Difference Between Paresis and Plegia
Paresis refers to partial or incomplete loss of voluntary motor function, while plegia (paralysis) indicates complete loss of voluntary motor function in the affected body part. 1, 2
Core Definitions
Paresis is defined as incomplete ability to move the face or affected body part, representing a partial movement impairment of neural or muscular origin 1, 2
Plegia (Paralysis) is defined as complete inability to move the face or affected body part, representing total loss or impairment of motor function due to a lesion of the neural or muscular mechanism 1, 2
Clinical Application and Terminology
The suffix "-paresis" should be used for partial paralysis of a limb or body part, while "-plegia" should be used for total paralysis 3
In facial nerve disorders specifically, facial paresis indicates incomplete facial movement ability, whereas facial paralysis indicates complete inability to move the face 1, 2
For vocal fold disorders, vocal fold paralysis refers to loss or impairment of motor function, while paresis is a partial movement impairment, both of neural or muscular origin 1
Important Clinical Distinction
The terms "complete" and "incomplete" should NOT be used as qualifiers with "plegia" - patients with any preservation of motor strength should be described as "paretic" rather than "incomplete plegic" 4
When the basis for movement impairment is unknown or results from mechanical limitations (such as joint pathology or mass effect), the term "immobility" should be used rather than paresis or paralysis 1
Grading Severity
Motor weakness exists on a spectrum, with paresis representing intermediate weakness (typically strength scores of 1-3 out of 5) and plegia representing complete absence of movement (strength score of 0) 5
The distinction is clinically significant because prognosis and treatment approaches may differ - for example, in Bell's palsy, patients with incomplete paralysis (paresis) have recovery rates up to 94%, compared to approximately 70% for those with complete paralysis 6, 2
Common Pitfalls to Avoid
Do not use "incomplete paraplegia" when "paraparesis" is the correct term - this represents inadequate use of terminology when "incomplete" is associated with "plegia" as a qualifier 4
Avoid confusing neurological impairment (paresis/plegia) with mechanical immobility, which requires different terminology and has different treatment implications 1