“You Can’t Make Interesting
Without Teres”
or
“PNS Envy”
Zach London
Objective
Use the motor exam to distinguish focal
peripheral lesions that cause:
1.
2.
3.
4.
5.
Finger drop
Foot drop
Interosseus weakness
Thumb weakness
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.
Finger Drop
Posterior
Interosseus n.
Radial nerve
(Spiral Groove)
Radial nerve
(Axilla)
Posterior Cord
Plexus
C7 root
Extensor
digitorum
Brachio
radialis
Triceps
Deltoid
Finger
extension
Elbow
flexion
Elbow
extension
Shoulder
Abduction
Deltoid (C5, C6)
Posterior
Cord
Radial Nerve
Plexopathy
(Axilla)
Radial
Tricepsnerve
(C6, C7,(Spiral
C8)
Groove)
Posterior
Brachioradialis (C5, C6)
Interosseus
Extensor Digitorum
Communis (C6, C7)
C7 Root
Deltoid (C5, C6)
Triceps (C6, C7, C8)
Brachioradialis (C5, C6)
Extensor Digitorum
Communis (C6, C7)
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.
2.
3.
4.
5.
Finger drop
Foot drop
Interosseus weakness
Thumb weakness
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.
Foot Drop
Tibialis
Anterior
Ankle
dorsiflexion
Peroneus Tibialis
longus Posterior
Ankle
eversion
Ankle
inversion
Gastrocnemius
Gluteus
Medius
Ankle
plantarflexion
Hip
abduction
Deep
peroneal n.
Common
peroneal n.
Sciatic nerve
Lumbosacral
plexus
*
L5 root
* If S1 fibers are also involved
Gluteus Medius
(L5, S1)
Lumbosacral
Plexus
Sciatic
Common Peroneal
Gastrocnemius
(S1, S2)
Deep Peroneal
Peroneus Longus (L5, S1)
Tibialis Posterior
(L5, S1)
Tibialis Anterior (L4, L5)
L5 Root
Gluteus Medius
(L5, S1)
Gastrocnemius
(S1, S2)
Peroneus Longus (L5, S1)
Tibialis Posterior
(L5, S1)
Tibialis Anterior (L4, L5)
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.
2.
3.
4.
5.
Finger drop
Foot drop
Interosseus weakness
Thumb weakness
Quadriceps weakness
Interosseous Weakness
Ulnar nerve
(elbow)
Medial cord
plexus
Lower trunk
plexus
C8-T1 root
Interossei
Abductor
pollicis
brevis
Extensor
indicis
Spreading
out fingers
Thumb
abduction
Index finger
extension
Lower trunk plexus
Medial cord plexus
or C8 Root
Ulnar (elbow)
Extensor Indicis
(C7, C8)
Interossei (C8, T1)
Abductor Pollicis
Brevis (C8, T1)
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.
2.
3.
4.
5.
Finger drop
Foot drop
Interosseus weakness
Thumb weakness
Quadriceps weakness
Thumb weakness
Median nerve
(carpal tunnel)
Anterior
Interosseous
nerve
Median nerve
(proximal)
C8 Root
Abductor
pollicis brevis
Flexor Pollicis
Longus
Interossei
Thumb
Abduction
Thumb
Flexion
Spreading out
Fingers
C8 root,
medial cord
or lower
trunk
Proximal Median
Anterior
Interosseus
Median (carpal
tunnel)
Flexor Pollicis
Longus (C7, C8)
Interossei (C8, T1)
Abductor Pollicis
Brevis (C8, T1)
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.
2.
3.
4.
5.
Finger drop
Foot drop
Interosseus weakness
Thumb weakness
Quadriceps weakness
Quadriceps Weakness
Femoral n.
(below inguinal
ligament)
Femoral n.
(above inguinal
ligament)
Lumbar Plexus
L3 root
L4 root
Quadriceps
Iliopsoas
Adductor
Longus
Knee
extension
Hip flexion
Hip
adduction
L4 RootPlexus
Lumbar
Femoral (above
Obturator
or
L3
Root
inguinal
ligament)
Iliopsoas (L2, L3)
Femoral (below
inguinal ligament)
Adductors (L2, L3, L4)
Quadriceps (L3, L4)
Q: What muscle can be used to
distinguish a proximal femoral
mononeuroapathy from a
lumbar plexopathy?
A: The adductor muscles
Review
1.
2.
3.
4.
5.
Finger drop
Foot drop
Interosseus weakness
Thumb weakness
Quadriceps weakness
Which Muscles are Affected?
Finger
extension
Radial
mononeuropathy
at the axilla
Elbow flexion
Elbow
extension
Shoulder
abduction
Deltoid (C5, C6)
Radial
Nerve
(Axilla)
Triceps (C6, C7, C8)
Brachioradialis (C5, C6)
Extensor Digitorum
Communis (C6, C7)
Which Muscles are Affected?
Ankle
dorsiflexion
L5 Radiculopathy
Ankle
Plantarflexion
Ankle
Inversion
Ankle
Eversion
L5 Root
Gluteus Medius
(L5, S1)
Gastrocnemius
(S1, S2)
Peroneus Longus (L5, S1)
Tibialis Posterior
(L5, S1)
Tibialis Anterior (L4, L5)
Which Muscles are Affected?
Thumb
abduction
Medial cord
plexopathy
Finger
abduction
Index
finger
extension
C8 Root
Medial Cord
Ulnar Nerve
Interossei
Lower Trunk
C8 Root
Median
Nerve
Abductor
pollicis
brevis
Medial Cord
Lower Trunk
C8 Root
Radial Nerve
Extensor
indicis
Posterior
Cord
Lower Trunk
Which Muscles are Affected?
Thumb
abduction
Medial cord
plexopathy
Finger
abduction
Index
finger
extension
Which Muscles are Affected?
Thumb
abduction
Anterior
interosseus
mononeuropathy
Thumb flexion
Finger
abduction
Median
nerve
Anterior
Interosseus
Flexor
pollicis
longus
Abductor
pollicis
brevis
Which Muscles are Affected?
Knee
extension
L4 radiculopathy
Hip flexion
Hip
adduction
L4 Root
Iliopsoas (L2, L3)
Adductors (L2, L3, L4)
Quadriceps (L3, L4)
Thank You