or

“PNS Envy”

Zach London

“You Can’t Make Interesting Without Teres”

ObjectiveUse the motor exam to distinguish focal

peripheral lesions that cause:

1. Finger drop

2. Foot drop

3. Interosseus weakness

4. Thumb weakness

5. Quadriceps weakness

The rules

• Pick a symptom (foot drop, interosseous weakness, etc.)

• In the left column, write relevant localizations from distal to proximal.

• Localizations should be a nerve, part of the plexus, or root.

• Fill out the chart, checking off which muscles would be weak with lesions in each localization.

Radial nerve (Spiral Groove)

C7 root

Posterior Cord Plexus

Radial nerve (Axilla)

Posterior Interosseus n.

Shoulder Abduction

Elbow extension

Elbow flexion

Finger extension

DeltoidTricepsBrachioradialis

Extensor digitorum

Finger Drop

Deltoid (C5, C6)

Triceps (C6, C7, C8)

Brachioradialis (C5, C6)

Extensor Digitorum Communis (C6, C7)

Posterior Interosseus

Radial nerve (Spiral Groove)Radial Nerve

(Axilla)

Posterior Cord Plexopathy

Deltoid (C5, C6)

Triceps (C6, C7, C8)

Brachioradialis (C5, C6)

Extensor Digitorum Communis (C6, C7)

C7 Root

Q: What muscle can distinguish a posterior interosseus

mononeuropathy from a radial mononeuropathy at the

spiral groove?

A: Brachioradialis (elbow flexion with thumb up)

1. Finger drop

2. Foot drop

3. Interosseus weakness

4. Thumb weakness

5. Quadriceps weakness

The rules, again

• Pick a symptom (foot drop, interosseous weakness, etc.)

• In the left column, write relevant localizations from distal to proximal.

• Localizations should be a nerve, part of the plexus, or root.

• Fill out the chart, checking off which muscles would be weak with lesions in each localization.

*

Ankle plantarflexion

Gastroc-nemius

Common peroneal n.

L5 root

Lumbosacral plexus

Sciatic nerve

Deep peroneal n.

Hip abduction

Ankle inversion

Ankle eversion

Ankle

dorsiflexion

Gluteus Medius

Tibialis Posterior

Peroneus longus

Tibialis Anterior

Foot Drop

* If S1 fibers are also involved

Tibialis Posterior (L5, S1)

Peroneus Longus (L5, S1)

Tibialis Anterior (L4, L5)

Deep Peroneal

Common Peroneal

Sciatic

Lumbosacral PlexusGluteus Medius

(L5, S1)

Gastrocnemius (S1, S2)

Peroneus Longus (L5, S1)Tibialis Posterior

(L5, S1)Tibialis Anterior (L4, L5)

Gluteus Medius (L5, S1)

Gastrocnemius (S1, S2)

L5 Root

Q: What muscles can be used to distinguish a common

peroneal neuropathy from an L5 radiculopathy?

A: Tibialis Posterior (inversion)Gluteus Medius (hip abduction)

1. Finger drop

2. Foot drop

3. Interosseus weakness

4. Thumb weakness

5. Quadriceps weakness

Medial cord plexus

C8-T1 root

Lower trunk plexus

Ulnar nerve (elbow)

Index finger extension

Thumb abduction

Spreading out fingers

Extensor indicis

Abductor pollicis brevis

Interossei

Interosseous Weakness

Abductor Pollicis Brevis (C8, T1)

Extensor Indicis (C7, C8)

Interossei (C8, T1)

Ulnar (elbow)

Medial cord plexusLower trunk plexus

or C8 Root

Q: What muscle can be used to distinguish an ulnar

mononeuropathy at the elbow from a C8 radiculopathy?

A: Abductor pollicis brevis and extensor indicis

1. Finger drop

2. Foot drop

3. Interosseus weakness

4. Thumb weakness

5. Quadriceps weakness

C8 Root

Median nerve (proximal)

Anterior Interosseous

nerve

Median nerve (carpal tunnel)

Spreading out Fingers

Thumb FlexionThumb

Abduction

InterosseiFlexor Pollicis

LongusAbductor

pollicis brevis

Thumb weakness

Abductor Pollicis Brevis (C8, T1)

Flexor Pollicis Longus (C7, C8)

Interossei (C8, T1)

Median (carpal tunnel)

Anterior Interosseus

Proximal Median

C8 root, medial cord

or lower trunk

Q: What muscle can be used to distinguish carpal tunnel syndrome from a

median mononeuropathy at the elbow?

A: Flexor pollicis longus (Thumb flexion)

1. Finger drop

2. Foot drop

3. Interosseus weakness

4. Thumb weakness

5. Quadriceps weakness

Quadriceps Weakness

Femoral n. (above inguinal

ligament)

L4 root

L3 root

Lumbar Plexus

Femoral n. (below inguinal

ligament)

Hip adduction

Hip flexionKnee

extension

Adductor Longus

IliopsoasQuadriceps

Quadriceps (L3, L4)

Adductors (L2, L3, L4)

Iliopsoas (L2, L3)

Femoral (below inguinal ligament)

Femoral (above inguinal ligament)Obturator

Lumbar Plexus

or L3 Root

L4 Root

Q: What muscle can be used to distinguish a proximal femoral

mononeuroapathy from a lumbar plexopathy?

A: The adductor muscles

1. Finger drop

2. Foot drop

3. Interosseus weakness

4. Thumb weakness

5. Quadriceps weakness

Review

Shoulder abduction

Elbow extension

Elbow flexion

Finger extension

Which Muscles are Affected?

Radial mononeuropathy

at the axilla

Deltoid (C5, C6)

Triceps (C6, C7, C8)

Brachioradialis (C5, C6)

Extensor Digitorum Communis (C6, C7)

Radial Nerve (Axilla)

Ankle Eversion

Ankle Inversion

Ankle Plantarflexion

Ankle dorsiflexion

Which Muscles are Affected?

L5 Radiculopathy

Tibialis Posterior (L5, S1)

Peroneus Longus (L5, S1)

Tibialis Anterior (L4, L5)

Gluteus Medius (L5, S1)

Gastrocnemius (S1, S2)

L5 Root

Index finger

extension

Finger abduction

Thumb abduction

Which Muscles are Affected?

Medial cord plexopathy

Ulnar NerveMedial Cord

Lower Trunk

C8 Root

Interossei

Median Nerve

Medial CordLower Trunk

C8 Root

Abductor pollicis brevis

Radial Nerve Posterior Cord

Lower Trunk

C8 Root

Extensor indicis

Index finger

extension

Finger abduction

Thumb abduction

Which Muscles are Affected?

Medial cord plexopathy

Finger abduction

Thumb flexion

Thumb abduction

Which Muscles are Affected?

Anterior interosseus

mononeuropathy

Median nerve

Carpal Tunnel

Abductor pollicis brevis

Flexor pollicis longus

Elbow

Anterior Interosseus

Hip adduction

Hip flexion

Knee extension

Which Muscles are Affected?

L4 radiculopathy

Quadriceps (L3, L4)

Adductors (L2, L3, L4)

Iliopsoas (L2, L3)

L4 Root

Thank You