Chapter 19 Ulnar Neuropathy Flashcards
Compared to median neuropathy is it easy or difficult to localize ulnar neuropathy?
Difficult many must be described as non-localizable
Is the ulnar groove the same thing as the cubital tunnel?
No. Ulnar groove is between the medial epicondyle and the olecranon process. The cubital tunnel is distal to the ulnar groove.
What structures form the cubital tunnel?
The cubital tunnel is formed from the tendinous arch of the two heads of the flexor Carpi ulnaris muscle.
Does cubital tunnel entrapment spare the flexor carpi ulnaris?
The branches of the FCU travel in the cubital tunnel yet are usually spared or only mildly affected in the ulnar neuropathy at the elbow. It Isn’t known why but in General compression neuropathies are more often seen to affect distal muscles more.
Name all ulnar innervated muscles proximal to the wrist.
Flexi carpi ulnaris and the
flexor digitorum profundus to digits four and five.
How far distal to the elbow must you stimulate in order to ensure you are distal to the entrance of the cubital tunnel?
The distance Between the ulnar groove and the entrance of the cubital tunnel vary Between people, but no more than 2 cm Between the ulnar groove and the start of the cubital tunnel. Preston says Stimulate at least 3 cm distal to the elbow.
What an event usually precedes tardy ulnar nerve palsy by many years?
Tarty ulnar palsy results from elbow fracture followed by arthritic changes that compress the ulnar nerve at the ulnar groove.
What treatment for an elbow fracture could result in a less tardy ulnar palsy?
Compression by the cast.
What does someone with congenitally tight cubital tunnel do to put themselves at risk for cubital tunnel syndrome?
Frequent and persistent elbow flexion
In carpal tunnel syndrome sensory symptoms are more prominent than motor. is this also true with ulnar neuropathy at the elbow?
In ulnar neuropathy at the elbow, motor symptoms are more prominent sensory, especially in chronic cases. Patients often seek medical attention because of reduced dexterity.
Described benediction posture
- Finger abduction weakness (interossei) and
- clawing of digits 4 & 5 (Extension at the metacarpophalangeal joints and
- flexion of the distal and proximal interphalangeal joints from weakness of the third and fourth lumbricals.
Describe Wartenberg’s sign
This sign results from difficulty ADD ducting the fifth digit or because of preferential weakness in the third Palmer interosseous muscle. Notice the finger is held abducted.
Describe froment’s sign
Weakness of the ulnar Innervated adductor pollicis,
deep head of the flexor Pollis brevis and interossei results in weakness of pinch.
To Compensate the median innervated flexor pollicis longis and flexor digitorum profundis have to contract.
If a patient with in an ulnar nerve neuropathy has numbness on the dorsum of the hand, how does this help you localized lesion?
The mediodorsal hand is supplied by the dorsal ulnar cutaneous sensory branch, which branches from the ulnar nerve 5 to 8 cm proximal to the wrist. Numbness in this distribution with muscle abnormalities implies that a solitary lesion would be proximal to the wrist.
Name the provocative test of ulnar neuropathy besides Tinel’s at the elbow.
Cubital tunnel syndrome maybe provoked by elbow flexion.
Radiculopathy of which roots may be difficult to distinguish from ulnar Neuropathy?
C8 or t1
Which is more difficult to localize: an ulnar lesion resulting in demyelination or in axonal loss?
It is more difficult to localize a lesion if it results in axonal loss. Conduction block or slowing can sometimes Be localized with nerve conduction studies.
What elbow position allows for best measurement of the ulnar nerve across the elbow?
To avoid falsely slowed conduction velocity across the elbow, measure that ulnar nerve with the elbow flexed.
Normally proximal conduction velocities are faster. If the above the elbow conduction velocity is slower than the forearm velocity, what is the largest differential that is normal?
Deltas of greater than 10 to 11 m/s are abnormal.
Which is better at detecting abnormalities at the elbow: differential conduction velocity or absolute conduction velocity across the elbow?
Some Authors believe that a better measure of UL NARneuropathy across the elbow is low absolute conduction velocity.
What is the lower limit of normal for conduction velocities across the elbow?
Conduction velocity across the elbow lower than 49 m/s is abnormal. Some authors believe that a better measure of ulnar neuropathy across the elbow is low absolute conduction velocity, i.e. less than 49 m/s.
Compare ulnar finger SNAPs in the situations of pure demyelination and axonal loss.
In pure demyelination, ulnar snaps are normal. With axonal involvement, snap amplitudes are reduced distally and distal latency May be prolonged. The same findings in CMAPs help clarify the distinction of axonal versus demyelinating versus both.
What are the two NCS findings, Either one of which localizes ulnar neuropathy?
NCS localize neuropathy by demonstrating conduction block or a focal slowing. Without demonstration of either conduction block or focal slowing, the lesion is not localizable.
What positive findings on NCS are consistent with a non-localizable ulnar lesion with only axonal loss?
A non-localizable lesion with only axonal loss would result in reduced CMAP and SNAP amplitudes with mildly prolonged distal latency and mildly reduced conduction velocities.
