-Day Variability of Tear Fluid Regarding Flow Rate, Protein Concentration as well as Protein Composition

Purpose

The purpose of this study was to present the determination of inter- and intra-day variations in tear flow rate, and tear fluid protein concentration, as well as protein composition regarding their impact for future biomarker studies.

Methods

Tear fluid was collected noninvasively from 18 healthy subjects by performing Schirmer tests at 4 different time points repetitive in a period of 2 days. The tear flow rate on the Schirmer test strips was measured. Proteins were extracted from strips and quantified using amino acid analysis. Protein composition was analyzed by the strips data-independent (DIA) based mass spectrometry. To exclude any impairments to health, volunteers underwent a detailed neurological as well as an ophthalmological examination.

Results

Whether tear fluid was collected from oculus sinister or oculus dexter did not affect the tear flow rate (P ≈ 0.63) or protein concentration (P ≈ 0.97) of individual subjects. Moreover, protein concentration was independent from the tear volume, so that a change in volume may only influence the total protein amount. When the examination days were compared, investigation of tear flow rate (P ≈ 0.001) and protein concentration (P ≈ 0.0003) indicated significant differences. Further, mass spectrometric analysis of tear fluid revealed 11 differentially regulated proteins when comparing both examination days.

Conclusions

Our findings provide evidence of inter-day variation in tear flow rate, tear proteome concentration, and composition in healthy subjects, suggesting that inter-day variation needs to be taken into consideration in biomarker research of tear fluid. Identified proteins were assigned to functions in the immune response, oxidative and reducing processes, as well as mannose metabolism.

Case-Control Study of Paresthesia Among World Trade Center-Exposed Community Members

OBJECTIVE

To investigate whether paresthesia of the lower extremities following exposure to the World Trade Center (WTC) disaster was associated with signs of neuropathy, metabolic abnormalities, or neurotoxin exposures.

METHODS

Case-control study comparing WTC-exposed paresthesia cases with "clinic controls" (WTC-exposed subjects without paresthesias), and "community controls" (WTC-unexposed persons).

RESULTS

Neurological histories and examination findings were significantly worse in cases than controls. Intraepidermal nerve fiber densities were below normal in 47% of cases and sural to radial sensory nerve amplitude ratios were less than 0.4 in 29.4%. Neurologic abnormalities were uncommon among WTC-unexposed community controls. Metabolic conditions and neurotoxin exposures did not differ among groups.

CONCLUSIONS

Paresthesias among WTC-exposed individuals were associated with signs of neuropathy, small and large fiber disease. The data support WTC-related exposures as risk factors for neuropathy, and do not support non-WTC etiologies.

Bilaterally prolonged latencies of pain-related evoked potentials in peripheral nerve injuries

OBJECTIVE

Cross-sectional study to test the applicability of pain-related evoked potentials (PREP) for the diagnosis of peripheral nerve injuries (PNI).

INTRODUCTION

Patients with generalized polyneuropathies show prolonged latencies and decreased amplitudes of PREP indicating an impairment of A-delta fibers. Although these fibers are frequently affected in PNI, it is unclear, if PREP-testing detects PNI comparable to Nerve Conduction Studies (NCS).

METHODS

23 patients with PNI of one upper limb underwent bilateral PREP-testing (using concentric surface electrodes) and NCS. 41 healthy controls underwent PREP-testing only. We determined pain thresholds, N1-latencies and N1P1-amplitudes of PREP and analyzed them for group and side-to-side differences. Small-fiber function was evaluated using thermal detection thresholds of Quantitative Sensory Testing (QST). N1-latencies above a cut-off calculated by ROC-analysis were defined as abnormal in order to compare detection rates of PREP and NCS.

RESULTS

Patients with PNI showed bilaterally prolonged N1-latencies (ipsilateral: 167.0 ± 40.7 ms vs. 141.2 ± 20.5 ms / contralateral: 160.0 ± 41.0 ms vs. 140.2 ± 23.9 ms) without a significant side-to-side difference. Pain thresholds were increased on the affected side only (4.6 ± 5.2 mA vs. 2.4 ± 1.4 mA (controls)). N1P1-amplitudes did not differ between patients and controls. 7 (32%) patients showed prolonged N1-latencies (>176 ms) of PREP. NCS were abnormal in 16 (73%) cases. 13 (59%) patients showed thermal hypoesthesia in QST.

CONCLUSION

Contrary to our expectations, we found bilaterally prolonged N1-latencies and normal N1P1-amplitudes in patients with PNI. Our findings support the hypothesis of a bilateral generation of PREP and indicate that PREP are not suitable for the diagnosis of PNI.