NCV FINDINGS IN LOWER LIMBS

NCV FINDINGS IN LOWER LIMBSLumbosacral plexopathyClinical picture:Lumbar plexopathyAbrupt onset of painLocation :- ante aspect of thighMuscle wasting and weakness after 2-3 weeksAbsent knee jerkTenderness of the femoral nervePositive femoral stretch sign

Sacral plexopathyLocation of pain: buttock ,posterior thighWeakness of knee flexorsAbsent ankle reflexPositive SLRNCS of femoral, peroneal,sural and saphenous nerves normalAmplitude is reducedFEMORAL NERVECauses:-Diabetes mellitusIntrapelvic hematomaAbscessPelvic surgeryTumor of vertebraFemoral vein and arterial cannulation Compression by inguinal ligament during coma

Femoral neuropathy:clinical pictureWeakness and wasting quadricepsAbsent knee reflexVariable sensory loss anteromedial aspect of thigh, medial aspect of leg.

NCS:Motor conduction studies :slowing of conduction velocitySmall CMAP amplitudeAt level of inguinal ligament: conduction blockStimulate above and below the inguinal ligament and compare CMAPSensory functions-> conduction in saphenous nerve

PARAMETERSFEMORALNEUROPATHYLUMBARPLEXOPATHYL3 RADICULOPATHYWEAKNESSQUADRICEPSQUADRICEPSADDUCTORSILIOPSOASQUADRICEPSADDUCTORS OF THIGHSAPHENOUS SNAPREDUCEDREDUCEDNORMALEMG CHANGESQUADRICEPSQUADRICEPSADDUCTORS OF THIGHPARASPINALILIOPSOASADDUCTORS OF THIGH,QUADRICEPSSAPHENOUS NERVE Uncommonly injuredPresents as-sensory impairment in the medial aspect of knee, leg, footCauses:Laceration injuriesEntrapment in subsartorial canalSurgery for varicose veinNCS- stimulation 1cm above the infe. Border of the patella btw gracilis and sartorious.

Recording 15cm distal to the point of stimulation, medial border of the tibia.

Conduction in the distal part checked by-nerve stimulation btw the medial head of the gastronemius and tibia, 12-14cm prox. To medial malleolus.Recording electrodeanterior to the medial malleolusNcv 49.03+_ 3.36SNAP amplitude 3.54+_1.52LATERAL CUTANEOUS NERVE OF THIGH Cause :-Entrapment at inguinal canal due to;Corsets, seat belts , obesityPsoas major abscess, retroperitoneal tumorPost op scarring of iliac fossaNCS:-Recording electrode 17-20 cm distal to ASISReference electrode 3cm distal to the active electrodeAntidromic stimulation:Stimulation above inguinal ligament 1cm medial to ASIS and below the inguinal ligament over origin of sartoriusLatency 2.8+_0.4 msAmplitude 6.0+_1.5 micro volts

SCIATIC NERVESciatic neuropathy results from:Fracture dislocation of hipTHR surgeryProlonged compression during comaGluteal injectionsMuscle scarringStretch injury following lithotomy positionClinical picture: Severe lesion weakness of hamstringsMuscles below the knee jointThe neurophysiological evaluation of a patient s/o sciatic neuropathy involves motor conduction studies of peroneal and posterior tibial nerves.Sciatic nerve conduction:-Recording electrode- ext. dig. Brevis /abd. hallucisStimulating electrode: below gluteal foldDistally stimulationMedial trunk apex of politeal fossaLateral trunk- head of fibulaNormal ncv 52.75+_4.66 m/sDifference btw.sciatic neuropathyand L5-s1 radiculopathySCIATIC NEUROPATHYL5 -S1 RADICULOPATHY GLUTEAL WEAKNESS-+SENSORY LOSSNERVE DISTRIBUTIONDERMATOMALDENERVATION:PARASPINAL MUSCLES-+GLUTEAL MUSCLES-+SURAL SNAPABNORMALNORMALCOMMON PERONEAL NERVECauses :-compression as it winds around the neck of the fibulaFracture neck of fibulaPlaster castTight bandageGangliaCystleprosyClinical picture:Weakness of dorsiflexorsWeakness of evertorsSlapping gaitSensory loss to superficial peroneal nerve distributionPeroneal conduction:Surface electrodes extensor digitorum brevisStimulating electrodes1.ankle 2cm distal to fibular neck2.Neck of fibula3. 5-8 cm above the fibular neckNcv below knee 48.3+_3.9 m/sAbove knee 52.0+_6.2 m/sLatency on ankle stimulation 3.77+_0.86 msDistal CMAP amplitude 5.1+_2.3 mVSuperficial peroneal nerve conduction:Recording active electrode-above junction of lateral third of a line connecting the malleoliReference electrode- 3cm distal to the active electrodeAnti dromic surface stimulation 10-15cm proximal to the upper edge of lateral malleolusNcv 49.0+_3.4m/sSNAP 3.5+_1.5 microVIn peroneal neuropathy Conduction block 22% reduction ofCMAP or reduced NCV exceeding 10m/s across head of the fibula localise the lesion at this site.In common peroneal nerve lesions the superficial peroneal nerve or its fasicles may not get damaged so fidnings are normal.SURAL NERVECompression may occur by: Bakers cystUpper edge of ski bootTendon sheath gangliaFracture fifth metatarsal boneParesthesia and numbness Recording lateral malleolus and tendoachilles Stimulation10-16cm proximal to the recording electrode, distal to lower border of gastronemiusNcv 50.9+_5.4 m/sSNAP 18.0+_10.5 micro VTIBIAL NERVECompression by:Bakers cystNerve sheath gangliaPopliteal artery aneurysmFrequently affected by leprosyClinical picture;Weakness of plantar flexors, invertors, intrinsic foot musclesSensory loss on sole

TARSAL TUNNEL SYNDROMECompression in the tarsal tunnel:Causes-Ill fitting foot wearTight plaster castPost traumatic fibrosisTenosynovitisRATendon sheath cyst

Clinical picturePain and paresthesia of sole Rarely, weakness of intrinsic foot muscles

Recording electrodeabductor hallucis/abd.digiti quintiStimulating electrodebehind and proximal to medial malleolus and in popliteal fossa along flexor crease of the kneeNCV 48.3+_4.5 m/sTarsal tunnel syndrome:The site of block can be accurately localised by serial stimulation at 1 cm interval along the tibial nerve across the tarsal tunnel.Site of block-abrupt prolonged latency