Atypical electrophysiologic findings in chronic inflammatory demyelinating polyneuropathy (CIDP) – diagnosis confirmed by nerve biopsy

Early Diagnosis in Cerebellar Ataxia, Neuropathy, Vestibular Areflexia Syndrome (CANVAS) by Focusing on Major Clinical Clues: Beyond Ataxia and Vestibular Impairment

CANVAS, a rare disorder responsible for late-onset ataxia of autosomal recessive inheritance, can be misdiagnosed. We investigated a series of eight patients with sensory neuropathy and/or an unexplained cough, who appeared to suffer from CANVAS, and we emphasized the clinical clues for early diagnosis. Investigations included clinical and routine laboratory analyses, skin biopsy, nerve biopsy and molecular genetics. The eight patients had clinical and/or laboratory evidence of sensory neuronopathy. All but one had neuropathic pain that had started in an asymmetric fashion in two patients. A chronic cough was a prominent feature in our eight patients and had started years before neuropathic symptoms in all but one. The course of the disease was slow, and ataxia remained mild in all. Five patients were initially thought to have immune-mediated sensory neuronopathy and received immunotherapy. Skin biopsies showed a near complete and non-length-dependent loss of intraepidermal nerve fibers. Moreover, nerve biopsy findings suggested a prominent involvement of small myelinated and unmyelinated fibers. The burden of CANVAS extends far beyond cerebellar ataxia and vestibular manifestations. Indeed, our study shows that a chronic cough and neuropathic pain may represent a major source of impairment in these patients and should not be overlooked to allow an early diagnosis and prevent unnecessary immunotherapy.

Relevance of Nerve Biopsy in the Diagnosis of Chronic Inflammatory Demyelinating Polyneuropathy—A Systematic Review

Chronic Inflammatory Demyelinating Polyneuropathy is an immune-mediated pathology of the peripheral nerves and nerve roots that leads to weakness and sensory symptoms. Given its clinical heterogeneity, often times diagnosis is challenging. Even though nerve conduction studies and clinical features are the main criteria used for diagnosis, supplementary investigations, such as nerve biopsies, cerebral spinal fluid examination and magnetic resonance studies, may be used in order to confirm the diagnosis. Given the fact that the hallmark in CIDP physiopathology is the demyelination process, nerve biopsies are used to demonstrate and assess the magnitude of the phenomenon. The question and the main interest of this review is whether histopathological findings are relevant for the diagnosis and can be useful in disease assessment.

Comprehensive approaches for diagnosis, monitoring and treatment of chronic inflammatory demyelinating polyneuropathy

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is the most common chronic inflammatory neuropathy. CIDP is diagnosed according to the European Federation of Neurological Societies/Peripheral Nerve Society (EFNS/PNS) criteria, which combine clinical features with the electrophysiological evidence of demyelination. However, firstly, diagnosis is challenging, as some patients e.g. with severe early axonal damage do not fulfil the criteria. Secondly, objective and reliable tools to monitor the disease course are lacking. Thirdly, about 25% of CIDP patients do not respond to evidence-based first-line therapy. Recognition of these patients is difficult and treatment beyond first-line therapy is based on observational studies and case series only. Individualized immunomodulatory treatment does not exist due to the lack of understanding of essential aspects of the underlying pathophysiology.

Novel diagnostic imaging techniques and molecular approaches can help to solve these problems but do not find enough implementation. This review gives a comprehensive overview of novel diagnostic techniques and monitoring approaches for CIDP and how these can lead to individualized treatment and better understanding of pathophysiology.

Diagnostic challenges in chronic inflammatory demyelinating polyradiculoneuropathy

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) consists of a spectrum of autoimmune diseases of the peripheral nerves, causing weakness and sensory symptoms. Diagnosis often is challenging, because of the heterogeneous presentation and both mis- and underdiagnosis are common. Nerve conduction study (NCS) abnormalities suggestive of demyelination are mandatory to fulfil the diagnostic criteria. On the one hand, performance and interpretation of NCS can be difficult and none of these demyelinating findings are specific for CIDP. On the other hand, not all patients will be detected despite the relatively high sensitivity of NCS abnormalities. The electrodiagnostic criteria can be supplemented with additional diagnostic tests such as CSF examination, MRI, nerve biopsy, and somatosensory evoked potentials. However, the evidence for each of these additional diagnostic tests is limited. Studies are often small without the use of a clinically relevant control group. None of the findings are specific for CIDP, meaning that the results of the diagnostic tests should be carefully interpreted. In this update we will discuss the pitfalls in diagnosing CIDP and the value of newly introduced diagnostic tests such as nerve ultrasound and testing for autoantibodies, which are not yet part of the guidelines.

COVID-19 as a Trigger of Recurrent Guillain-Barré Syndrome

Coronavirus 2019 (COVID-19) has been reported to trigger Guillain-Barré syndrome (GBS). While uncommon, recurrent GBS (rGBS) episodes, triggered by antecedent viral infections, have been reported in a small proportion of GBS patients, here we describe a patient with a recurrent case of GBS, occurring secondary to COVID-19 infection. Before this patient's episode, he had two prior GBS flares, each precipitated by a viral infection followed by complete recovery besides intermittent paresthesias. We also consider the nosology of this illness in the spectrum of rGBS and Chronic Inflammatory Demyelinating Polyneuropathy (CIDP), with their differing natural histories, prognosis, and therapeutic approaches. For patients who have a history of inflammatory demyelinating polyradiculopathies who develop COVID-19, we recommend close observation for neurologic symptoms over the next days and weeks.

Primary cauda equina lymphoma diagnosed by nerve biopsy: A case report and literature review

Primary cauda equina lymphoma (CEL) is a rare malignant tumor among various neoplasms that affects the cauda equina nerve roots. The present case report described the case of a 65-year-old man who presented with cauda equina syndrome with progressive motor palsy in the legs and gait disturbance over the last 5 months. Magnetic resonance (MR) images showed enlargement of the cauda equina occupying the dural sac from the L1-S1 level with isointensity to the spinal cord signal on both T1- and T2-weighted imaging. Enhancement of the cauda equina was seen on contrast MR images. On F-18 2-fluoro-2-deoxy-glucose positron emission tomography examination, diffuse accumulation of 2-fluoro-2-deoxy-glucose was observed in the cauda equina with a maximum standardized uptake value of 4.9. Based on elevation of soluble interleukin 2 receptor in cerebrospinal fluid and a biopsy of the enlarging cauda equina, a diagnosis of CEL of the diffuse large B-cell type was made. The present case report provided a detailed case discussion and a review of the available literature on this rare entity, focusing on clinical characteristics and imaging of primary CEL.

Quantitative muscle ultrasound is useful for evaluating secondary axonal degeneration in chronic inflammatory demyelinating polyneuropathy

INTRODUCTION

In chronic inflammatory demyelinating polyneuropathy (CIDP), exclusion of secondary axonal degeneration is challenging with conventional methods such as nerve conduction study (NCS), needle electromyography, and nerve biopsy. Increased echo intensity (EI) and decreased muscle thickness (MT) identified on muscle ultrasound (MUS) examination represent muscle denervation due to axonal degeneration in neurogenic disorders, suggesting MUS as a new tool to detect secondary axonal degeneration in patients with CIDP.

METHODS

EI and MT of abductor pollicis brevis, abductor digiti minimi, and first dorsal interosseous muscles were measured in 16 CIDP patients. Raw values were converted into z-scores using data from 60 normal controls (NCs).

RESULTS

Six of 45 muscles showed abnormally high EI and low MT, suggesting denervation following secondary axonal degeneration. These six muscles belonged to two patients with long disease history, unresponsiveness to treatment, and long interval from onset to initial therapy. There were no significant differences in EI and MT (p = .23 and .67, respectively) between the CIDP and NC groups, although NCS results revealed obvious demyelinating abnormalities in all CIDP patients, suggesting the fact that muscle structures will be preserved, and EI and MT will not change unless secondary axonal degeneration occurs in CIDP.

CONCLUSION

MUS is a promising tool for evaluating secondary axonal degeneration in patients with CIDP.

Diagnosis and treatment of chronic acquired demyelinating polyneuropathies

Chronic neuropathies are operationally classified as primarily demyelinating or axonal, on the basis of electrodiagnostic or pathological criteria. Demyelinating neuropathies are further classified as hereditary or acquired-this distinction is important, because the acquired neuropathies are immune-mediated and, thus, amenable to treatment. The acquired chronic demyelinating neuropathies include chronic inflammatory demyelinating polyneuropathy (CIDP), neuropathy associated with monoclonal IgM antibodies to myelin-associated glycoprotein (MAG; anti-MAG neuropathy), multifocal motor neuropathy (MMN), and POEMS syndrome. They have characteristic--though overlapping--clinical presentations, are mediated by distinct immune mechanisms, and respond to different therapies. CIDP is the default diagnosis if the neuropathy is demyelinating and no other cause is found. Anti-MAG neuropathy is diagnosed on the basis of the presence of anti-MAG antibodies, MMN is characterized by multifocal weakness and motor conduction blocks, and POEMS syndrome is associated with IgG or IgA λ-type monoclonal gammopathy and osteosclerotic myeloma. The correct diagnosis, however, can be difficult to make in patients with atypical or overlapping presentations, or nondefinitive laboratory studies. First-line treatments include intravenous immunoglobulin (IVIg), corticosteroids or plasmapheresis for CIDP; IVIg for MMN; rituximab for anti-MAG neuropathy; and irradiation or chemotherapy for POEMS syndrome. A correct diagnosis is required for choosing the appropriate treatment, with the aim of preventing progressive neuropathy.

Electrophysiologic correlations with clinical outcomes in CIDP

Data are lacking on correlations between changes in nerve conduction (NC) studies and treatment response in chronic inflammatory demyelinating polyneuropathy (CIDP). This report examined data from a randomized, double-blind trial of immune globulin intravenous, 10% caprylate/chromatography purified (IGIV-C [Gamunex]; n = 59) versus placebo (n = 58) every 3 weeks for up to 24 weeks in CIDP. Motor NC results and clinical measures were assessed at baseline and endpoint/week 24. Improvement from baseline in adjusted inflammatory neuropathy cause and treatment score correlated with improvement in proximally evoked compound muscle action potential (CMAP) amplitudes (r = -0.53; P < 0.001) of all nerves tested and with improvement in CMAP amplitude of the most severely affected motor nerve (r = -0.36; P < 0.001). Correlations were observed between improvement in averaged CMAP amplitudes and dominant-hand grip strength (r = 0.44; P < 0.001) and Medical Research Council sum score (r = 0.38; P < 0.001). Overall, the change in electrophysiologic measures of NC in CIDP correlated with clinical response to treatment.

Pain as the presenting symptom of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP)

Numerous clinical forms of CIDP have been described, but pain is generally considered a rare or secondary sign. We describe here the clinical, electrophysiological and neuropathological characteristics of five patients with CIDP and pain as the main presenting symptom, and their course with treatment. Between January 2003 and December 2004, we selected five patients with prominent or isolated pain among 27 patients diagnosed with CIDP. All patients were subjected to clinical and electrophysiological examinations, and had a complete laboratory work up to exclude other causes of neuropathy. In view of the atypical clinical presentation, all five patients underwent nerve biopsy. There were two men and three women. The mean age at onset of neuropathy was 70+/-7.39 years. All patients initially presented with pain in the lower limbs associated with modest motor impairment (1 case), distal paresthesia (4 cases), cramps (1 case) and fatigue (2 cases). CSF was normal in three cases. On electrophysiological examination, three patients had nerve conduction abnormalities with subtle or clear signs of demyelination: three (case 1, 2 and 4) fulfilled the criteria of Rotta et al. and two (case 2 and 4) the criteria of both Nicolas et al and the INCAT group. Patients were all given symptomatic treatment and four patients received an immunomodulatory treatment, which was constantly effective. Pain may be a major and disabling symptom in patients with CIDP, so this diagnosis has to be considered in patients referred for a painful polyneuropathy. Moreover, immunomodulatory treatment has to be considered in such patients as symptomatic therapy may be ineffective.

Dixièmes Journées des Maladies du Système Nerveux Périphérique Diagnostic des polyneuropathies axonales chroniques : les polyradiculonévrites chroniques méconnues

Chronic inflammatory demyelinating polyradiculoneuropathy is an autoimmune disease that target myelin sheats of peripheral nerves. Its diagnosis is often difficult to make, and a number of cases are probably not identified because of the clinical and electrophysiological heterogeneity. Typical cases associate progressive or relapsing-remitting motor and sensory deficit with increased CSF protein content and electrophysiological features of demyelination. In some cases electrophysiological studies fail to show evidence of demyelination, conventional electrophysiological diagnostic criteria are not filled yet the patient may respond to immunomodulatory treatments. In such cases, presence of clinical characteristics suggestive of CIDP (that means not compatible with a length-dependent axonal process) are critical justifying fully investigations including sural nerve biopsy. The main clinical characteristic are: a symmetric proximal and distal motor weakness predominantly affecting the lower limbs, a diffuse areflexia, a sensory deficit characterized by a preferential involvement of large fibers, an evolution which may be either chronic progressive or recurrent. Usual therapeutic agents (corticosteroids, intravenous immunoglobulins, plasma exchanges) seem to have the same efficacy whatever the electrophysiologic profile.

[Electrophysiological manifestations of chronic inflammatory demyelinating polyradiculoneuropathy]

There are four basic electrophysiological parameters of demyelination: reduced motor conduction velocity, prolonged distal motor latency and F waves, and motor conduction blocks. These parameters are combined to determine an electrophysiological set of criteria for chronic inflammatory demyelinating polyneuropathy (CIDP). Whereas their specificity is good, their sensitivity level does not exceed 75 percent. However, these sets of criteria are not commonly used especially in benign forms, at the beginning of the disease, in associated forms or in case of secondary axonal degeneration. We can push the limits using others criteria such as the terminal latency index, sensory criteria, or by the contribution of others electrophysiological procedures such as the radicular stimulation or sensory evoked potentials. Due to the therapeutic implications, any axonal neuropathy without aetiologia, with at least one demyelinating electrophysiological criteria, could be considered as a putative CIDP.

Les neuropathies périphériques : orientations et moyens diagnostiques

PURPOSES

Neuropathies are defined as dysfunction of peripheral nerves, which may show motor, sensory and autonomic symptoms. Although most neuropathies are symmetric, it is important to distinguish a polyneuropathy from a mononeuropathy, a multiple mononeuropathy or a polyradiculoneuropathy. Electrophysiological procedures are helpful in determining the pathological process which may be either an axonopathy, a myelinopathy or a neuronopathy.

MAIN POINTS

Major progresses have been made in the ten past years in the management and diagnostic approaches of peripheral neuropathy. The history and the physical examination are the first steps to the evaluation of patients with peripheral neuropathy. Electrodiagnostic studies and then laboratory tests are the next step in the diagnostic procedures of peripheral neuropathies. These will lead to a proper identification of the cause of neuropathy, allowing to develop a specific treatment for the patient. However, even after a careful work-up of a patient with neuropathy, 25 to 40% of patients with polyneuropathies remain undiagnosed.

PERSPECTIVES

Further development are focused in better understanding the pathogenesis and molecular mechanisms of peripheral nerve diseases in order to provide a specific and adequate treatment for each neuropathy.

Fatigue as the main presenting symptom of chronic inflammatory demyelinating polyradiculoneuropathy: a study of 11 cases

Fatigue has been shown to be more frequent than previously thought in immune-mediated polyneuropathies. However, fatigue has not been reported as the main cause of referral in chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) patients. Between January 2001 and December 2003, we investigated 11 patients referred for fatigue, for which we established a final diagnosis of CIDP. All patients had at least two clinical examinations including assessment of the fatigue severity scale (FSS) and one electrophysiological and laboratory work up. Additionally, 10 of the 11 patients had a nerve biopsy. There were 11 male patients. Mean age at onset was 53 +/- 11 years. Main cause of referral was fatigue in all patients. Additional symptoms included cramps (one case), distal paresthesias (six cases), limb pain (seven cases) and vasomotor disturbances (one case). Cerebrospinal fluid (CSF) analysis displayed a moderate increase in protein content in four patients. Electrophysiological analysis showed abnormalities in all patients. Among 11 patients, one fulfilled the American Academy of Neurology electrodiagnostic criteria for CIDP and three fulfilled the inflammatory neuropathy cause and treatment group or the Nicolas et al. criteria. In the eight remaining patients, a nerve biopsy confirmed the diagnosis of CIDP. Ten patients were treated, among which seven showed a significant improvement based on the FSS scale. This study shows that fatigue is a possible cause of referral for patients with CIDP and, like previous reports, emphasizes the lack of sensitivity of widely accepted electrophysiological criteria of CIDP. Long-term follow up of these patients is warranted to determine the prognosis of these minimal forms of CIDP and establish the best therapeutic strategy in such cases.