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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.
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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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