1. Electromyography in Clinical Practice A Case Study Approach
Chapter 9.

2. History & P/Ex 38/M C.C> Right hand weakness, atrophy
Onset> several months ago
Numbness (-), pain (-)
Prior EMG = > cervical radiculopathy
=> cervical MRI, cevical myelogram/CT, MRI of the brachial plexus, brain MRI/MRA  All were normal , but his hand weakness worsened.
He was suspected to have early motor neuron disease.

3. History & P/Ex Right hand “ulnar” clawing
Positive Froment sign with severe weakness, and atrophy of all interossei
The strength and bulk of the thenar and hypothenar muscles were normal
Deep tendon reflexes : normal
Mild, deep, boring pain in the palm near the hypothenar eminence and some tenderness over the hypothenar eminence to deep pressure

4. History & P/Ex

5. Nerve conduction study

6. Needle EMG

7. EDX findings
1. Absent ulnar CMAP, recording first dorsal interosseus borderline-low ulnar CMAP, recording abductor digiti minimi - borderline distal latency, normal proximal conduction velocity 2. Normal ulnar and dorsal ulnar SNAP 3. Normal median motor conduction study 4. Prominent active denervation and loss of MUAP in all dorsal interossei and the adductor pollicis in the setting of minimial neurogenic changes in the ADM 5. Normal median and radial C8/T1-innervated muscles (Abductor pollicis brevis, flexor pollicis longus, extensor indicis)

8. EDX findings
This is consistent with ulnar mononeuropathy at the wrist, affecting the motor branch exclusively, distal to the main branch to the hypothenar muscles, but proximal to the branch to the fourth dorsal interosseus (i.e., at the pisohamate hiatus)

9. Discussion- Applied anatomy

10. Discussion- Applied anatomy

11. Discussion- Applied anatomy

12. Discussion- Clinical features
Patients with ulnar neuropathy at the wrist
 painless unilateral hand atrophy

13. Discussion- Clinical features
The signs and symptoms of distal ulnar lesions vary
with the site of compression .
All types of ulnar mononeuropathy at wrist
=> sensation over the dorsal medial hand and the dorsal aspect of the fifth and ring fingers (territory of DUCN) is normal
Deep palmar motor and superficial cutaneous branch may be
compressed at Guyon canal.
Only the deep palmar motor branch is potentially compressed
at PHH

14. Discussion- Clinical features

15. Discussion- Clinical features
MRI imaging of the wrist is helpful in identifying structural lesions

16. Discussion- Clinical features
Fracture, ganglia, or mass lesions
=> surgical intervention is necessary
Not an obvious mass or fracture
Predominantly demyelinating lesion
=> sources of the trauma should be eliminated
Then, the patient should be followed clinicaly and by serial
EDX studies.
Surgical exploration of Guyon canal extending into PHH should
be done, if recovery is not evident.
The prognosis for patients with this disorder is usually good after
surgical decompression.

17. Electrodiagnosis
Purpose => To localize the ulnar nerve lesion To differentiate ulnar mononeuropathy Several other strategic EDX study to diagnosis of the ulnar nerve lesion 1. Ulnar motor NCS recording first DI => essential in the accurate diagnosis of ulnar nerve lesions at the wrist (e.g at the PHH or in the palm) => in most cases, low in amplitude stimulating at the wrist, and distal latency is either borderline or slightly delayed

18. Electrodiagnosis
Several other strategic EDX study to diagnosis of the ulnar nerve lesion 1. Ulnar motor NCS recording first DI => palm stimulation recording first DI - conduction block

19. Electrodiagnosis
Several other strategic EDX study to diagnosis of the ulnar nerve lesion 1. Ulnar motor NCS recording first DI => short segment stimulation across the wrist recording first DI

20. Electrodiagnosis
Several other strategic EDX study to diagnosis of the ulnar nerve lesion 2. Dorsal ulnar SNAP => Useful since an absent or low-amplitude response exclude a lesion at the wrist or hand 3. Second lumbrical-interosseous motor distal latencies comparison => Most often used in the diagnosis of CTS => Useful in identifying focal ulnar slowing at the wrist or palm in ulnar nerve lesions at Guyon canal or deep palmar motor branch lesions at the PHH => A motor distal latency difference greater than 0.5ms suggests focal slowing across the wrist => Not useful when there is a coexisting CTS

21. Electrodiagnosis
Several other strategic EDX study to diagnosis of the ulnar nerve lesion 4. Medial antebrachial SNAP => Pure sensory nerve that originates from the medial cord of the brachial plexus and innervates the skin of the medial forearm => Normal MABC SNAP is useful in excluding the possibility of a lower brachial plexopathy 5. Needle EMG of hand intrinsics => ADM => first DI, fourth DI, adductor pollicis => Flexor digitorum profundus(ulnar part), FCU => APB, FPL(median), EIP (radial) => Lower cervical paraspinals muscles

22. Electrodiagnosis

23. Electrodiagnosis
Several features on the EDX exam are not consistent with an ulnar neuropathy at the wrist 1. Low-amplitude or absent dorsal ulnar SNAP 2. Focal slowing, conduction block, or differential slowing across the elbow * Significant number of ulnar nerve lesions at the elbow, especially those resulting in axonal loss, there is no focal slowing, if slowing is present, it is diffuse. 3. Denervation of the flexor carpi ulnaris or the flexor digitorum profundus(ulnar portion) => only denervated in ulnar mononeuropathy around the elbow

24. Electrodiagnosis
Among all ulnar mononeuropathies at the wrist, selective lesion of the deep motor branch at the PHH, sparing the hypothenar muscles completely or partially, is the most common. => Wasting and weakness of all intrinsic muscles of the hand except the thenar and hypothenar muscles and without sensory manifestations

25. Follow-Up
The patient recalled that a month before the onset of symptoms,
he had spent an entire weekend vigorously chopping wood.
The patient demonstrated no improvement
=> surgical exploration of the proximal portion of Guyon canal
was performed
=> revealed normal structure
There was no evidence of clinical or electrophysiologic
improvement over the ensuing 6 months
=> 2nd operation was performed
=> more distal exploration of the deep palmar branch into the PHH
=> fibrous band constricting the deep motor branch at the PHH
=> resected

26. Follow-Up
The patient had significant and gradual improvement of strength
and experienced reversal of atrophy over the next year.
12 months after the 2nd decompression, the ulnar CMAP
amplitude, which recorded the first DI and the ADM, showed
significant improvement .
Needle EMG of the first and fourth DI showed significant
reinnervation and a decline in fibrillation potential.

27. Diagnosis
Subacute deep palmar ulnar
mononeuropathy, at the pisohamate hiatus,
manifested by axonal loss