Science has been studying human anatomy for hundreds of years, but two Baltimore dentists say they have found a previously undescribed muscle that runs from behind the eye socket to the inside of the jawbone.
Drs. Gary Hack and Gwendolyn Dunn of the dental school at the University of Maryland say that they have found the 1 1/2-inch muscle in 25 cadavers and that a survey of anatomical literature suggests it has not been described before.
Hack says the muscle assists chewing and may be the source of some difficult-to-treat headaches.
The dentists presented their findings recently at the national meeting of the American Assn. for the Advancement of Science.
The human anatomy has been dissected, studied, sketched and analyzed by medical researchers, artists and students down through the ages, but the muscle Hack and Dunn call "sphenomandibularis" has not been described.
To anatomists, human tissue can be identified as a muscle if it meets five tests: origin and insertion, the two ends that attach to bone; innervation, the nerves that send signals to the muscle; blood supply, the veins and arteries that support it; and function.
These tests are met in their sphenomandibularis, Hack says.
Experts in the field are skeptical about the dentists' claim but say it is possible their discovery is real.
"Anatomical dissection has been done since Michelanglo, and it would be unusual that that muscle was missed," says Dr. Steven Ashman, a professor of oral and facial surgery at Johns Hopkins School of Medicine. "We'll need to have verification from other centers. If it is confirmed, then they have a discovery."
Hack says the muscle was identified because he and his team conducted a dissection of a head from an angle usually not used. They found the new muscle and a previously known muscle that is nearby were actually attached to different parts of the skull and had an independent blood supply.