Miroslaw F. Stranc

The anatomy of the accessory nerve and cervical lymph node biopsy

Injury to the accessory nerve is the most frequent complication of surgical procedures in the posterior triangle of the neck. The symptoms produced by paralysis of the trapezius are disabling. The components of this disability are pain, limitation of abduction, and drooping of the affected shoulder. A detailed knowledge of the course of the nerve and its anatomic relations are essential in avoiding injury. Useful anatomic landmarks are the proximal internal jugular vein in the anterior triangle and Erbs point in the posterior triangle. Prevention of accessory nerve injury is the best management. The indications for lymph node biopsies in the neck should be sound. The use of a general anesthetic without paralysis is recommended if an excisional biopsy is necessary. Adequate exposure is essential. Whether the nerve needs to be identified in all cases has to be individualized and requires careful judgment. A divided or injured nerve is best managed with primary repair within 3 months of injury.

Tissue viability by multispectral near infrared imaging: a fuzzy C-means clustering analysis

Clinically, skin color, temperature, and capillary perfusion are used to assess tissue viability following microvascular tissue transfer. However, clinical signs that arise as a consequence of poor perfusion become evident only after several hours of compromised perfusion. This study demonstrates the potential usefulness of optical/infrared multispectral imaging in the prognosis of tissue viability immediately post-surgery. Multispectral images of a skin flap model acquired within 1 h of surgical elevation are analyzed in comparison to the final 72 h clinical outcome with a high degree of correlation. Regional changes in tissue perfusion and oxygenation present immediately following surgery are differentiated using fuzzy clustering and image processing algorithms. These methodologies reduce the intersubject variability inherent in infrared imaging methods such that the changes in perfusion are reproducible and clearly distinguishable across all subjects. Clinically, an early prognostic indicator of viability such as this would allow for a more timely intervention following surgery in the event of compromised microvasculature.

Novel Approach in the Evaluation of Flap Failure Using near Infrared Spectroscopy and Imaging

Methods of tissue viability assessment should be classified into those that measure blood flow and those that monitor tissue metabolism. The problem with measuring blood flow is that it can be misleading due to the phenomenon of arteriovenous shunting. Near infrared (NIR) spectroscopy is capable of identifying certain molecules in the tissues. In this study, using the reverse McFarlane rat skin flap as a model, oxygen delivery to the tissue along the flap was demonstrated in the form of a spectrum. This was achieved by using the differential absorption of oxy- and deoxyhemoglobin between wavelengths of 650 nm and 900 nm. NIR imaging works on a similar principle, but an oxygen saturation image is obtained, with the darkest area indicating the most deoxygenated area of the flap and vice versa. There were two types of studies done. In the chronic study (n=10), NIR spectroscopy was done on the intact skin preoperatively for three days and then after elevation of the flap at various sites for three days. Preoperative measurements showed excellent reproducibility, and postoperative measurements showed progressive deoxygenation toward the distal aspect of the flap. NIR imaging at 1 h after flap elevation showed a zone of demarcation that corresponded with that noted clinically at 72 h. In the acute study (n=3), NIR spectroscopy, imaging and laser Doppler flowmetry were acquired before, immediately following and 1 h after raising the flap, and then measurements were taken after applying a vascular clamp across the base of the flap; reperfusion was evaluated after clamp release. Spectroscopy immediately following flap elevation indicated deoxygenation of the most distant part of the flap. Clamping the base of the flap caused deoxygenation of the whole flap; this was immediately evident on both spectroscopy and imaging. These changes recovered after releasing the clamp in the areas that were expected to survive. Laser Doppler flowmetry results generally correlated well with the NIR spectroscopy and imaging results. However, the method was very sensitive to fine movements during monitoring. The main advantage of NIR monitoring is that it looks directly at oxygen consumption rather than measuring blood flow. In addition, the NIR imaging gives a global picture of the eventual fate of the flap. These properties make these devices much more practical when the flaps well-being is concerned.