Follow up of patients with signs and symptoms of polyneuropathy not confirmed by electrophysiological studies

A test of the adaptive network explanation of functional disorders using a machine learning analysis of symptoms

The classification and etiology of functional disorders is controversial. Evidence supports both psychological and biological (disease) models that show, respectively, that functional disorders should be classified as one (bodily distress syndrome) and many (e.g., irritable bowel syndrome (IBS), fibromyalgia syndrome (FMS), and chronic fatigue syndrome (CFS)). Two network models (symptom network and adaptive network) can explain the specificity and covariation of symptomatology, but only the adaptive network model can explain the covariation of the somatic symptoms of functional disorders. The adaptive network model is based on the premise that a network of biological mechanisms has emergent properties and can exhibit adaptation. The purpose of this study was to test the predictions that symptom similarity increases with pathology and that network connection strengths vary with pathology, as this would be consistent with the notion that functional disorder pathology arises from network adaptation. We conducted a symptom internet survey followed by machine learning analysis. Participants were 1751 people reporting IBS, FMS or CFS diagnosis who completed a 61-item symptom questionnaire. Eleven symptom clusters were identified. Differences in symptom clusters between IBS, FMS and CFS groups decreased as overall symptom frequency increased. The strength of outgoing connections between clusters varied as a function of symptom frequency and single versus multiple diagnoses. The findings suggest that the pathology of functional disorders involves an increase in the activity and causal connections between several symptom causing mechanisms. The data provide support for the proposal that the body is capable of complex adaptation and that functional disorders result when rules that normally improve adaptation create maladaptive change.

Do all neuropathy patients need an EMG at least once?

EMG, which consists of nerve conduction studies and needle electromyography, is an essential diagnostic tool in the evaluation of patients with suspected peripheral neuropathy. Many neurologists order an EMG for all patients with suspected peripheral neuropathy. Not surprisingly, evidence now exists that shows EMG is a major driver of health care costs associated with neuropathy diagnoses. As neurologic practice evolves from fee for service to value-based compensation, neurologists will need to justify the diagnostic utility of EMG (outcome) relative to its cost. While carefully performed studies of diagnostic utility in many patient populations are lacking, a robust literature provides guidance regarding the potential role and limitations of EMG in neuropathy diagnosis as well as the pitfalls referring providers and electrodiagnostic consultants must consider. Do all neuropathy patients need an EMG at least once? This article attempts to answer this question using an illustrative case to highlight critical factors every neurologist must consider before ordering an EMG for neuropathy diagnosis.

HIV treatment and associated mitochondrial pathology: review of 25 years of in vitro, animal, and human studies

Antiretroviral therapy has dramatically reduced mortality in human immunodeficiency virus (HIV) infection. In 1988, the suggestion that the first antiretroviral drug, zidovudine, was the potential cause of muscle pathology in HIV-infected persons resulted in structural and biochemical patient studies demonstrating acquired mitochondrial dysfunction. Assessment of subsequent nucleoside analog reverse transcriptase inhibitor (NRTI) antiretroviral drugs has indicated that mitochondria are a common target of NRTI toxicity in multiple tissues, leading to a wide variety of pathology ranging from lipodystrophy to neuropathy. Overwhelmingly, these complications have emerged during post-licensing human studies. Subsequent animal and in vitro studies have then elucidated the potential pathological mechanisms, suggesting that NRTI-associated mitochondrial toxicity arises principally from inhibition of the sole mitochondrial DNA (mtDNA) polymerase gamma, leading to a reduction in mtDNA content (depletion). Millions of patients have been treated with mitochondrially toxic NRTIs and these drugs remain the backbone of antiretroviral rollout in much of sub-Saharan Africa. Here we describe the 25-year history of antiretroviral associated mitochondrial pathology and critically review the strength of evidence linking clinical, histopathological, and molecular data. We discuss recently described novel mechanisms of NRTI-associated mitochondrial damage and whether or not recently licensed NRTIs may be considered free from mitochondrial toxicity.

Feasibility and cost efficiency of a diagnostic guideline for chronic polyneuropathy: a prospective implementation study

BACKGROUND

Extensive investigations are often performed to reveal the cause of chronic polyneuropathy. It is not known whether a restrictive diagnostic guideline improves cost efficiency without loss of diagnostic reliability.

METHODS

In a prospective multicentre study, a comparison was made between the workup in patients with chronic polyneuropathy before and after guideline implementation.

RESULTS

Three hundred and ten patients were included: 173 before and 137 after guideline implementation. In all patients, the diagnosis would remain the same if the workup was limited to the investigations in the guideline. After guideline implementation, the time to reach a diagnosis decreased by two weeks. There was a reduction of 33% in the number and costs of routine laboratory investigations/patient, and a reduction of 27% in the total number of laboratory tests/patient, despite low guideline adherence.

CONCLUSION

The implementation of a diagnostic guideline for chronic polyneuropathy can reduce diagnostic delay and the number and costs of investigations for each patient without loss of diagnostic reliability. Continuous evaluation strategies after guideline implementation may improve guideline adherence and cost efficiency.