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Disease involving the cerebellopontine angle (CPA) may arise from structures located within the cistern or from extension of lesions located primarily outside the cistern—from the brainstem, fourth ventricle, choroid plexus and bony skull base. The symptoms and signs of CPA disease are non-specific, relating either to compression of the neural structures found within it or from compression of the fourth ventricle with resulting obstructive hydrocephalus. Imaging is vital for diagnosis and management planning. The main features to note are the site of origin, shape, density, signal intensity and pattern of enhancement of the lesion.
The CPA is an inverted, triangular subarachnoid space containing cranial nerves (5–11) and blood vessels bathed in cerebrospinal fluid (CSF), located in the lateral aspect of the posterior fossa (figure 1). The tentorium forms the base of the triangle and the posterior temporal bone forms its lateral boundary. The pons is located medially and the cerebellum is posterior. The cistern extends into the petrous bone as the internal auditory canal, its medial aperture being known as the porus acousticus. The trigeminal nerve crosses the superior aspect of the cistern from the lateral pons to Meckel's cave. The facial and vestibulocochlear nerves arise from low in the CPA cistern at the lateral aspect of inferior medulla; they emerge at the level of the foramen of Luschka and ascend to the porus acousticus. The facial nerve lies anterior and superior to the vestibulocochlear nerve. Both are intimately related to the anterior inferior cerebellar artery, which in two-thirds of people loops into the internal auditory canal on at least one side.
Cranial nerves 9–11 arise from the medulla and upper cervical cord, cross the inferolateral aspect of the …
Competing interests None.
Provenance and peer review Commissioned; internally peer reviewed.