Compression Syndromes of the Stylohyoid Complex: Neural, Arterial, and Venous Phenotypes in a Dynamic Neurovascular...

Background/Objectives: Compression syndromes of the stylohyoid complex (SHC) encompass neural, arterial, and venous presentations extending beyond classic Eagle syndrome. Symptomatic disease is increasingly recognised as a dynamic neurovascular conflict determined not by styloid process (SP) length alone, but by three-dimensional orientation, vessel and nerve proximity, and positional musculoskeletal interactions. This review synthesises that literature and proposes a phenotype-based framework integrating neural, arterial, venous, and mixed presentations. Methods: This is a narrative, pathophysiologically organised review rather than a systematic or scoping review. Landmark anatomical, clinical, and cohort studies were synthesised alongside systematic reviews, meta-analyses, osteological data, and selected case reports illustrating mechanisms not captured at cohort level. Evidence strength was interpreted by study design, distinguishing pooled estimates from retrospective series and proposed mechanisms. Results: The SHC and adjacent C1 transverse process form a narrow corridor containing the internal jugular vein, carotid arteries, and lower cranial nerves. SP elongation is common, but symptomatic compression depends more on orientation, SP-to-C1 distance, vessel proximity, and dynamic positional factors than on length. Three-dimensional CT angiography/venography is the anatomical cornerstone for defining morphology and vessel relationships, whereas catheter venography with manometry remains the haemodynamic reference standard in selected venous cases. Jugular narrowing is frequent in asymptomatic individuals and is not diagnostic without clinical and haemodynamic correlation. Surgical decompression appears favourable in selected patients, whereas primary endovascular stenting, evaluated only in single-centre observational series, carries a substantial complication profile and should generally be reserved for refractory or combined presentations. Conclusions: SHC compression syndromes are best understood as overlapping neural, arterial, venous, and mixed phenotypes within a dynamic neurovascular corridor. A phenotype-based classification and a cautious "styloidectomy-first" strategy for osseous venous compression are proposed as practical frameworks, but require prospective validation.