The Evaluation of Elongated Styloid Processes in regard to possible Clinical and Pathological Outcomes - A Case Series

Background: Eagle’s syndrome (ES) is defined as elongation or ossification of the styloid process that may compress adjacent anatomy, producing variable symptomology. ES is subclassified into Classic ES or Stylocarotid syndrome. Classic ES may present asymptomatically, or with dull, recurring cervicofacial pain, and Stylocarotid syndrome may present with parietal headaches, and presyncope/syncopal episodes. The etiology of the abnormal ossification of the styloid process or stylohyoid ligament is unknown but likely caused by reactive metaplasia/hyperplasia or anatomical variance. Although a styloid process greater than 30mm in length is generally considered elongated, clinical guidelines for measuring styloid process length, and specific histological characterizations for ES have not been formally established. However, elongated styloid processes can be structurally classified as uninterrupted (one unsegmented process), pseudo-articulated (two parts in close proximity), or segmented (three or more parts). Styloid processes may also be classified into four calcification patterns including outlined calcification, partial calcification (multiple bone pieces surrounded by a continuous calcified process), nodular calcification (segmented, bumpy surfaced bone pieces due to thickened calcifications), and complete calcification. However, no clinical correlation has been identified between patient presentation and morphology/calcification pattern.

Case Information: A 62-year-old deceased Caucasian male (147lbs / 5’6”) with an elongated stylohyoid process was discovered during routine dissection. Medical history was significant for liver and renal disease. Cause of death was reported as “chronic alcoholism”. Social history was significant for off-and-on incarceration for more than 40 years, and chronic alcohol, tobacco, and non-prescription illicit drug use of unknown types, amount, frequency, or duration. No other history was available.

The styloid processes of the patient were imaged in-situ using a 3D C-arm X-ray machine. Furthermore, bilateral styloid processes were collected from the patient and seven other anatomical donors (6 M/1 F, age range 61-76) by detaching them from the base of the temporal bone and excising portions of the hyoid bone to maintain the stylohyoid ligament intact. Calipers were used to measure the length of the styloid processes and their calcifications. The primary donor exhibited elongated, asymmetrical processes (31.9 mm left, 37.8 mm right). Significant variation in styloid process lengths were observed in this sample (mean length 28.5 mm; standard deviation 13.5 mm; range 14.5-68.3 mm). Generally, the styloid processes demonstrated bilateral asymmetry across the sample. This asymmetry was notably pronounced in one donor with a significantly elongated styloid process (20.5 mm left, 68.3 mm right), co-occurrent with thyroid cartilage calcification.

Conclusions: There is presently no consistent diagnostic measure of an elongated stylohyoid process available for providers to assess patient risk for Eagle’s Syndrome or its future progression. In this study, styloid length was found to be a continuous variable with no clear “cutoff” between elongated and normal lengths at 30mm. Furthermore, the lack of histological evidence detailing the condition's progression hinders diagnostic measures and risk assessment. We recommend further studies perform histologic analysis to better understand the progression of elongated styloid processes. Based on additional samples, a standardized diagnostic measurement can be created to improve treatment regimens and health risk screenings.