Title: Central vs. Peripheral Nervous System Lesions A Summary of Clinical Findings

Category: Neurology

Keywords: CNS, PNS, UMN, LMN, reflex, Babinski, tone (PubMed Search)

Posted: 10/14/2020 by WanTsu Wendy Chang, MD

When dealing with weakness and sensory complaints in the ED, the time course of symptoms and physical exam findings help identify emergent conditions.
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.
Characteristics that differentiate between central vs. peripheral nervous system pathology include:

	Central Nervous System	Peripheral Nervous System
Pattern of Symptoms	• Hemibody involvement • Weakness of UE extensors • Weakness of LE flexors	• Distal involvement in polyneuropathy • Distal and proximal involvement in polyradiculoneuropathy • Proximal involvement in polyradiculopathy • Sensory often precedes motor symptoms • Pure proximal>distal weakness may be due to myopathy or NMJ disorder
Sensory Symptoms	• Central poststroke pain (hyperalgesia, allodynia) • Sensory level in spinal cord pathology • Proprioception involved early in dorsal column disorders	• Neuropathic pain (burning, tingling, shock-like) • Ascending sensory loss involving distal BLE>BUE in polyneuropathy • Proprioception involved late in polyneuropathy
Reflexes	• Hyperreflexia in affected limb(s) after acute period • Positive Babinski’s sign	• Hyporeflexia in affected limb(s)
Tone	• Increased after acute period	• Decreased

UE = upper extremity

LE = lower extremity

NMJ = neuromuscular junction

Bottom Line: A systematic approach to the evaluation of weakness and sensory complaints in the ED help differentiate between central vs. peripheral nervous system pathology.

References

London ZN. A structured approach to the diagnosis of peripheral nervous system disorders. Continuum Minneap Minn) 2020;26(5, Peripheral Nerve and Motor Neuron Disorders):1130-60.

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