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7 Articles in Volume 6, Issue #8
Hyoid Bone Syndrome
Minimally Invasive Interventional Spine Treatment – Part 1
Mobile MRI—Imaging on Wheels
On the Role of Primary Care Within a System of Integrative Multi-disciplinary Pain Management
Pediatric Headaches
Practical Applications of Low Level Laser Therapy
Strength Testing in Pain Assessment

Hyoid Bone Syndrome

A condition characterized by both dental and non-dental referral sites, this degenerative injury of the middle pharyngeal constrictor muscle is confirmed by photomicroscopic evidence of insertion tendinosis.

first published in the Journal of Prosthetic Dentistry1 in 1991, this report of hyoid bone syndrome has been updated by the authors to reflect the latest information on the condition

The hyoid bone has been identified with a specific, although not well recognized, pain syndrome for over 40 years.2 The painful symptoms are generally caused by trauma at the greater cornu of the hyoid bone with the pain radiating to other sites.3

Treatment for the condition ranges from injections of local anesthetic or cortisone to resection of the greater cornu. The pain usually radiates from the greater cornu of the hyoid bone to the throat, mandible, mandibular molar teeth, zygomatic arch, condyle, face, ear, and temple superiorly; anteriorly to the neck, clavicle, upper half of the breast, shoulder, arm, and over the shoulder to the scapula of the back inferiorly on the same side.4

Figure 1. Figure 1. Hyoid bone with arrows indicating (a) middle pharyngeal constrictor muscle origin, (b) greater cornu tip, (c) hyoglossus muscle origin, (d) greater cornu, (e) lesser cornu and tip, (f) body of hyoid, (g) stylohyoid ligament. (Reprinted with permission from Ernest EA. Temporomandibular joint and craniofacial pain. 3rd ed. Montgomery, Ala: Ernest Publications.)

The condition is not well known in medicine and dentistry for at least two reasons: (1) the diffuse and seemingly unrelated radiation of symptoms and (2) the apparent absence of histopathologic evidence of injury.

Hyoid bone syndrome was first described by Brown2 in 1954, and later by Steinmann,5 Kopstein,6 Lim,3 and Ernest.4 The syndrome represents a group of confounding head and neck symptoms that may suggest carotodynia7 to the unsuspecting clinician. The primary site of pain is associated with the region of the greater cornu tip of the hyoid bone. Steinmann,5 Kopstein,6 Lim,7 and Ernest have reported surgical removal of the greater cornu with remarkable resolution of pain for the affected patient. However, some clinicians deny the existence or the validity of hyoid bone syndrome because reports offer no objective evidence other than the signs, symptoms, and results of surgery.

This article presents photomicroscopic evidence to validate the hyoid bone syndrome, and reports a focal, degenerative injury of the middle pharyngeal constrictor muscle (MPCM) as the site of a painful injury associated with hyoid bone syndrome. The site of injury involving the MPCM is consistent on a clinical, anatomic, and histopathologic basis with a description of the somatic tissue responsible for the painful constellation of symptoms of hyoid bone syndrome.

Anatomy

The hyoid bone is the only bone that has no direct contact with any other bone in the human body (see Figure 1). It is a U-shaped structure lying between the root of the tongue and mandible and the thyroid cartilage. The hyoid bone forms a movable base for the tongue and its varied movements and is held in position by a large number of muscles. The hyoid bone has connections with muscles to the mandible (mylohyoid), tongue (hyoglossus), skull (stylohyoid), thyroid cartilage (thyrohyoid), sternum (sternohyoid), to the medial border of the scapular notch (omohyoid), and to the pharyngeal median raphe (MPCM) (see Figure 2).

Most patients with symptoms of hyoid bone syndrome report pain radiating to the ear, throat, temple, zygomatic arch, temporomandibular joint (TMJ), mandibular molar teeth on the same side, and a vertical axis of pain that runs from the temple superiorly down through the TMJ, continuing inferiorly to the clavicle, and terminating in the middle of the breast without extending below the nipple (see Figure 3).4 The connections to the hyoid bone explain the radiating symptoms experienced by the patient suffering from hyoid bone syndrome.

Methods and Material

A 43-year-old woman was referred for evaluation of chronic pain, of 13 years’ duration, of the left side of the head, face, neck, and shoulder. Although trauma is usually the source of such a complaint, the patient could not recall a specific event correlating with the onset of her symptoms. She had undergone multiple surgical procedures in the hope of achieving remission of the pain. The right and left TMJs were operated by open reduction without successful relief of pain. Subsequently, two separate surgical procedures were performed on the left maxillary sinus, again without benefit to the patient.

Figure 2. Anatomic dissection of hyoid bone. (a) Middle pharyngeal constrictor muscle origin, (b) greater cornu tip, (c) hyoglossus muscle origin, (d) greater cornu, (e) lesser cornu and tip, (f) body of hyoid, (g) stylohyoid ligament, (h) tongue.

Diagnostic testing included digital or bimanual palpation with the index finger on the greater cornu of the non-affected side. This procedure directed the entire hyoid toward the surface of the skin of the affected side, with the thumb stabilizing the affected cornu at the site of injury, as recommended by Brown.2 When pressure was applied to the left cornu, the radiation of painful symptoms was intensified when pressure was maintained. Next, a local anesthetic syringe with a 30-gauge, 1-inch needle containing bupivacaine (0.5%) with epinephrine 1:200,000 (Marcaine) was inserted on the superior surface of the left greater cornu at the site of pain (see Figure 4). One cubic centimeter of Marcaine deposited at the site of injury resolved more than 95% of the pain present at all reference sites and at the point of origin within a few minutes. The sites included the ear, temple, TMJ, zygomatic arch, mandible and mandibular molar teeth, throat, anteriorly to the neck, clavicle, shoulder, arm, and upper half of the breast.

This test was repeated the following day with identical successful results. An anesthetic block for treatment of hyoid bone syndrome eliminates almost all of the pain, yet the patient still has a persistent soreness that is not affected by the block. However, the soreness is eliminated by surgical operation.

Figure 3. Drawing depicts site of injury at greater cornu tip and reference sites of painful symptoms of hyoid bone syndrome. (Reprinted with permission. Ernest EA. Temporomandibular joint and craniofacial pain. 3rd ed. Montgomery, Ala. Ernest Publications.)

Each time after the effect of the anesthetic wore off, the patient’s original pain pattern reappeared. Consultation was sought with a radiology service, and neck radiographs with lateral, oblique, and Allen position views were obtained. No evidence of fracture of the hyoid body or cornua, or other unusual findings were revealed.

Figure 4. Photograph of Brown’s method of displacing hyoid to side of injury and insertion of 30-gauge anesthetic needle into site of injury, with distal edge of thumb displacing carotid artery posteriorly, prior to careful injection with aspirating syringe.

The other structures tested that could mimic hyoid bone syndrome included the anterior scalene muscle (Scalenus Anticus Syndrome), the stylomandibular ligament (Ernest Syndrome), the temporal tendons (Temporal Tendinitis), the carotid artery (carotodynia), the pharynx (tumors and infections), and the trigeminal and glossopharyngeal cranial nerves (neuralgias). With the differential diagnosis reduced to the left greater cornu of the hyoid bone, the patient was scheduled for surgery.

Figure 5. Photograph of greater cornu of hyoid bone. Arrow at (A) indicates tip of cornu. Arrow at (B) indicates region of degenerative change. Arrow at (G) indicates bony matrix.

With the patient under general anesthesia with oro-tracheal intubation, the head and neck were positioned in lateral hyperextension, with the face positioned to the right. A skin marker was used to identify the relative position of the body and left greater cornu of the hyoid bone. Local anesthetic was infiltrated into the skin and underlying tissues to reduce hemorrhage at the site of surgery. The skin incision was carried subcutaneously to identify the platysma muscle. Next, palpation and blunt dissection of the greater cornu was aided by displacement of the hyoid bone as reported by Brown,2 thus providing easier location and dissection of the greater cornu.

Figure 6. Photograph represents original magnification X2 of region of atrophic change. Arrow at (B) indicates atrophic muscle fibers with increase in centrally placed nuclei, many pleomorphic and multinucleated. Arrow at (C) indicates sarcolemmal chains of nuclei in elongated muscle fiber. Arrow at (D) indicates hyalinization of muscle fiber (smudged appearance). Arrow at (H) represents normal cell type with laterally placed nucleus.

The muscles attached to the greater cornu were incised and reflected from the tip of the cornu to the junction of the greater cornu with the body of the hyoid bone. The greater cornu was then removed at the junction of the body with bone rongeurs, the site was irrigated, a Penrose drain was placed, and the incision was closed with sutures.

Figure 7. Photograph represents original magnification X3 with arrow at (B) showing atrophic fibers and increased numbers of centrally placed nuclei. Arrow at (F) indicates collagen separating muscle fascicles. Arrow at (H) represents normal cell type, and arrow at (I) indicates necrotic area in tissue characterized by histocytic phagocytosis. There is “rounding-up” arrangement of degenerative fibers, which is significant histopathic sign of myopathy (along with finding of pleomorphic, multinucleated, sarcolemmal nuclei-forming “chains”).

Histopathologic Findings

The greater cornu with its muscle attachments was submitted to pathology service for microscopic examination to determine whether insertion tendinosis was responsible for the painful condition of hyoid bone syndrome. The pathologist noted in his report that no inflammatory changes were seen within the cartilage of the surrounding connective tissue, and the hematopoietic cells of the bone marrow were normal (see Figure 5). However, the findings of interest were the presence of “focal, degenerative changes of the striated muscle surrounding the cornual end of the hyoid, characterized by focal necrosis, mild atrophic changes, and cytoplasmic basiophilia. These degenerative changes do not appear to be accompanied by a significant inflammatory infiltrate” (see Figures 6 through 8).

Figure 8. Photograph represents original magnification X4 with arrow at (B) indicating atrophic fibers with increased numbers of centrally placed nuclei of different sizes in center of sarcolemma. Arrow at (C) indicates increased numbers of nuclei-forming nuclei chains (sign of focal degeneration.) Arrow at (D) shows hyalinization of cell fiber.

The descriptions of the specimen were consistent with the findings of Pedersen and Key,8 Sandstrom and Wahlgreen,9 Schallock and Linder,10 and Ernest et al.,11 in their respective investigations of insertion tendinosis found in other parts of the body. In their studies, Schallock and Linder10 reported precipitate formation in the ground substance, followed by swelling, then shriveling of the attachment fibers, with disintegration of the fine structure. This condition was followed by fatty degeneration, foci of necrosis, appearance of hyalin, and in the late stage of degeneration, deposition of calcium. The same degenerative process has been identified and reported concerning injury to the lateral tendon of the temporal muscle called temporal tendinitis.11,12

Muscle Attachments

Two muscles have their attachments at the distal cornual end of the hyoid bone. The MCPM has origin fibers located on the greater cornual tip and occasionally the mediosuperior surface of the greater cornu, whereas the hyoglossus muscle lies more laterally (see Figure 1). Further, the MPCM has its origin on the most distal end of the stylohyoid ligament, the lesser cornu, and the length of the superior surface and/or tip of the greater cornu. In this specimen, the degenerated tissue site was medially oriented to the superior surface of the greater cornu. This location is consistent with the anatomic and surgical locations given for the origin fibers of the MPCM.

Discussion

A patient with signs and symptoms of hyoid bone syndrome was evaluated and subsequently underwent surgical operation. The hyoid greater cornu was identified as the site of injury and was excised. The tissue was identified as origin fibers of the MPCM at the greater cornu. Pathologic microscopic findings of focal, degenerative changes with foci of necrosis, hyalin, chaining of centrally placed multiple nuclei, and elongation of muscle fibers—consistent with myopathy—were confirmed.

The patient’s postoperative course included initial difficulty in swallowing and eating, followed by progressive improvement and elimination of the painful symptoms. The patient also noted immediate cessation of temple headache and ear pain in the afternoon of that same day after the morning surgical procedure.

The thermal lesioning modality is now the treatment of choice for other focal, degenerative, somatic attachments in the head, jaw, and neck.13-18 Because the region of injury is focal, studies are underway to confirm the efficacy of using radiofrequency thermal lesioning to treat hyoid bone syndrome.19

Summary

This article describes the condition known as Hyoid Bone Syndrome, its diagnosis by exclusion, and the histopathologic evidence of focal, degenerative muscle injury with signs and symptoms of interest to dentists and physicians has been reported. The injury involves the origin fibers of the middle pharyngeal constrictor muscle on the greater cornu of the hyoid bone. The microscopic evidence of injury to the middle pharyngeal constrictor muscle of the pharynx, as described, lends validity to other clinical reports of patients who suffer hyoid bone syndrome.

Acknowledgement

We express special appreciation to Danny G. Harvey, MD, neuropathologist at Baptist Medical Center, Montgomery, Alabama, for his assistance in the photomicroscopy of the pathology tissues obtained.

Last updated on: May 16, 2011
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