ulnar neuropathy at wrist- electrophysiological approache
DESCRIPTION
Electrophysiology study of ulnar neuropathy at wrist.TRANSCRIPT
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Ulnar Neuropathy at wristElectrophysiological Approach
Dr.Roopchand.PSSenior Resident AcademicDepartment of Neurology.
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Introduction:
• Rare than ulnar neuropathy at elbow.• Can mimic early MND.• Good knowledge of local anatomy required.
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Anatomy:• Ulnar nerve enters the wrist at Guyons canal.– Proximally pisiform bone– Distally hook of hamate– Floor : transverse carpel ligament, hamate,
triquetrous bone– Roof loosely formed at inlet and thick band of
tissue at outlet – pisiohamate hiatus.– At the hiatus divides in to ulnar sensory branch
and deep palmar motor branch.
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Supply:
1. Hypothenar motor: At hiatus – ADM, Opponence digiti minimi, flexor digiti
minimi, palmaris brevis.
2. Superficial sensory br:– Volar 5th and medial 4th digit.
3. Deep palmar motor br:– 3rd and 4th lumbricals, four dorsal and three
palmar interossei, adductor pollicis, flexor pollicis brevis deep head.
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Clinical:
• Can be typed according to location of lesion and fibers affected.– Distal deep palmar motor lesion.– Proximal deep palmar motor lesion.– Proximal canal lesion.– Pure sensory lesion (rare).
Most common
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Presentation:
• Weakness and atrophy of ulnar intrinsic muscle.
• Thenar and hypothenar wasting can be seen• Benediction hand posture, Forment’s sing,
Wartenberg’s sign can be seen.• Sensory disturbance over volar 5th and medial
4th finger.– Dorsal medial aspect spared.
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Etiology:
• Repeated work related trauma.• Wrist fracture.• Ganglion cyst in Guyon’s canal.• Neurofibroma.
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Differentials:
• Early MND: – UNW not all C8 T1 muscles affected.
• Ulnar neuropathy at elbow.– Correlating sensory loss.
• C8 T1 radiculopathy• Lower trunk, medial cord brachial
plexopathies.
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Electrophysiological evaluation.
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Normal Values:
• FDI latency: < 4.5ms• FDI VS ADM Latency comparison: <2ms• Side to side comparison FDI: <1.3ms• 2nd lumbrical Vs ulnat interossei: <0.4ms
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Ulnar motor study recording FDI:
• Distal deep palmar br lesion:– Latency and CMAP
amplitude affected.– When compared with
ADM latency – highly s/o UNW
– ADM recordings also affected in more proximal lesions
• >2ms difference significant..
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Dorsal cutaneous Sensory study:
• Normal SNAP in UNW.• If abnormal suggests
UNE.
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Median Second lumbrical VS Ulnar Int DML:
• Same as Median study in CTS.
• Latency diff > 0.4 significant.
• If there is associated CTS – difficult to interpret.
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Wrist and Palm stimulation:
• FDI recorded.• Stimulated 3cm above
the wrist and 4cm distal to distal palmar crease.
• Drop in amplitude or decrease in CV.
• Any CV <37m/s is of localizing value.
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Short segment Incremental studies.
• Inching done from 2 to 4 cm above and 4 to 6 cm below distal wrist crease.
• 1 cm intervals.• NL 0.1 to 0.3 ms/cm• Latency >0.5ms – focal
slowing.
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• Wrist and palm stimulation showing focal slowing 100% specific.
• Inching is also very sensitive and specific.• In lumbrical-interossei study increasing the cut
off value to 0.7 can eliminate the problem of co existent median neuropathy.
• FDI vs ADM latency comparison is least sensitive.
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EMG approach:
• FDI and ADM sampled to look for distal/proximal deep br involvement.
• FDP5 and FCU : to r/o ulnar neuropathy proximal to wrist.
• Radial and Median innervated C8 muscles & lower cervical paraspinal muscles: to r/o radiculopathy.– Abd. Pollicis brevis, flex. Pollicis longus, ext.
indices proprius.
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Recommended EMG Protocol for UNW:
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THANK YOU