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- Anatomy of the Spinal Accessory Nerve Plexus: Relevance to Head and Neck Cancer and Atherosclerosis


  1. The foregoing review leads to the conclusion that in doing surgical neck dissection, one should avoid removing any nerve, including cervical plexus nerves, each of which may have important sensory as well as motor functions. Especially, the spinal accessory nerve and the mandibular branch of the facial nerve should not be cut because their loss almost always increases morbidity such as functional loss and pain; and, in the case of the facial nerve, unacceptable disfigurement and drooling as well. Furthermore, removal of those two nerves is nearly always unnecessary since, as a rule, their loss does not influence outcome.
  2. The same may be said for leaving structures which had been commonly removed in radical neck dissections in the past, since their removal, too, rarely affects outcome. Those structures no longer commonly removed include the sternocleidomastoid muscle, the internal jugular vein, and even some lymph nodes. Another compelling reason for leaving these structures is that their dissection and removal also increases the risk of iatrogenic injury to the spinal accessory nerve plexus.
  3. Great variability of interconnections within the spinal accessory nerve plexus occurs both intracranially and extracranially. These anatomic findings probably explain at least in part why in different patients functional loss also may be very different when the same parts of the plexus have been removed. Hence, cutting those parts of the plexus in the same location in different patients may give a whole spectrum of impairments from almost none to very severe.
  4. It follows then that the spinal accessory nerve itself need not be cut in some patients for severe impairment to follow. This impairment may occur in the head, neck, shoulder and upper extremity.
  5. Laboratory dissections also strongly suggest that loss of blood vessels to any of the plexus could lead to both sensory and motor impairment such as pain or swallowing dysfunction. Laboratory dissections also suggest that ischemia of the brachial plexus may be one reason for otherwise unexplained shoulder pain in elderly patients which has been commonly observed in the author’s personal clinical experience. Even though some clinical evidence would corroborate these theories, more clinical evidence is required for a clinical correlation to be firmly established.
  6. From all of the above, the trend toward more and more conservative surgical neck dissection is indicated in head and neck cancer. Historically, this viewpoint has been confirmed. Over the past century, the more radical dissections not only have made little difference in outcome, but have been shown to increase morbidity greatly.

It is evident that gross and microscopic study continues to be needed to know the anatomy and blood supply of the spinal accessory nerve plexus. Despite centuries of intensive study by learned and capable scholars, many aspects of the anatomy of this structure still remain unknown. More knowledge in this area will assist us in better planning surgical head and neck dissections to improve outcomes; and, even more importantly, to improve our patients’ well being and quality of life.

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