Anastomosis Patterns between the Median and Ulnar Nerves in the Upper Limbs

There are four types of anastomoses between themedian and ulnar nerves in the upper limbs. It consists of crossings of axons that produce changes in the innervation of the upper limbs, mainly in the intrinsic muscles of the hand. The forearm has two anatomical changes ­ Martin-Gruber: branch originating close to the median nerve joining distally to the ulnar nerve; and Marinacci: branch originating close to the ulnar nerve and distally joining the median nerve. The hand also has two types of anastomoses, which are more common, and sometimes considered a normal anatomical pattern ­ Berrettini: Connection between the common digital nerves of the ulnar and median nerves; and Riche-Cannieu: anastomosis between the recurrent branch of the median nerve and the deep branch of the ulnar nerve. Due to these connection patterns, musculoskeletal disorders and neuropathies can be misinterpreted, and nerve injuries during surgery may occur, without the knowledge of these anastomoses. Therefore, knowledge of them is essential for the clinical practice. The purpose of the present review is to provide important information about each type of anastomosis of the median and ulnar nerves in the forearm and hand.

Nerve Conduction Study Findings in Ulnar-Median Nerve Intercommunications in the Upper Limb: A Short Review

Intercommunications between ulnar and median nerves in the forearm and hand are a commonly encountered phenomenon. Clinicians should be aware of these communications for better diagnosis and management of the patient, as the clinical presentation can often be misleading. Surgeons should be aware of these anastomoses so as to prevent any iatrogenic injury during the course of treatment. Furthermore, these intercommunications can distort the findings on nerve conduction studies, leading to misinterpretation and misdiagnosis. In the forearm region, there are two prominent median-ulnar anastomoses, namely, Martin–Gruber anastomosis (MGA) and reverse MGA (Marinacci anastomosis). Similarly, in the palm too, there are two major anastomoses, namely, Riche–Cannieu anastomosis and Berrittini anastomosis. Here, in this review, we would like to emphasize on electrophysiological findings that can be observed in the presence of such anastomoses.

Communicating branches between the median and ulnar nerves: proposal for inclusion in terminologia anatomica / Ramos comunicantes entre los nervios mediano y ulnar: propuesta de inclusión en terminologia anatomica

The ulnar and median nerves are widely distributed, innervating the muscles of the forearm and hand. In the latter, it also registers the sensitivity of a significant part of the skin. A series of communicating branches (CB) is described on the path of these nerves, including: 1) the Martin-Gruber communicating branch, 2) the Marinacci communicating branch, 3) the Riché-Cannieu communicating branch and 4) the Berrettini communicating branch. The aim of this study was to establish a correct denomination of these CB, using Latin and eliminating the use of eponyms. The exploratory study included books on anatomy and scientific articles that detailed the anatomical aspects of these CB. To these were added the terms that these branches presented in the various anatomical lists and terminologies. Each term proposal was done in Latin, using the corresponding gender, number and case. The CB between the median and ulnar nerves are described in anatomy texts as well as a plethora of publications. The prevalence rates of the CB range between 1.7 and 94 %; however, their inclusion in the anatomical terminologies has been limited. Based on the description of these branches and the presence of some of them in the existing terminologies, a proposal was prepared in line with the indications of the Federative International Programme on Anatomical Terminologies (FIPAT): 1) Ramus comunicans cum nervo ulnari, 2) Ramus comunicans cum nervo mediano, 3) Ramus communicans cum ramo profundo nervi ulnaris y 4) Ramus communicans cum nervo digitali palmari communi. Considering that terminologies are dynamic linguistic corpora, it is important to analyze constantly the incorporation of new terms that are in harmony with the scientific findings. The incorporation of new structures must follow FIPAT guidelines and include the grammatical aspects of Latin.

Los nervios ulnar y mediano presentan una amplia distribución que permite inervar músculos del antebrazo y mano, en esta última, también registran la sensibilidad de un importante territorio cutáneo. En el recorrido de estos nervios se describen una serie de ramos comunicantes (RC), entre los cuales destacan: 1) Ramo comunicante de Martin-Gruber 2) Ramo comunicante de Marinacci 3) Ramo comunicante de Riché-Cannieu y 4) Ramo comunicante de Berretini. El propósito de este trabajo fue establecer una correcta denominación de estos RC, usando para ello el latín y eliminando el uso de epónimos. El estudio exploratorio incluyó libros de anatomía y artículos científicos que detallaran los aspectos anatómicos de estos RC. A lo anterior se sumaron los términos que estos ramos presentaron en las diversas nóminas y terminologías anatómicas. Cada propuesta de denominación se realizó en latín, utilizando el género, número y caso correspondiente. Los RC entre los nervios mediano y ulnar se encuentran descritos tanto en textos de anatomía como en un sinnúmero de publicaciones. Las tasas de prevalencia de los RC fluctúan entre 1,7 y 94 %; a pesar de ello; su inclusión en las terminologías anatómicas ha sido limitado. En base a la descripción de éstos ramos y la presencia de algunos de ellos en las terminologías existentes, se elaboró una propuesta alineada con las indicaciones del Programa Federativo Internacional de Terminología Anatómica (FIPAT): 1) Ramus comunicans cum nervo ulnari, 2) Ramus comunicans cum nervo mediano, 3) Ramus communicans cum ramo profundo nervi ulnaris y 4) Ramus communicans cum nervo digitali palmari communi. Considerando que las terminologías son cuerpos lingüísticos dinámicos, resulta importante analizar constantemente la incorporación de nuevos términos que se encuentren en sintonía con los hallazgos científicos. La incorporación de nuevas estructuras debe seguir los lineamientos de FIPAT y considerar los aspectos gramaticales del latín.

Anastomosis between median nerve and ulnar nerve in the forearm

Anastomosis between the median nerve and ulnar nerve can occur in the forearm region. It consists in crosses of axons which may produce changes in innervation of the upper limb muscles, mainly motor part of intrinsic muscles in the hand. Anastomosis in the forearm can be classified in two types: Martin Gruber anastomosis and Marinacci anastomosis. This study has as purpose to report the incidence, type, topography of anastomosis found and assess the length of this anastomosis. Material and Methods: For this study, 30 forearms were dissected in the Anatomy Institute of Severino Sombra University. In order to check the incidence of anastomosis and its topography, the length of the anastomotic branch was measured with a measuring tape (3M). In addition schematic drawings were executed. Results: Three (3) anatomical pieces that contained the Martin-Gruber anastomosis with an average length of 6.6 cm were found. One (1) anatomical piece with a 7.4 cm long Marinacci anastomosis was found, even though such type of anastomosis shows low incidence, and was found only in electroneuromyography studies. Conclusion: The study of anomalous communications between median and ulnar nerves in the forearm deserves great attention for its incidence and its clinical importance, mainly in the correct diagnosis of peripheral neuropathies, for example in the Carpal Tunnel Syndrome, which produces changes in the upper limb innervation. The importance of its verification and delimitation is also crucial to avoid lesions in surgical procedures.

Anastomosis of Motor Fibers between Median and Ulnar Nerve in the Forearm: an Electrophysiological Study

OBJECTIVE: To evaluate the frequency of forearm anastomosis in healthy Korean subjects. METHOD: Healthy Korean adult subjects (70 males, 30 females) were included. Median and ulnar nerves were stimulated at wrist and elbow and recorded with the surface electrodes over abductor pollicis brevis (APB), first dorsal interossei (FDI) and abductor digiti quinti (ADQ). RESULTS: Martin-Gruber anastomosis (MGA) was found in 18 males and 8 females (26/100, 26%). MGA was found in 37 arms (18.5%). But, Marinacci anastomosis was not observed. For each type of MGA, type II was found in 36 arms (97.3%) whereas type I was found in 11 arms (29.7%), and type III was found in 1 arm (2.7%). Anastomosis was comprised 67.6% of type II, 2.7% of type III, and 29.7% of coexistence of type II and type I. Average innervation ratio of crossing fibers was the highest in FDI (16.2%). CONCLUSION: Compound muscle action potential (CMAP) comparison method using modified incremental technique is a simple and sufficient method for evaluating forearm anastomosis without stimulus spread to adjacent nerve. In evaluating MGA, the FDI is a very important muscle because of high frequency and innervation ratio.