Nerve Conduction Studies- Lower Leg

NCV OF THE LOWER LIMBSBY- DR SAUMYA MITTAL

18th NOVEMBER 2014

LUMBAR PLEXUS

L1-L4

LUMBAR PLEXUS

Formed by the

ANTERIOR RAMI of

L1-4.

Anterior rami join to

form OBTURATOR N.

Posterior divisions of

the rami join to form

FEMORAL N.

OTHER NERVES

Other nerves include-

LATERAL

CUTANEOUS NERVE

OF THIGH (pure

sensory).

ILIOHYPOGASTRIC N

ILIOINGUINAL N

GENITOFEMORAL N

LUMBAR PLEXOPATHY

Abrupt onset pain in

anterior aspect of thigh.

Muscle wasting and

weakness in 2-3

weeks.

Absent knee reflexes.

Tender femoral N

Positive femoral stretch

sign

Clinical features Signs

Sensory symptoms are partial and seen in 1/3rd

patients.

NCV shows normal nerves- femoral, peroneal, suraland saphenous N.

May show reduced amplitude.

EMG may show changes of denervation andrenervation.

Recovery may be spontaneous over months-years.

FEMORAL NFrom dorsal portion of anterior rami of L2-L4

Mixed Nerve

Normal femoral conduction velocity – 70.0 ± 5.5 m/S

FEMORAL NERVE

In intraabdominal

course, supplies the

iliopsoas muscle.

Divides to anterior and

posterior division after

crossing Inguinal

ligament.

FEMORAL NERVE

Medial cut N

Supplies medial thigh

Intermediate cut N

Supplies anterior thigh

Supply to Pectineus

and Sartorius

Supplies

Knee and hip joint

Quadriceps musc.

Terminates as

Saphenous N

Anterior Division Posterior Division

FEMORAL NEUROPATHY

Causes

Weakness of Quadri.

Wasting of Quadri.

Loss of knee reflexes

Sensory loss in medial

aspect of thigh and leg

Causes

Diabetes mellitus

Intrapelvic collection

Pelvic surgery

Hip arthroplasty

Tumor of vertebra

Cannulation of Femoral

vein/artery

Inguinal lig

compression in

lithotomy

Renal transplant

ELECTROPHYSIOLOGY

Surface recording

electrode: belly of

vastus medialis

Reference electrode

prox to patella.

Stimulating electrode:

lateral to femoral artery.

NCV

Slowing of conduction velocity

Small CMAP amplitude.

Conduction block (if compressed at inguinal lig)

Saphenous vein can be used to evaluate sensory loss.

Normal femoral conduction velocity – 70.0 ± 5.5

m/S

SAPHENOUS NERVE

Largest and longest pure sensory

branch of Femoral N .

Supplies skin over medial aspect of

leg and foot.

Normal Saphenous conduction velocity- 49.03 ± 3.36 m/s.

SNAP Amplitude- 3.54 ± 1.52 µV

SAPHENOUS N

Arises from posterior

division of Femoral N

Becomes superficial

just above medial

condyle

Continues down to

head of 1st metatarsal

SAPHENOUS NEUROPATHY

Uncommon

Follows

Laceration injuries

Entrapment in subsartorial canal

Surgery for varicose veins

Causes sensory impairment in medial aspect of

knee, leg and foot.

SAPHENOUS NERVE CONDUCTION

Stimulate 1 cm above

inferior border of

patella between gracilis

and sartorius.

Recording electrode-

15 cm distal on medial

border of tibia.

Stimulate between

medial head of

gastrocnemius and

tibia, 12- 14 cm

proximal to med

malleolus

Recording electrode is

placed anterior to

medial malleolus

Normal Saphenous conduction velocity- 49.03 ± 3.36 m/s.

SNAP Amplitude- 3.54 ± 1.52 µV

LATERAL FEMORAL

CUTANEOUS NERVE

OF THIGH

L2-3.

Sensory supply to

Anterolateral aspect of

thigh.

Latency and Amplitude of SNAP

above Inguinal Lig- 2.8±0.4ms

and 6±1.5 µV

MERALGIA PARESTHETICA

Entrapment of the

nerve at Inguinal tunnel

Seat belts

Obesity

Unknown

Proximal lesions

Psoas abscess

Retroperitoneal tumor

Post op scarring

Pain & paresthesia over

lateral surface of thigh.

Symptoms increase on

standing and prolonged

walking.

Sensory loss is in area

smaller than supplied by

the nerve

NCV- abnormal conduction in Lat Cut N of Thigh

EMG- normal study of paraspinal, iliopsoas, quadriceps.

NERVE CONDUCTION-

LAT CUT N OF THIGH

Surface Electrode- 17-

20 cm distal to Ant

Supr Iliac Spine

(ASIS).

Reference electrode- 3

cm distal to surface

electrode.

Antidromic stimulation

above inguinal

ligament 1 cm medial

to ASIS

Latency and Amplitude of SNAP above Inguinal Lig- 2.8±0.4ms

and 6±1.5 µV

SACRAL PLEXUSL4-S3 roots

SACRAL PLEXUS

Branches

Sup Gluteal N(L4-S1)

Gluteus medius

Gluteus minimus

Tensor facsia lata

Inf Gluteal N(L5-S1)

Gluteux maximus

Sciatic N (L4-S3)

SACRAL PLEXOPATHY

Abrupt onset pain in

posteror aspect of the

thigh and buttocks.

Weakness of knee

flexor

Absent reflexes.

Sciatic N tenderness

Positive SLR test.

SCIATIC NERVE

L4-S3

Comes out of sciatic notch

Supplies all hamstrings (medial trunk) except short head of biceps femoris

All muscles distal to knee

Normal Sciatic N Conduction

velocity- 52.75±4.66 m/s

SCIATIC NEUROPATHY

Causes include-

Trauma

Fracture/disloc of hip joint

Injection

Puncture wound

Muscle scarring

Vasculitis

Compression Anesthesia

Coma

Lymphoma & tumours

Symptoms

Involvement of hamstrings

Involvement of muscles below knee

Variable sensory loss.

Needs motor conduction studies of

Peroneal N

Post Tibial N

Sural N

Sup Peroneal N

EMG

SCIATIC N CONDUCTION

Difficult d/t deep location.

Surface Electrode on distal peroneal innervated muscle egabd hallucius

Stimulation-

Just below gluteal fold

Medial trunk- apex of popliteal fossa

Lateral trunk- head of fibula

NCV

EMG

Helps differentiate the condition and levels

Denervation in paraspinal muscle + normal sural snap

s/o L5/S1 radiculopathy

Involvement of gluteal muscles- involvement prior to

sciatic notch

Peroneal neuropathy v/s sciatic neuropathy-

Lat trunk- short head of biceps

Med trunk- hamstrings and other tibial supp muscles

Normal Sciatic N Conduction velocity- 52.75±4.66 m/s

COMMON PERONEAL NERVE

Lateral trunk of Sciatic N descends as Common

Peroneal N

COURSE & BRANCHES

Branches-

Lat Cut N of Calf

Supplying anterior,

lateral and posterior

surface of leg

Superficial Peroneal N

Also supplies lateral and

dorsal portion of leg and

dorsum of foot.

Deep Peroneal N

COMMON PERONEAL NEUROPATHY

Occurs due to

compression around

head of fibula.

In sleep/coma

Anesthesia

Plaster/tight bandage

Cross legging

Fracture of fibula

Callus/cyst/lipoma

Vasculitis

Leprosy

Weakness of

Dorsiflexion of foot and

toes

Eversion of foot

Cause foot drop and

slapping gait

Sensory loss

In distribution of

superficial peroneal N

or lat cut N of calf,

depending on level of

lesion

ELECTROPHYSIOLOGY

Evaluation by conduction study of

Different segments of common peroneal nerve

Superficial peroneal nerve

EMG of peroneal nerve innervated muscles.

Sural conduction and EMG of short head of biceps

differentiate from sciatic neuropathy

PERONEAL NERVE

CONDUCTION

Surface recording- ext

digi brev

Stimulation –

2cm distal to fibular

neck,

At fibular neck

5-8cm above fibular

neck

Conduction velocity

Below knee segment-

48.3±3.9ms

Above knee segment-

52±6.2ms

Latency on ankle stimulation

3.77±0.86ms

Distal CMAP amplitude

5.1±2.3mV

SUPERFICIAL PERONEAL

NERVE CONDUCTION

Active electrodeJust above junction of lateral third of a line connecting the malleoli.

Reference electrode3cm distal to active electrode.

Stimulation10-15cm proximal to upper edge of lateral malleolus anterior to peroneus longus

Normal peroneal nerve conduction velocity-49±3.4ms and amplitude of SNAP 3.5±1.5µV

In peroneal neuropathy conduction block and

reduction in motor nerve conduction velocity >10ms

across head of fibula localizes the lesion at this site.

In common peroneal neuropathy muscles supplied

by the deep branch are frequently/severely

affected.

Common peroneal nerve and lateral trunk of sciatic

nerve- EMG of short head of biceps are useful

SURAL NERVE

S1 and S2

Medial derived from Tibial N

Lateral derived from Peroneal N

Pure sensory N

Sural N conduction velocity- 50.9±5.4 m/s, amplitude of SNAP 18±10.5µV

SURAL NEUROPATHY

Uncommon

Part of generalised neuropathies

Compression

Baker’s cyst

Against hard object

Tendon sheath ganglia

Scar tissue

# 5th metatarsal

Presents with

Numbness and paresthesia in supplied region

Low conduction velocity and amplitude in NCV

SURAL

Leg should be relaxed

and in lateral position.

Surface Electrode-

between lateral malleolus

and tendoachilles.

Stimulated 10-16 cm

proximal to recording

electrode, distal to lower

border of gastrocnemius

at the junction of middle

and lower third of leg.

Sural N conduction velocity- 50.9±5.4 m/s, amplitude of SNAP 18±10.5µV

TIBIAL NERVE

Continuation of medial trunk of sciatic nerve

TIBIAL NEUROPATHY

Damage at popliteal

fossa uncommon.

Causes-

Baker’s cyst

Nerve sheath ganglia

Popliteal A Aneurysm

Leprosy

Weakness of

plantar flexors

Invertors

Intrinsic foot muscles

Sensory loss in sole

TARSAL TUNNEL SYNDROME

Rare picture

Pain and paresthesia

of sole

Weakness of intrinsic

foot muscles (rare)

Causes

Ill-fitting footwear

Tight plaster cast

Post traumatic fibrosis

Tenosynovitis

RA

Hypothyroidism

Idiopathic

ELECTROPHYSIOLOGY

Needs tibial N conduction, medial and lateral plantar N conduction, EMG.

Tibial N conduction-

Surface recording-abductor hallucis/abductor digitiquinti below and ant to navicular tuberosity.

Stimulation behind and proximal to medial malleolus/in poplitealfossa.

Motor conduction of medial and lateral plantar N

Recording electrode (M)- abductor hallucis (belly)

Recording electrode (L)-abductor digiti quinti

Nerve stimulation- behind and above medial malleolus

Sensory conduction of

medial and lateral

plantar nerves:

Stimulation- 1st and 5th

toes- M and L

respectively.

Recording electrode-

just below medial

malleolus.

In Tarsal Tunnel Syndrome

Conduction block and latency prolongation across tarsal

tunnel

Accurate localisation by inching technique (1cm)-abrupt

prolongation in latency.

Normal conduction velocity of Tibial N-48.3±4.5ms

Motor conduction

Latency for medial plantar nerve-3.8±0.5ms

Latency for lateral plantar nerve-3.9±0.5ms

Sensory conduction for

Latency for medial plantar nerve-2.4±0.2ms, 3.2±0.3ms,

4±0.2ms (10,14 and 18 cm segment).

Latency for lateral plantar nerve-3.2±0.3ms,4±0.3ms (14

and 18 cm segment).

THANK YOU