Chronic Inflammatory Demyelinating Polyneuropathy (CIDP)

Chronic inflammatory demyelinating polyneuropathy (CIDP) is an acquired autoimmune disorder of the peripheral nervous system in which T cells and autoantibodies attack the myelin sheath surrounding peripheral nerve fibers. It is best understood as the chronic counterpart of Guillain-Barré syndrome (GBS): where GBS is an acute, monophasic illness that typically peaks within four weeks and then resolves, CIDP progresses or relapses over more than eight weeks and, without treatment, leads to sustained disability. With a prevalence of 3–8 per 100,000, CIDP is the most common treatable chronic peripheral neuropathy. Recognizing its hallmark pattern — symmetric proximal and distal weakness with large-fiber sensory loss, absent reflexes, and an elevated CSF protein — unlocks access to highly effective therapies that can restore function in the majority of patients.

  1. Pathogenesis and Immune Mechanisms
  2. CIDP vs. Guillain-Barré Syndrome
  3. Nodal and Paranodal Antibody Subtypes
  4. Clinical Features
  5. Clinical Variants
  6. Diagnosis: Nerve Conduction Studies and CSF
  7. Treatment
  8. Prognosis and Long-Term Management
  9. Key Research Papers
  10. Featured Videos
  11. Connections

Pathogenesis and Immune Mechanisms

CIDP is driven by a dual-arm immune attack on the peripheral myelin sheath. On the cellular side, activated CD4+ and CD8+ T lymphocytes breach the blood-nerve barrier, infiltrate peripheral nerve tissue, and release pro-inflammatory cytokines including interferon-gamma, TNF-alpha, and interleukin-17. These mediators amplify local inflammation and recruit macrophages that physically strip myelin from the underlying axon — a process called macrophage-mediated demyelination. Serial nerve biopsies show endoneurial macrophages interdigitating between layers of compact myelin, confirming this direct stripping activity.

On the humoral side, autoantibodies directed at peripheral myelin proteins initiate complement activation at the outer myelin surface. The result is the membrane attack complex (C5b-9), which punches holes in the Schwann cell membrane, triggering vesicular disruption of compact myelin from within. The targets include myelin protein zero (MPZ, the most abundant structural protein of compact peripheral myelin), peripheral myelin protein 22 (PMP22), myelin-associated glycoprotein (MAG, particularly in the DADS variant associated with IgM paraprotein), and the paranodal junction proteins neurofascin-155 (NF155), contactin-1 (CNTN1), contactin-associated protein 1 (CASPR1), and neurofascin-186 (NF186). The nodal and paranodal antibody subtypes — discussed in their own section below — define clinically and therapeutically distinct subgroups of CIDP.

The consequence of repeated demyelination and attempted remyelination is the formation of onion-bulb structures: concentric rings of redundant Schwann cell processes that wrap, incompletely, around a demyelinated axon in successive repair cycles. These onion bulbs are visible on nerve biopsy and are one of the pathological hallmarks of CIDP. Over time, if demyelination outpaces remyelination — or if secondary axonal loss accumulates — permanent disability results. Early, effective treatment prevents this axonal attrition and is the principal reason CIDP should be treated aggressively once diagnosed.

Genetic susceptibility. CIDP is not a straightforwardly heritable disease, but HLA associations and family clustering studies suggest an immune-genetic predisposition. HLA-A*24 and HLA-DRB1*15:01 have been associated with CIDP susceptibility in genome-wide studies, though effect sizes are modest, and environmental triggers — infections, vaccinations, pregnancy — can precipitate new episodes in genetically predisposed individuals.

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CIDP vs. Guillain-Barré Syndrome

CIDP and GBS share the same fundamental mechanism — autoimmune demyelination of peripheral nerves — yet they behave so differently in time course and management that distinguishing them is one of the most consequential distinctions in neuromuscular medicine. The eight-week threshold is the single most important boundary: by definition, GBS plateaus and begins recovery within four weeks; a patient still deteriorating at eight weeks almost certainly has CIDP. The practical implications are significant: GBS is treated with a single course of IVIg or plasma exchange and then monitored for spontaneous recovery; CIDP requires ongoing immunotherapy for months to years.

Feature GBS (AIDP) CIDP
Time course to nadir Acute: peaks within 4 weeks, monophasic Chronic: progresses or relapses beyond 8 weeks
Preceding infection Common (Campylobacter, CMV, EBV, Zika) Less consistent; sometimes no clear trigger
Autonomic involvement Prominent and potentially life-threatening Less common; present in some patients
Pain Severe back and radicular pain common Present but less dramatic
Cranial nerve involvement Facial diplegia in ~50%; Fisher variant Cranial nerve involvement unusual
CSF Elevated protein, no pleocytosis (late first week) Elevated protein, no pleocytosis (present throughout)
Treatment course Single course IVIg or plasma exchange; steroids ineffective Ongoing IVIg, steroids, or plasma exchange; months to years
Prognosis 80% walk independently at 6 months; 5% mortality Good if treated; some relapse dependency; rare spontaneous remission

The eight-week rule is not perfectly clean in practice. Acute-onset CIDP — in which a CIDP patient presents with rapid deterioration mimicking GBS — can cause diagnostic confusion in the first weeks. The clues that suggest acute-onset CIDP rather than true GBS include: very high CSF protein (>200 mg/dL), prominent proximal weakness, absence of a convincing preceding infection, and a family history of neuropathy. If a patient diagnosed with GBS deteriorates after an initial improvement or fails to improve at all within six months, CIDP should be reconsidered and nerve conduction studies repeated.

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Nodal and Paranodal Antibody Subtypes

The node of Ranvier — the bare segment of axon between adjacent myelin internodes — is not merely a gap in insulation. It is a specialized signaling domain where sodium channels cluster in extraordinary density to regenerate the action potential, and where a complex molecular scaffold locks the myelin terminus to the axon surface. This scaffold involves a trio of cell-adhesion molecules that span the paranodal junction (the region just beside the node): neurofascin-155 (NF155) on the myelin side, and contactin-1 (CNTN1) paired with contactin-associated protein 1 (CASPR1) on the axon side. Together they form the paranodal septate-like junctions that anchor myelin, maintain the ion-channel organization of the node, and are essential for normal saltatory conduction.

In the past decade, IgG4 autoantibodies against these paranodal proteins have been discovered in a subgroup of CIDP patients, defining clinically and therapeutically distinct entities. These patients tend to have more aggressive disease, more severe sensory ataxia (loss of proprioception disrupting balance), higher CSF protein levels, nerve biopsy showing paranodal demyelination without the classic onion-bulb pattern, and — critically — a poorer response to intravenous immunoglobulin (IVIg). Because IgG4 antibodies do not fix complement and do not engage Fc receptors efficiently, IVIg (which works partly by saturating Fc receptors and modulating complement) is mechanistically less effective against them. Anti-rituximab therapies that deplete the B cells producing these IgG4 antibodies achieve excellent responses in this subgroup.

Key paranodal/nodal antibodies in CIDP:

Testing for these antibodies has moved from research to clinical practice. In any CIDP patient who responds poorly to IVIg, or who has prominent sensory ataxia with tremor at a young age, anti-NF155 and anti-CNTN1 serology should be checked before concluding that CIDP is refractory — the correct diagnosis may be a paranodal neuropathy that requires a different treatment algorithm.

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Clinical Features

The cardinal presentation of classic CIDP is progressive or relapsing-remitting symmetric weakness affecting both proximal and distal muscles, combined with large-fiber sensory loss and absent or reduced deep tendon reflexes. The proximal predominance of weakness — hip flexors, knee extensors, shoulder abductors — is more prominent than in hereditary neuropathies such as Charcot-Marie-Tooth disease, where distal weakness dominates. Many patients have difficulty climbing stairs, rising from a chair, and lifting objects overhead, as well as trouble with fine hand tasks as distal hand muscles weaken over time.

Sensory features. Large-fiber sensory dysfunction manifests as impaired vibration perception (typically tested with a 128 Hz tuning fork at the medial malleolus and first metatarsal head), impaired proprioception (the sense of limb position), and Romberg's sign (worsening imbalance on eye closure). The clinical result is sensory ataxia — a wide-based, unsteady gait that worsens dramatically in the dark or with eyes closed, reflecting the absence of visual compensation for lost proprioceptive input. Some patients describe a sensation of walking on cotton wool or numb pads. Small-fiber function (pain and temperature) is relatively preserved in classic CIDP, a useful distinguishing feature from small-fiber neuropathies.

Reflexes. The deep tendon reflexes are absent or markedly reduced in virtually all patients with established CIDP — generalized areflexia is nearly universal. The absence of the ankle jerk is present even in patients with primarily proximal weakness, reflecting diffuse segmental demyelination across long nerves. Preserved reflexes in a patient suspected of CIDP should prompt reconsideration of the diagnosis.

Course patterns. CIDP presents in one of three temporal patterns: (1) Chronic progressive — a slow, steady worsening over months without remission; (2) Relapsing-remitting — episodes of worsening separated by partial or complete recovery; (3) Monophasic — a single episode that improves with treatment and does not recur (this pattern occurs in about 5–10% and may represent treated acute-onset CIDP that does not declare itself as relapsing). The relapsing-remitting course is more common in younger patients; the progressive course is more typical of older onset.

Associated conditions. CIDP occurs in association with several systemic diseases that should be actively sought: diabetes mellitus (diabetic CIDP is under-recognized; the neuropathy is out of proportion to the degree of glycemic control), monoclonal gammopathy of undetermined significance (MGUS, particularly IgG and IgA — these patients must be screened for POEMS syndrome and osteosclerotic myeloma), HIV infection, hepatitis B and C, thyroid disease, and inflammatory bowel disease. Up to 15% of CIDP patients carry a monoclonal protein.

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Clinical Variants

Classic CIDP — the symmetric proximal-and-distal pattern — accounts for roughly half of all cases. The remaining patients present with one of several recognized variants that differ in distribution, fiber type involvement, and associated serological findings. Recognizing variants matters because some respond differently to standard therapies and require tailored investigation.

DADS (Distal Acquired Demyelinating Symmetric neuropathy). DADS presents predominantly with distal sensory loss and mild distal weakness, with relative sparing of proximal muscles. The sensory involvement is prominent — vibration loss reaching the knees or thighs, sensory ataxia, pseudoathetosis (involuntary writhing movements of outstretched fingers from proprioceptive loss). Approximately half of DADS patients have an associated IgM paraprotein, often with anti-MAG (myelin-associated glycoprotein) antibodies. Anti-MAG DADS responds poorly to steroids and IVIg; rituximab has the best evidence in the anti-MAG subtype. Non-anti-MAG DADS responds more like classic CIDP.

MADSAM (Multifocal Acquired Demyelinating Sensory and Motor neuropathy), also called Lewis-Sumner syndrome. MADSAM presents as an asymmetric, multifocal neuropathy — individual nerves are affected one at a time in a pattern resembling mononeuritis multiplex, but nerve conduction studies demonstrate demyelination rather than the axonal loss of vasculitic mononeuropathy. Upper limb nerves are often more affected than lower limb. Conduction block on nerve conduction studies is a hallmark. MADSAM must be distinguished from multifocal motor neuropathy (MMN) — in MMN, sensory fibers are spared and anti-GM1 IgM antibodies are present; in MADSAM, sensory fibers are also affected. MADSAM responds to IVIg and steroids.

Pure sensory CIDP. In rare patients, only sensory fibers are affected — weakness is absent or subclinical. Sensory ataxia and large-fiber sensory loss dominate the picture, with demyelinating slowing on sensory nerve conduction studies and elevated CSF protein. This variant can be difficult to distinguish from sensory ganglionopathies (which damage the dorsal root ganglion cell body rather than the myelin, and are not treatable with immunotherapy). Skin punch biopsy and autonomic testing can help clarify the level of the lesion.

Focal CIDP. Occasional patients have demyelinating neuropathy confined to one limb or one plexus — a focal or regional pattern. Nerve conduction studies demonstrate the demyelinating character (conduction block, temporal dispersion, prolonged distal latency) and distinguish focal CIDP from compressive neuropathy. Imaging (MRI of the brachial or lumbar plexus) frequently shows nerve enlargement and enhancement at the affected level.

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Diagnosis: Nerve Conduction Studies and CSF

The diagnosis of CIDP is established by a combination of clinical criteria, electrodiagnostic criteria, and supportive investigations. The European Federation of Neurological Societies and Peripheral Nerve Society (EFNS/PNS) criteria — last updated in 2021 — are the accepted diagnostic standard and classify patients as definite, probable, or possible CIDP based on the number of demyelinating features on nerve conduction studies.

Nerve conduction studies (NCS) — demyelinating features. The EFNS/PNS criteria require at least two of the following demyelinating abnormalities in at least two different nerves:

The pattern of demyelination in CIDP is characteristically multifocal and diffuse — abnormalities are found in multiple nerves, including nerves not typically compressed by anatomical structures (e.g., the median nerve at a site other than the carpal tunnel, or the ulnar nerve at the mid-forearm). This diffuse distribution distinguishes CIDP from multifocal compressive neuropathies.

EMG (needle electromyography). Needle EMG is usually normal or shows only mild changes in early or pure demyelinating CIDP, because denervation (fibrillations and positive sharp waves) appears only when secondary axonal loss occurs. In long-standing or severe CIDP, denervation potentials reflect axonal damage downstream of chronic demyelination. The presence of extensive denervation at diagnosis suggests that significant irreversible axonal loss has already accumulated, which correlates with a less complete treatment response.

CSF analysis. Lumbar puncture typically reveals elevated CSF protein — usually 50–200 mg/dL, occasionally higher in paranodal subtypes — without a concomitant increase in white cells. This pattern of albuminocytologic dissociation is present in 80–90% of CIDP patients and reflects increased permeability of the blood-nerve barrier at inflamed nerve roots. CSF protein is a useful supportive criterion but not a standalone diagnostic test; some patients have normal CSF protein early in the course, and some hereditary neuropathies also cause modest CSF protein elevation.

Nerve biopsy. Sural nerve biopsy is reserved for diagnostically uncertain cases — when electrophysiology and CSF are equivocal, or when hereditary demyelinating neuropathy (Charcot-Marie-Tooth type 1) or vasculitic neuropathy needs to be excluded. The histological hallmarks of CIDP are perivascular endoneurial inflammatory infiltrates of T cells and macrophages, active demyelination with macrophage-stripped myelin, and onion-bulb formations in chronic cases. The biopsy is not routinely required and involves a 10–20% risk of permanent sensory deficit at the biopsy site.

Antibody testing. Anti-NF155, anti-CNTN1, and anti-CASPR1 should be tested in patients with prominent sensory ataxia, poor IVIg response, or young-onset severe disease. Anti-MAG IgM should be tested in patients with the DADS phenotype and an IgM paraprotein. Serum protein electrophoresis and immunofixation should be performed in all CIDP patients to exclude a paraproteinemia.

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Treatment

Three first-line treatments have proven efficacy in CIDP in randomized controlled trials: corticosteroids, intravenous immunoglobulin (IVIg), and plasma exchange (PLEX). All three are approximately equivalent in short-term efficacy; the choice between them depends on the clinical scenario, patient comorbidities, convenience, and antibody subtype.

Corticosteroids. Oral prednisone (starting at 1 mg/kg/day or 60 mg/day, tapered over months) or pulse intravenous methylprednisolone (500–1000 mg monthly) are both effective. Steroids improve both motor and sensory function. Their principal limitation is the broad toxicity of long-term use: osteoporosis, glucose dysregulation, hypertension, cataracts, adrenal suppression, weight gain, and mood disturbance. Steroid-sparing agents (azathioprine, mycophenolate mofetil, cyclosporine) are commonly added to allow dose reduction but lack large randomized trial evidence in CIDP specifically. Of note, steroids are effective in CIDP but are not effective in GBS — an important distinguishing practical point.

Intravenous immunoglobulin (IVIg). IVIg is given as an induction course (2 g/kg total over 2–5 days) followed by maintenance infusions (typically 1 g/kg every 3–4 weeks, adjusted by response). The ICE trial (2008) and subsequent Bayesian adaptive trials demonstrated significant improvement in grip strength and disability scores compared to placebo. IVIg acts through multiple mechanisms: saturating neonatal Fc receptors (FcRn) to accelerate IgG catabolism (including pathogenic autoantibodies), modulating complement activation, suppressing Fc receptor-mediated macrophage activity, and providing anti-idiotypic antibodies that neutralize specific autoantibodies. IVIg is preferred when rapid improvement is needed, in pregnant patients, and when steroid side effects are unacceptable. Its main limitations are cost, venous access requirements, and rare adverse effects (headache, thrombosis, renal failure with high-osmolarity preparations).

Subcutaneous immunoglobulin (SCIg). SCIg (administered by the patient at home using a small pump) has been shown in the PATH trial (2019) to maintain response in patients stabilized on IVIg. SCIg offers the convenience of home administration, a smoother pharmacokinetic profile (avoiding IVIg peaks and troughs), and may be preferred for long-term maintenance.

Plasma exchange (PLEX). PLEX works by directly removing pathogenic autoantibodies from the circulation. Standard courses involve five exchanges over 10–14 days. PLEX is as effective as IVIg for acute treatment but requires vascular access (often a central line) and a specialized apheresis unit. It is used when IVIg is contraindicated (IgA deficiency with anti-IgA antibodies, renal failure, thromboembolic risk) or when rapid reduction of antibody levels is needed. Its benefits are short-lived without ongoing maintenance, which limits its use as a sole long-term strategy.

Steroid-sparing immunosuppressants. Azathioprine (2–3 mg/kg/day) and mycophenolate mofetil (1500–3000 mg/day) are the most commonly used steroid-sparing agents, added after months of initial treatment to allow prednisone dose reduction. Cyclosporine is occasionally used. These agents take 3–6 months to become effective and require monitoring for bone marrow suppression and hepatotoxicity.

Rituximab. Rituximab (anti-CD20 monoclonal antibody that depletes B cells) is the treatment of choice for paranodal CIDP — particularly anti-NF155 and anti-CNTN1 subtypes — that fail IVIg. Case series and small open-label studies report substantial improvement after 1–2 cycles (375 mg/m² weekly ×4, or 1000 mg ×2). Rituximab is increasingly used in classical CIDP as well when first-line therapies fail or are poorly tolerated.

Efgartigimod and FcRn antagonists. The same class of drugs now approved for myasthenia gravis — efgartigimod, rozanolixizumab, batoclimab — that reduce IgG levels by blocking the FcRn recycling pathway are in Phase 2 and 3 trials for CIDP. Early results are promising, and these agents may provide a more selective way to reduce pathogenic IgG without the broad immunosuppression of steroids or the logistics of IVIg.

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Prognosis and Long-Term Management

With appropriate treatment, the majority of CIDP patients achieve meaningful functional improvement. Large natural history series report that about 60% of treated patients show good functional recovery, approximately 30% are left with moderate residual disability, and fewer than 10% progress to severe or refractory disability. The key prognostic factors are: time from symptom onset to diagnosis (longer delays allow more axonal loss), age at onset (older patients have less remyelination capacity), disease course (progressive worse than relapsing), and antibody subtype (paranodal subtypes have more severe initial presentations but can achieve remission with rituximab).

Treatment-dependency. A major challenge in CIDP management is that most patients require ongoing treatment to remain stable — spontaneous, sustained remission without any therapy occurs in only about 5–15% of patients and is more common in younger patients with relapsing-remitting disease. For the remainder, the practical question is whether treatment can be safely reduced or spaced. Guidelines recommend attempting gradual dose reduction (of IVIg intervals or steroid dose) every 6–12 months in stable patients, with monitoring for relapse. Some patients discover they can be maintained on minimal treatment; others relapse promptly with any reduction.

Monitoring response. The Medical Research Council (MRC) muscle scale, the Inflammatory Neuropathy Cause and Treatment (INCAT) disability scale, and grip strength dynamometry are the most widely used outcome measures. Nerve conduction studies are not reliable short-term treatment-response measures (remyelination of nerve fibers lags weeks to months behind clinical improvement) but are useful for baseline documentation and for identifying secondary axonal loss in patients plateauing despite immunotherapy.

Rehabilitation. Physical therapy targeting proximal and distal muscle strengthening, balance training, and gait rehabilitation is an essential adjunct to immunotherapy. Sensory ataxia responds partially to proprioceptive training and balance exercises. Occupational therapy addresses fine motor deficits and activities of daily living. Orthotics (ankle-foot orthoses) may be needed for foot drop from peroneal nerve involvement.

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Key Research Papers

  1. Hughes RAC, Donofrio P, Bril V, et al. Intravenous immune globulin (10% caprylate-chromatography purified) for the treatment of chronic inflammatory demyelinating polyradiculoneuropathy (ICE study): a randomised placebo-controlled trial. Lancet Neurol. 2008;7(2):136–144. PMID: 18178525
  2. Van den Bergh PYK, van Doorn PA, Hadden RDM, et al. European Academy of Neurology/Peripheral Nerve Society guideline on diagnosis and treatment of chronic inflammatory demyelinating polyradiculoneuropathy. Eur J Neurol. 2021;28(11):3556–3583. PMID: 34327760
  3. Doneddu PE, Cocito D, Manganelli F, et al. Atypical CIDP: diagnostic criteria, progression and treatment response. Data from the Italian CIDP database. J Neurol Neurosurg Psychiatry. 2019;90(2):125–132. PMID: 30224558
  4. Querol L, Nogales-Gadea G, Rojas-Garcia R, et al. Neurofascin IgG4 antibodies in CIDP associate with disabling tremor and poor response to IVIg. Neurology. 2014;82(10):879–886. PMID: 24523483
  5. Miura Y, Devaux JJ, Fukami Y, et al. Contactin 1 IgG4 associates to chronic inflammatory demyelinating polyneuropathy with sensory ataxia. Brain. 2015;138(Pt 6):1484–1491. PMID: 25867675
  6. Van den Berg LH, Mollee I, Wokke JH, Logtenberg T. Increased frequencies of HCMV-specific CD8+ T cells in the blood of patients with chronic idiopathic axonal polyneuropathy and chronic inflammatory demyelinating polyneuropathy. J Neuroimmunol. 1995;58(2):217–224. PMID: 7730452
  7. Rajabally YA, Narasimhan M. The value of sensory electrophysiology in chronic inflammatory demyelinating polyneuropathy. Clin Neurophysiol. 2007;118(6):1375–1380. PMID: 17452015
  8. Léger JM, De Bleecker JL, Guimarães-Costa R, et al. Efficacy and safety of subcutaneous immunoglobulin (0.2 g/kg per week) in patients with multifocal motor neuropathy who responded to IVIg treatment (SCIM study). J Neurol Neurosurg Psychiatry. 2018;89(10):1036–1044. PMID: 29648372
  9. Markvardsen LH, Harbo T, Sindrup SH, et al. Subcutaneous immunoglobulin preserves muscle strength in chronic inflammatory demyelinating polyneuropathy. Eur J Neurol. 2014;21(12):1465–1470. PMID: 25060817
  10. Mathey EK, Park SB, Hughes RAC, et al. Chronic inflammatory demyelinating polyradiculoneuropathy: from pathology to phenotype. J Neurol Neurosurg Psychiatry. 2015;86(9):973–985. PMID: 25677463
  11. Allen JA, Lewis RA. CIDP diagnostic pitfalls and perception of treatment benefit. Neurology. 2015;85(6):498–504. PMID: 26136516
  12. Eftimov F, Winer JB, Vermeulen M, de Haan R, van Schaik IN. Intravenous immunoglobulin for chronic inflammatory demyelinating polyradiculoneuropathy. Cochrane Database Syst Rev. 2013;(12):CD001797. PMID: 24338261

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Connections

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