ABSTRACT
The anterior inferior cerebellar artery (AICA) is situated within the posterior cranial fossa and typically arises from the basilar artery, usually at the pontomedullary junction. AICA is implicated in various clinical conditions, encompassing the development of aneurysms, thrombus formation, and the manifestation of lateral pontine syndrome. Furthermore, owing to its close proximity to cranial nerves within the middle cerebellopontine angle, AICA's pulsatile compression at the root entry/exit zone of cranial nerves may give rise to specific neurovascular compression syndromes (NVCs), including hemifacial spasm (HFS) and geniculate neuralgia concurrent with HFS. In this narrative review, we undertake an examination of the influence of anatomical variations in AICA on the occurrence of NVCs. Significant methodological disparities between cadaveric and radiological studies (CTA, MRA, and DSA) were found, particularly in diagnosing AICA's absence, which was more common in radiological studies (up to 36.1%) compared to cadaver studies (less than 5%). Other observed variations included atypical origins from the vertebral artery and basilar-vertebral junction, as well as the AICA-and-PICA common trunk. Single cases of arterial triplication or fenestration have also been documented. Specifically, in relation to HFS, AICA variants that compress the facial nerve at its root entry/exit zone include parabola-shaped loops, dominant segments proximal to the REZ, and anchor-shaped bifurcations impacting the nerve's cisternal portion.
ABSTRACT
Purpose: The purpose of this study was to assess in vivo regional variability in the densitometry parameters of corneal stroma and the modulating effect of age on those parameters using statistical characterization of optical coherence tomography (OCT) speckle. Methods: OCT imaging of central and peripheral cornea was performed in a group of 20 younger (24 to 30 years old) and 19 older (50 to 87 years old) subjects. The sample size was estimated using normal assumptions and previously reported data on speckle parameter variability. Statistical parameters of corneal OCT speckle were calculated in the regions of interest (ROI) encompassing central and peripheral stroma as well as taking into account their anterior and posterior subregions. Both parametric (Burr-2 parameters: α and k) and a nonparametric approach (contrast ratio [CR]) were considered. Two-way analysis of variance was used to test for differences in densitometry parameters with respect to ROI position and age. Results: Both approaches showed statistically significant differences within the ROI positions (all P < 0.001 for α, k, and CR) and age (P < 0.001, P = 0.002, and P = 0.003, for α, k, and CR, respectively) indicating substantial stromal asymmetry. Additionally, CR showed statistically significant differences between anterior and posterior subregions (P < 0.001). Conclusions: Corneal OCT-based densitometry is inherently asymmetrical and are influenced by age. The results indicate that regional variability of stromal structure is not limited to the central and peripheral regions but that differences exist also between the nasal and temporal parts of the cornea. Translational Relevance: The in vivo acquired parameters of corneal OCT speckle can be used to indirectly assess corneal structure.
