Neuralgia-inducing Cavitational Osteonecrosis (NICO) has been described in medical literature since 1976, is known under a number of names including, Ratner bone cavities, alveolar cavitational osteopathosis, Robert's bone cavity, trigger point bone cavity, interference field, and most commonly, NICO. In NICO, it is claimed that small areas of bone in the upper or lower jaw become infected or inflamed and die, producing neuralgia-like pain. Most often, no sign of inflammation appears on x-ray. NICO is said to appear after tooth extraction, jaw surgery, endodontic therapy or crown preparation and is speculated to be the result of a long-standing low-grade infection.
The pain felt is constant and is often burning and cramping, much like atypical facial pain symptoms. Usually there are trigger points immediately over the areas of infected jawbone that will produce pain when pressed. NICO can cause "referred pain" in that the neuralgia-like symptoms are "referred" to other parts of the face, intraoral cavity and head.
Some cases of NICO appear to be caused or aggravated by infection. Others speculate that minor trauma from extractions, root canal and other dental procedures are common initiators of NICO but believe this only happens in people already susceptible because of a pre-existing blood clotting disorder. Some believe that NICO can develop when blood vessels are injured in the area, resulting in poor circulation which in turn can lead to bone death.
It is difficult to diagnose this problem as the pain symptoms often are similar to other conditions such as Myofascial Pain Disorder (MPD), Temporal Mandibular Joint (TMJ) problems, atypical facial pain, trigeminal neuralgia, phantom toothache, or headache. X-rays of the jawbone most often appear normal. However, a bone biopsy of the affected area can show positive signs of jawbone inflammation.
The only treatment for NICO is jawbone curettage, in which the jawbone is opened, the infected area drilled out, and the bone biopsied to confirm the presence of inflammation or infection. Often the bone cavity is packed with antibiotics such as teramyacin. A course of antibiotic treatment may be prescribed. Jawbone curettage is not currently done routinely, and it is too early to say whether or not it will ever become generally accepted.
NICO is not generally accepted as a cause of Trigeminal Neuralgia by most medical and dental professionals. It is possible that NICO is involved in some cases of facial neuralgia, especially atypical facial pain. One long-term study has reported considerably or totally reduced pain in 74% of facial neuralgia patients who had jawbone curettage. However, the pain returned for about 30% of these patients of whom most had been diagnosed with either TN or atypical facial pain.
In dental circles, there appears to be two distinct "schools of thought" on NICO. Some medical and dental professionals consider NICO a controversial diagnosis. Not only do they not consider it a possible cause of trigeminal neuralgia or other facial neuralgias, they doubt the condition exists as a disorder. They point to data suggesting bone cavitations are found routinely in cadaver jawbones, casting doubt on the theory that bone cavities cause facial neuralgias.
Another group of dentists believe NICO is the culprit in many facial pain syndromes and that these painful conditions can be cured by jawbone curettage (scraping and removing infected tissue). They point to studies that show a high success rate for jawbone curettage. Some dentists in this group believe that root canals and mercury fillings are partly responsible for NICO.