Peripheral nerve entrapments.

Peripheral nerve entrapment is a rare, but important, cause of foot and ankle pain that often is underdiagnosed and mistreated. A peripheral nerve may become entrapped anywhere along its course, but certain anatomic locations are characteristic. Clinically,nerve entrapment is divided into three stages: in stage I patients feel rest pain and intermittent paresthesias which are worse at night; in stage II, continued nerve compression leads to paresthesias, numbness, and, occasionally, muscle weakness that does not disappear during the day, and in stage III, patients describe constant pain, muscle atrophy, and permanent sensory loss. Diagnostic confusion abounds because of the multiple etiologies of peripheral nerve entrapments and their complex physical and temporal relation. A thorough understanding of the causes of peripheral nerve entrapments, the anatomic course and variation of the peripheral nerves, the diagnostic modalities, and the treatment options can simplify this complex problem.