|Year : 2019 | Volume
| Issue : 1 | Page : 62-64
Unilateral and isolated absence of opponens pollicis and adductor pollicis: Could it be Cavanagh's syndrome?
NA Priyadharshini1, V Dinesh Kumar2, R Rajprasath3
1 Department of Anatomy, Sri Manakula Vinayagar Medical College and Hospital, Puducherry, India
2 Department of Anatomy, Jawaharlal Institute of Postgraduate Medical Education and Research, Puducherry, India
3 Department of Anatomy, Pondicherry Institute of Medical Sciences, Puducherry, India
|Date of Submission||01-Feb-2019|
|Date of Acceptance||19-Feb-2019|
|Date of Web Publication||19-Jun-2019|
V Dinesh Kumar
Department of Anatomy, Jawaharlal Institute of Postgraduate Medical Education and Research, Puducherry
Source of Support: None, Conflict of Interest: None
Functions of the human hand such as grasping and releasing require synchronous action of thenar muscles and thereby require considerable mechanical complexity. Isolated absence of thenar muscles is often reported in association with syndromes such as Cavanagh's syndrome or Holt–Oram syndrome (in addition to cardiac defects). During routine anatomical dissection of an approximately 55-year-old male formalin-embalmed cadaver, we observed a unique variation in the left palm where opponens pollicis and adductor pollicis muscle were completely devoid of muscle fibers and solely constituted by fibrous tissue. We could not make out any other nervous/vascular/musculoskeletal abnormalities or signs of surgical procedures on the left superior extremity. We followed a step-wise approach rule out possible clinical syndromes and etiologies. The presumable hypothesis would be focal deficiency in the proliferation of premyogenic cells in the limb bud. This rare variation would be of paramount importance to plastic surgeons who can offer surgical correction (tendon transfers) if presented at earlier ages.
Keywords: Adductor pollicis, Cavanagh's syndrome, opponens pollicis, thenar muscles
|How to cite this article:|
Priyadharshini N A, Kumar V D, Rajprasath R. Unilateral and isolated absence of opponens pollicis and adductor pollicis: Could it be Cavanagh's syndrome?. J Curr Res Sci Med 2019;5:62-4
|How to cite this URL:|
Priyadharshini N A, Kumar V D, Rajprasath R. Unilateral and isolated absence of opponens pollicis and adductor pollicis: Could it be Cavanagh's syndrome?. J Curr Res Sci Med [serial online] 2019 [cited 2021 Feb 28];5:62-4. Available from: https://www.jcrsmed.org/text.asp?2019/5/1/62/260643
| Introduction|| |
The intrinsic muscles of the hand acting collectively on the thumb are grouped as thenar eminence. Functions of the human hand such as grasping and releasing require synchronous action of thenar muscles and thereby require considerable mechanical complexity. Muscles of the thumb establish a “guy-rope” action in the metacarpal positioning, such that any activity is accompanied by rotation. Isolated absence of thenar muscles is often reported in association with syndromes such as Cavanagh's syndrome or Holt–Oram syndrome (in addition to cardiac defects). Even though few clinical cases with congenital absence of thenar muscles, have been reported, many cases would have gone undiagnosed or been misdiagnosed. We present a rare case observed during cadaveric dissection, where opponens pollicis and adductor pollicis were absent only on the left hand. Owing to the rarity of presentation and importance in hand surgeries, this case report gains relevance.
| Case Report|| |
During routine anatomical dissection of an approximately 55-year-old male formalin-embalmed cadaver, we observed a unique variation in the left palm. In the course of blunt dissection of the thenar muscles according to the standard guidelines, we found that the opponens pollicis [Figure 1] and adductor pollicis muscle [Figure 2] were completely devoid of muscle fibers and solely constituted by fibrous tissue. Corresponding muscles of the contralateral side had muscle fibers proportionate to the adjacent muscles. The thickness of the left adductor pollicis was 9.4 mm and that of the right adductor pollicis was 13.2 mm. To exclude the subjectivity, we asked the interpretation of three anatomists who were not involved in case reporting and thereby confirmed the unusual thinning of the muscles.
|Figure 1: Dissection of the left hand showing fibrotic opponens pollicis after reflecting abductor and flexor pollicis brevis|
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|Figure 2: Dissection of the left hand showing fibrous remnant of adductor pollicis|
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The branches of median and ulnar nerves showed no variation. We could not make out any other vascular/musculoskeletal abnormalities or signs of surgical procedures on the left superior extremity. There were no evident signs of fibrosis elsewhere.
| Discussion|| |
Opponens pollicis is a small, triangular muscle lying lateral to the flexor pollicis brevis muscle and deep to the abductor pollicis brevis muscle. It is innervated by the lateral terminal branch of median nerve and supplied by superficial palmar arch. Adductor pollicis arises from two heads: oblique and transverse. It is mostly innervated by the deep branch of ulnar nerve and supplied by arteria princeps pollicis and arteria radialis indices.
Cavanagh et al. had reported a series of five cases with unilateral or bilateral hypoplasia of thumb, along with their radiological and electrophysiological abnormalities. Their cases had metacarpal-phalangeal joint instability along with ulnar collateral ligament laxity. Electromyography findings such as normal distal latency, normal conduction velocity, and low-amplitude compound motor action potentials were also observed. Any case, particularly children, presenting with isolated hypoplasia of thenar muscles with fulfillment of other two criteria can be conferred with Cavanagh's syndrome. Iyer and Stanley had reported a case of congenital absence of the abductor pollicis brevis and flexor pollicis brevis muscles associated with laxity of ulnar and radial collateral ligaments of the metacarpal-phalangeal joints. In our case, because of the rigidity arising out of embalming, the laxity of ligaments could not be assessed. By the fact that there were no evident signs of surgery/injury in thefirst web-space or thumb, we could presume that the absence of muscles is not due to traumatic denervation. Sahin et al. had reported a clinical case of a 21-year-old male with a bilateral absence of abductor pollicis brevis and opponens pollicis muscles and the patient in that report had mild dysfunction in opposition and abduction, not accounting for any limitations of activities of daily living. Lee et al. corroborated thenar hypoplasia and aberrant radial artery in a case with Klippel–Feil syndrome. We could not observe any abnormality in the radial artery. There were no marks suggestive of chronic hemodialysis in the upper limb of the cadaver ruling out the chances of local ischemia and thereby leading to muscle weakness.
We procure unclaimed cadavers for educational dissection, and this left us handicapped regarding the antemortem clinical history and functional deficits. However, we tried to rule out all possible causes of acquired hypoplasia of thenar muscles. In the present case, the other intrinsic muscles supplied by median nerve and ulnar nerve in the hand were of normal thickness and shape, ruling out the neurological or muscular abnormalities [Figure 3]. Adductor pollicis, being a muscle with well-defined anatomical references and surrounded by a small amount of fat, makes the assessment of thickness of the adductor pollicis muscle (TAPM) a surrogate marker for the magazine muscle protein. It is said that TAPM can be used as one of the early indicators to predict malnutrition and in chronically ill and bedridden patients. In our case, the adductor pollicis muscle thickness of the opposite side was normal, thereby ruling out the existence of earliest sign of global malnutrition in the antemortem period.
|Figure 3: Approach for figuring out the plausible reasons for unilateral absence of opponens pollicis and adductor pollicis|
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We could not find any evidence of an embryological basis for the isolated absence of these intrinsic muscles. The presumable hypothesis would be focal deficiency in the proliferation of premyogenic cells in the limb bud. The process mediated by the symphony of Pax3 – Myf5 - Meox2 is needed for the development of the appropriate number of myogenic cells in the limb, and abnormal expression of Meox2 function would lead to abnormal patterning of few muscles. Recently, a male with dystrophin gene mutation causing heterogenous weakness of upper limb was observed which was significantly pronounced in abductor pollicis brevis and extensor pollicis longus. In the absence of cardiomyopathy, this probability is also ruled out, and thus, this case gains paramount importance.
| Conclusion|| |
We conclude that the knowledge regarding the absence of thenar muscles is a rare variation with paramount importance to plastic surgeons who can offer possible surgical correction (tendon transfers) if presented at earlier ages. In addition, awareness regarding this might also prevent the orthopedic surgeons from mislabeling children presenting with flattening of thenar eminences as childhood-onset carpal tunnel syndrome.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]