Three patterns of supracollicular fluid accumulations

VRU 2016

MULTIDETECTOR COMPUTED TOMOGRAPHIC AND LOW-FIELD MAGNETIC RESONANCE IMAGING ANATOMY OF THE QUADRIGEMINAL CISTERN AND CHARACTERIZATION OF SUPRACOLLICULAR FLUID ACCUMULATIONS IN DOGS

G Bertolini, M Ricciardi, M Caldin

Background
Quadrigeminal cistern (QC) anomalies, termed "quadrigeminal cysts" or "supracollicular fluid accumulations" (SFAs), are noted in dogs and may be subclinical or linked to neurological deficits. Despite their prevalence, imaging-based anatomical studies of the QC in dogs remain sparse. This study aimed to describe normal QC anatomy using imaging modalities and evaluate the prevalence, patterns, and characteristics of SFAs in dogs.

Methods
The study used a two-part observational and cross-sectional approach:
1. Anatomical Study: Multidetector CT (MDCT) cisternography was performed on a cadaver and on four healthy living dogs to establish baseline QC imaging anatomy.
2. Epidemiological Study: Retrospective analysis of 4427 MDCT and 626 MRI brain scans (2005–2015) was conducted to identify SFAs, determine their prevalence, and characterize associated clinical and anatomical abnormalities.


Results
Normal Anatomy: The QC in dogs exhibits a consistent H-shaped structure, separated from the third ventricle by a thin membrane.


Prevalence: SFAs were identified in 2.19% of MDCT scans and 2.2% of MRI scans.


Demographics: SFAs were more common in young dogs and certain breeds (Shih-Tzu, Chihuahua, Maltese).

Patterns: Three SFA types were noted: Expansion of the third ventricle (49.54%), Expansion of the QC (13.51%), Combined expansion of the third ventricle and QC (36.93%).


Concomitant Findings: Cerebellar compression and other congenital anomalies, such as occipital dysplasia, were documented in a subset of cases.


Limitations
The study was limited by:
- Anatomical validation from only one mesaticephalic dog in the cisternography study.
- Lack of histopathological confirmation for the fluid accumulations.
- Retrospective data inconsistencies, especially for MRI cases, which limited further analyses.


Conclusions
The study provides a detailed imaging description of the QC and proposes the term "supracollicular fluid accumulation" (SFA) instead of "quadrigeminal cyst." It identifies key anatomical and breed predispositions, contributing to better diagnostic clarity and potential surgical planning for symptomatic cases.

FIG. 7. Different patterns of SFAs as seen on midsagittal MR (A, B, C) and MDCT (D, E, F) images of the brain. (A) Balance steady-state free precessionsequence of the brain of a 2-year-old male Pug (dog 4) with dilation of the quadrigeminal cistern (q). (B) T2-weighted image of the brain of a 4-year-oldmale Chihuahua (dog 5), with moderate dorsocaudal dilation of the third ventricle (tv) and moderate dilation of the quadrigeminal cistern. Lateral ventricles(LV) are also enlarged. (C) T2-weighted image of the brain of a 1-year-old male Mongrel with large dorsocaudal expansion of the III ventricle. Moderateenlargement of the lateral ventricles (LV). (D) MDCT image of the brain in a 11-year-old, female, Shih-Tzu with dilation of the quadrigeminal cistern. (E)Midsagittal view in a 2-year-old, male Chihuahua with dorsocaudal outpocketing of the III ventricle and moderate enlargement of the quadrigeminal cistern.(F) Dorsocaudal supracollicular dilation only of the III ventricle in a 8-months-old, male, Yorkshire Terrier. In each image, note the thin membrane thatseparates the III ventricle from the quadrigemina cistern (arrows) and the displacement of the quadrigeminal plate (p). Enlargement of the quadrigeminalcistern leads to the dorsoventral compression of the cerebellum (C). Enlargement of III ventricle leads to an anteroposterior cerebellar compression. Largedilations of quadrigeminal cistern and third ventricle lead to displacement of the occipital lobes (A, C, D, F); at, interthalamic adhesion

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