Ulnar neuropathy at wrist- Electrophysiological approache
Ulnar Neuropathy at wrist
Senior Resident Academic
Department of Neurology.
• Rare than ulnar neuropathy at elbow.
• Can mimic early MND.
• Good knowledge of local anatomy required.
• Ulnar nerve enters the wrist at Guyons canal.
– Proximally pisiform bone
– Distally hook of hamate
– Floor : transverse carpel ligament, hamate,
– 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.
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.
• 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).
• Weakness and atrophy of ulnar intrinsic
• 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
– Dorsal medial aspect spared.
Repeated work related trauma.
Ganglion cyst in Guyon’s canal.
• Early MND:
– UNW not all C8 T1 muscles affected.
• Ulnar neuropathy at elbow.
– Correlating sensory loss.
• C8 T1 radiculopathy
• Lower trunk, medial cord brachial
FDI latency: < 4.5ms
FDI VS ADM Latency comparison: <2ms
Side to side comparison FDI: <1.3ms
2nd lumbrical Vs ulnat interossei: <0.4ms
Ulnar motor study recording FDI:
• Distal deep palmar br
– Latency and CMAP
– When compared with
ADM latency – highly s/o
– ADM recordings also
affected in more
• >2ms difference
Dorsal cutaneous Sensory study:
• Normal SNAP in UNW.
• If abnormal suggests
Median Second lumbrical VS Ulnar Int
• Same as Median study
• Latency diff > 0.4
• If there is associated
CTS – difficult to
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
Short segment Incremental studies.
• Inching done from 2 to
4 cm above and 4 to 6
cm below distal wrist
• 1 cm intervals.
• NL 0.1 to 0.3 ms/cm
• Latency >0.5ms – focal
• 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
• 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
– Abd. Pollicis brevis, flex. Pollicis longus, ext.