# Distinguishing true from pseudo-absent styloid process: a case-prompted critical analysis

## TL;DR

This study clarifies the difference between true and pseudo-absent styloid processes using a case and literature review, improving radiological and surgical understanding.

## Contribution

The paper introduces clear criteria to distinguish true from pseudo-absent styloid processes, addressing a long-standing ambiguity in the literature.

## Key findings

- True absence involves aplasia of both tympanohyal and stylohyal segments, while pseudo-absence involves a hidden hypomineralised tympanohyal.
- Previous studies often misidentified the vaginal process as a short or duplicate styloid process.
- A CBCT case revealed bilateral pseudo-absent SPs, the first documented using this imaging technique.

## Abstract

The styloid process (SP) of the temporal bone is well-documented for its morphological variability, yet the distinction between true absence and pseudo-absence remains poorly defined in the literature. This study critically examines published reports of SP absence and proposes clear terminological criteria to differentiate these entities. True absent SP denotes aplasia of both tympanohyal and stylohyal segments, whereas pseudo-absent SP indicates a hypomineralised tympanohyal concealed beneath the vaginal process of the tympanic plate. Analysis of the literature indicates that previous studies using CT, panoramic radiography, and dry skull analysis have frequently conflated these variants, with some authors misidentifying the inferiorly projecting vaginal process as a duplicate or short SP. This critical reappraisal was prompted by a cone-beam computed tomography (CBCT) case demonstrating bilateral pseudo-absent SPs in a 39-year-old female, in which low-density tympanohyal segments (10.5 mm) were entirely masked by extensively developed vaginal processes (15.5 mm). To our knowledge, this represents the first CBCT-documented case of this morphology and only the third reported evidence, following dry-skull observations. Accurate differentiation between true and pseudo-absent SP has implications for radiological interpretation, surgical planning, and understanding stylohyoid complex development.