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Quadrigeminal cysts. Katie Phillips DVM August 16, 2010. Intracranial Arachnoid Cysts. Intra-arachnoid accumulations of CSF Pathogenesis: Aberrant CSF into embryologic perimedullary mesh that will make up the leptomeningies.
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Quadrigeminal cysts Katie Phillips DVM August 16, 2010
Intracranial Arachnoid Cysts • Intra-arachnoid accumulations of CSF • Pathogenesis: • Aberrant CSF into embryologic perimedullary mesh that will make up the leptomeningies. • The choroid plexus propulses CSF into perimedullary mesh dividing it into pia matter and arachnoid membrane.
Intracranial Arachnoid Cysts • Most commonly in the quadrigeminal cistern in dogs • 56 cases in veterinary literature. • Predominantly brachycephalics • Shih tzus are overrepresented 15/56 • Dogs in literature ages 2 months – 12 years. • Usually incidental finding in humans • Represent 1% of intracranial masses in humans.
Intracranial arachnoid cysts • May be incidental • Concurrent disease • Cause a compressive lesion • Other developmental anomalies • Present with central vestibular or forebrain signs. • Histologically the cyst lining will look like normal arachnoid membrane.
Imaging intracranial arachnoid cysts • Fluid is the same as CSF • On CT – cysts are isodense to CSF • Do not contrast enhance • On MRI – cysts are isointense to CSF • Do not contrast enhance • Extra-axial
Ultrasound intracranial arachnoid cysts • Persistent bregmaticfontonelle – best images if available • Temporal window – Between zygomatic arch, parietal and temporal bones, area of thinnest bone. Can get majority of brain in image. Depends on thickness of bone. • Foramen magnum – Can see cranial to the thalamic adhesion. Careful ventroflexion.
Ultrasound quadrigeminal cysts Transverse image through bregmatic fontanelle. Lateral ventricles are enlarged. Mesencephalic aqueduct ventral Triangular shaped cysts Sagittal through bregmaitc fontanelle Quadrigeminal cysts (arrow) Interthalamicadehesion (astrix)
References • Dewey CW, Scirvani PV, Ursula K, Cerda-Gonzalez. Intracranial arachnoid cysts in dogs. Compendium: Continuing education for veterinarians. 2009. • Vernaud, Kortz, Koblick, et al. Magnetic resonance and computed tomography of intracranial intra-arachnoid cysts in six dogs. Vet rad and us. 1997 38:3 • Saito M, Olby N, Spaulding K. Identification of arachnoid cysts in the quadrigeminal cistern using ultrasonography. Vet rad us. 2001. 42:5