Table 2

 Methods used in localising lower 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.
Common
Lateral cutaneous nerve of the thighInguinal ligamentNANAElectrodiagnostic studies limited in this common mononeuropathy
Common peronealFibular head+++++++
InterdigitalBetween heads of metatarsalsNANADifficult nerves to study
Uncommon
FemoralNANA+++Distinguish from plexopathy/radiculopathy
SciaticPelvis, buttock or thighNA+++++
Tibial, at ankleTarsal tunnel+++++
PerinealAlcock’s canalNANANA
SaphenousThigh or kneeNA+NA
Rare
Tibial, at kneeNA+++++
Posterior cutaneous nerve of the thighNANANALimited use
ObturatorObturator foramenNANA++
GlutealNANA++
SuralNA+++NA