Key Facts

CIDP is the most common chronic acquired demyelinating neuropathy. Unlike GBS, steroids are effective. Many patients require long-term immunotherapy. Early treatment prevents irreversible axonal damage.

Epidemiology

Prevalence ~2-5 per 100,000. Mean onset 40-60 years. M:F 2:1. Accounts for ~5% of all neuropathies referred to specialist centres.

Aetiology

• Autoimmune: cell-mediated and humoral immune mechanisms target peripheral nerve myelin
• Associated with: diabetes mellitus, paraproteinaemias (IgG, IgA, IgM — check SPEP), hepatitis C, HIV, inflammatory bowel disease, connective tissue disease
• Some patients have anti-NF155, anti-CNTN1, or anti-Caspr1 antibodies ("nodopathies" — may respond differently to treatment)

Pathophysiology

Immune-mediated segmental demyelination and remyelination of peripheral nerves and nerve roots. Both T-cell and macrophage-mediated stripping of myelin sheaths and complement-mediated damage. Chronic demyelination leads to secondary axonal degeneration (irreversible — hence importance of early treatment). Onion bulb formation on nerve biopsy (repeated demyelination/remyelination cycles).

Typical CIDP

• Progressive symmetric proximal AND distal weakness: develops over >8 weeks; legs and arms affected; both proximal and distal (unlike most neuropathies which are length-dependent/distal)
• Areflexia or hyporeflexia: global
• Sensory loss: large-fibre predominant (vibration, proprioception); sensory ataxia; paraesthesiae
• Course: progressive (~65%) or relapsing-remitting (~35%)

Atypical Variants

• Distal variant (DADS): distal acquired demyelinating symmetric neuropathy; often with IgM paraprotein and anti-MAG antibodies
• Multifocal variant (Lewis-Sumner): asymmetric, upper limb predominant; sensory + motor
• Pure sensory CIDP: sensory ataxia without weakness
• Pure motor CIDP: weakness without sensory loss

Red Flags

• Progressive weakness over >8 weeks (not self-limiting like GBS)
• Proximal AND distal weakness (unusual for most neuropathies)
• Relapsing course in a neuropathy

Neurophysiology (Essential)

• NCS: demyelinating features in ≥2 nerves: prolonged distal motor latencies (>50% above ULN), reduced motor conduction velocities (<70% of LLN), conduction block (>50% CMAP amplitude drop), temporal dispersion, prolonged/absent F-waves
• Meets EFNS/PNS electrodiagnostic criteria for definite, probable, or possible CIDP

CSF

• Raised protein (often >0.45 g/L) with normal cell count (albuminocytological dissociation)
• Cell count >10/μL → consider alternative (HIV, lymphoma, sarcoid)

Bloods

• SPEP and immunofixation: exclude paraprotein (IgM paraprotein + anti-MAG → different treatment approach)
• HbA1c, glucose: diabetes (coexistent or causative)
• FBC, U&Es, LFTs, TFTs: baseline
• HIV, hepatitis B/C: associated infections
• Anti-NF155, anti-CNTN1 antibodies: specialist; nodopathies

Imaging

• MRI spine: nerve root enhancement (hypertrophy); supports diagnosis but not specific
• Nerve ultrasound: nerve enlargement at non-entrapment sites — increasingly used

Other

• Nerve biopsy (sural nerve): rarely needed; shows demyelination, remyelination (onion bulbs), inflammatory infiltrates; reserve for atypical cases

First-Line (All Three Effective)

• Corticosteroids: prednisolone 60 mg OD (or pulsed IV methylprednisolone 500 mg-1 g daily × 3 days monthly); taper once response achieved
• IVIg: 0.4 g/kg/day × 5 days (2 g/kg total) loading; then maintenance 1 g/kg every 3-4 weeks; titrate to lowest effective dose
• Plasma exchange: 5 exchanges; effective but requires regular vascular access

Second-Line (Steroid-Sparing)

• Azathioprine 2-3 mg/kg/day
• Mycophenolate mofetil 1-3 g/day
• Ciclosporin, methotrexate

Refractory

• Rituximab: especially for anti-MAG or nodopathy variants
• SCIg (subcutaneous immunoglobulin): alternative to IVIg for maintenance; patient self-administers

Rehabilitation

• Physiotherapy, occupational therapy, orthotics (foot drop)
• Falls prevention

Referral Criteria

• All suspected CIDP: neurology (neuromuscular specialist)
• Consider trial of treatment cessation periodically to assess ongoing need

~60-80% respond to first-line treatment (steroids, IVIg, or PE). Relapsing-remitting course: generally better prognosis than progressive. ~10% become treatment-refractory. Early treatment prevents irreversible axonal damage and disability. Long-term IVIg dependence in ~50%. Complete remission in ~10-20%. Anti-MAG neuropathy: often more refractory to standard treatment. Nodopathies (anti-NF155): may respond to rituximab better than IVIg.

CIDP vs GBS

EFNS/PNS CIDP Diagnostic Criteria (Simplified)