Sonographic demonstration of carpal tunnel and thoracic outlet syndrome in the setting of axon loss due to hereditary polyneuropathy

Abstract

BackgroundA patient suffering from long-standing hereditary polyneuropathy of CMT Type 1A presented with clinical signs of relatively recent onset suggestive of the presence of additional entrapment neuropathies in the left arm. Methods and ResultsElectrophysiological conformation was not possible because of the severe distal secondary axon loss due to her congenital neuropathy. Sonography of the supraclavicular brachial plexus showed the “wedge-sickle sign” corresponding to the lateral compression of the lower part of the brachial plexus by the medial edge of the middle scalene muscle causing neurogenic thoracic outlet syndrome and additionally a compression of the median nerve in the carpal tunnel. ConclusionThe clinical and electrophysiological confirmation of entrapment neuropathies is generally hampered by the presence of severe axon loss. We highlight that sonography may be of great diagnostic help in the identification of the compression site in entrapment neuropathies when severe axon loss no longer allows electrophysiological localization. The axon loss may occur in the setting of an unrelated underlying neuropathic condition, such as in our patient, or may also be caused by the entrapment neuropathy itself.