Electromyography in Clinical Practice A Case Study Approach Chapter 9.

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.

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

History & P/Ex

Nerve conduction study

Needle EMG

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)

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)

Discussion- Applied anatomy

Discussion- Applied anatomy

Discussion- Applied anatomy

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

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

Discussion- Clinical features

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

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.

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

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

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

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

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

Electrodiagnosis

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

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

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

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.

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