Title:Ventrikuloszkópia kutyában: parieto-occipitalis ciszta fenesztrációja endoszkóppal az oldalsó agykamra irányába
SUMMARY Background: Arachnoid cyst is a developmental disorder which can cause compression of the brain and due to this neurological symptoms could occur. A special intracranialintra arachnoid cyst (IAC) is called quadrigeminal cyst (QC) which can develop due to arachnoid duplication. A study described 4100 retrospective MRI evaluations and found 28 QC-affected dogs. Based on that study, a characteristic MRI sign of QC is a hypointense area on T1-weighted images, a hyperintense lesion on T2-weighted images and a non contrast-enhancing lesion with intravenous gadolinium administration and that suppressed on FLAIR in the midline, dorsal to the midbrain, caudal to the occipital lobe and rostral to the cerebellum. The size and place of the cyst determine the severity of the clinical signs. In most of the cases the cysts do not cause health damage. If the cyst causes neurological deficit, conservative or surgical therapy is recommended. In human medicine some surgical methods have been published. Microsurgical fenestration from craniotomy, endoscopy-guided fenestration, cystoperitoneal shunt placement are the most useful techniques. Most common complications during endoscopy-guided fenestration technique are postoperative epidural hemorrhage and haematoma.Materials and Methods, Results and Discussion: The parieto-occipitally located arachnoid cyst, as a special type of QC, was fenestrated by endoscopy towards the right lateral ventricle in the case of a 16-month-old Hungarian Grey-hound. The dog had a refractory epilepsy which was treated with antiepileptic drugs (AED) like phenobarbital, levetiracetam and carbamazepine tablets. Laboratory and abdominal ultrasound examinations did not find any abnormalities. MRI exami-nation found a 49.8 mm x 27.3 mm x 20.0 mm sized cyst-like material between the occipital lobe and cerebellum. The cyst-like lesion shown, a hyperintensity on T2-weighted images, hypointensity on T1-weighted area. During the surgery the cyst wall was fenestrated toward the right lateral ventricle with an endoscopic instrument. Despite the initially observed good signs, 12 hours after the surgery the dog died. Necropsy and histopathological examination showed epidural hae-matoma leading to transtentorial herniation and collapsed, empty arachnoid cyst.