Office immunotherapy in chronic inflammatory demyelinating polyneuropathy and multifocal motor neuropathy

Optimizing Anti-Myelin-Associated Glycoprotein and IgM-Gammopathy Testing for Neuropathy Treatment Evaluation

BACKGROUND AND OBJECTIVES

Patients with typical anti-myelin-associated glycoprotein (anti-MAG) neuropathy have IgM-gammopathy, mimic distal chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), and are treatment resistant. Anti-MAG patients go unrecognized when IgM-gammopathy is undetected or with atypical phenotypes. We investigated an optimal anti-MAG titration cutoff for excluding CIDP and the impact of IgM-gammopathy detection on neuropathy treatment evaluation without anti-MAG antibodies.

METHODS

European Academy of Neurology/Peripheral Nerve Society 2021 guidelines were used to assess patients with neuropathy using anti-MAG Bühlmann titration units (BTU) and IgM-gammopathy with Mass-Fix (mass spectrophotometry) and serum protein immunofixation electrophoresis (SPIEP). The immunotherapy outcome was reviewed by inflammatory neuropathy cause and treatment (INCAT) and summated compound muscle action potential (CMAP) nerve conduction changes.

RESULTS

Seven hundred and fifty-two patients (average age: 63.8 years, female: 31%) were identified over 30 months: (1) typical anti-MAG neuropathy (n = 104); (2) atypical anti-MAG neuropathy (n = 13); (3) distal or sensory-predominant CIDP (n = 25), including 7 without IgM-gammopathy; (4) typical CIDP (n = 47), including 36 without IgM-gammopathy; (5) axonal IgM-gammopathy-associated neuropathy (n = 104); and (6) IgM-gammopathy-negative, anti-MAG-negative axonal neuropathies (n = 426); and (7) without neuropathy (n = 33) anti-MAG negative. IgM-gammopathy was evaluated by Mass-Fix (n = 493), SPIEP (n = 355), or both (n = 96). Mass-Fix detected 4 additional IgM-gammopathies (3%, 4/117) among patients with anti-MAG antibodies and 7 additional patients (2%, 7/376) without anti-MAG not detected by SPIEP testing. Immunotherapy follow-up was available in 123 (mean: 23 months, range: 3-120 months) including 47 with CIDP (28 without IgM-gammopathy) and 76 non-CIDP (5 without IgM-gammopathy, 45 anti-MAG positive). Treatments included IVIG (n = 89), rituximab (n = 80), and ibrutinib or zanubrutinib (n = 24). An optimal anti-MAG-positive cutoff was identified at ≥1,500 BTU (78% sensitivity, 96% specificity) and at ≥10,000 BTU (74% sensitivity, 100% specificity) for typical anti-MAG neuropathy. Improvements in INCAT scores (p < 0.0001) and summated CMAP (p = 0.0028) were associated with negative anti-MAG (<1,500 BTU, n = 78) and absence of IgM-gammopathy (n = 34). Among 47 patients with electrodiagnostically confirmed CIDP, all anti-MAG negative, the presence of IgM-gammopathy (n = 19) also correlated with a worse treatment response (INCAT scores p = 0.035, summated CMAP p = 0.049).

DISCUSSION

A cutoff of 10,000 BTU seems optimal for typical anti-MAG neuropathy while ≥1,500 BTU reduces the likelihood of immune-treatable CIDP. Mass-Fix improves IgM-gammopathy detection in anti-MAG and other IgM-gammopathy neuropathies. Patients with IgM-gammopathy lacking MAG antibodies show reduced treatment response.

Paraneoplastic neuropathies and peripheral nerve hyperexcitability disorders

Peripheral neuropathy is a common referral for patients to the neurologic clinics. Paraneoplastic neuropathies account for a small but high morbidity and mortality subgroup. Symptoms include weakness, sensory loss, sweating irregularity, blood pressure instability, severe constipation, and neuropathic pain. Neuropathy is the first presenting symptom of malignancy among many patients. The molecular and cellular oncogenic immune targets reside within cell bodies, axons, cytoplasms, or surface membranes of neural tissues. A more favorable immune treatment outcome occurs in those where the targets reside on the cell surface. Patients with antibodies binding cell surface antigens commonly have neural hyperexcitability with pain, cramps, fasciculations, and hyperhidrotic attacks (CASPR2, LGI1, and others). The antigenic targets are also commonly expressed in the central nervous system, with presenting symptoms being myelopathy, encephalopathy, and seizures with neuropathy, often masked. Pain and autonomic components typically relate to small nerve fiber involvement (nociceptive, adrenergic, enteric, and sudomotor), sometimes without nerve fiber loss but rather hyperexcitability. The specific antibodies discovered help direct cancer investigations. Among the primary axonal paraneoplastic neuropathies, pathognomonic clinical features do not exist, and testing for multiple antibodies simultaneously provides the best sensitivity in testing (AGNA1-SOX1; amphiphysin; ANNA-1-HU; ANNA-3-DACH1; CASPR2; CRMP5; LGI1; PCA2-MAP1B, and others). Performing confirmatory antibody testing using adjunct methods improves specificity. Antibody-mediated demyelinating paraneoplastic neuropathies are limited to MAG-IgM (IgM-MGUS, Waldenström's, and myeloma), with the others associated with cytokine elevations (VEGF, IL6) caused by osteosclerotic myeloma, plasmacytoma (POEMS), and rarely angiofollicular lymphoma (Castleman's). Paraneoplastic disorders have clinical overlap with other idiopathic antibody disorders, including IgG4 demyelinating nodopathies (NF155 and Contactin-1). This review summarizes the paraneoplastic neuropathies, including those with peripheral nerve hyperexcitability.

Plexus MRI helps distinguish the immune-mediated neuropathies MADSAM and MMN

BACKGROUND

Among immune-mediated neuropathies, clinical-electrophysiological overlap exists between multifocal acquired demyelinating sensory and motor neuropathy (MADSAM) and multifocal motor neuropathy (MMN). Divergent immune pathogenesis, immunotherapy response, and prognosis exist between these two disorders. MRI reports have not shown distinction of these disorders, but biopsy confirmation is lacking in earlier reports. MADSAM nerves are hypertrophic with onion bulbs, inflammation, and edema, whereas MMN findings are limited to multifocal axonal atrophy.

OBJECTIVES

To understand if plexus MRI can distinguish MADSAM from MMN among pathologically (nerve biopsy) confirmed cases.

METHODS

Retrospective chart review and blinded plexus MRI review of biopsy-confirmed MADSAM and MMN cases at Mayo Clinic.

RESULTS

Nine brachial plexuses (MADSAM-5, MMN-4) and 6 lumbosacral plexuses (MADSAM-4, MMN-2) had fascicular biopsies of varied nerves. Median follow-up in MADSAM was 93 months (range: 7-180) and 27 (range: 12-109) in MMN (p = 0.34). MRI hypertrophy occurred solely in MADSAM (89%, 8/9) with T2-hyperintensity in both. There was no correlation between time to imaging for hypertrophy, symptom onset age, or motor neuropathy impairments (mNIS). At last follow-up, on diverse immunotherapies mNIS improved in MADSAM (median - 4, range: -22 to 0), whereas MMN worsened (median 3, range: 0 to 6, p = 0.03) on largely IVIG.

CONCLUSION

Nerve hypertrophy on plexus MRI helps distinguish MMN from MADSAM, where better immunotherapy treatment outcomes were observed. These findings are consistent with the immune pathogenesis seen on biopsies. Radiologic distinction is possible independent of time to imaging and extent of motor deficits, suggesting MRI is helpful in patients with uncertain clinical-electrophysiologic diagnosis, especially motor-onset MADSAM.

A Case of Probable Multifocal Motor Neuropathy With Clinical Stability for Ten Years After a Single Treatment of Rituximab

ABSTRACT

Multifocal motor neuropathy is a rare, immune-mediated motor neuropathy with asymmetric, often debilitating progressive weakness. The efficacy of intravenous immunoglobulin in this disease is well established; however, the response typically wanes over time. No other agent has shown similar therapeutic efficacy. We describe a case of anti-ganglioside GM1 IgM-positive multifocal motor neuropathy with typical incomplete and diminishing response to intravenous immunoglobulin over time. Sixteen years after symptom onset, rituximab was administered at 2 g/m2 over 2 weeks. No significant progression of disease has occurred over the following 10 years despite no additional treatments, including intravenous immunoglobulin, being given. Only case reports and small, mostly uncontrolled studies have reported the use of rituximab in multifocal motor neuropathy with mixed results. However, given its potential benefits and lack of an established second-line agent, treatment with rituximab may be considered in select patients with refractory multifocal motor neuropathy.

Neurofascin-155 Immunoglobulin Subtypes: Clinicopathologic Associations and Neurologic Outcomes

BACKGROUND AND OBJECTIVE

Multiple studies highlighting diagnostic utility of neurofascin 155 (NF155)-IgG4 in chronic demyelinating inflammatory polyradiculoneuropathy (CIDP) have been published. However, few studies comprehensively address the long-term outcomes, or clinical utility of NF155-IgM or NF155-IgG, in the absence of NF155-IgG4. In this study we evaluate phenotypic and histopathological specificity, and differences in outcomes between these NF155 antibody isotypes or IgG subclasses. We also compare NF155-IgG4 seropositive cases to other seropositive demyelinating neuropathies.

METHODS

In this study, neuropathy patient sera seen at Mayo Clinic were tested for NF155-IgG4, NF155-IgG and NF155-IgM autoantibodies. Demographic and clinical data of all seropositive cases were reviewed.

RESULTS

We identified 32 NF155 patients (25 NF155-IgG positive [20 NF155-IgG4 positive], 7 NF155-IgM seropositive). NF155-IgG4 seropositive patients clinically presented with distal more than proximal muscle weakness, positive sensory symptoms (prickling, asymmetric paresthesia, neuropathic pain) and gait ataxia. Cranial nerve involvement (11/20, 55%) and papilledema (4/12, 33%) occurred in many. Electrodiagnostic testing (EDX) demonstrated demyelinating polyradiculoneuropathy (19/20, 95%). Autonomic involvement occurred in 45% (n=9, median CASS score 3.5, range 1-7). Nerve biopsies from the NF155-IgG4 patients (n=11) demonstrated grouped segmental demyelination (50%), myelin reduplication (45%) and paranodal swellings (50%). Most patients needed 2^nd and 3^rd line immunosuppression but had favorable long-term outcomes (n=18). Among 14 patients with serial EDX over 2 years, all except one demonstrated improvement after treatment. NF155-IgG positive NF155-IgG4 negative (NF155-IgG positive) and NF155-IgM positive patients were phenotypically different from NF155-IgG4 seropositive patients. Sensory ataxia, neuropathic pain, cerebellar dysfunction and root/plexus MRI abnormalities were significantly more common in NF155-IgG4 positive compared to MAG-IgM neuropathy. Chronic immune sensory polyradiculopathy (CISP)/CISP-plus phenotype was more common among Contactin-1 neuropathies compared to NF155-IgG4 positive cases. NF155-IgG4 positive cases responded favorably to immunotherapy compared to MAG-IgM seropositive cases with distal acquired demyelinating symmetric neuropathy (p<0.001) and had better long-term clinical outcomes compared to contactin-1 IgG (p=0.04).

DISCUSSION

We report long-term follow-up and clinical outcome of NF155-IgG4 patients. NF155-IgG4 but not IgM or IgG patients have unique clinical-electrodiagnostic signature. We demonstrate NF155-IgG4 positive patients, unlike classical CIDP with neuropathic pain and dysautonomia common at presentation. Long-term outcomes were favorable.

CLASSIFICATION OF EVIDENCE

This study provides Class III evidence that NF155-IgG4 seropositive patients, compared to typical CIDP patients, present with distal more than proximal muscle weakness, positive sensory symptoms, and gait ataxia.

Electrodiagnostic Assessment of Polyneuropathy

This article focuses on principles of nerve conduction studies and needle electromyography applied to the electrodiagnosis of polyneuropathy. The components of the electrodiagnostic evaluation of polyneuropathy and the electrophysiological characteristics of axonal and demyelinating neuropathies and nodo-paranodopathies are reviewed.

Pure Motor Onset and IgM-Gammopathy Occurrence in Multifocal Acquired Demyelinating Sensory and Motor Neuropathy

BACKGROUND AND OBJECTIVES

To longitudinally investigate patients with multifocal acquired demyelinating sensory and motor neuropathy (MADSAM), quantifying timing and location of sensory involvements in motor onset patients, along with clinicohistopathologic and electrophysiologic findings to ascertain differences in patients with and without monoclonal gammopathy of uncertain significance (MGUS).

METHODS

Patients with MADSAM seen at Mayo Clinic and tested for monoclonal gammopathy and ganglioside antibodies were retrospectively reviewed (January 1, 2007-December 31, 2018).

RESULTS

Of 76 patients with MADSAM, 53% had pure motor, 16% pure sensory, 30% sensorimotor, and 1% cranial nerve onsets. Motor-onset patients were initially diagnosed with multifocal motor neuropathy (MMN). MGUS occurred in 25% (89% immunoglobulin M [IgM] subtype), associating with ganglioside autoantibodies (p < 0.001) and higher IgM titers (p < 0.04). Median time to sensory involvements (confirmed by electrophysiology) in motor onset patients was 18 months (range 6-180). Compared to initial motor nerve involvements, subsequent sensory findings were within the same territory in 35% (14/40), outside in 20% (8/40), or both in 45% (18/40). Brachial and lumbosacral plexus MRI was abnormal in 87% (34/39) and 84% (21/25), respectively, identifying hypertrophy and increased T2 signal predominantly in brachial plexus trunks (64%), divisions (69%), and cords (69%), and intrapelvic sciatic (64%) and femoral (44%) nerves. Proximal fascicular nerve biopsies (n = 9) more frequently demonstrated onion-bulb pathology (p = 0.001) and endoneurial inflammation (p = 0.01) than distal biopsies (n = 17). MRI and biopsy findings were similar among patient subgroups. Initial Inflammatory Neuropathy Cause and Treatment (INCAT) disability scores were higher in patients with MGUS relative to without (p = 0.02). Long-term treatment responsiveness by INCAT score reduction ≥1 or motor Neuropathy Impairment Score (mNIS) >8-point reduction occurred in 75% (49/65) irrespective of MGUS or motor onsets. Most required ongoing immunotherapy (86%). Patients with MGUS more commonly required dual-agent immunotherapy for stability (p = 0.02).

DISCUSSION

Pure motor onsets are the most common MADSAM presentation. Long-term follow-up, repeat electrophysiology, and nerve pathology help distinguish motor onset MADSAM from MMN. Better long-term immunotherapy responsiveness occurs in motor onset MADSAM compared to MMN reports. Patients with MGUS commonly require dual immunotherapy.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that most clinical, electrophysiologic, and histopathologic findings were similar between patients with MADSAM with and without MGUS.

Chronic inflammatory demyelinating polyradiculoneuropathy-Diagnostic pitfalls and treatment approach

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is characterized by progressive weakness and sensory loss, often affecting patients' ability to walk and perform activities of daily living independently. With the lack of a diagnostic biomarker, the diagnosis relies on clinical suspicion, clinical findings, and the demonstration of demyelinating changes on electrodiagnostic (EDx) testing and nerve pathology. As a result, patients can often be misdiagnosed with CIDP and unnecessarily treated with immunotherapy. Interpreting the EDx testing and cerebrospinal fluid findings in light of the clinical phenotype, recognizing atypical forms of CIDP, and screening for CIDP mimickers are the mainstays of the approach to patients suspected of having CIDP, and are detailed in this review. We also review the currently available treatment options, including intravenous immunoglobulin (IVIg), corticosteroids (CCS), and plasma exchange (PE), and discuss how to approach treatment-refractory cases. Finally, we emphasize the need to adopt objective outcome measures to monitor treatment response.

Multifocal motor neuropathy: controversies and priorities

Despite 30 years of research there are still significant unknowns and controversies associated with multifocal motor neuropathy (MMN) including disease pathophysiology, diagnostic criteria and treatment. Foremost relates to the underlying pathophysiology, specifically whether MMN represents an axonal or demyelinating neuropathy and whether the underlying pathophysiology is focused at the node of Ranvier. In turn, this discussion promotes consideration of therapeutic approaches, an issue that becomes more directed in this evolving era of precision medicine. It is generally accepted that MMN represents a chronic progressive immune-mediated motor neuropathy clinically characterised by progressive asymmetric weakness and electrophysiologically by partial motor conduction block. Anti-GM1 IgM antibodies are identified in at least 40% of patients. There have been recent developments in the use of neuromuscular ultrasound and MRI to aid in diagnosing MMN and in further elucidation of its pathophysiological mechanisms. The present Review will critically analyse the knowledge accumulated about MMN over the past 30 years, culminating in a state-of-the-art approach to therapy.

Therapeutic Plasma Exchange in Guillain-Barre Syndrome and chronic inflammatory demyelinating polyradiculoneuropathy

Therapeutic plasma exchange (TPE) has been used as a treatment modality in many autoimmune disorders, including neurological conditions, such as Guillain-Barre syndrome (GBS) and chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). The American Society for Apheresis (ASFA) publishes its guidelines on the use of therapeutic apheresis every 3 years based on published evidence to assist physicians with both the medical and technical aspects of apheresis consults. The ASFA Guidelines included the use of TPE in both GBS and CIDP as an acceptable first-line therapy, either alone and/or in conjunction with other therapeutic modalities. In this article, we briefly reviewed GBS and CIDP, discussed the role of apheresis in these conditions as well as various technical aspects of the TPE procedure, such as apheresis calculation, number of volume exchange, replacement fluid, and management of potential complications.

History, Diagnosis, and Management of Chronic Inflammatory Demyelinating Polyradiculoneuropathy

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is probably the best recognized progressive immune-mediated peripheral neuropathy. It is characterized by a symmetrical, motor-predominant peripheral neuropathy that produces both distal and proximal weakness. Large-fiber abnormalities (weakness and ataxia) predominate, whereas small-fiber abnormalities (autonomic and pain) are less common. The pathophysiology of CIDP is inflammatory demyelination that manifests as slowed conduction velocities, temporal dispersion, and conduction block on nerve conduction studies and as segmental demyelination, onion-bulb formation, and endoneurial inflammatory infiltrates on nerve biopsies. Although spinal fluid protein levels are generally elevated, this finding is not specific for the diagnosis of ClDP. Other neuropathies can resemble CIDP, and it is important to identify these to ensure correct treatment of these various conditions. Consequently, metastatic bone surveys (for osteosclerotic myeloma), serum electrophoresis with immunofixation (for monoclonal gammopathies), and human immunodeficiency virus testing should be considered for testing in patients with suspected CIDP. Chronic inflammatory demyelinating polyradiculoneuropathy can present as various subtypes, the most common being the classical symmetrical polyradiculoneuropathy and the next most common being a localized asymmetrical form, multifocal CIDP. There are 3 well-established, first-line treatments of CIDP-corticosteroids, plasma exchange, and intravenous immunoglobulin-with most experts using intravenous immunoglobulin as first-line therapy. Newer immune-modulating drugs can be used in refractory cases. Treatment response in CIDP should be judged by objective measures (improvement in the neurological or electrophysiological examination), and treatment needs to be individualized to each patient.

Blink R1 latency utility in diagnosis and treatment assessment of polyradiculoneuropathy-organomegaly-endocrinopathy-monoclonal protein-skin changes and chronic inflammatory demyelinating polyradiculoneuropathy

INTRODUCTION

In polyradiculoneuropathy-organomegaly-endocrinopathy-monoclonal protein-skin changes (POEMS) and chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), limb nerve conduction studies (NCSs) are limited in identifying demyelination and in detecting treatment effects in severely affected patients. Blink R1 latency may improve these assessments.

METHODS

POEMS and CIDP patients who had undergone NCS and blink reflex were identified. Correlations among R1 latency, limb NCS, and neuropathy impairment scores (NIS) were compared.

RESULTS

Among 182 patients (124 POEMS, 58 CIDP) who were identified, R1 prolongation (>13 ms) occurred in 64.3% (65.3% POEMS, 62.1% CIDP). R1 prolongation correlated with more severely affected NCS in both POEMS (ulnar CMAP 2.6 mV vs. 4.5 mV, P = 0.001) and CIDP (2.0 mV vs. 6.1 mV, P < 0.001). In severely affected patients (ulnar CMAP ≤0.5 mV [10%:18/182]), R1 (>13 ms) helped establish demyelination. In 31 patients (16 POEMS, 15 CIDP), the R1 latency changes were concordant with NIS changes in 94% of patients with POEMS and 60% of patients with CIDP.

DISCUSSION

Blink R1 latencies are valuable in defining demyelination and detecting improvement in severely affected POEMS and CIDP patients. Muscle Nerve 57: E8-E13, 2018.

Assessing mNIS+7Ionis and international neurologists' proficiency in a familial amyloidotic polyneuropathy trial

INTRODUCTION

Polyneuropathy signs (Neuropathy Impairment Score, NIS), neurophysiologic tests (m+7_Ionis ), disability, and health scores were assessed in baseline evaluations of 100 patients entered into an oligonucleotide familial amyloidotic polyneuropathy (FAP) trial.

METHODS

We assessed: (1) Proficiency of grading neurologic signs and correlation with neurophysiologic tests, and (2) clinometric performance of modified NIS+7 neurophysiologic tests (mNIS+7_Ionis ) and its subscores and correlation with disability and health scores.

RESULTS

The mNIS+7_Ionis sensitively detected, characterized, and broadly scaled diverse polyneuropathy impairments. Polyneuropathy signs (NIS and subscores) correlated with neurophysiology tests, disability, and health scores. Smart Somatotopic Quantitative Sensation Testing of heat as pain 5 provided a needed measure of small fiber involvement not adequately assessed by other tests.

CONCLUSIONS

Specially trained neurologists accurately assessed neuropathy signs as compared to referenced neurophysiologic tests. The score, mNIS+7_Ionis , broadly detected, characterized, and scaled polyneuropathy abnormality in FAP, which correlated with disability and health scores. Muscle Nerve 56: 901-911, 2017.

What is new in 2015 in dysimmune neuropathies?

This review discusses and summarizes the concept of nodopathies, the diagnostic features, investigations, pathophysiology, and treatment options of chronic inflammatory demyelinating polyradiculoneuropathy, and gives updates on other inflammatory and dysimmune neuropathies such as Guillain-Barré syndrome, sensory neuronopathies, small-fiber-predominant ganglionitis, POEMS syndrome, neuropathies associated with IgM monoclonal gammopathy and multifocal motor neuropathy. This field of research has contributed to the antigenic characterization of the peripheral motor and sensory functional systems, as well as helping to define immune neuropathic syndromes with widely different clinical presentation, prognosis and response to therapy.

Subcutaneous immunoglobulins in the treatment of chronic immune-mediated neuropathies

Intravenous immunoglobulins represent an established therapy for the treatment of chronic immune-mediated neuropathies, specifically chronic inflammatory demyelinating polyradiculoneuropathies (CIDPs) as well as multifocal motor neuropathies (MMNs). For the treatment of antibody deficiency syndromes, subcutaneous immunoglobulins (SCIgs) have represented a mainstay for decades. An emerging body of evidence suggests that SCIg might also exhibit clinical efficacy in CIDP and MMN. This article reviews the current evidence for clinical effectiveness, as well as safety of SCIg for the treatment of immune-mediated neuropathies, and addresses remaining open questions in this context. We conclude that despite the need for controlled long-term studies to demonstrate long-term efficacy of SCIg in immune-mediated neuropathies, SCIg may already represent a potential therapeutic alternative for selected patients.