Harrison's Manual of Medicine
Chapter 196: Peripheral Neuropathies, Including Guillain-Barré Syndrome
Approach to the patient: Peripheral Neuropathy
Peripheral neuropathy (PN) refers to a peripheral nerve disorder of any cause. Nerve involvement may be single (mononeuropathy) or multiple (polyneuropathy); pathology may be axonal or demyelinating. An approach to pts with suspected neuropathy appears in Fig. 196-1.
Seven initial questions:
- What systems are involved? Determine if symptoms and signs are predominantly motor, sensory, autonomic, or a combination of these. If only weakness is present without sensory or autonomic dysfunction, consider a motor neuropathy, neuromuscular junction disorder, or myopathy; myopathies usually have a proximal, symmetric pattern of weakness.
- What is the distribution of weakness? Polyneuropathy involves widespread and often symmetric dysfunction of the peripheral nerves that is usually distal more than proximal; mononeuropathy involves a single nerve, usually due to trauma or compression; multiple mononeuropathies (mononeuropathy multiplex) can be a result of multiple entrapments, vasculitis, or infiltration.
- What is the nature of the sensory involvement? Temperature loss or burning/stabbing pain suggests small fiber involvement. Vibratory or proprioceptive loss implicates large fibers.
- Is there evidence of upper motor neuron involvement? The most common cause is combined system degeneration with B12 deficiency, but should also consider copper deficiency, HIV infection, severe hepatic disease, and adrenomyeloneuropathy.
- What is the temporal evolution? Most neuropathies are insidious and slowly progressive. Rapidly evolving neuropathies are often inflammatory, including acute inflammatory demyelinating polyneuropathy (AIDP) or Guillain-Barré syndrome (GBS); subacute evolution suggests an inflammatory, toxic, or nutritional cause; chronic neuropathies that are long-standing over years may be hereditary.
- Is there evidence for a hereditary neuropathy? Consider in pts with a slowly progressive distal weakness over many years with few sensory symptoms but significant sensory deficits on clinical examination. Most common is Charcot-Marie-Tooth disease (CMT; look for foot abnormalities such as high or flat arches and hammer toes as well as scoliosis).
- Does the pt have other medical conditions? Inquire about associated medical conditions (e.g., diabetes, systemic lupus erythematosus); preceding or concurrent infections (e.g., diarrheal illness preceding GBS); surgeries (e.g., gastric bypass and nutritional neuropathies); medications (toxic neuropathy); over-the-counter vitamin preparations (B6); alcohol, dietary habits; and use of dentures (because fixatives contain zinc that can lead to copper deficiency).
Based on the answers to these seven key questions, neuropathic disorders can be classified into several patterns based on the pattern of sensory, motor, and autonomic involvement (Table 196-1).
Pattern 1: Symmetric proximal and distal weakness with sensory loss Consider: inflammatory demyelinating polyneuropathy (GBS and CIDP) Pattern 2: Symmetric distal sensory loss with or without distal weakness Consider: cryptogenic or idiopathic sensory polyneuropathy (CSPN), diabetes mellitus and other metabolic disorders, drugs, toxins, familial (HSAN), CMT, amyloidosis, and others Pattern 3: Asymmetric distal weakness with sensory loss With involvement of multiple nerves Consider: multifocal CIDP, vasculitis, cryoglobulinemia, amyloidosis, sarcoid, infectious (leprosy, Lyme, hepatitis B, C, or E, HIV, CMV), HNPP, tumor infiltration With involvement of single nerves/regions Consider: may be any of the above but also could be compressive mononeuropathy, plexopathy, or radiculopathy Pattern 4: Asymmetric proximal and distal weakness with sensory loss Consider: polyradiculopathy or plexopathy due to diabetes mellitus, meningeal carcinomatosis or lymphomatosis, sarcoid, amyloid, hereditary plexopathy (HNPP, HNA), idiopathic Pattern 5: Asymmetric distal weakness without sensory loss With upper motor neuron findings Consider: motor neuron disease Without upper motor neuron findings Consider: progressive muscular atrophy, juvenile monomelic amyotrophy (Hirayama’s disease), multifocal motor neuropathy, multifocal acquired motor axonopathy Pattern 6: Symmetric sensory loss and distal areflexia with upper motor neuron findings Consider: Vitamin B12, vitamin E, and copper deficiency with combined system degeneration with peripheral neuropathy, chronic liver disease, hereditary leukodystrophies (e.g., adrenomyeloneuropathy) HSP-plus Pattern 7: Symmetric weakness without sensory loss With proximal and distal weakness Consider: SMA With distal weakness Consider: hereditary motor neuropathy (“distal” SMA) or atypical CMT Pattern 8: Focal midline proximal symmetric weakness Neck extensor weakness Consider: ALS Bulbar weakness Consider: ALS/PLS, isolated bulbar ALS (IBALS), Kennedy’s syndrome (X-linked, bulbospinal SMA), bulbar presentation GBS Diaphragm weakness (SOB) Consider: ALS Pattern 9: Asymmetric proprioceptive sensory loss without weakness Consider causes of a sensory neuronopathy (ganglionopathy): Cancer (paraneoplastic) Sjögren’s syndrome Idiopathic sensory neuronopathy (possible GBS variant) Cisplatin and other chemotherapeutic agents Vitamin B6 toxicity HIV-related sensory neuronopathy Pattern 10: Autonomic symptoms and signs Consider neuropathies associated with prominent autonomic dysfunction: Hereditary sensory and autonomic neuropathy Amyloidosis (familial and acquired) Diabetes mellitus Idiopathic pandysautonomia (may be a variant of Guillain-Barré syndrome) Porphyria HIV-related autonomic neuropathy Vincristine and other chemotherapeutic agents |
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