Title: Central vs. Peripheral Nervous System Lesions – A Summary of Clinical Findings<br/>Author: WanTsu Wendy Chang<br/><a href='http://umem.org/profiles/faculty/1322/'>[Click to email author]</a><hr/><ul>
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<span style="font-size:14px;"><span style="font-family:arial,helvetica,sans-serif;">When dealing with weakness and sensory complaints in the ED, the time course of symptoms and physical exam findings help identify emergent conditions.</span></span></li>
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<span style="font-size:14px;"><span style="font-family:arial,helvetica,sans-serif;">We often talk about upper motor neuron vs. lower motor neuron signs that distinguish whether a lesion is in the central or peripheral nervous system.</span></span></li>
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<span style="font-size:14px;"><span style="font-family:arial,helvetica,sans-serif;">Characteristics that differentiate between central vs. peripheral nervous system pathology include:</span></span></li>
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<span style="font-size:14px;"><span style="font-family:arial,helvetica,sans-serif;"><strong>Central Nervous System</strong></span></span></td>
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<span style="font-size:14px;"><span style="font-family:arial,helvetica,sans-serif;"><strong>Peripheral Nervous System</strong></span></span></td>
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<span style="font-size:14px;"><span style="font-family:arial,helvetica,sans-serif;"><strong>Pattern of Symptoms</strong></span></span></td>
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<span style="font-size:14px;"><span style="font-family:arial,helvetica,sans-serif;">•<span style="white-space:pre"> </span>Hemibody involvement</span></span></div>
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<span style="font-size:14px;"><span style="font-family:arial,helvetica,sans-serif;">•<span style="white-space:pre"> </span>Weakness of UE extensors</span></span></div>
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<span style="font-size:14px;"><span style="font-family:arial,helvetica,sans-serif;">•<span style="white-space:pre"> </span>Weakness of LE flexors</span></span></div>
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<span style="font-size:14px;"><span style="font-family:arial,helvetica,sans-serif;">•<span style="white-space:pre"> </span>Distal involvement in polyneuropathy</span></span></div>
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<span style="font-size:14px;"><span style="font-family:arial,helvetica,sans-serif;">•<span style="white-space:pre"> </span>Distal and proximal involvement in polyradiculoneuropathy</span></span></div>
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<span style="font-size:14px;"><span style="font-family:arial,helvetica,sans-serif;">•<span style="white-space:pre"> </span>Proximal involvement in polyradiculopathy</span></span></div>
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<span style="font-size:14px;"><span style="font-family:arial,helvetica,sans-serif;">•<span style="white-space:pre"> </span>Sensory often precedes motor symptoms </span></span></div>
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<span style="font-size:14px;"><span style="font-family:arial,helvetica,sans-serif;">•<span style="white-space:pre"> </span>Pure proximal>distal weakness may be due to myopathy or NMJ disorder</span></span></div>
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<span style="font-size:14px;"><span style="font-family:arial,helvetica,sans-serif;"><strong>Sensory Symptoms</strong></span></span></td>
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<span style="font-size:14px;"><span style="font-family:arial,helvetica,sans-serif;">• Central poststroke pain (hyperalgesia, allodynia)</span></span></div>
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<span style="font-size:14px;"><span style="font-family:arial,helvetica,sans-serif;">• Sensory level in spinal cord pathology </span></span></div>
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<span style="font-size:14px;"><span style="font-family:arial,helvetica,sans-serif;">• Proprioception involved early in dorsal column disorders</span></span></div>
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<span style="font-size:14px;"><span style="font-family:arial,helvetica,sans-serif;">•<span style="white-space:pre"> </span>Neuropathic pain (burning, tingling, shock-like) </span></span></div>
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<span style="font-size:14px;"><span style="font-family:arial,helvetica,sans-serif;">•<span style="white-space:pre"> </span>Ascending sensory loss involving distal BLE>BUE in polyneuropathy</span></span></div>
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<span style="font-size:14px;"><span style="font-family:arial,helvetica,sans-serif;">•<span style="white-space:pre"> </span>Proprioception involved late in polyneuropathy</span></span></div>
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<span style="font-size:14px;"><span style="font-family:arial,helvetica,sans-serif;"><strong>Reflexes</strong></span></span></td>
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<span style="font-size:14px;"><span style="font-family:arial,helvetica,sans-serif;">•<span style="white-space:pre"> </span>Hyperreflexia in affected limb(s) after acute period</span></span></div>
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<span style="font-size:14px;"><span style="font-family:arial,helvetica,sans-serif;">•<span style="white-space:pre"> </span>Positive Babinski’s sign</span></span></div>
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<span style="font-size:14px;"><span style="font-family:arial,helvetica,sans-serif;">•<span style="white-space: pre;"> </span>Hyporeflexia in affected limb(s)</span></span></td>
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<span style="font-size:14px;"><span style="font-family:arial,helvetica,sans-serif;"><strong>Tone</strong></span></span></td>
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<span style="font-size:14px;"><span style="font-family:arial,helvetica,sans-serif;">•<span style="white-space: pre;"> </span>Increased after acute period</span></span></td>
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<span style="font-size:14px;"><span style="font-family:arial,helvetica,sans-serif;">•<span style="white-space: pre;"> </span>Decreased</span></span></td>
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<em><span style="font-size:14px;"><span style="font-family:arial,helvetica,sans-serif;">UE = upper extremity</span></span></em></div>
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<em><span style="font-size:14px;"><span style="font-family:arial,helvetica,sans-serif;">LE = lower extremity</span></span></em></div>
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<em><span style="font-size:14px;"><span style="font-family:arial,helvetica,sans-serif;">NMJ = neuromuscular junction</span></span></em></div>
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<span style="font-size:14px;"><span style="font-family:arial,helvetica,sans-serif;"><strong><u>Bottom Line</u>:</strong> A systematic approach to the evaluation of weakness and sensory complaints in the ED help differentiate between central vs. peripheral nervous system pathology.</span></span></div>
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<fieldset><legend>References</legend>
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London ZN. A structured approach to the diagnosis of peripheral nervous system disorders. <em>Continuum Minneap Minn)</em> 2020;26(5, Peripheral Nerve and Motor Neuron Disorders):1130-60.</div>
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<em><strong>Follow me on Twitter @EM_NCC</strong></em></div>
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