Intracranial Cysts
Amar Bhide, Asma Khalil, Aris T Papageorghiou, Susana Pereira, Shanthi Sairam, Basky Thilaganathan in Problem-Based Obstetric Ultrasound, 2019
Cystic structures in the posterior fossa include: Enlarged cisterna magna when it is >10 mm in the transverse cerebellar view. Detailed ultrasound is needed to demonstrate this is isolated and that the cerebellum and vermis are normal. It can be associated with ventriculomegaly, but if it remains isolated and does not progress, prognosis is generally good.Blake's pouch cysts represent a communication between the 4th ventricle into the cisterna magna and appear as a unilocular cyst without any Doppler flow. Careful assessment is mandatory to ensure the remainder of the brain—in particular cerebellum and vermis—are normal. This is usually isolated, and most will resolve spontaneously.In Dandy-Walker malformation there is dilation of the fourth ventricle in the posterior fossa and that extends into the cisterna magna. The cerebellar vermis will be hypoplastic or absent. The condition is often associated with chromosomal abnormalities (mainly trisomy 18 and 13) or genetic syndromes. Coexisting abnormalities are very common, as is severe ventriculomegaly. The outlook is guarded.
Anatomical considerations
Hemanshu Prabhakar, Charu Mahajan, Indu Kapoor in Manual of Neuroanesthesia, 2017
The CSF fills the subarachnoid space as well as the ventricles of the brain and central canal of the spinal cord. It is formed by the choroid plexuses in the lateral, third and fourth ventricles of the brain.1,2,10 The CSF formed in each of the lateral ventricles flows through the foramen of Monro (interventricular foramen) into the third ventricle and then through the cerebral aqueduct (aqueduct of Sylvius) to the fourth ventricle. From the fourth ventricle, it passes to the subarachnoid space through the three openings in the roof of the fourth ventricle (two lateral openings called the foramen of Luschka and a median opening called the foramen of Magendie) and into the central canal of the spinal cord. The CSF flows through the subarachnoid space around the brain and spinal cord and drains into the superior sagittal sinus through arachnoid granulations (arachnoid villi) (Figure 1.13).2,10 The subarachnoid space closely follows the contours of the brain, but in certain regions the arachnoid mater diverges away to form large spaces filled with the CSF, called cisterns. The largest of these cisterns is called the cisterna magna or cerebellomedullary cistern, which is located between the cerebellum and the medulla oblongata. The CSF from the fourth ventricle passes into this cistern through the foramen of Luschka and foramen of Magendie.1 Other major cisterns present are the superior cistern or cisterna ambiens between the cerebellum and midbrain, pontine cistern or prepontine cistern in front of the pons, and interpeduncular cistern between cerebral peduncles.
Cheryl
Walter J. Hendelman, Peter Humphreys, Christopher R. Skinner in The Integrated Nervous System, 2017
There is a circulation of CSF within the ventricles, with the flow being from lateral ventricles to the third ventricle, and then via a narrow aqueduct in the midbrain to the fourth ventricle in the pontine region (black arrows in Figure 9.5). At the lower end of this ventricle, CSF ‘escapes’ into the subarachnoid space, the cerebello-pontine cistern, known generally as the cisterna magna. Cisterns are enlargements of the subarachnoid space, and several others are found around the brainstem; the largest of these is the cisterna magna, located behind the brainstem and below the cerebellum, in the posterior cranial fossa, just above the foramen magnum (see Figure 9.5).
Pure endoscopic resection of pineal region tumors through supracerebellar infratentorial approach with ‘head-up’ park-bench position
Published in Neurological Research, 2023
Wei Hua, Hao Xu, Xin Zhang, Guo Yu, Xiaowen Wang, Jinsen Zhang, Zhiguang Pan, Wei Zhu
Patients were placed in the modified left ‘head-up’ park-bench position, with the upper body elevated and the head slightly extended instead of anteflexion. The head was then secured in place with a Mayfield three-pin head clamp and slightly flexed. Neuronavigation was registered in the Stryker Navigation System (Stryker, Kalamazoo, Michigan) and used to determine the optimal ‘head-up’ angle. An occipital midline skin incision and craniotomy approximately 3 × 3 cm in size were made (Figure 1 d and e). A U-shaped dural incision was made, and the cerebrospinal fluid of the cisterna magna was slowly released to further decrease the intracranial pressure. Through the combination of gravity assistance and reduced pressure, the corridor between the cerebellum and the tentorium could be easily opened.
Prenatal diagnosis of Emanuel syndrome – case series and review of the literature
Published in Journal of Obstetrics and Gynaecology, 2022
Patrycja Piwowarczyk, Diana Massalska, Izabela Obodzińska, Sylwia Gawlik Zawiślak, Julia Bijok, Anna Kucińska-Chahwan, Tomasz Roszkowski
The third unrelated patient at the age of 36 years (gravida 2 para 1) was referred to our department at 13 gestational weeks due to foetal cerebral malformations visualised during routine first-trimester scan and increased nuchal translucency (3.9 mm). Her medical history was unremarkable and there was no family history of genetic disorders. The ultrasound examination performed in our department revealed an enlarged cisterna magna, parallel cerebral peduncles and dilated cerebral aqueduct (Figure 3). Additionally, hypoplastic right ventricle was diagnosed. Chorionic villus sampling was performed due to foetal abnormalities and a pathogenic genomic imbalance, consistent with ES, was diagnosed by CMA – 11q23.3q25x3, 22q11.1q11.21x3. After genetic counselling, the patient decided to terminate the pregnancy. Parental karyotyping is pending.
Case report: Development of syringomyelia after anatomically successful craniovertebral decompression for Chiari I malformation without syrinx
Published in British Journal of Neurosurgery, 2022
The development or worsening of syringomyelia is a recognised complication in Chiari I patients who undergo craniovertebral decompression. It is usually seen in the context of a recurrent obstruction to CSF flow across the craniovertebral junction and then raises the question of whether the original surgery achieved sufficient patency of the Foramen Magnum to CSF flow, particularly in terms of reduction of the cerebellar tonsils and the use of a duraplasty graft. The phenomenon of “cerebellar slump” is also a recognised, occasional development after craniovertebral decompression and could result either from elevated pressure above or reduced pressure below. In our case, however, late post-operative MRI and CISS imaging revealed a well-formed artificial cisterna magna and good flow of CSF at the level of the foramen magnum, despite the relatively low position of the cerebellum. Post-operative cicatrix was confined to the region of Magendie but with no evidence of ventriculomegaly. Given the patient’s modestly elevated intracranial pressure, this was initially thought to be the syrinx filling mechanism and insertion of a VP shunt was seen to be less risky than a re-exploration of the craniovertebral junction. In the event, CSF diversion did not produce any clinical or radiological improvement. It was only when Magendie was re-explored, and the IVth ventricle opened into the previously created artificial cisterna magna, that the syrinx collapsed.
Related Knowledge Centers
- Fourth Ventricle
- Glossopharyngeal Nerve
- Median Aperture
- Meninges
- Posterior Inferior Cerebellar Artery
- Medulla Oblongata
- Vertebral Artery
- Subarachnoid Cisterns
- Spinal Canal
- Vagus Nerve