Different windowing options apart from standard brain window are available such as narrower subdural, bone and soft tissue windows should be viewed in all planes. Looking for grey white matter differentiation and CSF spaces are mandatory in all planes. Systematic approach of posterior cranial fossa on various views is listed below:
Axial
- Midbrain: vermis, cisterns - quadragerminal and interpeduncular cisterns, superior saggital sinus
- Pons - CP angle, transverse and sigmoid sinus, inner ear ossicles, cisterns – prepontine and fourth ventricle, mastoid air cells – mastoiditis
- Medulla - foramen magnum and jugular foramen
Coronal
- Tentorium cerebelli
- Mastoid air cells, cranio-cervical junction
- Hypoglossal canal
Saggital
- Foramen magnum
- Cisterns and CSF spaces
Some of the common pathologies encountered within the posterior cranial fossa are listed below:
- Congenital malformations - Arnold-Chiari malformations
- Dandy-walker variants - vermian hypoplasia, fourth ventricular enlargement, increased posterior fossa fluid spaces.
- Infarction - Mortality within this region is quite high with figures reaching up to 50% due to brainstem compression and obstructive hydrocephalus. [1]
- Tumours - metastasis and hemangioblastoma are most common. Cerebellopointine angle tumours like vestibular schwannoma
- Vascular – hyperdense basilar artery sign
- Dural venous sinus - thrombosis
- CSF spaces – intraventricular hemorrhage, cisterns obliterated due to adjacent mass effect, tumours, tonsillar herniation
Pitfalls:
- Arachnoid granulations being interpreted as filling defects
- Hyperdense choroid plexus at the foramina of Luschka commonly mistaken for hemorrhage.
- Variant anatomy such as mega cisterna magna