gms | German Medical Science

Objective: The lumbar spine and cauda equina of the rat has become a widely used model for biodynamic, pharmaceutical and neurological experiments. Especially neurophysiological and anatomical studies need sufficient exposure of the dorsal and ventral nerve roots. However, no standard procedure to approach this region in rats has been published in detail. We present a description of a safe dorsal approach to the cauda equina of the rat. This method provides sufficient exposure of the neural structures to perform extended microsurgery, neuro-labeling and neurophysiological testing at the spinal nerve-roots under a surgical microscope. Perioperative management, anaesthesia and anatomical landmarks are discussed and common pitfalls are described.

Methods: The procedure is performed in female Wistar rats weighing between 250 and 300 g on a self-designed OR-table. Anaesthesia with Ketamine and Medetomidine provides a sufficient analgesia even for extended surgical procedures. Skin incision and preparation of the spinous processes is done without magnification, during a laminectomy a surgical microscope is used. The lumbar spinal canal is opened and the dural sac exposed. Careful lateral preparation opens the recesses with the emerging spinal nerves. After the dura is opened, ventral and dorsal roots can be identified anatomically or with neurophysiological methods. These nerves can be used to perform intradural anastomosis or anterograde/retrograde tracing studies.

Results: Certain pitfalls may complicate surgery or even be fatal. Landmarks are used for identification of the correct level, and certain regions near to and within the spine need to be avoided. It is essential to provide enough irrigation during laminectomy, and before the dura is opened, the rat needs to be repositioned for safer intraspinal manipulation. After intraspinal surgery, the surgical wound is closed and the rats recover.

Conclusions: If certain pitfalls are identified, the described procedure provides a fast and safe approach to the lumbar spinal canal. A skilled surgeon only needs a few operations to get used to these surgical steps, and with more experience, the whole procedure takes about 2 hours.