Role of sonography in the diagnosis of the most common peripheral neuropathies
Berta Kowalska1, Marta Walentowska-Janowicz2
In the practice of a general practitioner, the most common peripheral neuropathy reported by patients is carpal tunnel syndrome followed by cubital tunnel syndrome. Carpal tunnel syndrome results from entrapment of the median nerve at the level of the transverse carpal ligament, and cubital tunnel syndrome is a consequence of a compression on the ulnar nerve at the level of the groove of the humerus. The diagnosis of these syndromes is based on a specific interview, clinical examination and additional examinations. The aim of a clinical examination is to assess sensory disorders and muscle atrophy. Until today, standard additional examinations have been electrophysiological tests. At present, however, they are more and more frequently replaced by high-frequency sonography. As in other types of ultrasound examinations, the assessment of peripheral nerves, including the median and ulnar nerves, is non-invasive, well-tolerated by patients, relatively inexpensive and readily available. The examiner must possess knowledge on nerve topographic anatomy and criteria for ultrasound assessment of peripheral neuropathies. During an ultrasound examination, the following are assessed: shape, cross-sectional area of the nerve trunk, its echogenicity, vascularity and relation to adjacent tissues. Motor and sensorimotor nerves may also be assessed indirectly by analysing ultrasound images of the skeletal muscle innervated by these nerves. Furthermore, an important element of an ultrasound examination is dynamic assessment of the nerves. Carpal and cubital tunnel syndromes belong to so-called entrapment neuropathies whose common sonographic features are nerve oedema and hyperaemia proximally to the compression site.