Proximal vs. Distal Radial Nerve
Paralysis
Answer Question 1
• The radial nerve is principally derived from
which spinal cord segments in the dog?
A.
B.
C.
D.
E.
C5-T3
C6-T2
C7-T1 Correct Answer
C7-8
T1-2
Although some contributions
may come from C6 and T2,
more than 95% of the
contributions are from these
three nerves: C7, C8, T1
Answer Question 2
• Weight support can be radically affected by radial
nerve lesions since it is the principle nerve
innervating the _____ of the thoracic limb.
A.
B.
C.
D.
E.
Shoulder extensor muscles
Distal extensor muscles
Elbow flexor
So-called “antigravity” muscles Correct Answer
Majority of all muscles
Extensors of the elbow joint (Triceps brachii m.) are
innervated by the radial nerve- extension of this joint is
the principle action countering gravitational forces on
the thoracic limb needed to support weight
Answer Question 3
• Which principle muscle group is innervated by
the proximal divisions of the radial nerve?
A.
B.
C.
D.
E.
Triceps brachii  Correct Answer
Abductor pollicis longus
The triceps brachii muscle
passes distally from the
Extensor carpi radialis
scapula and proximal
Common digital extensor
humerus and attaches to the
olecranon; it is the largest
Biceps brachii
mass of muscle extending
the elbow joint
Answer Question 4
• Which diagram is correct for sensory
innervation by the radial nerve? (area
innervated in red)
Answer C is correct.
Sensory innervation
emanating primarily from
the superficial branch of the
radial nerve innervates the
distal two-thirds of the
cranial antebrachium and
dorsum of the manus
C
Answer Question 5
• Which muscle is innervated by the deep
branch of the radial nerve?
A.
B.
C.
D.
E.
Triceps brachii
Biceps brachii
Extensor carpi radialis  Correct Answer
Deep digital flexor
The extensor carpi radialis a
principle member of the
Latissimus dorsi
craniolateral extensor group
all of which are innervated
by the deep branch of the
radial nerve
Answer Question 6
• “Knuckling over” during attempts to walk with
radial nerve paralysis are due, in part, to
Knuckling over is loss of
paralysis of which muscle?
A.
B.
C.
D.
E.
extension in the distal limb
from paralysis of the
craniolateral extensor group;
the CDE muscle is a principle
member of this group that
extends the carpus,
metacarpus and digits
Triceps brachii
Anconeus
Flexor carpi radialis
Deep digital flexor
Common digital extensor  Correct Answer
Answer Question 7
• Patients with distal radial nerve injury will:
A. Have the same motor deficits as with proximal
injuries
B. Have the same sensory deficits as with proximal
injuries Correct Answer
C. Have profound limping from lack of weight
support
In either proximal or distal
injuries, the sensory branches in
D. Not have sensory deficits
the superficial branch are
E. Will have only motor deficits
afflicted leading to sensory
deficits over the distal two-thirds
of the dorsal antebrachium and
dorsal manus
Answer Question 8
This is due to the preservation of the
caudal brachial muscles (triceps brachii)
which extend the elbow and counter
gravity
• The main difference in proximal versus distal
radial nerve injuries is:
A. Preserved weight support in those with proximal
injuries
B. Preserved weight support in those with distal
injuries Correct Answer
C. Preserved sensation in those with proximal
injuries
D. Preserved sensation in those with distal injuries
E. NOTHING: clinically, they are identical
Answer Question 9
The location of the paresthetic
sensations is in the area of deficits thus
they chew on the dorsal distal aspects of
the limb; self-mutilation can be extreme
and they will auto-amputate digits
• Patients with paresthesia (burning, itching,
tingling) from radial nerve injuries often:
A. Chew on their armpits
B. Chew on the paw, especially over the dorsal
aspect Correct Answer
C. Chew on the medial elbow region
D. Chew on the paw, especially on the palmar
aspect damaging the pads
E. Chew on their lateral scapular region
Answer Question 10
• Paralysis of the proximal radial nerve is
common in cases of:
A.
B.
C.
D.
E.
Radial fractures
Elbow region tumors
Ulnar fractures
Brachial plexus avulsion Correct Answer
Cephalic injection trauma
Brachial plexus avulsion is a nerve root disorder and will
likely include the roots of C7-T1 which give rise to the
radial nerve; All other choices here are too far distal on
the limb to affect the proximal divisions of the radial nerve
that innervate the triceps brachii muscle