Gut microbiota depletion delays somatic peripheral nerve development and impairs neuromuscular junction maturation.

Gut microbiota is responsible for essential functions in human health. Several communication axes between gut microbiota and other organs via neural, endocrine, and immune pathways have been described, and perturbation of gut microbiota composition has been implicated in the onset and progression of an emerging number of diseases. Here, we analyzed peripheral nerves, dorsal root ganglia (DRG), and skeletal muscles of neonatal and young adult mice with the following gut microbiota status: a) germ-free (GF), b) gnotobiotic, selectively colonized with 12 specific gut bacterial strains (Oligo-Mouse-Microbiota, OMM12), or c) natural complex gut microbiota (CGM). Stereological and morphometric analyses revealed that the absence of gut microbiota impairs the development of somatic median nerves, resulting in smaller diameter and hypermyelinated axons, as well as in smaller unmyelinated fibers. Accordingly, DRG and sciatic nerve transcriptomic analyses highlighted a panel of differentially expressed developmental and myelination genes. Interestingly, the type III isoform of Neuregulin1 (NRG1), known to be a neuronal signal essential for Schwann cell myelination, was overexpressed in young adult GF mice, with consequent overexpression of the transcription factor Early Growth Response 2 (Egr2), a fundamental gene expressed by Schwann cells at the onset of myelination. Finally, GF status resulted in histologically atrophic skeletal muscles, impaired formation of neuromuscular junctions, and deregulated expression of related genes. In conclusion, we demonstrate for the first time a gut microbiota regulatory impact on proper development of the somatic peripheral nervous system and its functional connection to skeletal muscles, thus suggesting the existence of a novel 'Gut Microbiota-Peripheral Nervous System-axis.'

Tetanus and tetanus neurotoxin: From peripheral uptake to central nervous tissue targets.

Tetanus is a deadly but preventable disease caused by a protein neurotoxin produced by Clostridium tetani. Spores of C. tetani may contaminate a necrotic wound and germinate into a vegetative bacterium that releases a toxin, termed tetanus neurotoxin (TeNT). TeNT enters the general circulation, binds to peripheral motor neurons and sensory neurons, and is transported retroaxonally to the spinal cord. It then enters inhibitory interneurons and blocks the release of glycine or GABA causing a spastic paralysis. This review attempts to correlate the metalloprotease activity of TeNT and its trafficking and localization into the vertebrate body to the nature and sequence of appearance of the symptoms of tetanus.

Appropriately Selected Nerve in Suspected Leprous Neuropathy Yields High Positive Results for Mycobacterium leprae DNA by Polymerase Chain Reaction Method.

Identification of Mycobacterium leprae DNA by polymerase chain reaction (PCR) is a reliable and an affordable method to confirm leprosy. DNA from 87 nerve samples (61 from paraffin blocks and 26 fresh samples) was extracted. Mycobacterium leprae DNA was amplified by PCR from 80/87 (92%) specimens. Patients were seen over a period of 11 years (2007-2019), and leprosy was diagnosed based on clinical and characteristic histopathology findings. The clinical diagnostic possibilities were as follows: leprous neuropathy in 73/80 (91.3%), mononeuritis multiplex of unknown etiology in four (5.0%), vasculitic neuropathy in two (2.5%), and distal symmetric sensory motor neuropathy in one (1.3%). The biopsied nerves were as follows: superficial radial = 34 (42.6%), dorsal cutaneous branch of ulnar = 19 (23.8%), sural = 18 (22.5%), and superficial peroneal = 9 (11.3%), and corresponding neurological deficits were recorded in 77 (96.3%) cases. The histopathological diagnoses in total group were as follows: (borderline tuberculoid (BT) = 52, tuberculoid (TT) = 8, borderline lepromatous (BL) = 8, borderline borderline (BB) = 3, nonspecific inflammation = 3, healed/fibrosed = 4, and axonopathy = 2). Acid fast bacilli (AFB) was demonstrated in 11 (13.7%) samples. For comparison, 31 clinically and histopathologically defined non-leprous disease control nerves (inherited neuropathy = 20, vasculitis = 8, and nutritional neuropathy = 3) subjected to PCR were negative for M. leprae DNA. In most instances, there are multiple thickened peripheral nerves in suspected cases of leprosy, but neurological deficits pertaining to the thickened nerve are not as widespread. The current findings emphasize the importance of selecting the most appropriate nerve for biopsy to obtain a positive PCR result. We infer that clinical, histopathological, and PCR tests complement each other to help achieve a definitive diagnosis of leprosy particularly in pure neuritic leprosy and in leprous neuropathy with negative skin smears/biopsy.

Cryptococcal meningitis presenting as acute flaccid paralysis: A case report.

Cryptococcus is a cosmopolitan fungus with tropism for the nervous system and a higher prevalence of infection in immunosuppressed patients. Neurological compromise caused by this microorganism mainly debuts as a meningeal syndrome (headache, fever, neck stiffness) with predominant encephalic involvement. In this report we present the rare case of a non-HIV patient with flaccid paralysis and peripheral nerve involvement due to crytpococcal meningitis. This is a 53-years-old woman, with a past-medical history of diabetes, who presented with dysarthria, unilateral peripheral facial paralysis, asymmetric ascending quadriparesis, generalized hyporeflexia and urinary retention. Neuroimaging was initially reported as negative for vascular or demyelinating diseases. Electrophysiological studies were performed, and acute flaccid paralysis of undetermined etiology was defined as a temporal clinical diagnosis. Cerebrospinal fluid molecular analysis confirmed the presence of Cryptococcus neoformans var. gatti; posteriorly, antifungal treatment with amphotericin B and fluconazole was started. Polyneuroradiculopathy symptoms significantly improved over the in-hospital stay. In conclusion, spinal cord and peripheral nerve involvement by Cryptococcus is an infrequent cause of acute flaccid paralysis that should be considered in the differential diagnosis even in HIV-negative patients.

Myelination key factor krox­20 is downregulated in Schwann cells and murine sciatic nerves infected by Mycobacterium leprae

Schwann cells (SCs) critically maintain the plasticity of the peripheral nervous system. Peripheral nerve injuries and infections stimulate SCs in order to retrieve homeostasis in neural tissues. Previous studies indicate that Mycobacterium leprae (ML) regulates the expression of key factors related to SC identity, suggesting that alterations in cell phenotype may be involved in the pathogenesis of neural damage in leprosy. To better understand whether ML restricts the plasticity of peripheral nerves, the present study sought to determine the expression of Krox­20, Sox­10, c­Jun and p75NTR in SC culture and mice sciatic nerves, both infected by ML Thai­53 strain. Primary SC cultures were stimulated with two different multiplicities of infection (MOI 100:1; MOI 50:1) and assessed after 7 and 14 days. Sciatic nerves of nude mice (NU­Foxn1nu) infected with ML were evaluated after 6 and 9 months. In vitro results demonstrate downregulation of Krox­20 and Sox­10 along with the increase in p75NTR­immunolabelled cells. Concurrently, sciatic nerves of infected mice showed a significant decrease in Krox­20 and increase in p75NTR. Our results corroborate previous findings on the interference of ML in the expression of factors involved in cell maturation, favouring the maintenance of a non­myelinating phenotype in SCs, with possible implications for the repair of adult peripheral nerves(AU).

Unsolved matters in leprosy: a descriptive review and call for further research.

Leprosy, a chronic mycobacterial infection caused by Mycobacterium leprae, is an infectious disease that has ravaged human societies throughout millennia. This ancestral pathogen causes disfiguring cutaneous lesions, peripheral nerve injury, ostearticular deformity, limb loss and dysfunction, blindness and stigma. Despite ongoing efforts in interrupting leprosy transmission, large numbers of new cases are persistently identified in many endemic areas. Moreover, at the time of diagnosis, most newly identified cases have considerable neurologic disability. Many challenges remain in our understanding of the epidemiology of leprosy including: (a) the precise mode and route of transmission; (b) the socioeconomic, environmental, and behavioral factors that promote its transmission; and

Leprous neuromyositis: A rare clinical entity and review of the literature.

Mycobacterium leprae, the causative agent of leprosy (Hansen's disease), is a slow growing intracellular acid-fast bacillus that affects the skin, peripheral nerves and respiratory tract. In patients with suppressed cell-mediated immunity, the infiltration of the Bacilli can produce disseminated illness such as leprous neuromyositis. We reported a case of 56-year-old gentleman presenting with pyrexia of unknown origin, asymmetric sensory motor axonal polyneuropathy and was on chronic exogenous steroid therapy. On evaluation, his skin, muscle, nerve and bone marrow biopsy showed numerous globi of acid-fast Bacilli suggestive of leprous neuromyositis, a rare form of disseminated Hansen's disease. We reported this case in view of its rarity, atypical manifestation of a relatively rare disease and literature review on poor electrophysiological correlation in the diagnosis of leprous neuromyositis as compared to the histopathological examination.

Ultrasonographic Evaluation of Peripheral Nerves.

There are a variety of imaging modalities for evaluation of peripheral nerves. Of these, ultrasonography (US) is often underused. There are several advantages of this imaging modality, including its cost-effectiveness, time-efficient assessment of long segments of peripheral nerves, ability to perform dynamic maneuvers, lack of contraindications, portability, and noninvasiveness. It can provide diagnostic information that cannot be obtained by electrophysiologic or, in some cases, magnetic resonance imaging studies. Ideally, the neurosurgeon can use US as a diagnostic adjunct in the preoperative assessment of a patient with traumatic, neoplastic, infective, or compressive nerve injury. Perhaps its most unique use is in intraoperative surgical planning. In this article, a brief description of normal US nerve anatomy is presented followed by a description of the US appearance of peripheral nerve disease caused by trauma, tumor, infection, and entrapment.

Infection related to ultrasound-guided single-injection peripheral nerve blockade: a decade of experience at toronto Western hospital.

The use of ultrasound guidance has revolutionized regional anesthesia practice. Ultrasound equipment disinfection techniques vary between institutions. To date, there are no large data set publications or evidence-based guidelines that describe risk-reduction techniques for infectious complications related to the use of ultrasound guidance for peripheral nerve blockade. We retrospectively reviewed the medical charts of 7476 patients who received ultrasound-guided single-injection peripheral nerve blockade from October 2003 to August 2013 using our institution's low-level disinfection technique in combination with a sterile transparent film barrier dressing to cover the ultrasound transducer. No indications of block-related infection were found. We conclude that using a practical and efficient low-level disinfection technique and sterile barrier dressing results in an extremely low rate of block-related infection following ultrasound-guided single-injection peripheral nerve blockade.

High resolution structural changes of Schwann cell and endothelial cells in peripheral nerves across leprosy spectrum.

A systematic ultrastructure of peripheral nerves across the spectrum of leprosy was studied with an aim to better understanding the pathogenesis of nerve involvement in leprosy using light and electron microscope. The pathogenesis of nerve destruction varies in leprosy considerably along the spectrum. The study has begun to shed new light on some aspects of the infection of Mycobacterium leprae (M. lepare) and phenomenon has opened new avenue of research and possible mechanism of pathogenesis in TT/BT/BL/LL leprosy. In tuberculoid type (TT) and borderline tuberculoid (BT) leprosy, the degenerative changes of Schwann cells (SCs) and presence of perineural and perivascular cuffing by mononuclear cells. The endoneurial blood vessel (EBV) showed thickening of basement membrane with hypertrophy of EC leading to narrowing or complete occlusion of lumen and causing ischemia. However, borderline lepromatous (BL) and lepromatous leprosy (LL) foamy macrophages and vacuolated SC contain numerous small dense materials, irregular in shape and size was prominent and, considered to be degenerated and fragmented M. Leprae. The dense materials were also found in the cytoplasm of vascular EC. It was revealed that besides SC, the EC of EBV frequently harbor M. leprae in LL. The lumen of the EBV was wide open with enlarged nucleus. In the present study, the ultrastructural characteristics suggest that hypersensitivity mechanisms are possibly responsible for nerve damage in TT/BT leprosy. However, the study indicates that the mechanisms of nerve damage in BL/LL are basically different wherein hypersensitivity appears to play a very limited role.

Late onset neuropathy in leprosy patients released from treatment: not all due to reactions?

OBJECTIVES: To evaluate the clinical, neurophysiological and histological features of cases of neuropathy developing after completion of anti-leprosy treatment, where biopsy showed inflammatory changes. PATIENTS AND METHODS: Seven patients were evaluated by a single neurologist. Electro-neuro-myography and peripheral nerve biopsy were performed in all patients. RESULTS: Median age was 50-6 years. Time from release from treatment and onset of symptoms ranged from 1 to 12 years (median of 6.6 years). Sensory symptoms were the most common complaint, including pain (71%) and paresthesiae (71%). Muscle weakness was found in 51% and muscle atrophy in 43% of the subjects. Peripheral nerve thickening was present in all patients. Neurophysiological studies suggested sensory-motor polyneuropathy and multiple mono-neuropathy. Nerve biopsy showed inflammatory processes with fibrosis of endoneurium, perineurium and epineurium and total or partial loss of fibres. No bacilli were detected with Wade staining. Patients treated with corticosteroids had some relief of symptoms. CONCLUSION: After release from treatment, leprosy patients may insidiously develop progressive peripheral nerve symptoms not fulfilling criteria for relapse or leprosy reactions. Sensory symptoms predominate and peripheral nerve thickening is an important finding. We speculate that these late onset symptoms are secondary to chronic immune-mediated processes in response to antigens of M. leprae.

Role of Campylobacter jejuni infection in the pathogenesis of Guillain-Barré syndrome: an update.

Our current knowledge on Campylobacter jejuni infections in humans has progressively increased over the past few decades. Infection with C. jejuni is the most common cause of bacterial gastroenteritis, sometimes surpassing other infections due to Salmonella, Shigella, and Escherichia coli. Most infections are acquired due to consumption of raw or undercooked poultry, unpasteurized milk, and contaminated water. After developing the diagnostic methods to detect C. jejuni, the possibility to identify the association of its infection with new diseases has been increased. After the successful isolation of C. jejuni, reports have been published citing the occurrence of GBS following C. jejuni infection. Thus, C. jejuni is now considered as a major triggering agent of GBS. Molecular mimicry between sialylated lipooligosaccharide structures on the cell envelope of these bacteria and ganglioside epitopes on the human nerves that generates cross-reactive immune response results in autoimmune-driven nerve damage. Though C. jejuni is associated with several pathologic forms of GBS, axonal subtypes following C. jejuni infection may be more severe. Ample amount of existing data covers a large spectrum of GBS; however, the studies on C. jejuni-associated GBS are still inconclusive. Therefore, this review provides an update on the C. jejuni infections engaged in the pathogenesis of GBS.

Complex regional pain syndrome secondary to leprosy.

INTRODUCTION: Leprosy is a chronic infectious disease caused by Mycobacterium leprae affecting the skin and the nerves. Complex regional pain syndrome (CRPS/Sudeck's dystrophy) is a painful and disabling condition--a triad of autonomic, sensory, and motor symptoms disproportionate to the inciting event (inflammatory, infective, or traumatic nerve damage). CASE: A 20-year-old male presented with continuous pain, aggravated by cold and emotions, loss of fine touch and temperature sensation, redness, swelling, along lateral aspect of left hand and forearm with weakness in the grip of 6 months' duration. There was a 5-year history of sensory loss only over left index finger that he ignored. Examination revealed abnormal sensory and autonomic functions along left radial and median nerve distribution that were confirmed by nerve conduction studies suggestive of mononeuritis multiplex. Radial cutaneous nerve biopsy was suggestive of leprosy. Magnetic resonance imaging and ultrasonography showed no compressive etiology; however, MRI showed involvement of brachial plexus. Antileprosy, anti-inflammatory drugs, and steroids were given in view of neuritis because of lepra reaction with supportive measures of physiotherapy, transcutaneous electrical nerve stimulation, to no avail. A surgical median nerve decompression also failed to relieve the pain. Temporary stellate ganglion block improved the pain scale. Thus, excluding all other causes, the final diagnosis was CRPS secondary to leprosy. There is only one reported case of CRPS with leprosy. CONCLUSION: Leprous neuropathy caused the nerve damage that lead to CRPS type 2. Very rarely leprosy can lead to CRPS. CRPS is a diagnosis of exclusion.

Chimpanzees used for medical research shed light on the pathoetiology of leprosy.

Leprosy is a chronic infectious disorder caused by Mycobacterium leprae, which mainly affects skin and peripheral nerves. It is classified as either paucibacillary or multibacillary based upon clinical manifestations and slit-skin smear results. It is speculated that leprosy develops after a long latency period following M. leprae infection. However, the actual time of infection and the duration of latency have never been proven in human patients. To date, four cases of spontaneous leprosy have been reported in chimpanzees who were caught in West Africa in infancy and used for medical research in the USA and Japan. One of these chimpanzees was extensively studied in Japan, and single-nucleotide polymorphism analysis for the M. leprae genome was conducted. This analysis revealed that the chimpanzee was infected with M. leprae during infancy in West Africa and the pathognomonic signs of leprosy appeared after at least 30 years of incubation. Analysis of leprosy in chimpanzees can contribute not only to medical research but also to the understanding of the pathoetiology of leprosy.

The effect of corticosteroids usage on bacterial killing, clearance and nerve damage in leprosy; part 3--Study of two comparable groups of 100 multibacillary (MB) patients each, treated with MDT + steroids vs. MDT alone, assessed at 6 months post-release from 12 months MDT.

OBJECTIVE: To investigate effects of therapeutic usage of corticosteroids on M. leprae killing and clearance, on clearance of granuloma and on nerve damage in multibacillary (MB) leprosy patients. DESIGN: From a cohort of 400 untreated MB patients, a comparable group of 100 each receiving MDT + steroids (group A) vs MDT alone (group B) were assessed at 18 months as compared to month zero with respect to clinical and granuloma regression, M. leprae killing and clearance, and nerve functions. Analysis was performed using SPSS version 10.0. The significance of association was tested using Chi square and Fisher's exact tests. RESULTS: Regression of lesions assessed clinically and by histopathology was seen in 52% and 53% patients in group A and 46% and 63% in B respectively (P not significant). Clearance of bacteria assessed by bacteriological index (BI) in slit skin smears (SSS) and extent and intensity of antigen using anti-BCG staining were also comparable in the two groups. Multiplication of M. leprae in the mouse foot pad (MFP) indicating the presence of viable bacilli was seen in 14% and 16% of SSS positive BL-LLs patients in groups A and B respectively (P not significant). The occurrence of viable M. leprae was higher among patients with repeat reaction (19%) than single (11%). Using clinical tests (nerve palpation, monofilament and voluntary muscle testing), the proportion of sensory and motor nerves showing improvement or deterioration were similar in the two groups. However using nerve conduction studies, the overall proportion of nerves showing deterioration (22%) was significantly higher than improvement (9%) (P < 0.001). CONCLUSIONS: Treatment with MDT + corticosteroids does not adversely affect the clearance of granuloma, M. leprae and/or its antigens and M. leprae killing. However the continued presence of viable bacteria in > 14% of BL-LLs patients indicate that 12 months of MDT may be insufficient for complete bacterial killing. In both groups nerve conduction studies indicated that deterioration of nerves was high suggesting, MDT + corticosteroids was not very efficacious in the prevention or reversal of nerve damage. A better immuno-modulatory drug or a modified corticosteroid regime is needed.

[Perineural spread by fungal cells. Case report and literature review]. / Infiltración perineural por células fúngicas. Presentación de un caso y revisión de la literatura.

The perineural spread by fungal cells during the progression of the infection could be an important prognostic factor, especially in mycoses localized in the rhino-orbito-cerebral and pulmonary areas. We present a clinical case of a 73-year-old male, with diabetes and acute myelomonocytic leukaemia that began with tumefaction on the left side of his face, spreading to the sinus with invasion of the soft tissues and fistulae in the oral cavity. Clinical examination showed cerebral involvement. The histopathological sections and the histochemical techniques showed perineural involvement by fungal cells. Although the patient was diagnosed and treated in a short period of time, he died due to the infection. We would like to alert that perineural spread could be a retrograde way of mycoses dissemination, particularly in infections located in areas rich in neural cells.

Usage of signaling in neurodegeneration and regeneration of peripheral nerves by leprosy bacteria.

Multiple signaling pathways play key regulatory roles during the development of peripheral nervous system (PNS) and also in neuroregeneration process following nerve degeneration. Schwann cells, the glial cells of the PNS, by interacting with neuronal (axonal) ligands, mainly neuregulins via receptor tyrosine kinase (RTK) complex, ErbB2/ErbB3, initiate intracellular signaling pathways to drive proliferation and differentiation of Schwann cells, both during development and the process of regeneration and re-myelination after nerve injury. One of the major signaling kinases, extracellular signal-regulated kinase-1/2 (ERK1/2), that is also a downstream signaling pathway of neuregulin-ErbB2/ErbB3 activation, has been identified as a key regulator of Schwann cell proliferation, differentiation, demyelination and nerve regeneration. Recent studies have provided evidence that the bacterium that causes human leprosy, Mycobacterium leprae that has a unique capacity to invade Schwann cells of the adult PNS, utilizes the neuregulin-ErbB2/ErbB3 associated signaling network to the bacterial advantage. M. leprae directly bind to ErbB2 on myelinated Schwann cells and activate the RTK by a novel route that bypasses the classical neuregulin/growth factor-induced ErbB2-ErbB3 heterodimerization, and subsequently induce downstream the canonical Erk1/2 signaling, leading to myelin breakdown and subsequent axonal damage. This initial injury provides a survival advantage for M. leprae as it induces de-differentiation and generates myelin-free cells, which are highly susceptible to M. leprae invasion and promote bacterial survival. Once invaded M. leprae activate Erk1/2 via a non-canonical pathway and subsequently increase the cell proliferation and maintain the infected cells in de-differentiated state, thereby preventing remyelination. Therefore, by subverting major RTKs and signaling pathways in adult Schwann cells M. leprae appear to propagate the bacterial niche and maintain survival within the PNS. These studies may also provide new insights into our understanding of signaling mechanisms involve in both neurodegeneration and neuroregeneration.

Perineuritis in acute lyme neuroborreliosis.

Perineuritis is an unusual cause of direct peripheral nerve injury. We describe the clinicopathologic features of a 56-year-old man with mononeuritis multiplex due to Lyme disease; sural nerve biopsy demonstrated florid perineuritis. Treatment with intravenous ceftriaxone resulted in marked neurologic improvement. This study supports the notion that perineuritis forms part of the pathogenesis in acute Lyme neuroborreliosis.

Does clofazimine (B663) reach Mycobacterium leprae persisting in Schwann cells and endothelial cells of endoneurial blood vessels in peripheral nerves?

Peripheral nerve biopsies from 10 Lepromatous leprosy (LL) patients who were on multidrug treatment (MDT) were investigated by light and electron microscopy. Clofazimine (CLF) has been included as an essential component of MDT, which is the standard WHO regimen for treatment of leprosy. The patients receiving continuous MDT for a long period had viable bacilli in Schwann cells (SCs) of peripheral nerves whereas they had disappeared from the skin. Our ultrastructural observations clearly indicated the presence of CLF crystals in SCs. The crystals were in the form of osmiophilic rods of various shapes and sizes. On the other hand, the blood nerve barrier was clearly noticed in endoneurial blood vessels (EBV), and the barrier seems to play an important role for penetration of antileprosy drugs especially CLF.