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Peripheral Nerve Examination
Published in J. Terrence Jose Jerome, Clinical Examination of the Hand, 2022
J Terrence Jose Jerome, Dafang Zhang
The most common median nerve communication at the level of the forearm is the Martin–Gruber anastomosis. The Martin–Gruber anastomosis is a communication between the median nerve and ulnar nerve, in which axons from the median nerve cross to join the ulnar nerve at the forearm level. This communication is estimated to be present in as high as 30 to 40% of the population [2]. Clinically, a median nerve lesion proximal to a Martin–Gruber anastomosis may affect the thenar muscles, whereas a median nerve lesion distal to the communication may not. A less common communication is the Marinacci communication, in which axons from the ulnar nerve cross to join the median nerve at the forearm level.
Hands
Published in Tor Wo Chiu, Stone’s Plastic Surgery Facts, 2018
AION syndrome is relatively rare, making up less than 1% of all nerve compression syndromes. Patients tend to present with pain in the forearm and weakness of pinch grip – when asked to make an ‘O’ or ‘OK’ sign between the index finger and the thumb to test for the FPL and the index FDP, those with the syndrome tend to make a triangle. There is no sensory deficit, and the presence of a Martin–Gruber anastomosis (see above) may complicate interpretation.
Neuroanatomy overview
Published in Michael Y. Wang, Andrea L. Strayer, Odette A. Harris, Cathy M. Rosenberg, Praveen V. Mummaneni, Handbook of Neurosurgery, Neurology, and Spinal Medicine for Nurses and Advanced Practice Health Professionals, 2017
In the forearm, the nerve passes beneath the flexor carpi ulnaris but superficial to the flexor digitorum profundus. A branch is given off to flexor digitorum profundus (IV and V), and to the flexor carpi ulnaris. A Martin-Gruber anastomosis may exist from the anterior interosseous branch of the median to the ulnar nerve in the proximal forearm.
Bilateral Martin-Gruber and Marinacci Anastomoses in the Same Patient: A Case Report
Published in The Neurodiagnostic Journal, 2020
Estimates of the prevalence of crossovers of median and ulnar nerves in the forearm vary greatly in the literature (Smith et al. 2019; Unver et al. 2009). Martin-Gruber anastomosis is the most common, with a reported incidence between 10% (Felippe et al. 2012; Kazakos et al. 2005) to 27% in cadaveric dissections Caetano et al. 2016), and as high as 54% based on some electrodiagnostic studies (Amoiridis and Vlachonikolis 2003). It is unilateral in almost two-thirds of cases with a right-sided predominance (Kazakos et al. 2005), and the connecting branch is usually between the anterior interosseous nerve and the ulnar nerve, supplying the FDI muscle (Roy et al. 2016); the thenar and hypothenar muscles are supplied less commonly (Saba 2017). Marinacci anastomosis (Marinacci 1964; Resende et al. 2000) is much rarer, and most dissection studies either fail to find the anomaly (Duran and Ferreira Arquez 2016; Kazakos et al. 2005; Sarikcioglu et al. 2003) or do so only rarely (only one out of 30 forearms dissections in the study by Felippe et al. 2012). The prevalence in electrodiagnostic studies ranges from 0.7% (Saba 2017) to 4% (Meenakshi-Sundaram et al. 2003). A case of purely sensory ulnar-to-median anastomosis in the forearm has been reported (Hopf 1990). Bilateral Marinacci anastomosis has not been previously described, and we are unaware of any reports of Martin-Gruber and Marinacci anastomoses occurring together, as was the case in our patient.