Types of CIDP Affecting Nerve Roots
The polyradiculoneuropathy variant of Chronic Inflammatory Demyelinating Polyneuropathy (CIDP) is the primary type that affects the nerve roots, characterized by symmetric proximal and distal weakness with preferential involvement of the nerve roots where the blood-nerve barrier is anatomically deficient. 1, 2
Typical CIDP (Polyradiculoneuropathy)
- Typical CIDP predominantly affects the nerve roots and distal nerve terminals, where the blood-nerve barrier is anatomically deficient, leading to symmetric polyneuropathy 1, 2
- This variant is characterized by symmetric proximal and distal muscle weakness with motor-dominant manifestations 2
- The pathogenesis likely involves antibody-mediated demyelination targeting these vulnerable areas of the peripheral nervous system 1, 2
- MRI can demonstrate diffuse and extensive hypertrophy of the spinal nerve roots, often with gadolinium enhancement in the nerve roots 3
Atypical CIDP Variants Affecting Nerve Roots
Multifocal Acquired Demyelinating Sensory and Motor Neuropathy (MADSAM or Lewis-Sumner Syndrome):
- Characterized by asymmetric involvement with preserved reflexes in areas not affected by weakness 4, 5
- Predominantly affects the nerve trunks rather than roots, resulting in multiple mononeuropathy or asymmetric polyneuropathy 2
- More likely involves cellular immunity in the breakdown of the blood-nerve barrier at sites of conduction block 2
- Can be misdiagnosed as focal compressive neuropathy due to its asymmetric nature 5
Hypertrophic CIDP variant:
- Features extensive and diffuse hypertrophy of the nerve roots and peripheral nerves 3
- Presents with slowly progressive sensory impairment and distally predominant limb weakness 3
- MRI shows diffuse hypertrophy of peripheral nerves and spinal nerve roots with gadolinium enhancement specifically in the nerve roots 3
Diagnostic Considerations
- MRI of the brachial or lumbosacral plexus can help identify focal or diffuse peripheral nerve abnormalities in CIDP variants 4
- Nerve biopsy may be particularly useful in evaluating atypical forms of CIDP, as these variants may have distinctive pathological features 4
- Electrophysiological studies can distinguish between CIDP and other conditions like Guillain-Barré syndrome (GBS), which also affects nerve roots but has an acute onset 6
- Cerebrospinal fluid analysis typically shows cytoalbuminologic dissociation (elevated protein with normal cell count) in both CIDP and GBS 6
Clinical Differentiation from Other Conditions
- Unlike Guillain-Barré syndrome, which is acute and monophasic with progression over days to weeks, CIDP progresses over more than 2 months 6, 7
- CIDP must be distinguished from other causes of polyradiculoneuropathy such as:
Treatment Implications Based on Subtype
- First-line treatments for typical CIDP with nerve root involvement include corticosteroids, intravenous immunoglobulin (IVIG), and plasma exchange 7, 8
- Patients with antibodies against paranodal junction proteins (neurofascin 155, contactin 1) may be refractory to IVIG and might benefit from rituximab 8
- The distribution of lesions in different CIDP subtypes may necessitate different treatment approaches 2, 8
- Subcutaneous administration of immunoglobulin provides a new treatment option that may increase independence and improve tolerability 7
Understanding the specific CIDP variant affecting the nerve roots is crucial for appropriate diagnosis and targeted treatment to prevent permanent nerve damage.