Approach to Foot Drop (focused on unilateral foot drop) - incomplete

Question 1

Foot drop algorithm

Answer 1

Question 2

Bilateral foot drop

Answer 2

Bilateral UMN foot drop: spinal cord lesion (see spastic paraparesis)

Bilateral LMN foot drop: peripheral neuropathy, distal myopathy (myotonic dystrophy, FSHD)

Question 3

Unilateral UMN foot drop

Question 4

Innervating nerves to the anterior tibialis muscle (bottom to top)

Answer 4

1. Offer distal myopathy, NMJ disease as cause
2. Deep peroneal nerve
3. Branch of common peroneal nerve
4. Sciatic nerve
5. Lumbar roots and sacral plexus
6. Cortical foot drop

(MRT diagram?)

Question 5

Unilateral foot drop

Answer 5

Deep peroneal nerve or higher defect
- Weakened tibialis anterior muscle causing ankle dorsiflexion weakness
- 1st dorsal webspace numbness
“All foot drops lead to tibialis anterior muscle”

Also look at extensor digitorum brevis (muscle bulk)
- Also innervated by deep peroneal nerve

Question 6

Three milestones of high level foot drop

Answer 6

Hip extension - sacral plexus (very high)
Knee flexion - sciatic nerve
Hip abduction - L4/L5 level

?? - attach picture and matrix table

Question 7

Very high level foot drop
- Sacral plexopathy

Answer 7

1. Hip extension weakness - gluteus maximus
   - Innervated by inferior gluteal nerve (from L5, S1, S2)
2. Hip abduction weakness - gluteus medius and minimus
   - Innervated by superior gluteal nerve (from L4/L5)
3. Variable sensory deficit, commonly L4/L5 (myotomal pattern)

Question 8

High level foot drop
- Sciatic nerve
- Tibial nerve

Answer 8

1. Knee flexion weakness - hamstrings
   - Innervated by sciatic nerve
2. Plantar flexion and inversion weakness - gastrocnemius, soleus, tibialis posterior
   - Innervated by tibial nerve
   - Inversion by L4/L5 and plantarflexion by S1
   (Tibialis anterior inverts ankle too, thus plantarflexion determines tibial nerve involvement)
3. Sensory deficit over common peroneal and tibial nerve

Question 9

Causes of high level foot drop

Answer 9

Question 10

Common peroneal foot drop

Answer 10

Common peroneal nerve branches to superficial peroneal nerve

1. Ankle eversion weakness - peroneus longus and brevis (supplied by superficial peroneal nerve)
2. Sensory deficit over lateral aspect of calf and dorsum of foot

Causes of common peroneal nerve lesion:
1. Compressive neuropathy of fibular head (prolonged bed rest, trauma)
2. Trauma/surgery to fibula head
3. Mononeuropathy (DM)
4. Mononeuritis multiplex (DM, vasculitis)

Question 11

Cortical foot drop and gait
(brain and brainstem lesion)

Answer 11

1. Cortical foot drop: UMN pattern
   - Features of hypertonic, clonus, hyperreflexia, upgoing plantars
2. Significant gait difference
   - UMN - circumduction gait (spasticity, pyramidal pattern of weakness over hip and knee flexors - difficult clearing foot off the ground)
   (Strumpell’s tibialis phenomenon)

(in comparison LMN - high stepping gait and flexing hip to elevate dropped foot off the ground)