DISEASESOF THE PERIPHERAL NERVE
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This document provides an overview of peripheral nervous system disorders and their diagnosis and management. It begins with a stepwise approach to diagnosis, considering etiology, inheritance, temporal profile, fiber involvement, and spatial distribution. Common causes of peripheral neuropathy like diabetes, toxins, and infections are reviewed. The roles of laboratory testing, nerve biopsy, and disease-modifying therapies are discussed. Specific neuropathies like Guillain-Barré syndrome are then described in more detail.
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DISEASESOF THE PERIPHERAL NERVE
- 1. DISEASES OF THE PERIPHERAL NERVE MUKESH SAH, MD UNITED KINGDOM
- 2. MOTOR UNIT
- 3. Stepwise approach to the diagnosis of peripheral nervous system disorders Does a medical disorder or neurotoxin exposure account for the neuropathy? Is the disorder familial? Axonal versus demyelinating? What is the temporal profile? Which fibers are involved? What is the spatial distribution? Does the patient have a peripheral nervous system disorder?
- 4. Stepwise approach to the diagnosis of peripheral nervous system disorders Is a specific etiology suggested? YES Confirmatory Studies (laboratory tests, selected tissue biopsies) NO Screening Laboratory Studies (based on clinical and electrophysiologic classification of the neuropathy)
- 5. Stepwise approach to the diagnosis of peripheral nervous system disorders Etiologic Diagnosis Established (+/- 80%) Cryptogenic Neuropathy (+/- 20%)
- 6. Peripheral nervous system disorders: spatial patterns FOCAL MULTIFOCAL (ASYMMETRIC) DIFFUSE (SYMMETRIC) Mononeuropathy Monoradiculopathy Brachial plexopathy Lumbosacral plexopathy Motor neuronopathy Dorsal root ganglionopathy Multiple mononeuropathies Polyradiculopathy Motor neuropathy Motor neuronopathy Polyneuropathy Dorsal root ganglionopathy Motor neuronopathy
- 7. Pattern of Nerve Fiber Type Involvement Sensory Motor Autonomic Large-caliber ◦Motor fibers ◦Type A-αand A- βsensory afferents Small-caliber ◦A-δand C fibers
- 8. TEMPORAL PROFILE ACUTE ◦Days to weeks SUBACUTE ◦6 weeks to 6 months CHRONIC ◦6 months to years Monophasic Progressive ◦Uniform or stepwise Relapsing, remitting
- 9. AXONAL vs DEMYELINATING Axonal ◦ Causes are abundant Demyelinating ◦ Suggests just a few etiologies ◦ Segmental (multifocal) or uniformly slow
- 10. FAMILY HISTORY Approximately 40% are hereditary neuropathies: ◦ Long-standing inherited neuropathies may produce characteristic deformities of the foot (pes cavus) and spine (kyphoscoliosis) ◦ Typical hereditary motor-sensory neuropathy has little in the way of positive sensory symptoms ◦ Clinical and electrodiagnostic examination of family members, even when asymptomatic, may reveal polyneuropathy
- 11. The under-recognition of hereditary neuropathies may be attributed to: Failure to elicit an adequate family history The occurrence of de novo mutations (e.g., peripheral myelin protein-22 gene duplication associated with CMT- 1A) Recessive and x-linked inheritance patterns The fact that neuropathy may remain asymptomatic for decades
- 12. Medical Comorbidity, Medications, and Toxins Diabetes mellitus Connective tissue disease Underlying malignancy Infection Malnutrition Megavitaminosis Exposure to drugs, alcohol, and toxins
- 13. ROLE OF LABORATORY TESTING Most patients with peripheral neuropathy, whether acute or chronic, should have a: ◦ Complete blood count ◦ Serum electrolytes ◦ Renal and liver function studies ◦ Screening for diabetes mellitus ◦ Fasting blood glucose ◦ Hemoglobin AIc
- 14. ROLE OF LABORATORY TESTING For patients with chronic sensorimotor polyneuropathies, they should be screened for: ◦Paraproteinemia with: ◦Serum immunofixation ◦Immunoelectrophoresis
- 15. ROLE OF NERVE BIOPSY Sural nerve Superficial peroneal nerve Radial sensory nerve Yields a diagnosis in 27% of cases and provides useful information in a further 37% Moderately involved nerve is preferable
- 16. ROLE OF NERVE BIOPSY Primary indication: ◦To identify potentially treatable neuropathies in undiagnosed progressive acute or subacute asymmetric and, less commonly, symmetric sensorimotor polyneuropathies May confirm a diagnosis of leprosy, if skin biopsy is not diagnostic
- 17. PITFALLS IN THE EVALUATION OF PERIPHERAL NEUROPATHY False-positive diagnosis of peripheral neuropathy: lumbosacral polyradiculopathy Not all distal weakness is due to peripheral neuropathy Amyotrophic Lateral Sclerosis Failure to consider age
- 18. PITFALLS IN THE EVALUATION OF PERIPHERAL NEUROPATHY Distinction between Acute Central and Peripheral Nervous System Disorders Erroneous Diagnosis of Chronic Inflammatory Demyelinating Polyneuropathy Diagnosis of Peripheral Neuropathy is Correct, but the Cause is Falsely Attributed False-Negative Diagnosis of Peripheral Neuropathy
- 19. Approach to the Management and Follow-up of Patients with Peripheral Neuropathy Therapeutic approaches ◦Those that alter the natural history of the disease ◦Symptomatic psychotherapies ◦Rehabilitative therapies to limit disability
- 20. Disease-modifying therapy in treatable neuropathies Plasmapheresis IVIg Corticosteroids Cytotoxics (e.g., cyclophosphamide) Endocrine treatment Vitamin replacement Interferon – α Antimicrobials Radiation/surgery
- 21. Neuropathies Facial Nerve Paralysis Brachial Plexus Injury Inflammatory Neuropathies Hereditary Neuropathies Friedreich’s Ataxia Giant Axonal Neuropathy Infantile Neuroaxonal Dystrophy Metabolic Neuropathies Toxic Neuropathies
- 23. Guillain - Barré Syndrome (GBS) A number of related immune polyneuropathies that cause acute generalized weakness Affects individuals of all races and ages An acute viral syndrome or other infectious illness occurs 1 – 4 weeks prior to the onset of GBS Most common viral trigger is CMV Most common infection preceding GBS is Campylobacter jejuni
- 24. Pathophysiology of GBS There is endoneurial inflammation predominantly affecting the nerve roots, and an immune-mediated attack directed against components of the myelin sheath or nerve axon
- 25. Clinical Features Weakness ◦Always bilateral, but some degree of asymmetry is common Reduced or absent deep tendon reflexes Cytoalbuminologic dissociation
- 26. GBS Variants Axonal Forms ◦ Acute motor-sensory axonal neuropathy ◦ Acute motor axonal neuropathy Miller-Fisher syndrome Pure motor GBS Pure sensory GBS Pure dysautonomia Pharyngeal-cervical-brachial weakness Paraparetic variant Ataxic with or without ophthalmoplegia Acral paresthesias with abducens palsies Acral paresthesias with peroneal palsies Facial diplegia with paresthesias
- 28. Thank you