Hypothenar hammer syndrome.

Hypothenar hammer syndrome is a rare, but likely underdiagnosed occupational or recreational malady, resulting from repetitive microtrauma to the ulnar artery at the level of Guyon's canal. Significant diagnostic and treatment delays are associated with high morbidity, therefore early recognition is of the utmost importance. We discuss specific imaging features, emphasizing findings at ultrasound, computed tomography, and magnetic resonance imaging, that favor the diagnosis in the appropriate clinical context. Definitive evaluation is made with catheter directed angiography, which remains the gold standard for diagnosis. The range of management options, which depend on the degree of severity and the presence or absence of ulnar artery aneurysm, are also presented.