Differential Diagnosis of Toothache Pain: Part 2, Nonodontogenic Etiologies

INTRODUCTION
I am sure we can all agree that Monday mornings in a dental office can seem like feeding time at the zoo. Your planned schedule goes to the dogs as it gets filled in with patients who badger you to see them because their temporaries fell off or fillings fell out, and patients who report that they have been in pain all weekend. You do the best you can to ferret out unnecessary interruptions and take the bull by the horns, but you know if one more patient is squeezed into your schedule, it will be the straw that breaks the camel’s back. Then, just when you think you have everything under control, in walks a zebra.

We are all familiar with the saying, “If you hear hoof beats, don’t think zebras; think horses.” In medicine, a “zebra” has become synonymous with a rare diagnosis. In part 1 of this article, the differential diagnosis of odontogenic toothache pain was discussed. As dentists, we are very comfortable inside that paradigm. But once we realize that there is no reproducible, corroborating evidence to make a dental diagnosis, we find ourselves out of our direct comfort zone, and everything starts to look like a zebra. Part 2 of this article will be devoted to nonodontogenic etiology of toothache pain. If the symptoms cannot be reproduced in the tooth, there is no dental treatment that will result in pain relief for the patient. There are many conditions of craniofacial origin that mimic toothache pain and should be considered in a differential diagnosis if dental etiology is eliminated. Only the most common syndromes that would be likely to present in the dental office will be discussed. As dentists, we should think of them not as zebras, but perhaps as a horse of a different color.

Pain that mimics toothache pain is referred from another area in the head and neck. While the patient perceives the pain as dental, there are no teeth that test abnormally. While it is not in our scope of practice to treat most of these disease entities, referral to the proper specialist will be received infinitely better than telling the patient you have no idea what is causing the pain.

MUSCULAR (WOLF IN SHEEP’S CLOTHING)
The “wolf in sheep’s clothing” is an analogy for something being different than what it seems to be. Simply put, it is a disguise. Pain of muscular origin is the most prevalent cause of nonodontogenic toothache. Since it frequently occurs concurrently with a true toothache, the symptoms are often disguised as odontogenic. Once the dental pain is treated, the mask comes off and the true nature of the muscular component is revealed. Muscular pain symptoms are characterized by a deep, dull ache sometimes with occasional sharp, lancinating pains in the ear, temple, or face. Included in this group are myospasm, myositis, local myalgia, fibromyalgia, and myofascial pain syndrome (MFPS).^1,2

MFPS is characterized by trigger points in muscles that, when stimulated, refer pain to other areas in the same region. Frequently felt and described as “knots,” these trigger points can actually weaken a muscle, limit range of motion, and cause stiffness and tenderness to palpation. It is common in all parts of the body, and the most prevalent cause of painful symptoms characteristic of temporomandibular joint disorders (TMD). The muscles of mastication are prime targets for MFPS, particularly in patients with parafunctional habits. When muscular trigger points are stimulated, pain can be referred to the teeth as depicted in the diagrams in Figures 1a and 1b.

The temporalis is the largest muscle of mastication. When pain is referred from the most anterior part of this muscle, it will cause deep, dull, aching pain in the maxillary anterior teeth, into the temple, temporomandibular joint (TMJ), ear, and over the brow. As the trigger points progress posterior-superior, the pain will refer back toward the maxillary premolar teeth and then to the maxillary molars. When trigger points are stimulated in the masseter muscle, pain can refer to the maxillary and the mandibular molars, the superficial and deep layers of the mandible, as well as the TMJ and ear. A trigger point in the digastric muscle will refer pain to the lower incisors. Another common head and neck referral pattern is from the sternocleidomastoid muscle to the periorbital area that may be felt in the ipsilateral canine.^1,2

I am particularly passionate about the diagnosis and treatment of myofascial pain because I am a blue ribbon bruxer. I can relate to patients on an academic level, but also having experienced TMD, I understand and can relate to them on a personal level. In part 1 of this article, the use of botulinim toxin A (Botox, Dysport, Xeomin) was discussed for use as a diagnostic tool to distinguish dental pain from muscular pain. And, while it is not a cure for TMD, botulinum toxin A can provide significant symptomatic relief for painful muscle spasms in the masseter and temporalis. Figure 2a shows a trigger point delineated with a red dot in a patient with significant hypertrophy of the masseter muscle. Figure 2b shows an injection of the neurotoxin into that trigger point. Figure 3 shows targets for injection in the temporalis muscle. Since the muscle is so large, the dose may be divided into multiple injection sites. Onset of action is 3 days to 2 weeks, and duration is 3 to 4 months. With consistent follow-up injections, the muscles tend to stay relaxed for longer durations as the therapy trains the muscles to relax.³ If the symptoms do not diminish, there is likely more than one etiology or it is not MFPS.

MFPS in the muscles of mastication is also a known cause of tension headaches. These headaches are characteristically bilateral. They frequently coexist with migraine headaches that have a vascular component and typically present with unilateral pain. In October of 2010, the US Food and Drug Administration approved the use of botulinum toxin A in the frontalis, procerus, and corrugator muscles as a primary treatment for migraine headaches. Because dentists are challenged with the differential diagnosis and treatment of head and neck pain, many practitioners are being trained to utilize this drug for diagnostic and therapeutic use.^3-5

TEMPOROMANDIBULAR JOINT: JOINT AND LIGAMENT (CHICKEN OR THE EGG)
“Which came first: the chicken or the egg?” is a phrase used to describe situations of circular cause and consequence. We could easily ask ourselves which came first: the MFPS or the TMD? The truth is that they are both subcategories of the same musculoskeletal disorder. Factors such as stress, trauma, hypermobility disorder, and developmental anomalies can induce TMJ dysfunction. Internal derangement of the joint, disc displacement, meniscus displacement, formation of intra-articular adhesions, and osteoarthritis are common conditions that can also cause pain in the TMJ. Characteristic findings include joint clicking, crepitus, deviation upon opening, limited range of motion, dislocation, and pain anterior to the tragus of the ear. The patient will complain of a dull, boring ache that worsens by chewing or opening wide. This pain is frequently exacerbated by parafunctional habits. Patients will commonly seek emergency dental treatment, believing the source of pain is in the maxillary posterior teeth. It can also be referred to the mandibular posterior teeth as well as the temple and cheek.^6,7

NEUROLOGIC (THE ALBATROSS)
“The Rime of the Ancient Mariner” is responsible for the albatross becoming synonymous with a burden, hindrance, or handicap that some unfortunate person has to carry. The metaphor is appropriate, as we know that neurological problems can be incapacitating. Neuropathic pains are caused by pathosis or a structural abnormality affecting the peripheral nerves.

Figure 5. Iatrogenic perforation of palatal plate and floor of nose.	Figure 6. Implant mishap.

Neuralgias, neuritis, neuromas, and neuropathies can all mimic odontogenic pain. While toothache pain is described as localized, intense, dull and throbbing, neuropathic pain presents as burning, tingling, stinging, electrical, piercing, cutting, or drilling. Once any form of neuropathology is diagnosed, referral to a neurologist is recommended for treatment and to rule out brain tumor as an etiology.

Trigeminal neuralgia, also called tic douloureux, presents with very specific clinical features. Patients report deep and lancinating pain. A trigger point, as small as 2 mm, is present in the facial skin, oral cavity, and, occasionally, in a specific tooth. The pain is of quick onset and short duration, but patients with this affliction will do anything to avoid stimulating this area. Because it radiates to the bone and teeth, it can be confused with pain of pulpal origin. The electrical nature of this pain and the distinct trigger point differentiates it from that of a dental infection.

Postherpetic neuralgia is a painful, adverse complication from shingles, a recurrent form of chicken pox. It is manifested in the head and neck area when the trigeminal ganglion harbors the latent varicella zoster virus. Characterized by a vesicular eruption of the entire sensory nerve pathway, the pain will continue for weeks to years once the vesicles have healed. As is common with other neuropathic disorders, the pain is described as burning, stabbing, and electrical. It can be confused with pain of pulpal origin because patients will describe sensitivity to touch and temperature changes, but this will not be dentally reproducible.

Glossopharyngeal neuralgia is characterized by repeated episodes of severe, jabbing pain in the tongue, throat, ear, and tonsils that can last from a few seconds to a few minutes. Caused by irritation to the glossopharyngeal (ninth cranial) nerve, it can be confused with dental pain because symptoms can be elicited during chewing, swallowing, coughing, laughing, and speaking.^2,8

NEUROVASCULAR AND VASCULAR (THE MONKEY)
Evan Esar wrote: “The quizzical expression of the monkey at the zoo comes from his wondering whether he is his brother’s keeper, or his keeper’s brother.” Of all the nonodontogenic sources of toothache pain, the neurovascular category is the most confusing. The patient history can be misleading because some treatments seem to randomly reduce the patient’s symptoms for a period of time. Or, the initiating factor took place many years prior to the first episode of pain. Sufferers of these elusive disorders seem to be on a constant crusade to try to get the monkey off their back.

Atypical odontalgia has symptoms similar to pulpitis, yet there is no reproducible evidence of pathology. Described as constant, throbbing pain in the teeth, bone, and gingiva, patients will generally point to a maxillary molar as the source. Invariably, if endodontic therapy is performed, the procedure does not relieve the patient’s pain. Many times patients will present with several endodontically treated teeth or edentulous spaces as a result of multiple dental procedures performed by clinicians unfamiliar with this conundrum. Often patients will report temporary relief from pain after these dental procedures with subsequent return of symptoms, which then complicates this diagnosis even further.

Neuralgia inducing cavitational necrosis, also called ischemic necrosis, is most often identified in areas of previous extraction sites, but also in areas of failed root canals and sinus infection perforation into the maxilla. Pain is described as throbbing or burning. While it is referred from the maxilla or mandible, symptoms occur in the face; behind the eye; and the back, top and sides of the head. Diagnosis is complicated when the pain occurs many years later after the initial trauma to the bone.

Patients with cluster headaches report excruciating, stabbing, eye pain, with a deep quick electric shocklike element lasting about 5 minutes that then dulls to an intense deep pain for up to an hour. Episodes occur in clusters for days to months, interspersed with pain-free periods. Usually limited to one side of the face, this syndrome can be mistaken for pain in the maxillary posterior teeth.

Temporal arteritis (also called giant cell arteritis) is quite rare; however, it is noteworthy because blindness is a serious, potential complication. Patients may seek dental consultation because the first, and sometimes the only, symptom is pain in the jaw or ear when chewing (“jaw claudication”). Hence, it can easily be mistaken for TMJ dysfunction, MFPS, acute alveolar abscess of the molar teeth, and sinusitis. The pain is localized to the anatomic area of the artery but may radiate down to the ear and teeth. It is usually unilateral and will frequently cause scalp tenderness in the ipsilateral occipital area. It can resemble a migraine, due to its persistent throbbing quality over the temple area. But unlike a migraine, it is characterized by burning pain as well. Other symptoms include fever, malaise, fatigue, and weight loss. If the patient reports transient vision loss immediate referral is vital. A case report by Guttenberg et al⁹ describes inappropriate, ineffective endodontic surgery where temporal arteritis mimicked dental pain.

SALIVARY GLAND (“PARROT”ITIS)
Sialolithiasis is caused by the accumulation of calcium phosphate salts that form a stone in a salivary gland duct. When it becomes large enough to occlude the duct, inflammation and pain are the result. This phenomenon is most common in the submandibular duct leading to swelling of the submandibular gland, hence mimicking infection of a posterior mandibular tooth. The nature of the pain is stringent and drawing. It can be reproduced when a patient sucks on a lemon drop to stimulate salivation. When the parotid gland is blocked by a stone, it is referred to as parotitis and can be confused with odontogenic pain, TMD, and MFPS.¹⁰

EAR AND NOSE (THE DUCKS)
“If it looks a duck, swims like a duck, and quacks like a duck, then it is probably a duck.” An expression for inductive reasoning, the implication is that an unknown subject can be identified by observing its habitual characteristics. Earaches and sinusitis are usually garden-variety diagnoses for family practitioners and otolaryngologists. Sufferers are so familiar with the symptoms for these diseases that they rarely seek medical care and tend to self medicate with over-the-counter decongestants and antihistamines as well as antibiotics “left over from last time.”

Otitis media (middle ear infection) is common, particularly in children, and caused by pyogenic bacteria. It may be confused with a dental infection because pain can be referred to the posterior teeth as well as to the posterior mandible and maxilla. Once dental infection and TMD are ruled out, referral to an otolaryngologist is advised.

Acute maxillary sinusitis and acute allergic sinusitis cause actual toothache pain in the maxillary teeth particularly when the roots of the teeth extend into or near the antrum. When fluid pressure caused by infection or inflammation builds up, the patient will experience bilateral tenderness in the cheekbone, facial swelling, throbbing headache, fatigue, runny nose and/or increased pain when the patient tilts his or her head in a downward position. It rarely involves just one tooth, and should be suspected when multiple teeth test positive to biting and percussion tests. In addition, about 2% of headaches are secondary to abnormalities or infections in the nasal or sinus passages, and they are commonly referred to as sinus headaches.2,10
It is possible that an acute alveolar infection can spread into the sinus, thereby creating an acute bacterial sinusitis. If the sinus is treated without elimination of the dental source, the sinus infection will reoccur. Figures 4a to 4c are radiographs of a patient with recurrent left side sinusitis that responded to antibiotic therapy for periods of time, but never completely resolved. The patient presented with both the symptoms of sinusitis and acute alveolar abscess localized in tooth No. 13 (Figure 4a). When the re-treatment was performed, the symptoms of the acute alveolar abscess were eliminated, but the sinus symptoms continued (Figure 4b). Surgical root canal confirmed the root apices had perforated the antrum (Figure 4c). Since the patient has not had recurrent sinusitis since the surgery, it can be deducted that the tooth was the source of the infection.

CARDIOGENIC (THE ELEPHANT)
“What did the zookeeper say when he saw 4 elephants walking toward him wearing sunglasses? Nothing; he didn’t recognize them.” Many heart attack symptoms go unrecognized, the most common of which is when it is mistaken for indigestion. While chest pain and pressure (like an elephant sitting on your chest) is pathognomonic, patients may experience left side jaw pain, toothache, or headache. While pain from a toothache would be described as throbbing or aching, pain of cardiac origin is described as pressure or burning. When pain occurs after exertion, cardiogenic etiology should be suspected. If patients are experiencing a cardiogenic toothache give them an aspirin, and make sure they get to a hospital emergency room immediately.

IATROGENIC (THE HORNET)
We all hate to stir up the hornets’ nest, but iatrogenic etiology must be considered in the differential diagnosis of pain. Figure 5 is the radiograph of a surgical procedure that aggressively perforated the buccal and palatal plates as well as the floor of the patient’s nose. As a result, the patient reported to my office with chronic pain in the anterior teeth that radiated to her nose. The pain could be reproduced in her teeth, including tooth No. 9 where the surgery had been performed. I referred this patient to an oral surgeon for reconstructive treatment.

The chief complaint of the patient in Figure 6 was numbness and palpation sensitivity in the buccal vestibule above her central incisors. No explanation is necessary.

NEOPLASM (THE ZEBRA)
While neoplasia in the jaws is rarely painful, and even more rarely encountered, a patient with this unfortunate disease can present with unusual symptoms.10 The radiographs in Figures 7a and 7b are of a 22-year-old female medical student who presented with irreversible pulpitis in tooth No. 19. The radiograph showed very narrow roots, with possible external resorption in the furcation area. While negotiating the root canal system, I discovered mid-root perforations resulting in communications with the furcal bone. It was impossible to get to the ends of the roots (not a case you want to show off). The patient reported pain relief and scheduled a 6-month reevaluation appointment. Upon reevaluation, she reported no pain, but was concerned because she thought the tooth was moving. Clinical examination confirmed that the tooth had migrated lingually. Referral and biopsy revealed a diagnosis of osteosarcoma.¹¹

IN SUMMARY
A variety of pain disorders involve the head, neck, jaws, and face. Many contradicting symptoms may exist when a patient presents with multiple problems. In order to diagnose and treat dental disease, a thorough understanding of both odontogenic and nonodontogenic etiologies of toothache pain is paramount.

Harvey McGehee, a noteworthy medical diagnostician, wrote: “In making the diagnosis of the cause of illness in an individual case, calculations of probability have no meaning. The pertinent question is whether the disease is present or not. Whether it is rare or common does not change the odds in a single patient. If the diagnosis can be made on the basis of specific criteria, then these criteria are either fulfilled or not fulfilled.”

Good diagnosticians in all fields of medicine are on the endangered species list. To become a successful diagnostician, one needs to have interest, intuition, curiosity, patience, and a quest for knowledge. Each day presents a new opportunity and you can either be the goat, or the GOAT (greatest of all time). The choice is yours.

References

1. Travell JG, Simons DG. Myofascial Pain and Dysfunction: The Trigger Point Manual. Baltimore, MD: Williams & Wilkins; 1983.
2. Yount K. Diagnosis and management of nondental toothache. Dent Today. 2002;21:130-135.
3. Malcmacher L. Botulinum Toxin (Botox and Dysport) Use for Dental and Facial Pain Treatment. American Academy of Facial Esthetics Web site. facialesthetics.org/esthetics/articles/botulinum_toxin_botox_and_dysport_use_for_dental_and_facial_pain_treatment. Accessed January 23, 2012.
4. Uyanik JM, Murphy E. Evaluation and management of TMDs, Part 1. History, epidemiology, classification, anatomy, and patient evaluation. Dent Today. 2003;22:140-145.
5. Uyanik JM. Evaluation and management of TMDs, Part 2. Dent Today. 2003;22:108-110, 112, 114-117.
6. Wright EF. Pulpalgia contributing to temporomandibular disorder-like pain: a literature review and case report. J Am Dent Assoc. 2008;139:436-440.
7. Alonso AA, Nixdorf DR. Case series of four different headache types presenting as tooth pain. J Endod. 2006;32:1110-1113.
8. Koratkar H, Parashar V, Koratkar S. A review of neuropathic pain conditions affecting teeth. Gen Dent. 2010;58:436-441.
9. Guttenberg SA, Emery RW, Milobsky SA, et al. Cranial arteritis mimicking odontogenic pain: report of case. J Am Dent Assoc. 1989;119:621-623.
10. Cohen S, Liewehr F. Diagnostic procedures. In: Cohen S, Burns RC, eds. Pathways of the Pulp. 8th ed. St. Louis, MO: Mosby; 2002:3-30, chapter 1.
11. Selden HS, Manhoff DT, Hatges NA, et al. Metastatic carcinoma to the mandible that mimicked pulpal/periodontal disease. J Endod. 1998;24:267-270.

Dr. Germain graduated from Boston University School of Graduate Dentistry with a specialty degree in endodontics in 1981. She is a Diplomate of the American Board of Endodontics, on the faculty of the American Academy of Facial Esthetics, and a Fellow of the International Congress of Oral Implantolgists. Dr. Germain maintains a private practice in New Orleans, La. She can be reached via e-mail at roots@bellsouth.net.

Disclosure: Dr. Germain reports no disclosures.