Imaging of Neuropathies about the Ankle and Foot

Abstract

Neuropathies about the ankle and foot may be the cause of chronic pain and disability. In most cases, these conditions derive from mechanical or dynamic compression of a segment of a nerve within a narrow osteofibrous tunnel, an opening in a fibrous structure, or a passageway close to a ligament or a muscle. Although the evaluation of nerve disorders primarily relies on neurological examination and electrophysiology, diagnostic imaging is currently used as a complement to help define the site and etiology of nerve compression and exclude other disease possibly underlying the patient' symptoms. In this article, a review of the anatomical and pathological features of nerve entrapments in the distal lower extremity is presented on ultrasound and magnetic resonance imaging, according to the nerve involved.

Ultrasound assessment of the sural nerve in patients with neuropathic pain after ankle surgery

“…All sural nerves could be identified, but 4 of 42 nerves (both patients and controls) did not show a clear fascicular pattern on US, which made it difficult to discriminate hypoechoic areas from hyperechoic areas. This may have been due to edema, which is known to cause marked alteration of echogenicity, or by scar tissue or callus around the nerve . The nerve may also be difficult to visualize when it is surrounded by fat, which has similar echogenic properties to nerve tissue.…”

“…This may have been due to edema, which is known to cause marked alteration of echogenicity, or by scar tissue or callus around the nerve. 38 The nerve may also be difficult to visualize when it is surrounded by fat, which has similar echogenic properties to nerve tissue. US frequencies also play a role in the visibility of the nerve; in the current study, 18 MHZ was used, but higher frequencies are available, such as 22 MHZ, as utilized by Liu et al 39 Other complicating factors in routine imaging of the sural nerve can be its small size, large number of terminal branches, and anatomical differences between patients.…”

High‐Resolution ultrasound of the pudendal nerve: Normal anatomy

“…The first is that the radiologists involved in the study have extensive experience in peripheral nerve imaging, and therefore it is possible that less experienced sonographers will have a long learning curve to obtain good results. However, pathological conditions of peripheral nerves usually result in an increased cross‐sectional area . For this reason, identification of pathological conditions should be easier than visualization of normal nerves.…”

“…The pudendal nerve was considered to be identified when a fascicular structure at the ischial spine was visible. Identification of the fascicular echotexture is normally used to identify large‐ and medium‐sized nerves on US . At the level of the ischial spine, an artery accompanies the nerve: color Doppler was used when appropriate to differentiate nerve from small vessels.…”

“…Direct peripheral nerve visualization is now possible with high‐resolution ultrasound for large fascicular nerves and for small monofascicular nerves . Visualization of peripheral nerve allows diagnosis of different conditions that alter morphological features …”