The Syndrome of Elongated Styloid Process, the Eagle’s Syndrome—From Anatomical, Evolutionary and Embryological Backgrounds to 3D Printing and Personalized Surgery Planning. Report of Five Cases

Abstract

Background and Objectives: The symptoms of Eagle’s syndrome are associated with the elongated styloid process of the temporal bone or calcification of the stylohyoid ligament. The first mention of pain syndrome associated with the elongated styloid process dates back to 1937, when it was described by Watt Weems Eagle. Over the last decade, experts in the field have shown a lively interest in the issue of the relationship between the elongated styloid process and various symptoms. This article presents the correlation between the clinical signs of Eagle’s syndrome and alterations in surrounding anatomical structures. It includes a brief review of the evolutionary, embryological and clinical anatomical background of the elongated styloid process. Materials and Methods: Between 2018 and 2019, five patients were admitted to our workplace with 1–3-year history of bilateral or unilateral throat pain, otalgia and pharyngeal foreign body sensation. As a therapeutic novelty in the surgical approach to this condition, we used individual 3D printed models to measure and identify the exact location of the resection of the styloid process without damaging the surrounding anatomical structures, such as the facial, accessory, hypoglossal, and vagal nerves; the internal jugular vein; and the internal carotid artery. Results: Compared to traditional surgical methods without 3D models, 3D models helped to better identify cutting edges and major landmarks used in surgical treatment of Eagle’s syndrome. Printed models provided assistance with the exact location of the styloid process resection position without damaging the surrounding anatomical structures such as the facial, accessory, hypoglossal, and vagal nerves; the internal jugular vein; and the internal carotid artery. Conclusion: In our clinical report, we used 3D printed models for navigation and planning during surgical procedures involving resections of the elongated styloid process. Additionally, we can formulate a new hypothesis: the elongated styloid process is a form of atavism of the bony hyoid apparatus in our evolutionary ancestors that is evolutionarily encoded or arises from disrupted degeneration of the middle portion of embryonal Reichert´s cartilage of the second pharyngeal arch. Under normal conditions, this portion does not ossify but degenerates and transforms into a connective tissue band, the future stylohyoid ligament.

The Mandibular and Hyoid Arches—From Molecular Patterning to Shaping Bone and Cartilage

“…It has been hypothesized that the elongated styloid process in humans is evolutionary coded and represents a form of atavism of the bony hyoid apparatus of our evolutionary ancestors. Clinically, the condition is characterized mostly by pain in the head and neck due to compression of the surrounding structures either by elongation or angulation of enlarged styloid process [ 93 ]. Multiple aetiologies of Eagle’s syndrome have been suggested in the literature, ranging from genetic, developmental, endocrine, traumatic, degenerative, and metaplastic.…”

Variant Anatomy and Its Terminology

“…Other variabilities that are easily traced on radiograms include the canalis arteriae vertebralis atlantis (also referred to as ponticulus posticus , foramen arcuale , or, incorrectly, “ foramen arcuatum ”; also known by the eponym Kimmerle’s anomaly [ 108 ]) in the vertebrae. In the skull, other examples include the foramen squamosum ossis temporalis , persistent foramen caecum ossis frontalis , foramen occipitale , foramen venosum (of Vesalius), foramen cricotaphicobuccinatorius ossis sphenoidalis (of Hyrtl) (for details, see Hauser and Steffano [ 28 ]), or the processus styloideus elongatus (which causes the syndrome of Eagle [ 109 , 110 ]). The paranasnal sinuses and their variability is of high importance for ear–nose–throat specialists, as presented by the Anatomical Terminology Group for Sinus Disease [ 111 ] as well as maxillofacial surgeons [ 112 ].…”

Vascular compression syndromes: a pictorial review

“…Therapy varies according to symptoms, severity of vascular compression and presence of thrombosis. In less severe cases it can be conservative with steroid, anticoagulants or anesthetics drugs [11]; while in cases of severe stenosis ( > 70%) endovascular stenting [12] or SP surgical removal [13], or calcific stylohyoid ligament surgical removal [14] may be indicated. Long-term prophylaxis with anticoagulant therapy with a daily dose of low-molecular weight subcutaneous injection of heparin:…”

“…Therapy varies according to symptoms, the severity of vascular compression, and the presence of thrombosis. In less severe cases, treatment can be conservative, such as steroids, anticoagulants, or anesthetic drugs [ 11 ]; while in cases of severe stenosis (>70%), endovascular stenting [ 12 ], SP surgical removal [ 13 ], or calcific stylohyoid ligament surgical removal [ 14 ] may be indicated. Furthermore, long-term prophylaxis with anticoagulant therapy with a daily dose of low-molecular-weight subcutaneous injection of heparin-with agents including Bemiparin (Ivor), enoxaparin (Clexane, Clexane T), nadroparin (Fraxodi, Fraxiparina, Seledie, Seleparina), parnaparin (Fluxum) is recommended in asymptomatic patients with ≥50% carotid or internal jugular vein stenosis and follow-up with DU at 6 or 12 months.…”