Estimating the Frequency of an Elongated Styloid Process of the Temporal Bone Along With its Anatomical Variations in...

The styloid process is a long, slender bone, part of the temporal bone, projecting downward, medially to variable length and angulation on both sides in the same individual and between two individuals, of different sexes and different ages. The object was to estimate the frequency of the elongated styloid process (ESP) of the temporal bone and variations in the length of the styloid process by using three-dimensional computerised tomography (3D CT) on lateral and posterior views in a population ranging from 18 to 80 years.

This is an observational study, conducted in the Department of Anatomy and Radiology of the National Institute of Medical Sciences and Research (NIMS), Jaipur, Rajasthan, India, on 150 3D CT scans showing the styloid process in the posterior and lateral view. The CT scans of the face and paranasal sinus in axial and coronal sections were collected, and a 360-degree 3D image of the face and skull showing the styloid process in lateral and posterior were generated by using the RadiAnt DICOM (Medixant, Poznan, Poland) viewer (64-bit) software. The length of the styloid process was measured with the help of this software. The broken styloid processes were excluded from the study.

Out of 150 3D CT, 113 were male, and 37 were female, age wise 29.3% of the 18 to 40 years age group, 34% of the 41 to 60 years age group, and 36.7% of the 61 to 80 years age group. The frequency of 2.01-3 cm long styloid processes was maximum on both views. The frequency of 3.01 cm to 4.00 cm long and less than 1 cm long styloid processes was significantly different on the lateral and posterior view, but in the rest of all groups, this difference in frequency was not statistically significant. The mean length of the styloid process on the right posterior view was 2.929 cm, SD=0.829; on the left posterior view, 2.965 cm, SD=0.904; on the right lateral view, 2.520 cm, SD=0.851; on the left lateral view, 2.569 cm, SD=0.869. The overall frequency of the ESP on the lateral view was 30%; in contrast, it was 53.3% on the posterior view. This difference in frequency was statistically significant (p value=.000042). In both genders, in all age groups, on both sides, the difference in frequency is not statistically significant on both views. The styloid process was bilaterally elongated on the lateral view in 17.3% of 3D CT and on the posterior view in 34%, and unilaterally elongated 12.7% on the lateral view and 19.35% on the posterior view. This difference is statistically significant with P-value=.004075.

The length of the posterior view of 3D CT should be used to estimate the frequency of ESP. The elongation of the styloid more than 3 cm is not only a criterion for the occurrence of symptoms of Eagle's syndrome, but also the angulation. The frequency of occurrence of symptoms increases with size, more than 4 cm. This also explains the lesser prevalence of development of symptoms of Eagle's syndrome.