Temporal tendinosis, a form of tendinopathy, is an “underrecognized and undertreated condition,” despite the fact that it is “one of the single most common complaints of patients presenting to physicians or dentists” and a frequent cause of chronic orofacial pain.

A recent paper in Current Pain and Headache Reports (2020;24[5]:18) reviews the pathophysiology and management of the condition.

“We decided to write this review because we have seen that this condition is often overlooked or misdiagnosed,” lead author and chronic pain physician Hart Bressler, MD, an assistant professor in the Department of Family and Community Medicine at the University of Toronto, told Pain Medicine News.

“Facial pain also tends to fall through the cracks because physicians who deal with tendons, such as orthopedic surgeons, physiatrists and rheumatologists, have little experience with facial pain,” Bressler said. “On the other hand, those that deal with facial pain, such as otolaryngologists, neurologists, anesthesiologists and dental practitioners, typically do not deal with tendon disorders.” Moreover, “many medical and dental professionals have little training in chronic pain management.”

As a result, “specific training for diagnosis and management of [temporal tendinosis] is inadequate, so patients often have extensive unnecessary tests and workups, suboptimal management, and no relief of their orofacial pain,” he said.

Tendinitis Versus Tendinosis

Chronic tendon disorders are debated in the medical literature and have no clear definitions. For example, “tendinitis” is often used even when there is no evidence of inflammation, Bressler said. “Tendinosis,” on the other hand, is usually defined as a chronic tendon disorder without classic clinical or histologic signs of inflammation that leads to pathologic changes over time. Radiologists tend to favor the term tendinosis, as these structural degenerative changes are seen on ultrasound or MRI.

‘Location, Location, Location’

“Real estate agents talk about ‘location, location, location,’ and the same can be said for the temporal tendon,” Bressler observed, adding that temporal tendinosis generally presents as “localized facial pain inferior to the region of the mid-zygomatic arch.

“A patient who complains of pain is usually asked to point to where the pain is,” he said. “However, pain experienced at the insertion point at the coronoid process in one location may actually be referred pain upwards the tendon to the temporalis muscle.”

Moreover, “the temporalis muscle, tendon and neighboring anatomical structures, including somatic and autonomic nerves, are enclosed in a small space, and buried deep within the complex anatomy of the face, making the tendon both hard to palpate and to visualize,” according to the review article.

“The anatomy of the jaw is complex, and temporal tendinosis occurs in a deep location that is often incompletely described or completely omitted in the majority of medical or dental anatomy textbooks,” Bressler observed.

Typically, injuries to the temporalis tendon originate in some type of direct trauma or hyperextension of the jaw, such as prolonged dental procedures or sudden traumatic intubation. Many cases resolve in the short term with no long-term sequelae. However, they sometimes develop over the long term, leading to chronic temporal tendinosis. A typical presentation is of progressive chronic facial pain and stiffness with gradual onset aggravated by jaw activity, Bressler said.

Other causes include long-standing abnormal repetitive strain or mastication of jaw movement over many years.

The clinical presentation of temporal tendinosis includes unilateral localized facial pain without referred pain—similar to patellar or Achilles tendinopathy—with patients frequently pointing to just below the zygomatic arch as the location of the pain, but away from the temporomandibular joint; and pain radiating from the distal temporalis tendon to the temporalis muscle possibly with or without unilateral temporal headache, similar to forearm pain associated with lateral epicondylitis.

Pain patterns may vary, “so it is important to assess the pain on a case-by-case basis,” Bressler advised.

Diagnosing Temporal Tendinosis

Palpation of temporal tendinosis can be challenging, as its position is deep in the zygomatic arch, Bressler stated. Suggested techniques include:

• intraoral single-digit palpation at the medial aspect of the coronoid process;
• using the pincer grasp technique to dynamically stress the tendon in the medial and lateral directions; and
• diagnostic imaging, which in conjunction with clinical examination, “allows a more precise diagnosis.”

Although imaging can detect chronic tendon pathology or tendinosis, it cannot detect acute tendinitis or general nonspecific inflammation.

Bressler recommended ultrasound as preferable to MRI because it is “time-efficient, less expensive, more readily available” and enables the examination of both the temporomandibular joint and temporalis tendon simultaneously.

Managing Temporal Tendinosis

For acute temporal tendinosis, noninvasive treatments include cessation of physical activity, oral dental appliance, passive deep physical therapy, anti-inflammatory drugs and physical therapy exercises to strengthen the temporalis muscle. However, these approaches are not effective for chronic tendinosis.

Chronic temporal tendinosis usually requires more invasive intratendinous approaches. Most commonly, local anesthetic corticosteroid injections have been documented with long-term success with temporalis tendinopathy (J Ultrasound Med 2017;36[10]:2125-2131; Br J Sports Med 2014;48[21]:1553-1557).

However, like with any other tendons, repeated injections carry risks, including long-term structural changes. Other possible management approaches include ultrasound-guided needle fenestration, prolotherapy and autologous blood/platelet-rich plasma injections.

Despite the availability of these options, “optimal treatment remains unclear,” Bressler noted.

He encouraged the development of more comprehensive training for both physicians and dentists, and for increased research to build the evidence base for optimal treatment of temporal tendinosis.

—Batya Swift Yasgur, MA, LSW