Palmaris Brevis Research Articles

Functional Anatomy of the Palmaris Brevis: Grasping for Answers

IntroductionThe palmaris brevis (PB) is a small, trapezoid‐shaped muscle found in the human hand and the forelimb of quadruped mammals, originating from the flexor retinaculum to insert in the skin of the medial palm. Although it may be considered a subcutaneous vestigial muscle, the function of the PB has been described as deepening the palm of the hand for grasping, or protecting the neurovasculature of the ulnar canal (Guyon's canal). Although the morphological characteristics of the palmaris brevis have been described through cadaveric dissection, the electromyographic (EMG) activity during hand movements has yet to be explored systematically. Recent clinical case studies investigating PB spasm syndrome reported that this muscle may not be under voluntary control, perhaps suggesting the presence of smooth muscle fibers. Thus, the primary objective of this study was to investigate the EMG activity of the PB during simple hand movements, and secondly to explore, histologically, the presence of smooth muscle fibers in the PB of human cadavers.MethodsTo date, seven healthy participants (6 males, 1 female; ages: 23–32y) were recruited from the University population to participate in this investigation. Palmaris brevis EMG activity was recorded from the subjects’ dominant hand by inserting a pair of intramuscular fine wires via a small diameter (27.5 gauge) hypodermic needle. Subjects were instructed to forcefully contract their hand muscles to achieve the following movements: abduction of the 5th digit, finger flexion at the metacarpophalangeal joints, and opposition of the 5th digit to the thumb. Palmaris brevis reflex activity was tested by compressing the ulnar nerve of right palm at the wrist (as described by Montagu 1952. Science. (115)). Integrated EMG analysis of the PB during the hand positions was measured offline using Spike2 software. For the histological analysis, PB samples were obtained from the hands (3 left, 3 right) of three fresh frozen cadavers (ages: 44–88y). These samples were prepared and stained using a typical H & E staining protocol.ResultsHistological examination of all six PB specimens revealed no evidence of smooth muscle fibers. Integrated EMG activity of the PB was greatest in all subjects during forceful abduction of the 5th digit. Opposition of the 5th digit to the thumb produced less muscle activity than observed during abduction (Mean: 59 ± 24% of abduction EMG activity). No measureable PB muscle activity was elicited during the simple finger flexion task in all participants. A palmaris brevis reflex producing dimpling of the skin and EMG activity could be elicited in ~60% of the subjects.ConclusionsThe proposed protective function of the PB in relation to the ulnar canal is supported by the observation that the EMG activity was greatest during abduction. Movements in which the hand is pressed against a flat surface, such as a push‐up exercise, would rely on abduction of the 5th digit in order to stabilize and support the hand. As the PB contracts, it provides a protective muscular barrier to the underlying neurovasculature of the ulnar canal. EMG activity recorded during opposition demonstrates the PB provides protection to the ulnar canal neurovasculature during grasping motions such as a cyclist holding their handlebars. Histological evidence demonstrates that the PB is composed of skeletal muscle fibers and can be voluntarily activated during specific hand movements; however, the muscle cannot be contracted in isolation.Support or Funding InformationSupported By NSERC

Andreas Vesalius' 500th anniversary: the initiation of hand and forearm myology.

Andreas Vesalius (1515-1564) was the first to market an illustrated text on the freshly dissected muscular anatomy of the human hand and forearm when he published his De Fabrica Corporis Humani Libri Septem, in 1543. To commemorate his 500th birthday, we searched the second of seven books composing De Fabrica, the annotated woodcut illustrations of De Fabrica, the Tabulae Sex, and Epitome, and an eyewitness report of a public dissection by Vesalius for references to the morphology and functions of these muscles. We found Vesalius to have recognized all currently distinguished muscles except the palmaris brevis and he noted occasional absence of some muscles. Generally, he limited the origin and insertion to bones, largely disregarding attachments to membranes and fascia. Functionally, he recorded the muscles as having a single vector and operating on only one joint. We conclude that Vesalius was nearly completely correct about the anatomy of the muscles of the forearm, but much less accurate about their function. 5.

A morphometric study of the ulnar nerve in Guyon's canal

Objectives:Guyon’s canal is clinically significant because it contains the ulnar nerve, artery and veins and is a location forcompression injury. This study was undertaken to determine the anatomy of the ulnar nerve in Guyon’s canal on 40 wristsof 20 adult formalin-fixed cadavers. Methods: 40 wrists of 20 formalin-fixed adult cadavers obtained from the Department of Anatomy, Ege University Facultyof Medicine were dissected. In each cadaver, the skin and the subcutaneous fatty tissues were removed starting from theforearm down to the palm of the hand. The palmaris brevis muscle and the palmar aponeurosis were dissected to exposeGuyon’s canal. Results: The length and diameter of the main trunk of the ulnar nerve in Guyon’s canal before dividing into its terminalbranches were measured as 11.72±1.99 mm and 3.41±0.5 mm, consequently. Within the canal, the main trunk divided intotwo terminal branches. The diameter of the deep branch was 1.77±0.47 mm and the superficial branch was 2.41±0.45 mm.The superficial branch divided into the proper palmar digital nerve supplying the medial side of the little finger and the common palmar digital nerve supplying the adjoining sides of little and ring fingers. Conclusion:An accessory abductor digiti minimi muscle was observed as a possible cause of compression in Guyon’s canal.Despite its clinical relevance, the diameters of the deep and superficial branches of the ulnar nerve in Guyon’s canal do notexist in previous studies

Pancaost syndrome related to hydatid cyst

Pancoast syndrome remains a rare presentation of pulmonary diseases. Even in endemic area of echinococcosis, lung's hydatid cyst is seldomly revealed by this syndrome. We report a case of a 38 year old male patient who presented to our department with neck and left superior limb pain associated with palmar muscle atrophy and Horner's syndrome. Radiological investigations suggested the diagnosis of hydatid cyst of the left lung apex which was confirmed by surgical excision and pathological examination of the lesion. This case highlights an uncommon etiology of Pancoast syndrome which might mislead physicians in their practice.

The Distal Ulnar Tunnel

The distal ulnar tunnel was described by anatomist and urological surgeon Felix Guyon in 1861 based on his anatomical dissections investigating the unique and small protrusion of fatty tissue into the distal forearm noted when pressure was applied to the hypothenar eminence (“Ollier phenomenon”).1 The triangular-shaped “loge” contained the ulnar nerve and artery with accompanying veins; Guyon postulated that this space may be a potential site of compression for the ulnar nerve, although this concept was presented more formally by others such as Hunt (1908),2 Grantham (1966),3 and, subsequently, by McFarlane et al through their considerations of the pisohamate tunnel.4 The distal ulnar tunnel, or the Guyon canal, is ∼4–4.5 cm in length and begins at the proximal edge of the volar carpal ligament in the volar-ulnar forearm and ends at the fibrous arch of the hypothenar muscles. The distal ulnar tunnel is defined by the flexor carpi ulnaris, the pisiform, and the abductor digiti minimi as its medial wall and by the transverse carpal ligament and the hamate as its lateral margin. The floor of the tunnel consists of the flexor digitorum profundus tendons in the distal forearm, the transverse carpal ligament, the pisohamate and pisotriquetral ligaments, and the opponens digiti minimi. The roof of the tunnel includes the volar carpal ligament, palmaris brevis muscle, and hypothenar fat (Figure 1).5 Figure 1 Close-up, distal view of the distal ulnar artery and ulnar nerve to demonstrate the relationship of the distal ulnar tunnel and the carpal tunnel. The ulnar nerve (un) is dorsal and ulnar to the ulnar artery (ua); both structures course volar to the ... Clinically, the distal ulnar tunnel has been divided into three zones.5 Zone 1 begins at the proximal aspect of the volar carpal ligament, ∼2 cm proximal to the pisiform, and ends at the bifurcation of the ulnar nerve, ∼1 cm distal to the pisiform. Nerve pathology typically involves combined motor and sensory deficit. Zone 2 follows the deep motor branch to the fibrous arch of the hypothenar intrinsic muscles, and Zone 3 involves the sensory branch of the ulnar nerve, which provides sensation to the small finger and (typically) to the ulnar aspect of the ring finger as well as providing motor innervation to the palmaris brevis muscle. Compressive nerve pathologies in Zone 2 and Zone 3 involve motor and sensory deficits, respectively.

An abnormally deep palmar muscle: a case description

A rare case of an abnormally deep palmar muscle is described. The muscle was found out in a female patient with the clinical picture of carpal tunnel syndrome. In the process of an operation, a thickened median nerve was revealed; a tendon, tightly connected to the above nerve with their common fascial coat, passed along the radial surface of the nerve. Separation of the tendon from the nerve and mesoepineurolysis were followed by transposition of the median nerve outside the carpal tunnel.

The functional and comparative anatomy of the forelimb muscles in the sun bear (Helarctos malayanus)

The sun bear (Helarctos malayanus) is the smallest extant member of the Ursidae, inhabiting the tropical mainland forests of Southeast Asia and the islands of Sumatra and Borneo. This study provides morphological data for the forelimb of Helarctos, whose anatomy has been scarcely documented. The left and right forelimbs of a 16 year old female sun bear from the Reid Park Zoo (Tucson, AZ) were dissected and photodocumented. In addition, muscle origins and insertions were recorded and muscle maps produced, providing a valuable resource for those analyzing the postcranial remains of fossil ursids. The forelimb musculature was compared to that of other carnivores and analyzed for functional adaptations. Dissections revealed common ursid features, such as powerful flexors of the digits, elbow and carpal joints, as well as traits particular to the sun bear. For example, m. flexor carpi radialis has an extensive insertion onto the scapholunatum and metacarpals II and III, assisting in adduction of the carpal joint. Mm. flexor digitorum brevis manus and palmaris brevis were also observed, which may contribute to increased grasping ability of the manus. Taken together, these findings are likely adaptations to the climbing and feeding behaviors which are central to the arboreal lifestyle of Helarctos.

Anatomical study of the third palmar interosseous muscle and its dominate nerve

目的 观察第三骨间掌侧肌及其肌支的解剖学特点,探讨腕尺管综合征中小指内收恢复困难的解剖学基础.方法 在2.5倍手术放大镜下对20具新鲜无外伤、无畸形成人手标本进行解剖,观察第三骨间掌侧肌及其肌支及邻近结构,测量了第三骨间掌侧肌的大小和第三骨间掌侧肌支的长度、宽度、厚度,并对所得数据进行统计学处理.结果 第三骨间掌侧肌及第三骨间掌侧肌支分别是骨间掌侧肌和骨间掌侧肌支中最细小的,部分第三骨间掌侧肌浅层存在明显的腱束,对第三骨间掌侧肌支形成潜在的卡压.结论 第三骨间掌侧肌及其肌支是骨间掌侧肌和肌支中最细小的,部分由第三骨间掌侧肌桡侧绕至尺侧入肌,而第三骨间掌侧肌掌侧存在明显的腱束,对第三骨间掌侧肌支形成潜在卡压,可以解释小指内收恢复困难的原因。

An unusually large palmaris brevis muscle and its clinical significance

An unusually large palmaris brevis muscle and its clinical significance

The first description of the palmaris brevis muscle

Giovanni Battista Canano was born in Italy in 1515 and his work has gone mostly unknown. Very few copies of this anatomist and physician's book are known to exist. Interestingly, Canano reported and depicted what we believe, to be the first description of the palmaris brevis muscle. This description would be some 200 years prior to what is thought to be the earliest mention of this muscle by William Cheselden in his book, The Anatomy of the Human Body, published in 1713.

An Anomalous Palmaris Brevis Muscle and its Clinical Implications

The palmaris brevis (PB) muscle is a small, thin, subcutaneous muscle of the palm. The palmaris brevis muscle is important muscle contributing to the grip of the hand. In the present case, during routine cadaveric dissection, we detected a PB muscle which was not subcutaneous but existed as a muscle deep to the dermis of the skin of the palm. The PB muscle stretched as a horizontal band over the hypothenar muscles of the palm. The anomalous location of the PB may result in compression of neurovascular structures on the ulnar side of the palm. The awareness of such anomalous muscle which is not subcutaneous, may be clinical important for surgeons operating on the hand and clinicians diagnosing compressive symptoms.

Clinically Significant Placebo Analgesic Response in a Pilot Trial of Botulinum B in Patients with Hand Pain and Carpal Tunnel Syndrome

We conducted a pilot trial to assess the effect of botulinum toxin B on palmar pain and discomfort in carpal tunnel syndrome (CTS) patients. Design. Randomized, double-blind, placebo-controlled. Twenty ambulatory CTS patients. Intervention. Botulinum toxin B or placebo injections into three hypothenar muscles anatomically linked or attached to the carpal tunnel and its tentorium, that is, the Opponens Digiti Minimi and Flexor Digiti Minimi, located with electromyography (EMG), and the Palmaris Brevis Muscle, anatomically located without EMG. New York City hospital. Outcomes were measured with numeric ratings, with higher scores indicating worse outcomes. Daily, subjects recorded their 0-10 numeric ratings of overall pain levels and pain-related sleep disturbances. During weekly telephone calls, they reported their 0-10 ratings for overall pain, pain-related sleep disturbance, and CTS-related tingling during the night and day as experienced over the preceding 24 hours. For each of four clinic visits, we averaged each subject's ratings of nine quality of life indicators from the West Haven-Yale Multidimensional Pain Inventory (WHYMPI), each measured on a 0-6 numeric scale. Over the 13-week trial, compared to baseline scores, the following outcomes predominantly showed decreases of statistical significance (P < or = 0.050) or borderline significance (0.050 < P < or = 0.10) for weeks 2 through 8: overall pain per daily diary entries and per weekly telephone reports, and pain-related sleep disturbance in the placebo group per phone report and in the botulinum toxin B group per diary report. CTS painful night tingling and day tingling, as well as the average scores of the WHYMPI quality of life indicators, showed improvements with statistical or borderline significance for almost each follow-up week. Between-group analyses, however, demonstrated that at each follow-up week, there was no statistically significant difference between the two study groups regarding changes from baseline in any study outcome. Botulinum toxin B is not dramatically superior to placebo for the relief of CTS symptoms. Possible explanations of the improvements in each study group are explored.

‘Neurographic’ palmaris brevis sign in type II° ulnar neuropathy at wrist

Objective To investigate the source of an unusual and previously unreported volume conducted potential on motor nerve conduction studies. In a case of subacute ulnar neuropathy at wrist (UNW) selectively involving the deep motor branch, we recorded from the hypothenar eminence a large positive wave (2.5 ms–2 mV) preceding the negative takeoff of the delayed distal ulnar motor response. Methods We performed multiple channels motor and sensory ulnar nerve (UN) conduction studies; these included selective electrical stimulation and anaesthetic block of UN branches and also selective recording of motor responses by single fibre needles; data were confirmed by an intraoperative neurophysiological study and correlated with MRI and surgical findings. Results Detailed neurophysiological investigation demonstrated the generation of this waveform from the palmaris brevis (PB) muscle. MRI and surgical exploration documented a hypertrophy of this muscle. Conclusions In type II° UNW, depolarization of a spared palmaris brevis muscle may be recorded as a positive wave preceding the delayed abductor digiti minimi motor response. Significance We underline the peculiar localizing value of this volume conducted ‘meaningful artefact’ in that particular setting. It actually represented an early neurographic analogue of what is known as the clinical ‘Palmaris Brevis Sign’ in long standing type II° UNW.

Hypothenar Hammer Syndrome Associated with Hipoplasia of Radial Artery: Clinical Case and Review of Literature

Aneurysmal degeneration of the ulnar artery is a rare cause of digital ischemia, which is usually described in workers exposed to repeated trauma over the hypothenar eminence, due to a relative lack of artery protection at this level. Hypothenar Hammer Syndrome (HHS) is most commonly found in men who are exposed to repetitive palmar trauma in one or both of their hands for years due to their occupation. The ulnar artery, after penetrating the hand through the Guyon’s canal, continues superficial to the hypothenar muscles, only covered by the palmaris brevis muscle, the palmar aponeurosis and the skin. In this area of scarcely two centimetres, the artery is stretched over the hook of the hamate bone, which acts as an anvil and contributes to its injury after prolonged repetitive trauma. Mural degeneration with intimal injury occurs which results in thrombosis, and/or medial injury, leading to the formation of true aneurysms. Acute ischemia, atheroembolism and neurologic compression are the most common complications, though not rupture. Some authors have suggested that trauma is not the only cause of the syndrome, but arterial fibrodysplasia is partly responsible for aneurysmatic degeneration. Digital perfusion is assured by two arterial trunks, ulnar and radial, which meet in the superficial and deep palmar arch. The coexistence of hypoplasia of the radial artery and an ulnar aneurysm, without precedent in the medical literature, makes management of the injury important since there is only a single arterial supply to the hand.

Palmaris brevis spasm: an occupational syndrome.

Described are five patients who developed palmaris brevis (PB) spasm syndrome following prolonged use of a computer mouse and keyboard. Electromyography showed spontaneous activity characterized by irregular discharges of single motor unit potentials and myokymia from PB muscle that did not disappear after ulnar nerve block at the wrist, suggesting a distal lesion.

A prospective study of the anatomic variations of the median nerve in the carpal tunnel in Asians.

A prospective study of anatomic variations of the median nerve and its relationship to the surrounding structures was performed of 354 consecutive operations in 192 patients with carpal tunnel syndrome at Korea University Anam Hospital from July 1995 to September 1997. A total of 184 patients were women and 8 patients were men. A total of 162 patients were bilateral and 30 were unilateral. Regarding the course of the motor branch, the extraligamentous type was most common (96.1%, 340 patients). A total of 81.1% of patients (N = 287) had the origin of the motor branch at the radial side of the median nerve (or radial one third), and 17.2% of patients (N = 61) had the origin of the motor branch at the anterior portion of the median nerve. Of these 61 patients, 30 patients (49.1%) were of the preligamentous type. Only one motor nerve branch was found in 89.5% of patients (N = 317), and multiple branches were found in 10.5% of patients. As a result of the comparison between two hands when both hands were operated, the origin and number of motor branches and their courses were identical in most patients (>60%). Hypertrophy of the flexor pollicis brevis was found in 8.5% of patients (N = 30), hypertrophy of the palmaris brevis was found in 4.2% of patients (N = 15), absence of the palmaris longus was discovered in 0.6% of patients (N = 2), existence of the median artery was found in 0.6% of patients (N = 2), and high division of the median nerve rejoining with the thenar motor nerve was found in 0.3% of patients (N = 1). Clearly, the anatomy of the carpal tunnel in Koreans is somewhat different, in part, from the results obtained from studies of whites, but overall results are not significantly different. These results can help obtain a better surgical outcome and complete decompression of the median nerve during operation while preventing inappropriate or inadvertent injury to the motor branch of the median nerve in Koreans.

Ｐａｌｍａｒｉｓ ｂｒｅｖｉｓ ｔｕｒｎｏｖｅｒ ｆｌａｐを用いて治療した手根管開放術後の２例

We successfully treated recurrent and persistent carpal tunnel syndromes with neurolysis and palmaris brevis turnover flap with hypothenar fat.A 53-year-old female received carpal tunnel release 19 months ago. Night pain and paresthesia were once resolved after surgery, however, symptoms recurred after 9 months. On examination, Tinel sign along the operative scar and positive Phalen test were found. Two-point discrimination of the thumb was 8mm but motor weakness was not found and terminal latency was within the normal range. Intraoperative findings revealed that the median nerve migrated volarly and adhered to the dorsal aspect of the sectioned flexor retinaculum. After the index surgery, night pain resolved immediately and only slight numbness remained at 18 months after surgery.A 67-year-old female received carpal tunnel release 12 months ago. Pain in the palm started, and night pain and paresthesia worsened after surgery. On examination, we found Tinel sign along the operative scar, positive Phalen test, weakness in thumb abduction and mild delay in terminal latency. Operative findings were volar migration of the median nerve surrounded by the scar tissue. After the index surgery, night pain disappeared immediately and she has been symptom-free for 16 months.

Electromyographic localization of the palmaris brevis muscle.

The palmaris brevis (PB) is the only muscle frequently innervated by the superficial branch of the ulnar nerve. It is clinically involved in patients with sensory impairment of the ulnar nerve sparing the deep branch as seen in mild cases of cyclist or crutch palsy. It is also involved in palmaris brevis spasm syndrome. A technique is described that makes it possible to localize the PB distinctly from its neighbors by electromyographic (EMG) pin examination. Methods include prospective (1) anatomic measurement in 10 cadavers and (2) EMG pin examination in 12 normal subjects measuring rise time (ms) and RMS voltage output (microV). Results showed (1) the area of the PB in elderly cadavers was 2.1+/-0.7 x 2.1+/-0.3 cm with a thickness of 0.2+/-.01 cm and (2) in the live subjects, the muscle could be located with identification of motor unit potentials having a rise time <1 ms 100% of the time. In conclusion, the PB can be localized for EMG analysis by using an approach parallel to surface of the palm. Clinically, it could be a useful complement to diagnose neuropathy involving the superficial fibers of the ulnar nerve.

Guyon's canal revisited: An anatomic study of the carpal ulnar neurovascular space

The boundaries of the space through which the ulnar neurovascular bundle crosses the wrist have been reinvestigated. Using gross dissections, transverse and sagittal sections, and histologic study, we determined that the roof of Guyon's canal, the "carpal ulnar neurovascular space," does not directly connect to the hamate bone, as is currently accepted. The roof of this space extends radially to the hook of hamate and attaches to the flexor retinaculum. This anatomic arrangement allows the ulnar artery and sensory component of the ulnar nerve to course radially to the hook of hamate, where they lie on the flexor retinaculum (transverse carpal ligament). The roof and radial border have three segments: (1) a proximal segment that begins near the pisiform and extends distally to the level of the hook of hamate but does not attach directly to it, (2) a central segment that contains only adipose tissue, and (3) a distal fascial layer that includes the palmaris brevis muscle. The floor of the space consists of the muscles of the hypothenar eminence, their fibers of origin, and the flexor retinaculum (transverse carpal ligament). Guyon accurately described the proximal portion of the carpal ulnar neurovascular space, but his description has been misinterpreted; the hook of hamate does not serve as the radial boundary of Guyon's canal. The anatomic relationships of the "carpal ulnar neurovascular space" need to be appreciated to avoid complications during carpal tunnel surgery.

The hypothenar adductor muscle: An anomalous intrinsic muscle compressing the ulnar nerve

Two cases of ulnar nerve compression by a transverse muscle, deep to the palmaris brevis muscle and inserting into the hypothenar fascia, were treated surgically. One patient had purely deep motor branch palsy, and the other had motor and sensory changes.