Anomalous muscle of the wrist

A case of an anomalous muscle found in the right wrist of a 52-year-old man during routine carpal tunnel decompression surgery is reported. The muscle was observed lying transversely across the carpal tunnel superficial and parallel to the flexor retinaculum. Its further definition was subsequently demonstrated by postoperative magnetic resonance imaging (MRI). No similar structure was detectable on MRI of the left wrist.     

Effects of chronic median nerve compression at the wrist on sensation and manual skills

 The aim of this study was to analyse the functional impairments caused by chronic median nerve compression at the wrist on hand sensation and manual skill. Hand function was assessed in 11 patients (8 women and 3 men) with severe carpal tunnel syndrome (CTS) and compared with that of an age- and sex-matched control group. Apart from CTS, the subjects were healthy and the electrodiagnostic examination was normal. The pressure and vibration detection thresholds of the index finger were partially impaired and statistically different (P<0.05) when compared with controls, suggesting a reduction of tactile acuity in the territory of the median nerve. The thermal thresholds were identical in both groups, suggesting that the small-diameter fibres were not affected. When a small object was lifted and positioned in space, the coordination between the grip force and the vertical lifting force did not seem to be affected in our patients. They were able to modify their grip force according to the friction between the fingertips and the object, i.e. the more slippery the object, the higher the grip force. The unimanual Purdue Pegboard subtest results suggest that digital dexterity was also not significantly perturbed in our sample of CTS patients when compared with controls. Despite the severe abnormalities of median nerve conduction, our results suggest that chronic median nerve compression occurring in CTS induces partial impairment of tactile sensibility with minor impact on grasp force regulation and digital dexterity. Received: 25 September 1998 / Accepted: 10 December 1998     

Anomalous muscle adjacent to temporalis

Temporalis is an important muscle of mastication. In recent years, there has been controversy about its detailed anatomy, and claims have been made about the existence of a variant muscle, sphenomandibularis. The present case report describes an anomalous muscle within the infratemporal fossa distinct from both temporalis and sphenomandibularis. Functionally the muscle could pull the buccinator laterally as the jaw closes.     

Undescribed variant muscle – “Deep abductor-flexor” of the little finger, in relation to ulnar nerve compression at the wrist

During routine anatomical dissection in the hypothenar region of the left hand of a 64-year-old female cadaver, a number of variant structures were observed. The most prominent finding in our case was a supernumerary muscle hitherto unknown in the anatomical literature. This variant muscle had a muscular body formed by the connection of two deeply situated muscular bellies--medial and lateral. The lateral belly originated from the flexor retinaculum, the medial one--from the hamate bone. The common muscular body inserted to the antero-lateral surface of the base of the fifth proximal phalanx. Due to its location and possible function, we named the variant muscle "deep abductor-flexor" of the little finger. The flexor digiti minimi brevis muscle showed two proximal tendons--the medial tendon was attached to the hamulus of the hamate bone while the aberrant lateral tendon originated from the lateral part of the flexor retinaculum. Both, the aberrant lateral tendon of the flexor digiti minimi brevis and the lateral belly of the "deep abductor-flexor", passed over the palmar branch of the ulnar nerve, which define their possible clinical significance in ulnar nerve compression. Therefore, the variations of the hypothenar muscles are reviewed and their relation to the compression of the ulnar nerve is discussed.     

带血供正中神经腕部感觉束转位桥接尺神经的解剖学基础

目的：探讨带血供正中神经腕部感觉束转位桥接尺神经缺损的解剖学基础。方法：14例成人上肢标本，观测腕部正中神经和尺神经的长度、神经束、血供等。摹拟带血供腕部正中神经感觉束转位桥接尺神经缺损术。结果：①正中神经腕部长度为7．8cm(7．5～8．1cm)。神经束数为19～27束，以感觉束为主，感觉束位于尺侧，运动束和混合束位于桡侧。感觉束无损伤分离长度为10．0～14．0cm。正中神经营养动脉距桡骨茎突上方6.2cm(6．1～6．6cm)处发自桡动脉，长度为5．7cm(5．1～6．1cm)，起始外径为1．2mm(1．1～1．4mm)。②尺神经腕部长度为9．4cm(8．9—9．7cm)，神经束数为14～19束，感觉束和运动束大致相等。感觉束位于掌挠侧，运动束位于背尺侧。结论：带血供正中神经腕部感觉束转位桥接尺神经缺损具有可行性。     

Congenital generalized fibromatosis causing spinal cord compression

An unusual case of congenital generalized fibromatosis in which involvement of the spinal dura mater was accompanied by flaccid paralysis in the lower limbs is presented.     

Pathology of experimental nerve compression

Acute, graded, nerve compression was applied to the sciatic nerves of 91 rats in whom an inflatable miniature Plexiglass compression device had been implanted in the thigh. The experiment was designed to study the pathogenesis of lesions in the nerve entrapment syndrome. Under general anesthesia, external pressures of 80 mm of Hg, 30 mm of Hg and 10 mm of Hg were used to compress nerves for 2 hours. Identical compression devices were placed around the contralateral sciatic nerves but remained uninflated so that these nerves could be used as controls. Nerves were excised at intervals of 4 and 24 hours, and at 1, 2, 5, 6, 7, 10, 14, and 28 days, and full thickness transverse sections were made from Araldite blocks. The first pathologic change was nerve edema which was observed at all time points and correlated with the severity of axonal injury. Axonal lesions were predominant in nerves exposed to 80 mm of Hg (7.5 +/- 1.9 nerve fibers per high power microscopic field (HPF)) while nerves compressed at 30 mm of Hg showed fewer damaged axons (2.6 +/- 1.4 per HPF). Demyelination was the predominant lesion in nerves subjected to 30 mm of Hg and was commonly present in nerves around which the compression chamber remained uninflated. Electron microscopy revealed demyelination to be associated with Schwann cell necrosis. The topography of nerve fiber injury was remarkable; subperineurial fibers were often damaged after compression of nerves in which nerve fibers at the core of the fascicle remained unaffected. The findings suggest that local external compression causes ischemia in nerve fibers served by transperineurial vessels, with severe compression causing axonal damage, while lesser degrees of compressive injury are associated with demyelination.     

拇收肌腱弓处尺神经卡压征的应用解剖

目的 :为拇收肌腱弓处的尺神经卡压征机理和治疗提供解剖学基础。方法 :解剖 2 0个 ( 4 0侧 )成人尸体标本手的拇收肌腱弓 ,对拇收肌起始部的纤维弓状结构进行观察、测量 ,对观测结果进行统计学处理。结果 :40侧中 3 7.5 % ( 15侧 )存在纤维弓状结构 ;其中呈膜性的 (A型 )占 73 .3 % ( 11侧 ) ;呈索带状(B型 )占 2 6.6% ( 4侧 )。肌纤维弓状结构长平均 3 .7± 0 .6mm。结论 :部分人手存在拇收肌起始部的纤维腱弓 ,形成神经血管腔隙 ,腔隙内压增高可导致尺神经终末运动支嵌压征。治疗是在第 3掌骨基底部切开腱弓减压。     

Anomalous head of the brachial muscle penetrates the deltoid muscle

We report here, for the first time a specimen in which the insertion of the deltoid muscle is divided into two parts, composing a canal. The brachial muscle was composed of medial, lateral, and anomalous heads. The anomalous head arose as a thin tendon from the surgical neck of humerus, passed through the canal, and then became confluent with the lateral head. The musculocutaneous nerve innervated the brachial muscle. The lateral head, but not the anomalous head, received a thin branch from the radial nerve.     

Anomalous muscle belly to the index finger.

An unusual variation of flexor digitorum superficialis was observed during the cadaver dissection. The flexor digitorum superficialis (FDS) had a normal origin and insertion, except to the index finger, where a muscle belly replaced the tendon of FDS. The unusual muscle belly originated as a continuation of FDS tendon in the carpal tunnel and inserted normally into the middle phalanx. A branch of the median nerve innervated the anomalous muscle belly. The anomalous muscle belly described here should be considered in the aetiology of carpal tunnel syndrome.     

A computational model of muscle recruitment for wrist movements

To execute a movement, the CNS must appropriately select and activate the set of muscles that will produce the desired movement. This problem is particularly difficult because a variety of muscle subsets can usually be used to produce the same joint motion. The motor system is therefore faced with a motor redundancy problem that must be resolved to produce the movement. In this paper, we present a model of muscle recruitment in the wrist step-tracking task. Muscle activation levels for five muscles are selected so as to satisfy task constraints (moving to the designated target) while also minimizing a measure of the total effort in producing the movement. Imposing these constraints yields muscle activation patterns qualitatively similar to those observed experimentally. In particular, the model reproduces the observed cosine-like recruitment of muscles as a function of movement direction and also appropriately predicts that certain muscles will be recruited most strongly in movement directions that differ significantly from their direction of action. These results suggest that the observed recruitment behavior may not be an explicit strategy employed by the nervous system, but instead may result from a process of movement optimization.     

Optic nerve compression analyzed by using plastination

Plastination is an excellent tool for studying different anatomical and clinical questions. The E12 technique provides transparent slices which show the anatomical structures in their initial position, especially those of the muscular, vascular and interstitial tissue. Here we demonstrate on a plastinated specimen optic nerve compression due to hypertrophy and degeneration of the extraocular muscles near the apex of the orbit. The paper aims to demonstrate the possibilities offered by the E12 plastination technique in analyzing anatomical structures. The plastinated slices obtained were scanned and then analyzed. In a further step the plastinated slices were cut into thin slices (150 microm), stained and finally examined histologically. We measured the intraorbital length (A-B), which had an average value of 25,93+/-0,03 mm. Dividing the optic nerve into uncompressed (UP) and compressed (CP) parts, we obtained the following values for optic nerve width: UP=4192+/-0,455 mm, CP=3215+/- 0,411 mm. Using the E12 plastination method we were able to take morphometric measurements on plastinated orbital slices with coincidentally detected optic nerve compression. This allowed the determination of different parameters of the optic nerve, as well as histological examination by hematoxylin and eosin staining up to a magnification of x40.