Toxic neuropathies associated with pharmaceutic and industrial agents

Peripheral Neuropathy Secondary to Ertapenem Administration for Treatment of Infectious Endocarditis

Ertapenem is a widely used broad-spectrum carbapenem antibiotic active against most species of gram-negative and gram-positive aerobes and anaerobes with specific targeting of the Amp C extended-spectrum beta-lactamases. It is advantageous for its once-daily dosing via IM or IV administration and minimal side effect profile for the treatment of community-acquired infections. We report an 80-year-old man presenting with reversible peripheral neuropathy following the administration and subsequent discontinuation of ertapenem for the treatment of acute infectious endocarditis. It is especially notable that our patient had less severe (i.e., stage 3) chronic kidney disease as opposed to current literature which only presents similar findings with more advanced kidney disease (stage 4-5). Upon cessation of ertapenem administration, our patient recovered to his baseline motor and sensory status over a period of four days. We believe there to be value in reporting this case, as well as value in reevaluating the current recommendations for ertapenem dosing in those with kidney compromise.

The Future of Neurotoxicology: A Neuroelectrophysiological Viewpoint

Neuroelectrophysiology is an old science, dating to the 18th century when electrical activity in nerves was discovered. Such discoveries have led to a variety of neurophysiological techniques, ranging from basic neuroscience to clinical applications. These clinical applications allow assessment of complex neurological functions such as (but not limited to) sensory perception (vision, hearing, somatosensory function), and muscle function. The ability to use similar techniques in both humans and animal models increases the ability to perform mechanistic research to investigate neurological problems. Good animal to human homology of many neurophysiological systems facilitates interpretation of data to provide cause-effect linkages to epidemiological findings. Mechanistic cellular research to screen for toxicity often includes gaps between cellular and whole animal/person neurophysiological changes, preventing understanding of the complete function of the nervous system. Building Adverse Outcome Pathways (AOPs) will allow us to begin to identify brain regions, timelines, neurotransmitters, etc. that may be Key Events (KE) in the Adverse Outcomes (AO). This requires an integrated strategy, from in vitro to in vivo (and hypothesis generation, testing, revision). Scientists need to determine intermediate levels of nervous system organization that are related to an AO and work both upstream and downstream using mechanistic approaches. Possibly more than any other organ, the brain will require networks of pathways/AOPs to allow sufficient predictive accuracy. Advancements in neurobiological techniques should be incorporated into these AOP-base neurotoxicological assessments, including interactions between many regions of the brain simultaneously. Coupled with advancements in optogenetic manipulation, complex functions of the nervous system (such as acquisition, attention, sensory perception, etc.) can be examined in real time. The integration of neurophysiological changes with changes in gene/protein expression can begin to provide the mechanistic underpinnings for biological changes. Establishment of linkages between changes in cellular physiology and those at the level of the AO will allow construction of biological pathways (AOPs) and allow development of higher throughput assays to test for changes to critical physiological circuits. To allow mechanistic/predictive toxicology of the nervous system to be protective of human populations, neuroelectrophysiology has a critical role in our future.

Essential References for Structural Analysis of the Peripheral Nervous System for Pathologists and Toxicologists

Toxicologic neuropathology for the peripheral nervous system (PNS) is a vital but often underappreciated element of basic translational research and safety assessment. Evaluation of the PNS may be complicated by unfamiliarity with normal nerve and ganglion biology, which differs to some degree among species; the presence of confounding artifacts related to suboptimal sampling and processing; and limited experience with differentiating such artifacts from genuine disease manifestations and incidental background changes. This compilation of key PNS neurobiology, neuropathology, and neurotoxicology references is designed to allow pathologists and toxicologists to readily access essential information that is needed to enhance their proficiency in evaluating and interpreting toxic changes in PNS tissues from many species.

Neurological and Psychiatric Adverse Effects of Antimicrobials

Antimicrobials are a widely used class of medications, but several of them are associated with neurological and psychiatric side effects. The exact incidence of neurotoxicity with anti-infectives is unknown, although it is estimated to be < 1%. Neurotoxicity occurs with all classes of antimicrobials, such as antibiotics, antimycobacterials, antivirals, antifungals and antiretrovirals, with side effects ranging from headaches, anxiety and depression to confusion, delirium, psychosis, mania and seizures, among others. It is important to consider these possible side effects to prevent misdiagnosis or delayed treatment as drug withdrawal can be associated with reversibility in most cases. This article highlights the different neurotoxic effects of a range of antimicrobials, discusses proposed mechanisms of onset and offers general management recommendations. The effects of antibiotics on the gut microbiome and how they may ultimately affect cognition is also briefly examined.

Post-9/11 Peripheral Neuropathy Symptoms among World Trade Center-Exposed Firefighters and Emergency Medical Service Workers

Peripheral neuropathy can result from numerous conditions including metabolic disorders, inflammatory disease, or exposure to environmental or biological toxins. We analyzed questionnaire data from 9239 Fire Department of the City of New York (FDNY) World Trade Center (WTC)-exposed firefighters and emergency medical service workers (EMS) to evaluate the association between work at the WTC site and subsequent peripheral neuropathy symptoms using the validated Diabetic Neuropathy Symptom (DNS) score. We grouped the population into an "Indicated" group with conditions known to be associated with paresthesia (N = 2059) and a "Non-Indicated" group without conditions known to be associated (N = 7180). The level of WTC exposure was categorized by time of arrival to the WTC. Overall, 25% of workers aged 40 and older reported peripheral neuropathy symptoms: 30.6% in the Indicated and 23.8% in the Non-Indicated groups, respectively. Multivariable logistic models performed on the Non-Indicated group, and on the Non-Indicated in comparison with non-WTC exposed National Health and Nutrition Examination Survey (NHANES), found that the highest level of WTC-exposure was significantly associated with DNS positive outcomes, after controlling for potential confounders. In conclusion, this study suggests that symptoms of peripheral neuropathy and paresthesias are common and are associated with WTC-exposure intensity.

Emergency Neurological Life Support: Acute Non-traumatic Weakness

Acute non-traumatic weakness may be life-threatening if it involves the respiratory muscles and/or is associated with autonomic dysfunction. Most patients presenting with acute muscle weakness have a worsening neurological disorder that requires a rapid, systematic evaluation and detailed neurological exam to localize the disorder. Urgent laboratory tests and neuroimaging are needed to confirm the diagnosis. Because acute weakness is a common presenting sign of neurological emergencies, it was chosen as an Emergency Neurological Life Support protocol. Causes of acute non-traumatic weakness are discussed here by both presenting clinical signs and anatomical location. For each diagnosis, key features of the history, examination, investigations, and treatment are outlined in the included tables or in the "Appendix".

Clinical description of toxic neuropathies

Toxic neuropathy, although rare, is an important consideration in the setting of a known or suspected toxic exposure in the workplace or other environment. This chapter discusses the clinical and electrodiagnostic evaluation of peripheral neuropathies, highlighting findings that direct further workup and may point to specific toxins as etiology. The difficulty of establishing causality of a toxin in relation to peripheral neuropathy is discussed; guidelines for establishing causality are presented. Examples of common industrial toxins are listed, including their typical industrial uses and their mechanisms of action in producing neuropathy. Characteristic clinical presentations of specific toxic neuropathies are highlighted with selected case studies.

Unusual case of relapsing and remitting rash with progressive motor sensory neuropathy and spinal cord atrophy

The authors report a case of a 7-year-old girl with a progressive sensorimotor peripheral neuropathy with acute relapses associated with a desquamating purpuric rash, alopecia, and spinal cord atrophy. Distinctive features include systemic involvement with alopecia and rash, peripheral nervous system involvement with relapsing and remitting sensorimotor neuropathy, and central nervous system involvement with episodes of dystonic posturing and spinal cord atrophy. Extensive diagnostic evaluation for known causes of skin manifestations associated with peripheral neuropathy has failed to identify a cause for this patient's condition. The authors discuss the case as an approach to the differential diagnosis and to highlight unusual features of this yet to be identified clinical entity.

The effects of anesthesia on measures of nerve conduction velocity in male C57Bl6/J mice

Animal models, particularly mice, are used extensively to investigate neurological diseases. Basic research regarding animal models of human neurological disease requires that the animals exhibit hall mark characteristics of the disease. These include disease specific anatomical, metabolic and behavioral changes. Nerve conduction velocity (NCV) is the predominant method used to assess peripheral nerve health. Normative data adjusted for age, gender and height is available for human patients; however, these data are not available for most rodents including mice. NCV may be affected by animal age and size, body temperature, stimulus strength and anesthesia. While the effects of temperature, age and size are documented, the direct and indirect effects of anesthesia on NCV are not well reported. Our laboratory is primarily concerned with animal models of diabetic neuropathy (DN) and uses NCV to confirm the presence of neuropathy. To ensure that subtle changes in NCV are reliably assayed and not directly or indirectly affected by anesthesia, we compared the effects of 4 commonly used anesthetics, isoflurane, ketamine/xylazine, sodium pentobarbital and 2-2-2 tribromoethanol on NCV in a commonly used rodent model, the C57Bl6/J mouse. Our results indicate that of the anesthetics tested, isoflurane has minimal impact on NCV and is the safest, most effective method of anesthesia. Our data strongly suggest that isoflurane should become the anesthetic of choice when performing NCV on murine models of neurological disease.

Peripheral neuropathy in patients with primary antiphospholipid (Hughes') syndrome

The involvement of the peripheral nervous system in diverse autoimmune diseases is well established. However, no appropriately designed studies have been performed in primary antiphospholipid syndrome (PAPS)-related peripheral neuropathy. We aimed to investigate the occurrence of peripheral neuropathy in patients diagnosed with PAPS. Twenty-six consecutive patients with PAPS (Sapporo criteria) and 20 age- and gender-matched healthy controls were enrolled at two referral centers. Exclusion criteria were secondary causes of peripheral neuropathy. A complete clinical neurologic exam followed by nerve conduction studies (NCS) was performed. Paresthesias were reported in eight patients (31%). Objective mild distal weakness and abnormal symmetric deep tendon reflexes were observed in three patients (11.5%). With regard to the electrophysiologic evidence of peripheral neuropathy, nine patients (35.0%) had alterations: four (15.5%) had pure sensory or sensorimotor distal axonal neuropathy (in two of them a carpal tunnel syndrome was also present) and one (4%) had sensorimotor demyelinating and axonal neuropathy involving upper and lower extremities, while four patients (15.5%) showed isolated carpal tunnel syndrome. Clinical and serologic results were similar in all the patients with PAPS, regardless of the presence of electrophysiologic alterations. In conclusion, peripheral neuropathy is a common asymptomatic abnormality in patients with PAPS. The routine performance of NCS may be considered when evaluating such patients.

Not all neuropathy in diabetes is of diabetic etiology: differential diagnosis of diabetic neuropathy

Diabetic peripheral neuropathy is the most common peripheral neuropathy in the developed world; however, not all patients with diabetes and peripheral nerve disease have a peripheral neuropathy caused by diabetes. Several (although not all) studies have drawn attention to the presence of other potential causes of a neuropathy in individuals with diabetes; 10% to 50% of individuals with diabetes may have an additional potential cause of a peripheral neuropathy and some may have more than one cause. Neurotoxic medications, alcohol abuse, vitamin B(12) deficiency, renal disease, chronic inflammatory demyelinating neuropathy, inherited neuropathy, and vasculitis are the most common additional potential causes of a peripheral neuropathy in these series. The most common disorders in the differential diagnosis of a generalized diabetic peripheral neuropathy are discussed in this article. Prospective studies to investigate the prevalence of other disorders that might be responsible for a peripheral neuropathy in individuals with diabetes are warranted.

Arsenic trioxide associated toothache

Arsenic trioxide in the treatment of acute promyelocytic leukaemia is relatively safe with minimal side effects. Dental toxicities associated with its use are uncommon. We describe the first case report of toothache associated with arsenic trioxide. A 45-year-old male with relapsed APL was commenced on a treatment schedule of all-trans-retinoic acid 20mg four times a day for 14 days concurrent with a 10mg intravenous infusion of arsenic trioxide for 28 days. After 14 doses of the 6th cycle of treatment he experienced severe acute pain in various parts of the oral cavity. Extensive examination including an orthodontic review concluded there was no indication that the pain symptoms were due to a dental or endodontic cause. Four days after completing his 6th cycle the pain completely resolved. The mechanism of this adverse event remains unclear. Physicians with patients receiving arsenic trioxide with unexplained toothache should consider the arsenic as the cause of the pain.

Pedal neuroarthropathy in a nondiabetic patient as a result of long-term amiodarone use

In this article, we describe a case of a man without diabetes with a long history of amiodarone use. He presented with a foot deformity and plantar ulceration. Examination showed him to have a symmetrical peripheral neuropathy and findings consistent with a Charcot foot. Extensive investigations failed to find other causes for his neuropathy, other than his amiodarone use. We believe that this is the first reported case of a neuropathic foot deformity and ulceration occurring with amiodarone use, and we feel that it is important to point out the association of this commonly used antiarrythmic drug with this form of neuropathic osteoarthropathy.

LEVEL OF CLINICAL EVIDENCE

4.