Quadrigeminal cisterna arachnoid cyst diagnosed by MRI in five dogs

Abstract

Arachnoid cysts of the quadrigeminal cisterna are infratentorial cystic lesions located between the collicular plate and the incisural notch of the tentorium. We report here five cases of quadrigeminal cisterna arachnoid cysts in dogs. In this study, four of the five dogs were male, three showed signs of seizures, and one dog was over 10 years of age. In two of the dogs, cysts were discovered incidentally. In previous reports, most intracranial arachnoid cysts were located in the quadrigeminal cisterna. The presence of cysts should be considered in toy breeds presenting for seizures or ataxia.

Intracranial Intra-arachnoid Diverticula and Cyst-like Abnormalities of the Brain

“…Typical imaging characteristics include (1) extra-axial, midline, frequently supracollicular location; (2) fluid similar in appearance to that of CSF; and (3) lack of contrast enhancement of the tissue immediately surrounding the fluid on MRI or CT. 18 A hypointense fluid-filled structure on T1-weighted images, which is hyperintense on T2-weighted images and fully suppresses with fluid-attenuated inversion recovery (FLAIR) imaging, is typically seen on MRI. 5,16,30 Hemorrhage into the lumen of these cysts has been documented to have a signal intensity that is mixed or hyperintense to CSF in T1-weighted images and isointense to hypointense to CSF on T2-weighted images with lack of suppression on FLAIR. 9,14 The appearance of intracystic hemorrhage varies with its age, amount, hemoglobin oxygen state, and the strength of the magnetic field, but gradient echo images may aid in diagnosis.…”

“…10,11,14,[16][17][18][19][20] Subarachnoid diverticula have been reported within the fourth ventricle in five nonbrachycephalic large breed dogs, indicating that the brachycephalic predisposition may only occur for IADs in dogs. Age at presentation varies widely, and is likely related to whether the IAD is incidental or contributes to clinical signs along with another intracranial disease.…”

“…18,19 Some investigators believe that the breed predisposition for ventriculomegaly, where observed, is the same as the predisposition for IADs, indicating that these two developmental disorders may have a common cause given that there is inadequate evidence that the diverticula are the cause of hydrocephalus in dogs affected with both. 19 Diagnosis CT, MRI, and ultrasonography have all been described as imaging modalities used to assist in the diagnosis of IADs in veterinary medicine 5,[14][15][16][17][19][20][21]30 (Fig. 1).…”

“…19 Clinical signs that were attributable to the cysts in this study included focal or generalized seizures and cerebellar/vestibulocerebellar signs; however paresis, a reduced level of consciousness, facial nerve paresis, and neck pain have also been reported. 5,10,11,[14][15][16][17][18][19][20][21]30 Overall, clinical signs reflect the location of the cyst and most likely occur as a result of compression of the neural tissue. Based on an MRI study, occipital lobe compression greater than 14% is likely to cause clinical signs, whereas the degree of cerebellar compression is not significantly associated with the occurrence of clinical signs.…”

“…They might be an incidental imaging or postmortem finding 18,19,23,27-29 or give Platt et al rise to severe neurologic dysfunction. 5,11,15,16,[18][19][20][21]23,27,29,30 In more than half of dogs retrospectively evaluated for intracranial disease, an IAD was considered an incidental finding. 19 Clinical signs that were attributable to the cysts in this study included focal or generalized seizures and cerebellar/vestibulocerebellar signs; however paresis, a reduced level of consciousness, facial nerve paresis, and neck pain have also been reported.…”