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Iatrogenic nerve injuries can result from direct surgical trauma, mechanical stress on a nerve due to faulty positioning during anesthesia, the injection of neurotoxic substances into a nerve, and other mechanisms. Treating physicians should know the risk factors and the procedure to be followed when an iatrogenic nerve injury arises.This review is based on pertinent articles retrieved by a selective search in PubMed and on the authors' own data from the years 1990-2012.In large-scale studies, 25% of sciatic nerve lesions that required treatment were iatrogenic, as were 60% of femoral nerve lesions and 94% of accessory nerve lesions. Osteosyntheses, osteotomies, arthrodeses, lymph node biopsies in the posterior triangle of the neck, carpal tunnel operations, and procedures on the wrist and knee were common settings for iatrogenic nerve injury. 340 patients underwent surgery for iatrogenic nerve injuries over a 23-year period in the District Hospital of Günzburg (Neurosurgical Department of the University of Ulm). In a study published by the authors in 2001, 17.4% of the traumatic nerve lesions treated were iatrogenic. 94% of iatrogenic nerve injuries occurred during surgical procedures.A thorough knowledge of the anatomy of the vulnerable nerves and of variants in their course can lessen the risk of iatrogenic nerve injury. When such injuries arise, early diagnosis and planning of further management are the main determinants of outcome. If adequate nerve regeneration does not occur, surgical revision should optimally be performed 3 to 4 months after the injury, and 6 months afterward at the latest. On the other hand, if postoperative high resolution ultrasound reveals either complete transection of the nerve or a neuroma in continuity, surgery should be performed without any further delay. If the surgeon becomes aware of a nerve transection during the initial procedure, then either immediate end-to-end suturing or early secondary management after three weeks is indicated.

Surgical treatment of nerve lesions in continuity remains difficult, even in the most experienced hands. The regenerative potential of those injuries can be evaluated by intraoperative electrophysiological studies and/or intraneural dissection. The present study examines the value of intraoperative high-frequency ultrasound as an imaging tool for decision making in the management of traumatic nerve lesions in continuity.Intraoperative high-frequency ultrasound was applied to 19 traumatic or iatrogenic nerve lesions of differing extents. The information obtained was correlated with intraoperative electrophysiological, microsurgical intraneural dissection, and histopathological findings in resected nerve segments.The intraoperative application of high-resolution, high-frequency ultrasound enabled morphological examination of nerve lesions in continuity, with good image quality. The assessment of the severity of the underlying nerve injury matched perfectly with the judgment obtained from intraoperative electrophysiological studies. Both intraneural nerve dissection and neuropathological examination of the resected nerve segments confirmed the sonographic findings. In addition, intraoperative ultrasound proved to be very time efficient.With intraoperative ultrasound, the extent of traumatic peripheral nerve lesions can be examined morphologically for the first time. It is a promising, noninvasive method that seems capable of assessing the type (intraneural/perineural) and grade of nerve fibrosis. Therefore, in combination with intraoperative neurophysiological studies, intraoperative high-resolution ultrasound may represent a major tool for noninvasive assessment of the regenerative potential of a nerve lesion.

High-resolution ultrasonography is a noninvasive, readily applicable imaging modality, capable of depicting real-time static and dynamic morphological information concerning the peripheral nerves and their surrounding tissues. Continuous progress in ultrasonographic technology results in highly improved spatial and contrast resolution. Therefore, nerve imaging is possible to a fascicular level, and most peripheral nerves can now be depicted along their entire anatomical course. An increasing number of publications have evaluated the role of high-resolution ultrasonography in peripheral nerve diseases, especially in peripheral nerve entrapment. Ultrasonography has been shown to be a precious complementary tool for assessing peripheral nerve lesions with respect to their exact location, course, continuity, and extent in traumatic nerve lesions, and for assessing nerve entrapment and tumors. In this article, the authors discuss the basic technical considerations for using ultrasoniography in peripheral nerve assessment, and some of the clinical applications are illustrated.