clinical & electrodiagnostic approach to foot drop

1. Approach to foot drop
Dr Kr Vijay Anand, DM Resident
Bangur institute of neurosciences , kolkata

2. Anatomical Review
Three muscular compartment in leg
 Anterior
 Lateral
 Posterior

3. Anterior compartment of leg
 Tibialis anterior
 Extensor halluces longus
 Extensor digitorum longus
nerve: Deep peroneal – L5 , L4, S1
Chief Action: Dorsiflexion of ankle and
extension of toes

4. Lateral compartment of leg
 peroneus longus
 peroneus brevis
Nerve: Superficial peroneal nerve, L5.S1
Chief Action: Eversion of foot

5. Posterior compartment of leg
Superficial group
 Gastrocnemius
 Plantaris
 Soleus
Nerve: Tibial nerve- S1, S2
Chief action: plantar flexion of foot

6. Posterior compartment of leg contd…..
Deep group
 Flexor hallucis longus
 Flexor digitorum longus
Flexor of toes . Tibial nerve S2, S3
 Tibialis posterior
Invertor of toes . Tibial nerve L4, L5

7. Sciatic nerve

8. Sciatic nerve contd….

9. Deep peroneal nerve

10. Superficial peroneal nerve

11. action : root/nerve
 Hip flexion : L1 and L2;
 Knee extension : L3 and L4 / femoral
 Ankle dorsiflexion: L5/ peroneal: common or deep
 Ankle plantarflexion : S1 and S2/ tibial
 Ankle inversion: L5/ tibial
 Ankle eversion: L5, S1/peroneal - common or superficial

12. Sensory supply of lower limb
 Lateral cutaneous nerve of thigh
 Posterior cutaneous nerve of thigh
 Ilioinguinal nerve
 Genitofemoral nerve
 Obturator nerve
 Femoral nerve & Saphenous nerve
 Sciatic nerve
 Lateral cutaneous nerve of the calf
 Common, superficial & deep peroneal nerve
 Sural nerve
 Medial & Lateral plantar nerve

13. Sensory innervation: Nerve

14. Sensory innervation: Nerve

15. Sensory innervation: root

16. Possible anatomical localisation of foot drop
 Deep Peroneal Nerve
 Common Peroneal Nerve
 Sciatic Nerve
 Lumbosacral Plexus
 L5 root

17. Clinical approach to foot drop: motor exam
Deep
Peroneal
Nerve
Common
Peroneal
Nerve
Sciatic Nerve Lumbosacral
Plexus
L5 root
Weakness of
foot
dorsiflexion
Weakness of
foot eversion
Weakness of
foot inversion
Weakness of
knee flexion
Weakness of
glutei

18. Clinical approach to foot drop: sensory exam
Deep
Peroneal
Nerve
Common
Peroneal
Nerve
Sciatic
Nerve
Lumbosacra
Plexus
L5 root
Sensory loss
in web space
great toe
Sensory loss
in dorsum of
foot
Sensory loss
in lateral calf
Sensory loss
in lateral knee
Sensory loss
in sole foot
Sensory loss
in posterior
thigh

19. Clinical approach to foot drop: other sign
Deep
Peroneal
Nerve
Common
Peroneal
Nerve
Sciatic
Nerve
Lumbosacra
Plexus
L5 root
Tinel’s sign
at fibular
neck
Hip and
thigh pain
Back pain
Positive
straight-leg
raise test

20. NCS protocol for foot drop
 Peroneal motor study - recording extensor digitorum brevis
 If there is no focal slowing or conduction block at the fibular neck
 perform a peroneal motor study - recording tibialis anterior
 Tibial motor study- recording abductor hallucis brevis
 Superficial peroneal sensory study
 Sural sensory study
 Tibial and peroneal F responses

21. Electromyographic Protocol for foot drop: Routine
 At least two muscles innervated by the deep peroneal nerve (e.g., tibialis
anterior, extensor hallucis longus)
 At least one muscle innervated by the superficial peroneal nerve (e.g.,
peroneus longus, peroneus brevis)
 Tibialis posterior and at least one other tibial muscle (e.g., medial
gastrocnemius, soleus, flexor digitorum longus)
 Short head of the biceps femoris

22.  If the short head of the biceps femoris is abnormal
or
 If any tibial-innervated muscle is abnormal
or
 If nerve conduction studies demonstrate a non-localizing peroneal
neuropathy or abnormal tibial motor or sural responses
 more extensive needle examination of other sciatic, gluteal, and
paraspinal muscles should be performed to identify the level of the lesion
Electromyographic Protocol for foot drop: special

23. Nerve Conduction Study Findings
Deep Peroneal
Nerve
Common
Peroneal Nerve
Sciatic Nerve
Lumbosacral
Plexus
L5
Low peroneal
CMAP (if axonal)
Low tibial CMAP
(if axonal)
Abnormal
peroneal SNAP (if
axonal)
Abnormal sural
SNAP (if axonal)
Abnormal H reflex
Conduction
slowing/block at
fibular neck (if
demyelinating)

24. Electromyographic findings
Deep Peroneal
Nerve
Common
Peroneal Nerve
Sciatic Nerve
Lumbosacral
Plexus
L5
Tibialis
anterior
Extensor
hallucis longus
Peroneus
longus
Tibialis
posterior
Flexor
digitorum
longus
Short head of
the biceps
femoris

25. Electromyographic findings contd…..
Deep
Peroneal
Nerve
Common
Peroneal
Nerve
Sciatic
Nerve
Lumbosacral
Plexus
L5
Gluteus
medius
Tensor fascia
latae
Paraspinal
muscles

26. Methods
Peroneal Motor Study
 Recording Site: Extensor digitorum brevis (EDB) muscle
 G1 placed over the muscle belly
 G2 placed distally over the metatarsal–phalangeal joint of the little toe
Stimulation Sites
 Ankle: Anterior ankle, slightly lateral to tibialis anterior tendon
 Below fibular head: Lateral calf, one to two fingerbreadths inferior to fibular head
 Lateal popliteal fossa (above fibular neck): Lateral knee, adjacent to external hamstring
tendons, at a distance of 10–12 cm from the below-fibular head site

27. Distal stimulation site over
the anterior ankle, slightly
lateral to the tibialis anterior
tendon
Proximal stimulation site
below the fibular head.
Proximal stimulation site in
the lateral popliteal fossa
above the fibular neck.

28. Peroneal Motor Study
Tibialis anterior (TA) muscle
 G1 placed over the muscle belly
 G2 placed distally over the anterior ankle
 Distal stimulation site below the fibular head
 Proximal stimulation site in the lateral popliteal fossa above the fibular
neck.

30. Tibial Motor Study
Abductor hallucis brevis (AHB) muscle
 G1 placed 1 cm proximal and 1 cm inferior to the navicular prominence
 G2 placed over the metatarsal–phalangeal joint of the great toe
Stimulation Sites
 Medial ankle: Slightly proximal and posterior to the medial malleolus
 Popliteal fossa: Mid-posterior knee over the popliteal pulse

32. Superficial Peroneal Sensory Study
 G1 placed between the tibialis anterior tendon and lateral malleolus
 G2 placed 3–4 cm distally
Stimulation Site
 Lateral calf

34. Sural Sensory Study
 G1 placed posterior to the lateral malleolus
 G2 placed 3–4 cm distally
Stimulation Site
 Posterior–lateral calf

36. Soleus H Reflex Study
 G1 placed one to two fingerbreadths distal to where the soleus meets the
two bellies of the gastrocnemius
 G2 placed over the Achilles tendon
Stimulation Site
 Popliteal fossa: Mid-posterior knee over the popliteal pulse

38. EMG

39. Extensor Digitorum Brevis (EDB)
needle insertion:
• tangentially into the dorsum of the
foot two to three fingerbreadths distal
to the lateral malleolus.
• The muscle can often be easily felt by
having the patient extend all theirs toes
Activation
Have the patient extend the toes

40. Extensor Hallucis Longus (EHL)
Needle Insertion
• three to four fingerbreadths above
the ankle, just lateral to the tibialis
anterior tendon
Activation
• Have the patient extend the great toe

41. Tibialis Anterior (TA)
Needle Insertion
• just lateral to the tibial crest, two
thirds the distance up from the ankle
toward the knee
Activation
• Have the patient dorsiflex the ankle

42. Peroneus Longus (PL)
Needle Insertion
• lateral calf, three to four
fingerbreadths distal to the fibular
head
Activation
• Have the patient evert the ankle

43. Gastrocnemius–Medial Head (MG)
Needle Insertion
rostral, medial posterior calf
Activation
Have the patient plantar flex the ankle

44. Tibialis Posterior (TP)
Needle Insertion
medial to the tibia, slightly distal to the
mid-point between the ankle and knee,
deep to the flexor digitorum longus
Activation
Have the patient invert the ankle

45. Biceps Femoris–Short Head (BF–SH)
Needle Insertion
three to four fingerbreadths proximal to
the lateral knee, medial to the tendon to
the long head of the biceps femoris
Activation
Have the patient flex the knee

46. Gluteus Maximus (GMAX)
Needle Insertion
With the patient on their side, insert
the needle into the upper outer
quadrant of the buttock.
Activation
Have the patient extend the thigh
with the knee straight

47. Gluteus Medius (GMED)
Needle Insertion
With the patient lying on his or
her side and the side to be
studied placed upward, insert
the needle into the lateral thigh
two to three fingerbreadths
distal to the iliac crest
Activation
Have the patient abduct the
thigh

48. Lumbosacral paraspinal
Needle Insertion
two fingerbreadths from the midline spine
with the needle directed slightly medially.
To ensure that the needle is in the deeper
layer of muscles, it should be advanced to just
touch the lamina and then pulled back slightly
Activation
Have the patient extend the hip with the leg
straight

49. THANK YOU