Experimental model of alcohol-related peripheral neuropathy

Alcoholic neuropathy associated with chronic alcohol intake

Alcoholic neuropathy (AN), a debilitating condition that mainly affects chronic alcohol drinkers, is thought to cause lesions in the peripheral nervous system leading to sensory, autonomic, and motor dysfunctions. Despite many studies, the pathogenesis of these lesions is still not completely understood. We investigated few aspects on the development of alcohol-induced peripheral neuropathy, by assessing sensory, motor and autonomic functions, as well as stereological analysis of axonal fibers and myelin sheath of the sciatic nerve. Twelve male Wistar rats were divided into Control group and Alcohol group that was submitted to Two Bottle-Choice Paradigm of intermittent and voluntary alcohol solution intake (20%; v/v) during eight weeks. At the end of treatment, three different sensorium-motor tests were applied - Tactile Sensitivity, Thermal Sensitivity, and Functional Observational Battery (FOB). Quantitative morphometric analysis of sciatic nerve structures was performed by stereological method. Alcohol concentration in the blood was measured to analyze possible correlation between availability of alcohol in the blood and the magnitude of the peripheral nerve lesion. Our data showed a peripheral effect of chronic alcohol intake associated with hyperalgesia and a process of demyelination with a strong correlation with alcohol consumption. This process was associated with increased tactile sensitivity, with behavioral reflexes such as locomotor hyperactivity, changes in gait and balance, and autonomic reflexes such as piloerection.

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Alcoholic neuropathy and its consequences.

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Neuropathy and sensitive and motor alterations.

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Alcoholic neuropathy and thinner myelin sheath thickness.

Characterization and quantification of alcohol-related polyneuropathy by magnetic resonance neurography

BACKGROUND

We characterized and quantified peripheral nerve damage in alcohol-dependent patients (ADP) by magnetic resonance neurography (MRN) in correlation with clinical and electrophysiologic findings.

METHODS

Thirty-one adult patients with a history of excessive alcohol consumption and age-/sex-matched healthy controls were prospectively examined. After detailed neurologic and electrophysiologic testing, the patient group was subdivided into ADP with alcohol-related polyneuropathy (ALN) and without ALN (Non-ALN). 3T MRN with anatomical coverage from the proximal thigh down to the tibiotalar joint was performed using dual-echo 2-dimensional relaxometry sequences with spectral fat saturation. Detailed quantification of nerve injury by morphometric (cross-sectional area [CSA]) and microstructural MRN markers (proton spin density [ρ], apparent T2-relaxation-time [T2_app ]) was conducted in all study participants.

RESULTS

MRN detected nerve damage in ADP with and without ALN. A proximal-to-distal gradient was identified for nerve T2-weighted (T2w)-signal and T2_app in ADP, indicating a proximal predominance of nerve lesions. While all MRN markers differentiated significantly between ADP and controls, microstructural markers were able to additionally differentiate between subgroups: tibial nerve ρ at thigh level was increased in ALN (p < 0.0001) and in Non-ALN (p = 0.0052) versus controls, and T2_app was higher in ALN versus controls (p < 0.0001) and also in ALN versus Non-ALN (p = 0.0214). T2w-signal and CSA were only higher in ALN versus controls.

CONCLUSIONS

MRN detects and quantifies peripheral nerve damage in ADP in vivo even in the absence of clinically overt ALN. Microstructural markers (T2_app , ρ) are most suitable for differentiating between ADP with and without manifest ALN, and may help to elucidate the underlying pathomechanism in ALN.

Comparative Pathology of the Peripheral Nervous System

The peripheral nervous system (PNS) relays messages between the central nervous system (brain and spinal cord) and the body. Despite this critical role and widespread distribution, the PNS is often overlooked when investigating disease in diagnostic and experimental pathology. This review highlights key features of neuroanatomy and physiology of the somatic and autonomic PNS, and appropriate PNS sampling and processing techniques. The review considers major classes of PNS lesions including neuronopathy, axonopathy, and myelinopathy, and major categories of PNS disease including toxic, metabolic, and paraneoplastic neuropathies; infectious and inflammatory diseases; and neoplasms. This review describes a broad range of common PNS lesions and their diagnostic criteria and provides many useful references for pathologists who perform PNS evaluations as a regular or occasional task in their comparative pathology practice.

Peripheral Neuropathies Due to Vitamin and Mineral Deficiencies, Toxins, and Medications

PURPOSE OF REVIEW

Vitamin and mineral deficiencies, neurotoxins, and, particularly, prescription medications, are some of the most common causes of peripheral neuropathy. Recognition and prompt treatment of these neuropathies require a high index of suspicion and an accompanied detailed history. This article provides a comprehensive approach and list of items that must be considered in the setting of new-onset neuropathy.

RECENT FINDINGS

Although many of the neuropathies described in this article have decreased in prevalence in developed countries because of public health interventions and occupational/environmental regulations, new causes for this class of neuropathy continue to be uncovered.

SUMMARY

The peripheral nervous system is susceptible to a broad array of metabolic and toxic abnormalities, which most often lead to a length-dependent sensory-predominant axonal peripheral neuropathy. A careful history accompanied by recognition of multisystem clues can increase recognition of these neuropathies, which is important as many have specific treatments that may either improve the neuropathy or halt its progression.

Toxin-Induced Neuropathies

Peripheral neuropathies secondary to neurotoxicants are frequently considered but can be difficult to diagnose. Accurate diagnosis is important to avoid unnecessary testing, prevent further exposure, and initiate treatment when available. This article reviews key features of some of the more common or representative toxic neuropathies, including those caused by occupational and environmental exposure, medications, and chemotherapeutic agents.

Cholecalciferol in ethanol-preferring rats muscle fibers increases the number and area of type II fibers

The chronic use of ethanol causes neuropathy and atrophy of type II fibers and promotes vitamin D decrease. This study evaluated cholecalciferol effects on the deep fibular nerve and extensor digitorum longus (EDL) muscle using an UChB ethanol-preferring rats model. Blood analyses were carried out to measure levels of 25-hydroxycholecalciferol (25(OH)D), calcium (Ca²⁺), Phosphorus (P), and parathyroid hormone (PTH). It was used EDL muscle to evaluate oxidative stress. The deep fibular nerve and EDL muscle were used for morphologic and morphometric assessment. 25(OH)D plasma levels were higher in the supplemented group and no alterations were observed in other parameters including the oxidative stress evaluation. The G ratio remained constant which indicates nervous conduction normality. Cholecalciferol supplementation promoted an increase in the number and area of type II fibers and a decrease in the area of type I fibers. In the studied model, there was neither alcoholic myopathy nor neuropathy. The EDL muscle glycolytic patterns in the high-drinker UChB rats may be associated with the differential effects of cholecalciferol on metabolism and protein synthesis in skeletal muscle.

Alcoholism and sexual dimorphism in the middle longitudinal fascicle: a pilot study

Alcoholism can lead to a complex mixture of cognitive and emotional deficits associated with abnormalities in fronto-cortico-striatal-limbic brain circuitries. Given the broad variety of neurobehavioral symptoms, one would also expect alterations of postrolandic neocortical systems. Thus, we used diffusion tensor imaging (DTI) to study the integrity of the middle longitudinal fascicle (MdLF), a major postrolandic association white matter tract that extends from the superior temporal gyrus to the parietal and occipital lobes, in individuals with a history of chronic alcohol abuse. DTI data were acquired on a 3 Tesla scanner in 30 abstinent alcoholics (AL; 9 men) and 25 nonalcoholic controls (NC; 8 men). The MdLF was determined using DTI-based tractography. Volume of the tract, fractional anisotropy (FA), radial (RD), and axial (AD) diffusivity, were compared between AL and NC, with sex and hemispheric laterality as independent variables. The association of DTI measures with neuropsychological performance was evaluated. Men showed bilateral reduction of MdLF volume and abnormal diffusion measurements of the left MdLF. Analyses also indicated that the left MdLF diffusion measurements in AL men were negatively associated with Verbal IQ and verbal fluency test scores. Abstinent alcoholic men display macrostructural abnormalities in the MdLF bilaterally, indicating an overall white matter deficit. Additionally, microstructural deficits of the left MdLF suggest more specific alterations associated with verbal skills in men.

Evaluation of Peripheral Neuropathy of Unknown Origin in an Outpatient Foot and Ankle Practice

BACKGROUND

The foot and ankle surgeon can see peripheral neuropathy in the treatment of foot and ankle conditions. The purpose of this study was (1) to evaluate the demographics and presenting complaints of patients diagnosed with idiopathic peripheral neuropathy during an examination by a foot and ankle surgeon and (2) to identify the type and frequency of subsequent diagnosis of medical causes of neuropathy.

METHODS

This was a retrospective study of patients diagnosed with idiopathic peripheral neuropathy in our practice between January 1997 and December 2008. Ninety-five patients were identified, and demographic data, presenting complaints, and medical comorbidities were extracted from the medical record. Examination findings of decreased sensation to Semmes Weinstein 5.07 monofilament testing were documented, and electromyogram and nerve conduction study results were reviewed when available. Laboratory values were noted, as were neurologic evaluations performed to diagnose medical conditions associated with peripheral neuropathy.

RESULTS

The most common presentation was foot pain, in 36 patients (38%). Ninety-one patients had Semmes Weinstein 5.07 monofilament testing, with loss of protective sensation reported in 75 of the 91 tested (82%). Only 30 of the 95 patients had electromyogram and nerve conduction study results available, with a test positive for peripheral neuropathy in 20 of the 30 tested. Thirty-two patients were evaluated by a neurologist. A specific cause was identified in 12 of the 32 seen by a neurologist. Of the total group of 95 patients, 31 patients (33%) were diagnosed with a condition that may be associated with peripheral neuropathy.

CONCLUSIONS

Thirty-three percent of the patients presenting to our clinic and given a diagnosis of idiopathic peripheral neuropathy were ultimately diagnosed with a medical cause of neuropathy-most commonly, diabetes. For those patients with idiopathic neuropathy, a spectrum of disease was encountered, including pain, ulcer, infection, and Charcot neuroarthropathy.

LEVEL OF EVIDENCE

Level IV, retrospective case series.

Peripheral neuropathy due to vitamin deficiency, toxins, and medications

PURPOSE OF REVIEW

Peripheral neuropathies secondary to vitamin deficiencies, medications, or toxins are frequently considered but can be difficult to definitively diagnose. Accurate diagnosis is important since these conditions are often treatable and preventable. This article reviews the key features of different types of neuropathies caused by these etiologies and provides a comprehensive list of specific agents that must be kept in mind.

RECENT FINDINGS

While most agents that cause peripheral neuropathy have been known for years, newly developed medications that cause peripheral neuropathy are discussed.

SUMMARY

Peripheral nerves are susceptible to damage by a wide array of toxins, medications, and vitamin deficiencies. It is important to consider these etiologies when approaching patients with a variety of neuropathic presentations; additionally, etiologic clues may be provided by other systemic symptoms. While length-dependent sensorimotor axonal peripheral neuropathy is the most common presentation, several examples present in a subacute severe fashion, mimicking Guillain-Barré syndrome.

Small-fiber degeneration in alcohol-related peripheral neuropathy

BACKGROUND

Alcohol-related peripheral neuropathy (ALN) is generally characterized as an axonal large-fiber polyneuropathy caused by thiamine deficiency. We hypothesized, based on clinical observations, that ALN is associated with a small-fiber polyneuropathy that can be diagnosed with skin biopsy in heavy alcohol drinking subjects with normal thiamine status.

METHODS

Eighteen individuals (9 heavy alcohol drinking subjects and 9 healthy control subjects) were assessed for the potential utility of skin biopsies in detecting ALN-associated small nerve fiber degeneration. Heavy drinking was defined as greater than 4 drinks/d and 5 drinks/d in women and men, respectively, as determined by the Timeline Follow-Back and lifetime drinking history. All subjects underwent neurological examination, nerve conduction studies, and skin biopsies to quantify end nerve fiber densities (ENFD). Other causes of neuropathy were excluded and thiamine status was assessed.

RESULTS

Average ENFD were significantly decreased at the calf in the alcohol group as compared with control group (p < 0.0001). Histological sections demonstrated striking attrition and architectural simplification of intraepidermal nerve fibers in the heavy alcohol drinking subjects. There were no significant intergroup differences with respect to clinical assessments of neuropathy or thiamine status.

CONCLUSIONS

ALN is associated with a small-fiber neuropathy that can be detected with skin biopsy in heavy alcohol drinking individuals with normal thiamine status. Skin biopsy is a useful, minimally invasive biomarker that could extend studies to understand the effect of alcohol on the peripheral nerves and to evaluate potential therapeutic agents in larger clinical trials.