"New" Neck Discovery Hits Gray's, Offers Clue to Tension Headaches

After evoking much surprise and polite skepticism from anatomists worldwide, a 1995 discovery of a previously unknown connective neck tissue by researchers at the University of Maryland, Baltimore has made Gray¡¯s Anatomy, at last.

The latest Gray's Anatomy, its 150th anniversary edition, is known worldwide as an essential reference for medical students, and, health care professionals.

Delayed tribute for a new discovery is understandable in a field where anatomists have been rigorously studying the human body for more than 500 years, said co-discoverer Gary Hack, DDS, associate professor at the University of Maryland Dental School.

Hack and his colleagues found the ¡®new¡¯ muscle-dura connective tissue while using an unusual dissecting approach to examine head and neck muscles in cadavers. They supported their discovery through digital cadaver images from the National Institutes of Health¡¯s (NIH) Visible Human Project. The newly discovered tissue connects a deep neck muscle to a highly sensitive covering called the dura that covers the brain and spinal cord.

The researchers suggest that their finding may help explain the relationship between muscle tension and headaches. They speculate that the connection may transmit pressure from the neck muscles to the pain-sensitive dura and possibly lead to certain headaches. Gray¡¯s states, ¡°There is usually a soft-tissue attachment to the posterior atlanto-occipital membrane, which itself is firmly attached to the spinal dura in the same area.¡±

Shortly after their discovery¦¡as if surprising the world¡¯s anatomists once was not enough¦¡Hack and his colleagues, while studying muscles that affect chewing, also uncovered a jaw muscle that had never been described as separate and distinct from the many other jaw muscles. Hack thinks the ¡®new¡¯ muscle had been observed many times before, but was thought to be part of known chewing muscles. The new muscle, called sphenomandibularis, may be a fifth chewing muscle.

The muscle has not yet appeared in Gray¡¯s Anatomy. But after a similar chorus of skepticism in some medical journals, the 1 ¨ö inch long muscle has gotten its share of props. Sphenomandibularis is described in the Textbook of Head and Neck Anatomy, one of the leading medical textbooks. It has been recognized by the 1998 Medical and Health Annual of the Encyclopaedia Britannica, the book Staging Anatomies:Dissection and Spectacle in Early Stuart Tragedy by Hillary Nunn, in a poem called Claudia Gary Annis, and in articles in The New York Times and Discovery. The muscle was also a clue on the TV show, Jeopardy: ¡°In 1996 Gary Hack discovered the sphenomandibularis…which is one of these.¡± The correct answer: ¡°What is a muscle?¡±

Hack¡¯s team included Baltimore orthodontist Gwendolyn Dunn, DDS; Mi Young Toh, MS, MA, a biomedical imaging researcher at the national Library of Medicine; neurosurgeon Walker Robinson, MD; and Richard Koritzer, DDS, MLA, PhD, an adjunct research associate at the Dental School.