How do you differentiate between mild, incomplete, and complete paralysis of the median nerve?

Classification of Median Nerve Paralysis Severity

Classify median nerve paralysis based on clinical examination of motor function: mild paralysis presents with weakness but preserved movement against gravity, incomplete paralysis shows some antigravity effort but inability to sustain position, and complete paralysis demonstrates no voluntary movement at all in median nerve-innervated muscles.

Clinical Classification Framework

The distinction between mild, incomplete, and complete paralysis relies primarily on clinical motor examination rather than electrodiagnostic testing for initial classification 1.

Complete Paralysis

• No visible voluntary muscle contraction in median nerve-innervated muscles (thenar muscles, lateral lumbricals) 1
• Patient cannot initiate any movement despite maximal effort 1
• Complete inability to oppose the thumb or flex the index and middle fingers at the interphalangeal joints 2
• Electrodiagnostic testing becomes informative only after 7 days following symptom onset due to Wallerian degeneration progression 1

Incomplete Paralysis

• Some antigravity motor effort present but cannot sustain position 1
• Visible muscle contraction occurs but movement is weak and fatigues rapidly 1
• Patient can initiate thumb opposition or finger flexion but cannot maintain against resistance 1
• Partial thenar muscle function remains with weakness rather than complete loss 2

Mild Paralysis (Paresis)

• Facial weakness with preserved function - this terminology derives from facial nerve grading but applies to peripheral nerve assessment 1
• Movement against gravity is maintained for the full duration of testing 1
• Weakness is detectable on examination but functional movements remain possible 1
• Patient can perform opposition and precision pinch, though with reduced strength 3, 2

Key Clinical Examination Points

Motor testing should assess:

• Thumb opposition strength (abductor pollicis brevis) - ask patient to touch thumb to little finger and resist your attempt to break the position 2
• Index finger flexion at distal interphalangeal joint (flexor digitorum profundus to index) 2
• Thenar muscle bulk - compare to contralateral side for atrophy 3, 4

Sensory examination findings:

• Sensory deficit on radial aspect of palm and radial 3½ digits suggests median nerve involvement 2
• Two-point discrimination >5mm indicates severe involvement 4

Critical Timing Considerations

Electrodiagnostic testing timing matters significantly:

• Testing before 7 days is unreliable due to ongoing Wallerian degeneration 1
• Testing after 14-21 days may be less reliable 1
• Optimal window is 7-14 days after symptom onset for complete paralysis 1

When Electrodiagnostic Testing Adds Value

Do NOT perform electrodiagnostic testing for incomplete paralysis - it provides no additional benefit and clinical examination suffices 1

Consider electrodiagnostic testing only for complete paralysis to provide prognostic information 1:

• Electroneuronography (ENoG) comparing affected to unaffected side 1
• If response amplitude >10% of contralateral side, most patients recover normal function 1
• If amplitude <10%, higher percentage experience incomplete recovery 1

Common Pitfalls to Avoid

Do not rely solely on patient symptoms - there is notable discordance (22% difference) between symptom-based diagnosis and objective testing for mild-to-moderate neuropathy 4

Do not confuse sensory symptoms with motor paralysis classification - pain and paresthesias in median nerve distribution do not define paralysis severity 3

Avoid premature electrodiagnostic testing - testing before 7 days will be misleading as nerve degeneration is still progressing 1

Do not overlook functional assessment - the ability to perform precision pinch and grasp is the most clinically relevant outcome measure 2