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Chronic Inflammatory Demyelinating Polyneuropathy

Chronic Inflammatory Demyelinating Polyneuropathy: Pathogenesis & clinical findings Unknown trigger (e.g., surgery, trauma, autoimmune disorder, environmental factors) Systemic illness (e.g., hepatitis B, Hepatitis C, HIV, thyroid Disease, nephrotic syndrome, irritable bowel syndrome) Authors: Andrea Soumbasis Reviewers: Braxton Phillips Shahab Marzoughi Sina Marzoughi* * MD at time of publication Autoimmune response initiation Lumbar Puncture: Cytoalbuminologic Dissociation CSF protein count elevated with normal cell count Cell-mediated response: Putative antigen (unidentified immune target) presents to auto-reactive T cells Activated T cells secrete inflammatory mediators (matrix metalloproteinases) Inflammatory response ↑ peripheral nerve permeability & T cells cross blood-nerve barrier Humoral Response: Immunoglobulin & complement deposits on compact myelin & nodal regions Autoantibodies target unknown epitope (antigen molecule recognized by antibody) on outer surface of Schwann cells IgG4 antibodies target axoglial junction (Contactin-1, Neurofascin 155) that maintain Node of Ranvier of myelinated axons ↑ Permeability of blood- nerve barrier allows large proteins to leak into CSF CD8+ T cells, CD4+ T cells & macrophages infiltrate peripheral nerves Macrophages form clusters around endoneurium, release proinflammatory cytokines & strip away myelin via phagocytosis Abnormal expression & distribution of Contactin-1 & Neurofascin 155 antibodies along axoglial junction Disrupted ion channel segregation & paranodal structure ↓ Saltatory conduction Nodopathy & Paranodopothy: Neurofascin 155 – Distal sensorimotor ataxia Contactin-1 – Sensorimotor ataxia Caspr-1 – Neuropathic pain & nephrotic syndrome Onion bulb formation: Nerve biopsy showing concentric, circular layers of cells surrounding the axon Segmental demyelination & remyelination of peripheral nerves ↑ Demyelination Chronic Inflammatory Demyelinating Polyneuropathy Progressive weakness & sensory loss over a period of greater than 8 weeks due to autoimmune dysfunction Peripheral nerve degeneration & conduction velocity Nerve Conduction Study: Partial nerve conduction block, conduction velocity slowing, prolonged distal motor latencies, delay or disappearance of CMAP (compound muscle action potential) Lesions of larger myelinated fibers in the dorsal columns for vibration & position sense Lesions of peripheral motor nerves in non-length dependent pattern (does not only affect longest nerves first) Motor Deficits ↓ Sensory input and/or ↓ motor output Abnormal Reflexes Globally ↓ reflexes Lesions affecting sympathetic & parasympathetic nerve fibers Autonomic Deficits Bladder & bowel dysfunction, heart rate irregularities, blood pressure fluctuation Sensory Deficits Gait ataxia Proximal weakness (muscles closer to the trunk or center of the body): Difficulty climbing stairs, rising from seated position, lifting objects overhead, frequent falls Distal weakness (muscles farther from the trunk or the extremities): Tripping due to foot drop, difficulty with fine motor tasks ↓ Vibration & proprioception Paraesthesias (e.g., tingling, numbness) Legend: Pathophysiology Mechanism Sign/Symptom/Lab Finding Complications Published Dec 29, 2024 on www.thecalgaryguide.com