Communications of the median nerve in foetuses.

BACKGROUND: Communications between the median, ulnar and musculocutaneous nerves in the arm, forearm and hand were reported in adult cadaveric and electrophysiological studies. These communicant branches may lead conflicting clinical and electrodiagnostic outcomes. While there are many studies on adult patients or cadavers, there is poor regarding foetuses. The present study was conducted to examine the frequencies of these communications and their coexistences in human foetuses. MATERIALS AND METHODS: Anterior aspect of the forearms of 50 foetuses (29 females, 20 males, and 1 unknown) were dissected bilaterally (totally 100 sides) for this purpose. RESULTS: Communications between the median and the musculocutaneous nerves in the arm were found unilaterally in 4%. Communications from the median to the ulnar nerve in the forearm were encountered unilaterally in 22%, and bilaterally in 12%; from the ulnar to the median nerve in the hand unilaterally in 28%, and bilaterally in 12%. Coexistence of all these variations was not encountered in any foetus. But coexistence of two different types of communicant branch was encountered in 4%. CONCLUSIONS: Precise knowledge of nerve communications, variations and rate of coexistences in foetuses may have significance for clinicians and researchers dealing with subjects in foetal period.

Ulnar nerve innervation of the triceps muscle: real or apparent? An anatomic study.

BACKGROUND: Since the 18th century, the existence of ulnar nerve innervation of the medial head of the triceps brachii muscle has been controversial. The evidence for or against such innervation has been based on macroscopic dissection, an unsuitable method for studying intraneural topography or intramuscular branching. The study of smaller specimens (embryos or fetuses) by means of serial histologic sections may resolve the controversy. QUESTIONS/PURPOSES: Using fetal specimens and histology we determined the contributions of the ulnar and radial nerves to innervation of the triceps brachii muscle. METHODS: We histologically examined 15 embryonic and fetal arms. Radial nerve branches obtained from six adult arms were analyzed immunohistochemically to determine motor fiber content. RESULTS: The medial head of the triceps brachii muscle was always innervated by the radial nerve (ulnar collateral branch). The branches seeming to leave the ulnar nerve at elbow level were the continuation of the radial nerve that had joined the ulnar nerve sheath via a connection in the axillary region. Immunohistochemistry revealed motor and nonmotor fibers in this radial nerve branch. CONCLUSIONS: A connection between the radial and ulnar nerves sometimes may exist, resulting in an apparent ulnar nerve origin of muscular branches to the medial head of the triceps, even though in all our specimens the fibers could be traced back to the radial nerve. CLINICAL RELEVANCE: Before performing or suggesting new muscle and nerve transpositions using this apparent ulnar innervation, the real origin should be confirmed to avoid failure.

The digital venous drainage in the human embryonic hand.

The histogenesis and morphology of the digital venous drainage in human embryonic and fetal hands, aged from 6 to 12 weeks, were studied by light microscopy in 18 fingers. In the sixth week, capillaries could be identified around the cartilaginous models of the phalanges. By the ninth week, the neurovascular bundles were identifiable in the palmar part of the finger. In 12 week fetuses, all of the superficial and deep vascular venous system could be seen easily in the palmar aspect of the finger in positions similar to those in the adult hand. However, the arch systems, present on the dorsum of the finger in the adult hand, were not yet differentiated.

The motor branches of median and ulnar nerves that innervate superficial flexor muscles: a study in human fetuses.

PURPOSE: We aimed to describe the distribution of the motor branches of the median and ulnar nerves that innervate the superficial flexor muscles in detail, as well as to determine any communication between these two nerves in a series of 100 human fetuses. METHODS: This study was performed on 200 upper limbs from 100 fetuses. However, the motor branches of the median nerve were determined on 50 upper limbs because of the developmental properties of medial epicondylar muscles. RESULTS: The motor branch, which innervates the pronator teres, is classified into two types and four subtypes. The flexor carpi radialis branch arose as a single branch in 30% of the cases. The innervation of the flexor digitorum superficialis was also performed by a single muscular branch in 88% of the cases and by two branches in 12% of the cases. The ulnar nerve was classified into two types according to the number of muscular branches in the forearm. Martin-Gruber anastomosis was observed in 7.5% of the cases. CONCLUSIONS: These results show differences from classical definitions regarding the muscular branching patterns of the median and ulnar nerves. We suggest revisiting the classical descriptions of innervation patterns of pronator teres, palmaris longus and flexor carpi radialis muscles, since the variations observed in their innervation patterns are more diverse than has been described.

Motor nerve conduction velocity in very preterm infants.

Sufficient reference values for motor nerve conduction velocity (MNCV) in very preterm infants are not yet available. In the placebo infants within an L-thyroxine supplementation trial, born at less than 30 weeks' gestation, ulnar and posterior tibial MNCV measurements were performed shortly after birth. Repeated measurements were done at 2 weeks, at term, and at 6 months corrected age. Cross-sectional MNCV values obtained in 50 infants and longitudinal MNCV values obtained in 15 infants were analyzed in relation to postmenstrual age (PMA). Mean ulnar MNCV increased from 13 to 44 m/s and mean tibial MNCV from 11 to 37 m/s. Motor nerve conduction velocity was clearly related to PMA. Longitudinal MNCV values were consistent with cross-sectional MNCV values. Possible confounding factors did not have any significant effect on MNCV. In the ulnar nerve, extrauterine maturation during the first 2 weeks of life was delayed compared with intrauterine maturation.

Abnormal cutaneous nerve outgrowth: a secondary effect of methyl triazene teratology in developing mouse limb buds.

The cutaneous branches originating from the superficial distal division of the ulnar nerve exhibit abnormal developmental features in 70.2% of the forelimb buds from embryos submitted 2 or 3 days earlier to methyl triazene administered to their pregnant mother. Similar abnormalities characterize the preaxial ventral cutaneous nerve of the thumb in 17.8% of forelimb primordia. The affected nerves undergo anticipated growth with respect to the normal schedule, follow abnormal pathways through areas of extensive cell death, and finally reach the apical ectoderm where they run in close contact with the basement membrane without forming a plexus. Histological observations gathered in pyronin-methyl green stained serial sections as well as in whole limb buds after cholinesterase method suggest that three factors probably contribute to modify nerve outgrowth: (1) a discrepancy between the rate of nerve progression and that of mesodermal growth in the prospective zeugopod territory which is preferentially affected by the teratogen; (2) facilitated nerve pathfinding into areas strongly hit by triazene-induced mesodermal cell death; and (3) alteration or abolition of some unknown ectodermal influence necessary to stimulate selective guidance of terminal sensory afferents and to maintain them transiently at some distance from the epidermis.

Topographical anatomy of the posterior elbow region during fetal development.

We studied the topography of the elbow region with special regard to the ulnar nerve during fetal life. Plastinated 600 microns thick sections through the right and left arms of ten fetuses with a crown-rump length (CRL) of 105 to 360 mm and of a newborn infant were investigated. The ulnar groove does not appear on the dorsal side of the medial humeral epicondyle earlier than at a crown-rump length of 130 mm. It provides the entrance into a formerly described fibro-osseous tunnel called the cubital tunnel. Its floor is formed by the posterior bundle of the ulnar collateral ligament, which bulges medially on flexion of the elbow joint. Up to 270 mm CRL it is composed of rather loosely arranged connective tissue fibres. Later on, its fibres are densely packed and show a parallel orientation. The ulnar nerve is pushed medially but remains behind the medial epicondyle. None of the specimens showed displacement to the anterior site of the elbow joint. An aponeurotic arch bridging the humerus and ulna and covering the ulnar nerve medially could not be identified. The findings in the newborn infant did not reveal any significant differences compared to the fetal specimens.