US of Nerve Entrapments in Osteofibrous Tunnels of the Upper and Lower Limbs

Abstract

The diagnosis of nerve entrapment at osteofibrous tunnels relies primarily on clinical and electrodiagnostic findings. Recently, the refinement of high-frequency broadband transducers with a range of 5-15 MHz, sophisticated focusing in the near field, and sensitive color and power Doppler technology have improved the ability to evaluate peripheral nerve entrapment in osteofibrous tunnels with ultrasonography (US). In the upper limb, osteofibrous tunnels amenable to US examination include the carpal tunnel for the median nerve and the cubital and Guyon tunnels for the ulnar nerve. In the lower limb, these tunnels include the fibular neck for the common peroneal nerve, the tarsal tunnel for the posterior tibial nerve, and the intermetatarsal spaces for the interdigital nerves. High-resolution US allows direct imaging of the involved nerves, as well as documentation of changes in nerve shape and echotexture that occur in compressive syndromes. A spectrum of extrinsic causes of entrapment, such as tenosynovitis, ganglia, soft-tissue tumors, bone and joint abnormalities, and anomalous muscles, can also be diagnosed with US. With continued experience, it is likely that this technique will be increasingly used to evaluate nerve entrapment syndromes.

Carpal tunnel: Normal anatomy, anatomical variants and ultrasound technique

“…2). On the radial side it divides into two layers, a superficial layer and a deep layer to accommodate the tendon of the flexor carpi radialis [1].…”

Dorsal forearm muscles: US anatomy Pictorial Essay

“…In the various pathologies that can affect the dorsal compartment of the forearm, whether muscles, tendons or nerves, the role of diagnostic imaging and particularly US and MRI is increasingly essential for a correct diagnosis and therapy [8]. For this reason, a thorough knowledge of the compartmental anatomy of the forearm and any possible anatomical variants such as the presence of accessory muscles, is essential to perform US examination satisfactorily, make a correct diagnosis and be able to answer the still more detailed questions posed by the clinician.…”

Ultrasound of the nerves of the knee region: Technique of examination and normal US appearance

“…When examined with high-resolution transducers, the PN can be easily distinguished from tendons and other adjacent anatomic structures by their peculiar echostructure [11] (Fig. 1).…”

“…different nerves and their relations with adjacent anatomic structures obviously facilitates their detection. As with all districts of the musculoskeletal system, US examination of the knee is preceded by collection of the patient history and clinical evaluation of the region [6,7,11,13]. The knee is palpated, starting from the anterior aspect and moving systematically to the medial, lateral, and finally posterior aspect.…”

“…The nerves of the knee region can be visualized clearly with US because of their relatively superficial location. In experienced hands, US can be a reliable, noninvasive tool for PN imaging that is also highly cost-efficient [2,6,10,11].…”