Table 1

 Methods used in localising upper limb focal mononeuropathies

NerveSite of lesionDemonstration of focal slowingFinding changes in CMAP and SAPDennervation changes in nerve distributionComments
+++ high likelihood; ++ probable finding; + possible finding; – unlikely finding.
Findings will be dependant on severity of lesion.
CMAP, compound motor action potential; NA, not applicable; SAP, sensory action potential.
MedianCarpal tunnel+++++++EMG not usually needed
UlnarElbow (cubital tunnel)++++++
RadialUpper arm++++++
AxillaryHumeral headNANA++
UlnarWrist (Guyon’s canal) or hand++++++Depends on other ulnar studies being normal
Long thoracicNot clearNANA++Limited usefulness; small risk of pneumothorax
Anterior interosseous branch of median nerveJust below the elbowNANA++Depends on other median studies being normal
Posterior interosseous branch of radial nerveAs nerve enters supinator muscleNANA++Depends on other radial nerve studies being normal
SuprascapularSuprascapular notchNA++++