Anatomy
Which nerve roots feed into the radial nerve?
C5-T1
Kayla develops a radial neuropathy after falling asleep with his arm hanging over a chair.
Where is the likely site of injury?
Is elbow extension involved?
Spiral groove (aka Saturday night palsy)
Elbow extension not involved – triceps (& anconeus) occurs before the spiral groove
Can you differentiate a radial nerve injury (with axonal loss) at the axilla vs posterior cord based on radial NCS?
No. Both would show low CMAP and SNAP amplitudes throughout.
Where is the location if there are abnormalities in the EIP, ECU, brachioradialis,long head of ECR, but no issues with the triceps?
Spiral groove of humerus
What is the most common traumatic cause of radial neuropathy?
Mid-shaft fracture of the humerus
What muscle is innervated before the radial nerve passes the spiral groove?
Triceps (and anconeous)
Ben develops a radial neuropathy after using crutches for a month.
Where is the likely site of injury?
Which upper extremity reflexes could be affected?
Axilla
Triceps and brachioradialis reflexes
Where is the lesion if you find the following on NCS
Normal superficial radial SNAP
Motor study to EIP: normal CMAPs at the forearm, elbow, with a drop in amplitude between proximal and distal humerus
Radial neuropathy at the spiral groove (demyelinating lesion)
Where is the location if there are abnormalities in the EIP, ECU, Triceps, pronator teres, and FCR?
C7 Radiculopathy
When was PM&R officially recognized by the American Board of Medical Specialties?
1947
What muscle does the radial nerve pass through near the Arcade of Frohse?
Supinator
Alexa cannot extend her fingers, can only weakly extend her wrist when radially deviated, and has no issues with elbow extension/flexion.
Where is the site of injury?
Would you expect sensory issues?
Posterior interosseous nerve – triceps, brachioradialis, ECR spared
No – Posterior interosseous nerve is purely motor
What is the upper limit of normal for the increase in median peak latency compared to radial peak latency in the CSI to the thumb?
0.4 msec
Transcarpal orthodromic – 0.3 msec
Digit 4 – 0.4 msec
Where is the location if there are abnormalities in the EIP, EDC, and ECU but no issues with brachioradialis, long head of ECR, and triceps?
Posterior interosseous nerve
When were boxes of chocolate first produced for Valentine's Day?
Richard Cadbury introduced the first box of Valentine's Day chocolates in 1868
Which branch of the radial nerve supplies sensation to the hand? Where is the origin of this branch?
Superficial radial sensory nerve
Splits from the deep radial nerve distal to the elbow and proximal to the Arcade of Frohse
Tony develops a radial neuropathy after being in handcuffs.
What is the expected sensory dysfunction?
What is the expected motor dysfunction?
The superficial radial sensory nerve runs superficial over the radial bone over the extensor tendons of the thumb
Sensory – lateral dorsum of hand, dorsal thumb, dorsal proximal digits 2-4
Motor – none
You suspect a patient has posterior interosseous neuropathy. What do you expect to find on the radial SNAP?
Normal snap – posterior interosseous nerve does not carry cutaneous sensory fibers
Where is the location if there are abnormalities in the EIP, ECU, ECR, triceps, deltoid, and latissimus dorsi?
Posterior cord involving radial, axillary, and thoracodorsal nerves.
Where was the first PM&R residency founded?
Mayo Clinic (Rochester) by Dr. Frank H. Krusen
What muscles innervated by the radial nerve do not have the word "extensor" as part of their names?
Triceps/anconeus, brachialis, brachioradialis, supinator, abductor pollicis longus
Joe was shot in the shoulder by Tony and develops weakness with finger/wrist/elbow extension. The normal function of what muscle(s) could distinguish whether the radial nerve vs posterior cord injury?
Preserved strength of deltoid (axillary n.) and latissimus dorsi (thoracodorsal n.) would indicate the injury is at the axilla and not the posterior cord
You perform a radial motor NCS on the extensor indicis proprius and there is an initial positive deflection. What is the cause of this positive deflection?
There is volume conduction to nearby radially-innervated structures (extensor pollicis brevis & longus) which affect the CMAP response.
In a complete radial neuropathy at the spiral groove, what is the only radially-innervated muscle in the forearm that will be normal?
Anconeus - supplied above spiral groove
Origin: Lateral epicondyle of humerus
Insertion: Lateral surface of olecranon and superior part of posterior surface of ulna
Where was the first department of PM&R founded? And what year was it founded?
Dr. Frank Krusen at Temple University Medical School in 1928-1929