Neuropatía motora multifocal: ¿cómo diagnosticar un caballo de Troya? / Multifocal motor neuropathy: how to diagnose a trojan horse?

Introducción: La neuropatía motora multifocal con bloqueos de la conducción (NMMBC) es una enfermedad crónica inmunomediada, con un compromiso exclusivo de los nervios motores. Es importante diferenciarla de otras enfermedades que cursan con afectación motora, debido a que ésta es una enfermedad tratable. Cuadro clínico: Paciente varón de 56 años, con compromiso motor progresivo en el miembro superior del lado derecho desde el año 2016. El examen neurofisiológico demostró la presencia de múltiples bloqueos de la conducción nerviosa. Los anticuerpos antigangliósidos fueron negativos. Se indicó tratamiento con inmunoglobulina endovenosa en varios ciclos, con mejoría progresiva del cuadro. Discusión: Se discute el plan diagnóstico clínico y electrofisiológico, los diagnósticos diferenciales, las hipótesis fisiopatológicas y el tratamiento de esta enfermedad de rara ocurrencia

Introduction: Multifocal motor neuropathy with conduction blocks (NMMBC) is a chronic immunemediated disease that exclusively involves the motor nerves. It is important to differentiate it from other diseases that present with motor involvement, because this is a treatable disease. Clinical picture: A 56-year-old male patient, with progressive motor involvement in the right upper limb since 2016. A neurophysiological examination revealed multiple nerve conduction blocks. Antiganglioside antibodies were negative. Treatment with intravenous immunoglobulin was indicated for several cycles with progressive improvement of the condition. Discussion: Clinical and electrophysiological diagnostic plans, differential diagnoses, pathophysiological hypotheses, and treatment of this rare disease are discussed

Peripheral neuropathy in limbic encephalitis with anti-glutamate receptor antibodies: Case report and systematic literature review.

INTRODUCTION: Autoantibodies to the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor and N-methyl-d-aspartate (NMDA) receptor are known to be the causes of autoimmune encephalitis particularly limbic encephalitis. The involvement of the peripheral nervous system is rarely reported. METHODS: We analyzed the serial nerve conduction studies of a previously reported case of anti-AMPA receptor encephalitis, who was presented with conscious disturbance and quadriplegia. Initial nerve conduction studies (NCS) revealed motor axonal polyneuropathy with active denervation. We also performed systematic review of similar cases with overlapped peripheral neuropathy and glutamate receptor encephalitis through Embase, PubMed, and MEDLINE. RESULTS: Follow-up NCS of the patient with anti-AMPA receptor encephalitis found reverse of the acute neuropathy, which was compatible with clinical recovery of quadriplegia. The systematic review identified 10 cases with overlapping peripheral neuropathy with anti-AMPA or NMDA receptor encephalitis. Motor or sensorimotor neuropathies were more common than pure sensory neuropathies. Anti-Hu, anti-amphiphysin, or anti-gnaglioside antibodies coexisted in some cases and might be associated with the peripheral symptoms. CONCLUSIONS: Both anti-AMPA and anti-NMDA receptor encephalitis could overlap with acute peripheral neuropathy. It is important to consider peripheral symptoms and perform diagnostic tests.

Guillain-Barré syndrome.

Guillain-Barré syndrome is the most common and most severe acute paralytic neuropathy, with about 100,000 people developing the disorder every year worldwide. Under the umbrella term of Guillain-Barré syndrome are several recognisable variants with distinct clinical and pathological features. The severe, generalised manifestation of Guillain-Barré syndrome with respiratory failure affects 20-30% of cases. Treatment with intravenous immunoglobulin or plasma exchange is the optimal management approach, alongside supportive care. Understanding of the infectious triggers and immunological and pathological mechanisms has advanced substantially in the past 10 years, and is guiding clinical trials investigating new treatments. Investigators of large, worldwide, collaborative studies of the spectrum of Guillain-Barré syndrome are accruing data for clinical and biological databases to inform the development of outcome predictors and disease biomarkers. Such studies are transforming the clinical and scientific landscape of acute autoimmune neuropathies.

Contactin-1 IgG4 antibodies cause paranode dismantling and conduction defects.

Paranodal axoglial junctions formed by the association of contactin-1, contactin-associated protein 1, and neurofascin-155, play important functions in nerve impulse propagation along myelinated axons. Autoantibodies to contactin-1 and neurofascin-155 define chronic inflammatory demyelinating polyradiculoneuropathy subsets of patients with specific clinical features. These autoantibodies are mostly of the IgG4 isotype, but their pathogenicity has not been proven. Here, we investigated the mechanisms how IgG subclasses to contactin-1 affect conduction. We show that purified anti-contactin-1 IgG1 and IgG4 bind to paranodes. To determine whether these isotypes can pass the paranodal barrier, we incubated isolated sciatic nerves with the purified antibody or performed intraneural injections. We found that IgG4 diffused into the paranodal regions in vitro or after intraneural injections. IgG4 infiltration was slow and progressive. In 24 h, IgG4 accessed the paranode borders near the nodal lumen, and completely fill the paranodal segments by 3 days. By contrast, control IgG, anti-contactin-1 IgG1, or even anti-contactin-associated-protein-2 IgG4 did not pass the paranodal barrier. To determine whether chronic exposure to these antibodies is pathogenic, we passively transferred anti-contactin-1 IgG1 and IgG4 into Lewis rats immunized with P2 peptide. IgG4 to contactin-1, but not IgG1, induced progressive clinical deteriorations combined with gait ataxia. No demyelination, axonal degeneration, or immune infiltration were observed. Instead, these animals presented a selective loss of the paranodal specialization in motor neurons characterized by the disappearance of the contactin-associated protein 1/contactin-1/neurofascin-155 complex at paranodes. Paranode destruction did not affect nodal specialization, but resulted in a moderate node lengthening. The sensory nerves and dorsal root ganglion were not affected in these animals. Electrophysiological examination further supported these results and revealed strong nerve activity loss affecting predominantly small diameter or slow conducting motor axons. These deficits partly matched with those found in patients: proximal motor involvement, gait ataxia, and a demyelinating neuropathy that showed early axonal features. The animal model thus seemed to replicate the early deteriorations in these patients and pointed out that paranodal loss in mature fibres results in conduction defects, but not conduction slowing. Our findings indicate that IgG4 directed against contactin-1 are pathogenic and are reliable biomarkers of a specific subset of chronic inflammatory demyelinating polyneuropathy patients. These antibodies appear to loosen the paranodal barrier, thereby favouring antibody progression and causing paranodal collapse.

[Fibromyalgia syndrome: A disease of the small nerve fibers?]. / Fibromyalgiesyndrom : Eine Erkrankung der kleinen Nervenfasern?

Fibromyalgia syndrome (FMS) is characterized by chronic widespread pain and additional associated symptoms, such as fatigue, sleep disturbances and depressive moods. The pathophysiology of pain in FMS is unclear. In recent years, an involvement of the thinly myelinated A-delta and the unmyelinated C-nerve fibers has been reported in FMS patients. Independent research groups published consistent objective and multidimensional findings of damage to these small nerve fibers, such as disturbances of fiber function, electrical properties and morphological changes. All these alterations are not specific for FMS; however, they were described for the first time in subgroups of FMS patients. While the reasons for this small fiber pathology and its contribution to FMS pain are still unclear, a new research field has now been opened that will focus on uncovering the underlying pathophysiology. This review article summarizes these new findings and discusses the significance for the understanding of FMS.

Laquinimod exerts strong clinical and immunomodulatory effects in Lewis rat experimental autoimmune neuritis.

Laquinimod is an immunomodulatory drug with neuroprotective potential. We used the animal model of experimental autoimmune neuritis (EAN) in the Lewis rat to study the effects of laquinimod treatment. After immunization with the neuritogenic peptide aa 53-78 of P2 myelin protein, preventive therapy with 12.5mg/kg laquinimod once daily inhibited neuritis in clinical and electrophysiological terms. Histology corroborated a lower degree of inflammatory lesions and demyelination in the sciatic nerve. The proportion of FoxP3-positive regulatory T cells in the peripheral lymph nodes of treated rats remained unchanged. We conclude that laquinimod may represent a therapeutic option in human autoimmune neuropathies.

Nodo-paranodopathy: beyond the demyelinating and axonal classification in anti-ganglioside antibody-mediated neuropathies.

In some anti-ganglioside antibody-mediated neuropathies, human and experimental data suggest a common pathogenic mechanism of dysfunction/disruption at the node of Ranvier resulting in a pathophysiologic continuum from transitory nerve conduction failure to axonal degeneration. The traditional classification of polyneuropathies into demyelinating or axonal may generate some confusion in the electrophysiological diagnosis of Guillain-Barré syndrome subtypes associated with anti-ganglioside antibodies. The axonal forms show, besides axonal degeneration, promptly reversible nerve conduction failure. This may be interpreted, by a single electrophysiological study, as demyelinating conduction block or distal axonal degeneration leading to errors in classification and in establishing prognosis. Moreover the term axonal may be misleading as it is commonly associated to axonal degeneration and not to a transitory, promptly reversible, dysfunction of the excitable axolemma. To focus on the site of nerve injury and overcome the classification difficulties, we propose the new category of nodo-paranodopathy which seems appropriate to various acute and chronic neuropathies associated with anti-ganglioside antibodies and we think better systematizes the neuropathies characterized by an autoimmune attack targeting the nodal region.

A-waves in Guillain-Barré syndrome: correlation with electrophysiological subtypes and antiganglioside antibodies.

OBJECTIVE: To investigate the relationship of A-waves with conventional electrophysiological subtypes of Guillain-Barré syndrome (GBS), as well as with anti-ganglioside antibodies. METHODS: The subjects consisted of 30GBS patients who were classified into acute inflammatory demyelinating polyradiculoneuropathy (AIDP), acute motor axonal neuropathy, and unclassified based on the results of nerve conduction studies. "Abundant A-waves" were defined for the upper-limb nerves (median and ulnar nerves) using receiver-operator characteristic curves. The presence or absence of IgG anti-ganglioside antibodies was also noted. RESULTS: Abundant A-waves at weeks 3-6 from onset were observed in 64% of the 14 AIDP patients and 0% of 16 non-AIDP patients, and in 60% of 15 antibody-negative patients and 0% of 15 antibody-positive patients. In the earlier period, this relationship was less clear. The correlation between the conventional electrophysiological subtypes and antibodies was present, but was much weaker. CONCLUSIONS: Abundant A-waves in GBS after the acute phase were strongly associated with demyelination that was not mediated by antiganglioside antibodies, possibly through the mechanism of proximal re-excitation induced by electrical inhomogeneities due to segmental demyelination. SIGNIFICANCE: Abundant A-waves are promising as a novel reliable marker of demyelination.

Conduction block in acute motor axonal neuropathy.

Guillain-Barré syndrome is divided into two major subtypes, acute inflammatory demyelinating polyneuropathy and acute motor axonal neuropathy. The characteristic electrophysiological features of acute motor axonal neuropathy are reduced amplitude or absence of distal compound muscle action potentials indicating axonal degeneration. In contrast, autopsy study results show early nodal changes in acute motor axonal neuropathy that may produce motor nerve conduction block. Because the presence of conduction block in acute motor axonal neuropathy has yet to be fully recognized, we reviewed how often conduction block occurred and how frequently it either reversed or was followed by axonal degeneration. Based on Ho's criteria, acute motor axonal neuropathy was electrodiagnosed in 18 patients, and repeated motor nerve conduction studies were carried out on their median and ulnar nerves. Forearm segments of these nerves and the across-elbow segments of the ulnar nerve were examined to evaluate conduction block based on the consensus criteria of the American Association of Electrodiagnostic Medicine. Twelve (67%) of the 18 patients with acute motor axonal neuropathy had definite (n=7) or probable (n=5) conduction blocks. Definite conduction block was detected for one patient (6%) in the forearm segments of both nerves and probable conduction block was detected for five patients (28%). Definite conduction block was present across the elbow segment of the ulnar nerve in seven patients (39%) and probable conduction block in two patients (11%). Conduction block was reversible in seven of 12 patients and was followed by axonal degeneration in six. All conduction blocks had disappeared or begun to resolve within three weeks with no electrophysiological evidence of remyelination. One patient showed both reversible conduction block and conduction block followed by axonal degeneration. Clinical features and anti-ganglioside antibody profiles were similar in the patients with (n=12) and without (n=6) conduction block as well as in those with (n=7) and without (n=5) reversible conduction block, indicating that both conditions form a continuum; a pathophysiological spectrum ranging from reversible conduction failure to axonal degeneration, possibly mediated by antibody attack on gangliosides at the axolemma of the nodes of Ranvier, indicating that reversible conduction block and conduction block followed by axonal degeneration and axonal degeneration without conduction block constitute continuous electrophysiological conditions in acute motor axonal neuropathy.

Chronic inflammatory demyelinating polyneuropathy and respiratory failure due to phrenic nerve involvement.

In this article, 2 patients with chronic inflammatory demyelinating polyneuropathy (CIDP) are presented. These patients developed respiratory failure which could not be explained by any cardiac or pulmonary pathology. The first case had pure motor involvement and probable CIDP, and the second case had severe sensorial dysfunction and an ataxic picture in addition to motor symptoms. His clinical picture was compatible with distal acquired demyelinating sensory neuropathy without M protein. Electrophysiologic investigations of both patients disclosed impaired phrenic nerve conduction and neurogenic motor unit changes in the diaphragm. Both patients showed a moderate response to immunotherapy. Distal acquired demyelinating sensory and pure motor variant of CIDP can be a cause of respiratory dysfunction. Different clinical patterns of CIDP should be evaluated for phrenic nerve involvement.

Selective expression and cellular localization of pro-inflammatory chemokine ligand/receptor pairs in the sciatic nerves of a severe murine experimental autoimmune neuritis model of Guillain-Barré syndrome.

AIMS: To determine if specific pro-inflammatory chemokine ligand/receptor pairs expressed in the peripheral nerves of Guillain-Barré syndrome patients are expressed in a severe murine experimental autoimmune neuritis (sm-EAN) model and to determine their cellular localization as a prerequisite to designing potentially therapeutic interventions in vivo. METHODS: Sm-EAN was induced in 8-12-week-old female SJL/J mice using bovine peripheral nerve myelin emulsified in complete Freund adjuvant with pertussis toxin and recombinant mouse interleukin-12 acting as co-adjuvants, with appropriate controls. Mice were evaluated for neuromuscular weakness and weighed daily. Dorsal caudal tail and sciatic nerve motor electrophysiological studies were performed at expected maximal severity. Sciatic nerves were harvested and specific chemokine ligand/receptor expression was determined using real-time quantitative reverse transcriptase polymerase chain reaction and indirect fluorescent immunohistochemistry. RESULTS: CCL2/CCR2, CXCL10/CXCR3 and CCL5/CCR1, CCR5 expression was significantly increased in the sciatic nerves of sm-EAN mice compared with controls. CCL2 was expressed on Schwann cells with CCR2 expressed on F4/80+ macrophages and CD3+ T cells. CXCL10 was expressed on endoneurial endothelial cells and within the endoneurial interstitium, with CXCR3 expressed on CD3+ T-lymphocytes. CCL5 co-localized to axons, with CCR1 and CCR5 expression on F4/80+ macrophages and rare CD3+ T cells. CONCLUSIONS: This study suggests that CCL2 expressed by Schwann cells and CXCL10 expressed by endoneurial endothelial cells may induce F4/80+ macrophage and CD3+ T cell-mediated inflammation and demyelination in sm-EAN. CCL2-CCR2 and CXCL10-CXCR3 signalling pathways are potential targets for therapeutic intervention in peripheral nerve inflammation.

Chronic inflammatory demyelinating polyneuropathy associated with tumor necrosis factor-alpha antagonists.

Biologic therapy with tumor necrosis factor (TNF)-alpha antagonists for rheumatoid arthritis has been well established. We describe two patients with rheumatoid arthritis who developed chronic inflammatory demyelinating polyneuropathy (CIDP) during their course of therapy with TNF-alpha antagonists. A 45-year-old woman and a 49-year-old man, both with a history of rheumatoid arthritis, were treated with etanercept and infliximab, respectively. Clinical signs of peripheral neuropathy developed 2 weeks and 12 months after the initiation of TNF-alpha antagonists. Electrodiagnostic studies at variable points during the disease course showed signs of acquired demyelination consistent with CIDP. Cerebrospinal fluid examination showed albuminocytologic dissociation (total protein concentration 118 mg/dl and 152 mg/dl, respectively). Both patients failed to improve after discontinuation of the offending agent, and they responded poorly to corticosteroids. However, there was clinical and electrophysiologic recovery after initiation of intravenous immunoglobulin (IVIg) therapy. CIDP may occur early or late during the treatment course with TNF-alpha antagonists. IVIg may reverse and stabilize the inflammatory process.

Nerve excitability changes after intravenous immunoglobulin infusions in multifocal motor neuropathy and chronic inflammatory demyelinating neuropathy.

Intravenous immunoglobulin (IVIg) infusions may provide clinical benefits in multifocal motor neuropathy (MMN) and chronic inflammatory demyelinating polyneuropathy (CIDP). The short delay in the clinical response to IVIg therapy is not consistent with a process of remyelination or axonal regeneration. We assessed whether or not the efficacy of IVIg infusions in MMN and CIDP could reflect changes in axonal membrane properties and nerve excitability. Ulnar motor nerve excitability was studied before and after three to five consecutive days of IVIg infusions (0.4 g/kg/day) in 10 patients with MMN, 10 patients with CIDP, and 10 neurological controls (CTRLs). Excitability recovery cycle, stimulus-response and strength-duration properties were investigated. The recovery cycle parameters (absolute and relative refractory period durations, refractoriness and supernormality) were similar in all groups and did not change after IVIg infusions. At baseline, patients with CIDP, but not with MMN, showed a reduced strength-duration time constant (chronaxie) and increased rheobase when compared to CTRLs. After IVIg infusions, strength-duration time constant remained stable in CTRLs, but decreased in patients with MMN or CIDP. Rheobase increased in the three groups after treatment. The decreased strength-duration time constant after IVIg infusions in patients with MMN or CIDP could reflect a reduction of persistent Na(+) current, able to limit intraaxonal Na(+) accumulation and then to produce neuroprotective effects. However, this could also reflect compensatory mechanisms that did not directly underlie the therapeutic effect. Whatever the underlying process, this result revealed that IVIgs were able to produce early nerve excitability changes.

Morvan syndrome following B-cell lymphoma.

Morvan syndrome is a rare autoimmune disease named after the French physician Augustin Marie Morvan. It is characterized by multiple, irregular contractions of the long muscles, weakness, pruritus, hyperhidrosis, insomnia, and delirium. Here, we describe a 17-year-old young man, previously diagnosed with B-cell lymphoma, who presented with multiple asynchronous fasciculations of the long muscles of his lower extremities accompanied by numbness. The patient responded initially to pulse corticosteroids with diminution of the fasciculations. He achieved complete remission following 7 consecutive, monthly intravenous immunoglobulin injections. The present case is described in the context of the available literature.

Chronic ataxic neuropathies associated with anti-GD1b IgM antibodies: response to IVIg therapy.

OBJECTIVE: To determine the responses to treatment of patients with chronic sensory ataxic neuropathy associated with anti-GD1b IgM antibodies. METHODS: Patients with chronic sensory ataxic neuropathy associated with anti-GD1b IgM antibodies followed in our department for at least 12 months between 2001 and 2008 were identified and studied retrospectively. Patients were tested at regular intervals using the INCAT disability score. Patients whose disability scores improved by at least one point were taken to have responded to the treatment. Intravenous immunoglobulin (IVIg; 2 g/kg) was administered for 3 to 5 days once every 6 weeks or corticosteroids at an initial daily dose of 1 mg/kg. RESULTS: 13 patients treated during the 8-year period of interest were included in this study. Seven of 13 patients displayed IgM anti-GQ1b, GT1b and GD3 antibodies suggesting reactivity against disialosyl epitope. IgM gammopathy was detected in four of six of serum with anti-disialosyl antibodies and two of the seven other sera. Nine of the 13 patients improved in response to IVIg. Oral corticosteroid treatment was attempted on four patients prior to IVIg treatment, and partial recovery occurred in one, who became steroid-dependent and showed little benefit in the long term. CONCLUSIONS: Screening for anti-GD1b IgM antibodies should be carried out on all patients with chronic ataxic sensory neuropathies. In 69% of the cases studied, the patients' condition improved in response to IVIg. This study shows the short-term efficiency of this treatment. Sustained responses were obtained in the long term by continuing the infusions.

Guillain-Barré syndrome: an update.

Guillain-Barré syndrome (GBS) is an acute polyneuropathy consisting of different subtypes. Acute inflammatory demyelinating polyradiculoneuropathy, the classic demyelinating form of GBS, accounts for 90% of all GBS cases in the Western world. Acute motor axonal neuropathy (AMAN) and acute motor and sensory axonal neuropathy (AMSAN) are axonal forms of GBS that are more prevalent in Asia, South and Central America, often preceded by infection by Campylobacter jejuni. AMAN and AMSAN may be mediated by specific anti-ganglioside antibodies that inhibit transient sodium ion (Na+) channels. The efficacy of plasmapheresis and intravenous immunoglobulin has been established in large international randomised trials, with corticosteroids proven ineffective. Although axonal demyelination is an established pathophysiological process in GBS, the rapid improvement of clinical deficits with treatment is consistent with Na+ channel blockade by antibodies or other circulating factors, such as cytokines. This review provides an update on the epidemiology, clinical features, diagnosis, pathogenesis and treatment of GBS.

Subacute inflammatory polyradiculopathy associated with Sjögren's syndrome.

Peripheral nervous system involvement is common in Sjögren's syndrome (SS); however, polyradiculopathy has been reported rarely in association with SS, and predominantly chronic forms have been described. We describe a patient with clinical, cerebrospinal fluid, neurophysiological, and neuroradiological evidence of subacute inflammatory polyradiculopathy in whom Sjögren's syndrome was diagnosed after the onset of neurological symptoms. Our case suggests that SS should be included in the differential diagnosis of subacute inflammatory polyradiculopathy.

Rituximab in cryoglobulinemic peripheral neuropathy.

Type II mixed cryoglobulinemia is sustained by an oligoclonal production of IgM sharing rheumatoid activity and can be associated with renal, cutaneous, rheumatologic or neurological manifestations. Peripheral neuropathy is a major cause of morbidity in hepatitis C virus-associated mixed cryoglobulinemia and is often refractory to any treatment. Rituximab induces a selective depletion of IgM-producing B cells, and both case reports on monoclonal IgM-related polyneuropathy as well as studies on small series of patients with interferon alpha-resistant mixed cryoglobulinemia have suggested that it may be beneficial. Thirteen patients affected by type II mixed cryoglobulinemia with polyneuropathy were treated. Rituximab was administered intravenously at a dose of 375 mg/m(2) on days 1, 8, 15 and 22. Two more doses were given 1 and 2 months later. No other immunosuppressive drugs were added. Response was evaluated by assessing the changes in the clinical neurological condition, in electromyographic indices and in laboratory parameters (including cryocrit, viral load, complement levels and rheumatoid factor) over at least 12 months. Sensory symptoms disappeared or improved following treatment. A significant improvement in the clinical neuropathy disability score was observed. Electromyography examination revealed that the amplitude of compound motor action potential had increased. Viral load did not significantly change. Side effects were negligible. In this open prospective study, rituximab appeared to be effective and safe in the treatment of patients with type II cryoglobulinemia-associated neuropathy.