Orbital-Inner Canthus Headache due to Medial Temporal Tendonitis
In 1983, this author documented the painful condition noted as temporal tendinitis. The described pain originated at the insertion of the lateral tendon of the temporal muscle at the mandibular coronoid process (not coracoid). The referral sites of pain included the cheekbone, retro-orbital, temple, upper and lower molar teeth, temporomandibular joint, and the ear.1,2 What was not listed in the constellation of symptoms was the presence of pain at the stylomandibular ligament insertion at the ramus of the mandible. However, stylomandibular pain was noted in the substance of the paper.
Also noted in the substance of the paper was pain originating at the insertion of the medial tendon of the temporalis muscle. The temporal muscle usually has two distinct bellies and two tendons. The origin of the medial belly of the Temporalis muscle is beneath the origin of the lateral muscle belly in some cases. However, in some cases the origin of the medial belly and its tendon takes its attachment at the inferior margin of the zygomatic arch, a location noted by Romaines (1968) in his dissection manual of the head and neck. The zygomatic arch attachment origin was subsequently noted by anatomist and dentist W.E. Shankland, III, with his designation of the zygomatic origin as the zygomandibularis muscle in the 1990s. It is the medial tendon insertion that relates to inner canthus headache.
The zygomandibularis muscle and its tendon—or the medial belly of the temporalis and its tendon—are of clinical importance as I noted in 1983. Since then, I have also noted other salient points as it pertains to the medial temporalis tendon or zygomandibularis muscle tendon. In a given patient, it would take a live dissection to determine the origin of the medial belly of the temporalis muscle. Since that is inappropriate in a patient suffering facial pain, I will use the term medial tendon of the temporalis muscle, as it relates anatomically to its painful insertion—not it’s origin. In most patients who suffer craniofacial pain, attachment injuries are a common finding. Dr. John L. Beck, MD, in his Letter to the Editor in last month’s issue of Practical Pain Management (Volume 8 Issue 5), emphasized the significance of Temporomandibular joint and related structural disorders with migraine headache. He also emphasized the physician’s responsibility to make the diagnosis and make appropriate referral for care.3
I do want to emphasize the fact that temple headache pain is often “temple” in origin. The fact that the pain may be originating in the muscle belly, or in the insertion of either lateral or medial tendon, or both, is simply a variable of location of pain origin.
Dr. Beck correctly identified the complex nature of the temporomandibular joint and its frequent implication in migraine-type and migraine-like head-aches. What is not routinely noted by dentists or physicians who specialize in craniofacial pain management is the often identical set of referred painful symptoms caused by the medial tendon of the temporalis muscle. The symptoms are similar to those caused by injury to the lateral tendon of the temporalis muscle, but many anatomical texts and atlases do not make mention of the medial belly and medial tendon of the temporalis muscle.
Small wonder then that there is a paucity of references to the medial tendon and an absence of references to insertion pain and painful referral pattern of symptoms in articles dealing with pain associated with the temporalis muscle and its two muscle bellies.
My mentors, Drs. William Farrar and William L. McCarty, wrote one of the early references to temporal pain associated with a growth and development issue. The problem was related to either a flaring of the mandibular coronoid process with subsequent impingement at the zygomatic arch; or with an osteoma on either the coronoid process or the zygomatic arch. The result was the same, a physical limitation that caused painful dysfunction requiring surgery to correct.
There are other rare conditions—such as tumors of muscle or bone—that can cause pain in the region, but this present article is concerned with referred musculoskeletal pain.
Typically, an insertion tendinosis of the medial tendon of the Temporalis muscle produces almost identical symptoms as the lateral tendon that inserts on the coronoid process. But in a smaller number of cases, the pain is either a low grade ache with little or no obvious referral pattern, or it may have a singular distant referral to the inner canthus of the eye. The patient describes the pain as a headache in the inner corner of the eye, not just as “eye pain.” Certainly, other possible conditions should be ruled out before a confirmed diagnosis is made. However, when glaucoma and pseudotumor, eye strain, ophthalmoplegic migraines, and other medical conditions have been ruled out, then the referred pain to the inner canthus of the eye may be established. It may be a referred painful headache from an insertion strain or insertion tendinitis of the medial tendon of the temporalis muscle.
An interesting feature of the headache is noted: the patient will place their index finger at the inner canthus of the eye or orbit and comment that the pain is an intense headache.
So far, I have not mentioned the actual site of insertion as the ground work needed to be laid before reaching a possible diagnosis. And, most physicians will likely choose to enlist the aid of a dentist to make the diagnostic test, as the test site of local anesthetic injection is immediately posterior and slightly lateral to the second or third molar tooth. Anatomically, the medial tendon inserts into the linear depression that lies between the external and internal oblique lines of the ramus of the mandible2 (see Figures 1 and 2 for dissection photos of lateral and medial temporal tendons).
Another landmark that should not be anesthetized in the immediate region is the lingual nerve to the tongue. If the local anesthetic needle is placed slightly medial to the internal oblique line, lingual nerve anesthesia to the tongue will likely result.
We often like to use digital pressure when examining the structures of the head or neck, but in some cases, such as this one, the tendon insertion is not painful to digital pressure, yet when the medial tendon was anesthetized (1/4 cc) the orbital headache stopped immediately and was pain-free for the two-hour duration of the local anesthetic. A subsequent block achieved the same results of relief. The seemingly odd referral site to the eye simply underlines the complexity of the trigeminal nerve and supports an anesthesiologist colleague’s wisdom to “think outside the box” in dealing with seemingly bizarre or unusual cases.
This case was complex as she also suffered splenius capitis muscle syndrome bilaterally, as well as lateral temporalis muscle tendinitis bilaterally. All of the patient’s two year history of symptoms seemed directly and immediately related to the general anesthetic intubation for C-section in 2006. Whether there were sub-clinical signs or symptoms prior to the C-section because of breast-reduction surgery in 2005 is difficult to determine.