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Isolated Compression of Deep Palmar Branch of Ulnar Nerve by a Midpalmar Ganglion: A Rare Case Report

Case Report Open Access
Jyoti Sureka* and Sanuj Panwar
Department of Radiology, Christian Medical College and Hospital, Vellore, Tamil Nadu, India
*Corresponding author: Jyoti Sureka, MBBS, MD, FRCR
Associate Professor
Department of Radiology
Christian Medical College and Hospital
Vellore, Tamil Nadu, India
Tel: +919894584945
Fax: +9104162232035
E-mail: drjyoticmch@rediffmail.com
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Received October 09, 2012; Published January 18, 2013
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Citation: Sureka J, Panwar S (2013) Isolated Compression of Deep Palmar Branch of Ulnar Nerve by a Midpalmar Ganglion: A Rare Case Report. 2:616 doi:10.4172/scientificreports.616
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Copyright: © 2013 Sureka J, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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Abstract
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Isolated compression of deep palmar branch of Ulnar Nerve (UN) by a midpalmar ganglion is very rare but treatable cause of ulnar neuropathy. We present such a case in a 24-year-old man with progressive hand weakness but no sensory loss had a clinical diagnosis of deep palmar branch lesion of the UN. MRI clearly showed a ganglion arising from the volar and ulnar aspect of base of 4th carpometacarpal joint causing compression of the deep motor branch of the UN with secondary denervation changes of dorsal interosseous muscle and nerve edema distal to the site of compression. We also discuss the anatomy of the region and a review of the reported cases of deep branch of UN compression.
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Keywords
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Compressive neuropathy; Deep branch of ulnar nerve; Ganglion; Magnetic Resonance Imaging (MRI)
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Introduction
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UN lesions in the wrist and hand can cause a variety of different clinical findings, depending on precise location. Findings might range from a pure sensory deficit to pure motor syndromes with weakness that may or may not involve the hypothenar muscles. This depends on whether the lesion involves the main trunk, the sensory branch only, or the deep palmar branch at different sites from just at the hypothenar muscles to the lateral palm. UN compression at the wrist can be caused by a variety of intrinsic and extrinsic factors [1]. Isolated compression of only the deep branch of UN by a ganglion is very rare [1,2]. We describe the clinical, neurophysiological and MRI findings in a patient with a clinical diagnosis of deep palmar branch lesion of UN. The purpose of this case report is to describe the MR imaging characteristics, presenting symptoms and electrophysiological findings with emphasis on the MR imaging anatomy of UN at wrist and palm.
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Case Report
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A 24-year-old gentleman presented to neurology outpatient department with a gradually worsening weakness and paraesthesia in the fourth and fifth digits of the right hand. On examination, lighttouch sensation and two-point discrimination were intact throughout the hand, including UN distribution. The Froment’s sign was positive. The hypothenar musculature was intact. A clinical diagnosis of deep branch of UN palsy was made, and Electromyography (EMG) was done. EMG study showed severe denervation of the deep branch of the UN. Further MRI of the wrist was acquired to look for space occupying lesion impinging upon the UN. The MRI of the wrist showed a multiloculated cystic lesion at proximal 4th and 5th metacarpal levels with proximal elongated neck like extension into the volar and ulnar aspect of 4th carpometacarpal joint (Figures 1A-C). This cystic lesion was compressing the deep branch of UN distal to the hypothenar muscle innervation. Mild T2 STIR (short tau inversion recovery) hyperintensity in the deep branch of UN just distal to the site of compression likely to be nerve edema was noted. Mild atrophy with hyperintensity in the 4th dorsal interosseous muscle suggestive of denervation hyperintensity (Figure 2). Final diagnosis of ganglion cyst of the palm arising from volar and ulnar aspect of base of 4th carpometacarpal joint compressing the deep palmar branch of UN distal to the hypothenar muscle innervation was made.
Discussion
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Compression of the deep motor branch of the UN was first described by Bowers and Hurst in 1979 [3]. In 1952, Seddon presented a case in which a ganglion arising from the pisohamate joint caused compression of the deep branch of UN distal to the hypothenar muscle innervations [2].
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Guyon's canal is located at the proximal part of the hand radial to the pisiform bone contains the UN and artery [4]. Distal UN bifurcates an average distance of 10 to 12 mm distal to the proximal margin of the pisiform bone [4]. The distal Guyon's canal is divided into three zones (Figures 3A-D) [5]. Zone 1 is that portion of the tunnel proximal to the bifurcation of the UN where the nerve carries both motor and sensory fibres and thus compression in this zone leads to combined motor and sensory deficits. Zone 2 encompasses the deep motor branch of the nerve distal to bifurcation where the nerve carries only motor fibres and leads to a pure motor neuropathy [5]. Further location of the lesions within Zone 2, in which lesion just distal to bifurcation but proximal to the branch to the hypothenar results in paralysis of the intrinsic muscles, distal to the hypothenar innervation where sparing of hypothenar occur and further distally where the lesion occurs just proximal to the branches going to the first dorsal interosseous and adductor pollicis muscles. Zone 3 surrounds the superficial branch where neuropathy leads to only sensory deficits [5]. MRI is the imaging modality for the evaluation of ulnar neuropathy.
Entrapment syndrome is neuropathy due to a structural abnormality, such as compression, displacement, or traction of the nerve, or by an intrinsic abnormality of the nerve, such as a nerve cell tumor. The diagnosis is suspected clinically, and the role of imaging is to identify the abnormality causing the entrapment or to show secondary findings such as nerve flattening or swelling or muscle edema or atrophy that confirm or support the diagnosis [6]. Compressive neuropathies of the UN occur mostly at elbow and less commonly at wrist. Various causes of UN compression at wrist include ganglion, trauma, giant cell tumors, neurofibromas, intraneural cysts, anomalous muscles, thrombosis, bursitis, thickened pisohamate ligament and rarely by Guyon's canal lipoma [7,8]. In most cases, a ganglion compressing the UN arises from the level of the pisiform–hamate–triquetral complex or slightly distal to it [9]. Midpalmar ganglion originating from the carpometacarpal joint is a rare cause of isolated compression of deep branch of UN distal to Guyon's canal [2,10]. To the best of our knowledge, only few such cases of ulnar neuropathy have been reported to date [2,10]. This is another such rare case with compression of the deep motor branch of the UN distal to Guyon's canal and hypothenar innervation (zone 2) [10] by a ganglion originating from volar and ulnar aspect of base of 4th carpometacarpal joint. MRI is extremely helpful in identifying the origin of ganglion cyst and its relationship to the deep branch of the UN as seen in our case and thus aids in surgical planning and excision.
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Conclusion
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Midpalmar ganglion arising from the carpometacarpal joint is an uncommon cause of isolated compression of deep branch of UN. MRI is a choice of modality for complete delineation including origin and extension of ganglion cyst thus aids in early treatment.
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References
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