Peripheral Neuropathies, Including Guillain-Barré Syndrome
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Approach to the patient
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. 193-1.
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 193-1).
|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, 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, hereditary leukodystrophies (e.g., adrenomyeloneuropathy)|
|Pattern 7: Symmetric weakness without sensory loss|
|With proximal and distal weakness|
|With distal weakness|
|Consider: hereditary motor neuropathy (“distal” SMA) or atypical CMT|
|Pattern 8: Asymmetric proprioceptive sensory loss without weakness|
|Consider causes of a sensory neuronopathy (ganglionopathy):|
|Idiopathic sensory neuronopathy (possible GBS variant)|
|Cisplatin and other chemotherapeutic agents|
|Vitamin B6 toxicity|
|HIV-related sensory neuronopathy|
|Pattern 9: Autonomic symptoms and signs|
|Consider neuropathies associated with prominent autonomic dysfunction:|
|Hereditary sensory and autonomic neuropathy|
|Amyloidosis (familial and acquired)|
|Idiopathic pandysautonomia (may be a variant of Guillain-Barré syndrome)|
|HIV-related autonomic neuropathy|
|Vincristine and other chemotherapeutic agents|