|Year : 2016 | Volume
| Issue : 1 | Page : 92-94
Ulnar neuropathy at wrist associated with a stab wound from iron fenced wall: A case report and review of electrodiagnostic methods to localize the lesion
Balaji Wasudeo Ghugare1, Manjiri Uttam Joshi2
1 Department of Physiology, GMERS Medical College, Gotri, Vadodara, India
2 Department of Oral Medicine and Radiology, Manubhai Patel Dental College, Vadodara, Gujarat, India
|Date of Web Publication||22-Dec-2015|
Balaji Wasudeo Ghugare
GMERS Medical College, Gotri, Vadodara - 390 021, Gujarat
Source of Support: None, Conflict of Interest: None
Diagnosis of ulnar neuropathy at wrist remains challenging domain for neurophysicians as the clinical picture resembles proximal ulnar neuropathies. Inching across wrist and conduction to first dorsal interosseous remains mainstay of electrodiagnostic (EDX) procedures for distal ulnar neuropathy. Here, we present a case of distal ulnar neuropathy with review of its EDX procedures.
Keywords: Electrodiagnosis, electromyography, ulnar neuropathy
|How to cite this article:|
Ghugare BW, Joshi MU. Ulnar neuropathy at wrist associated with a stab wound from iron fenced wall: A case report and review of electrodiagnostic methods to localize the lesion. CHRISMED J Health Res 2016;3:92-4
|How to cite this URL:|
Ghugare BW, Joshi MU. Ulnar neuropathy at wrist associated with a stab wound from iron fenced wall: A case report and review of electrodiagnostic methods to localize the lesion. CHRISMED J Health Res [serial online] 2016 [cited 2020 May 29];3:92-4. Available from: http://www.cjhr.org/text.asp?2016/3/1/92/172405
| Introduction|| |
When compared to ulnar neuropathy at the elbow (UNE), ulnar neuropathy at the wrist (UNW) is uncommon. Several causes of UNW in its order of occurrence are idiopathic, trauma, thrombosis, proliferation of synovium, a prominent hook of the hamate, a schwannoma, postoperative swelling, an aberrant fibrous band, a ganglion, a lipoma, etc. Standard electrodiagnostic (EDX) studies are generally insufficient in revealing UNW. Demonstration of conduction block (CB) and/or focal slowing of nerve conduction are the most definitive EDX evidence for the localization of segmental demyelination. Radiologic evaluation by ultrasonography and magnetic resonance imaging can rule out ulnar nerve compression in Guyon's canal due to ganglion, schwannoma, and other congenital aberrations. Traumatic ulnar neuropathy at or distal to the wrist is characterized by motor symptoms and sensory and motor axonal loss by electromyography (EMG). A case of traumatic ulnar neuropathy was reported to neurophysiology laboratory. Its clinical presentation and EDX evaluation is reported and discussed with emphasis on localization of lesion.
| Case Report|| |
A right handed 20-year-old medical student with a history of stab wound by sharp pointed iron wired wall compound at the right wrist, which was immediately closed by a surgeon in emergency department, reported to neurophysiology laboratory with complaints of weakness in the right hand. There was no history of any cumulative stress locally at wrist or any other systemic illness or neuromuscular disorders. On physical examination, closed wound was seen on ulnar side of the right wrist. There was vague tenderness at wrist and palm without any hypasthesia in palm. According to the medical research council scale, power of the first dorsal interosseous (FDI) muscle and other intrinsic muscles innervated by ulnar nerve was Grade 2, whereas power of abductor digiti minimi (ADM) was Grade 4. Power of other median innervated intrinsic muscles in hand and ulnar innervated flexor carpi ulnaris in forearm of right upper extremity was Grade 5. Froment's sign was positive in the right hand. Deep tendon reflexes were normal on both sides.
Patient underwent nerve conduction study (NCS) in both upper limbs for median and ulnar sensory and motor nerves. We observed following findings to support the diagnosis of right sided UNW with lesion located distal to hypothenar muscles in deep palmar motor branch.
- Abnormal FDI compound muscle action potential (CMAP) amplitude (0.6 mV) and latency across wrist (5.31 ms), normal values: Amplitude >4 mV and latency 4.5 ms
- Abnormal ulnar motor latency difference (4.06 ms) between CMAPs recorded from FDI and ADM, normal value: 2.0 ms
- Abnormal second lumbrical palmar interosseous median versus ulnar motor latency difference (3.23 ms), normal value: (0.5 ms).
Remaining NCS findings that is, median and ulnar sensory conductions, median (abductor pollicis brevis) and ulnar (ADM) motor conductions, F wave latencies were normal bilaterally. Inching could not be done due to fresh wound on wrist.
Patient reported to this laboratory 3 months later, after undergoing an operative procedure by a plastic surgeon. On physical examination, power of right FDI was 4 and ADM was 5. EDX evaluation including EMG showed no evidence of active denervation in FDI but large polyphasic motor unit potentials with rarified interference pattern, suggesting reinnervation [Figure 1].
|Figure 1: Electromyography finding on follow-up after 3 months showing large, polyphasic motor unit potential with rarified interference pattern in the right first dorsal interosseous muscle|
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| Discussion With Review of Literature|| |
Ulnar neuropathies at or distal to wrist are uncommon but have four distinct patterns of presentation: (1) At Guyon's canal: Main nerve trunk is affected, thus deficits in both the superficial and deep terminal branches (motor and sensory). (2) Deep, terminal branch proximal to hypothenar branch, thus no sensory loss but the weakness of all ulnar intrinsic hand muscles. (3) Deep, terminal branch distal to hypothenar muscle. No sensory loss, sparring of ADM, but the weakness of other ulnar intrinsic muscles. (4) Superficial terminal branch only; ulnar territory sensory loss. Of the four types of ulnar neuropathy at the wrist, pure motor neuropathies are the most common (50%), followed by mixed sensory and motor (33%), and most rarely, pure sensory lesions (14%).
Assessment of conduction to the FDI muscle, in addition to the routine motor latencies to the ADM, is integral to the evaluation of distal ulnar neuropathies. Olney and Wilbourn studied conduction to the FDI and ADM in 373 nerves, determining absolute distal motor latency (DML) to the FDI as well as differences between the latency to FDI and the ADM on the same side and differences in the side-to-side FDI latencies. In the present case, wherein short segment incremental study (SSIS) was not possible to locate lesion due to fresh wound, it was assessment of FDI conduction by which diagnosis of deep palmar branch neuropathy could be made. The presence of normal CMAP in ADM could delineate the lesion being distal to hypothenar muscles. A lesion of the deep palmar branch, beyond the branches to the hypothenar muscles, causes prolongation of the DML to the FDI with normal latency to the ADM and normal sensory studies. Even if the DML is not prolonged, the CMAP may demonstrate fragmentation, dispersion, or CB. In the present case, also CMAP from FDI was fragmented and dispersed with prolonged latency [Figure 2].
|Figure 2: Compound muscle action potential from first dorsal interosseous in the present case|
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Inching technique/SSIS across the wrist, even though a time-consuming and technically demanding method, it increases the EDX potential of detecting segmental demyelination in this location and hence CB. Seror in a prospective case series concluded that diagnostic sensitivity of the DML to ADM was 42% and to FDI was 66%. Inching across the wrist to search for CB improved the diagnostic sensitivity up to 90%. CB at the wrist in UNW was 2.7 times more frequent than at the elbow in UNE. In yet another study by Cowdery et al., only CB and slow wrist-palm FDI conduction velocity (<37 m/s) found specific for diagnosis of UNW as against traditional tests. EMG could not differentiate UNW from UNE because forearm ulnar-innervated muscles are typically normal in UNW but also often normal in mild UNE.
| Conclusion|| |
Ulnar neuropathy at elbow (UNE) is more commonly reported to EDX lab as compared to ulnar neuropathy at wrist (UNW). Inching across the wrist is the most helpful diagnostic clue to differentiate UNW from its close differentials including UNE or C8T1 radiculopathy. The present case was reported clinically as UNW and inching was not possible due to technical reasons. Nerve conduction to FDI and ADM successfully delineated EDX comparison studies are essential in the correct diagnosis of UNW as per individual case scenario.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]