or “PNS Envy” Zach London “You Can’t Make Interesting Without Teres”

Objective Use 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 DeltoidTriceps Brachio radialis 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 Plexus Gluteus 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 plexus Lower 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 Flexion Thumb Abduction Interossei Flexor Pollicis Longus Abductor 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 flexion Knee 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 Nerve Medial Cord Lower Trunk C8 Root Interossei

Median Nerve Medial Cord Lower 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