Anatomy of the cerebellar bridge angle
The cerebellar bridge angle (angulus pontocerebellaris) is the name of a certain anatomical structure of the brain. It is located between the brain stem (consisting of midbrain = mesencephalon, rhombic brain = rhombencephalon and bridge = pons) and the cerebellum and petrous bone. It is located in the posterior fossa.
The cerebellum bridge angle represents a niche through which important cranial nerves pass in a narrow space. The nervus intermedius and the nervus facialis (together forming the 7th cranial nerve) and the nervus vestibulicochlearis (the 8th cranial nerve) originate here from the brain structure and move to their supply areas. In addition, the arteria cerebelli inferior anterior and the arteria cerebelli inferior posterior pass through the cerebellar bridge angle. Brain veins belonging to the petrosiatic sinus also pass through here. The cerebellar bridge angle is so well known because tumors can frequently occur in this region, which quickly become symptomatic (cranial nerve deficits) due to the narrow anatomical situation.
Tumors in the cerebellar bridge angle
Spatial masses in the cerebellar bridge angle are conspicuous by early symptoms. The diagnosis of choice is an MRI. Often the tumors are benign.
However, due to the anatomical narrowing in the cerebellar bridge angle, their growth causes them to press on the cranial nerves running along there and thus lead to cranial nerve deficits. In order to understand the failure symptoms, it is necessary to know what functions the cranial nerves have. The 7th cranial nerve, the facial nerve, innervates the muscles in the face with its motor fibers.
If this nerve fails, the patient has facial paresis (one half of the face hangs limply down). The 8th cranial nerve, the nervus vestibulocachlearis, is responsible for hearing and balance. If it is affected, the patient will therefore have a hearing loss and possibly tinnitus and dizziness.
There are various tumors that can cause space-occupying symptoms. The most common are acoustic neuroma (vestibularis schwannom), but also meningiomas, epidermoids, glomus-jugular tumors and brain metastases. The acoustic neuroma is a benign tumor that originates from the Schwann cells of the 8th cranial nerve.
It can also be located in the inner ear canal, which is more common than its location in the cerebellar bridge angle. Patients complain of hearing loss, often associated with dizziness and tinnitus. Meningiomas are tumors originating from the meninges.
Epidermoids are congenital, rare tumors. Glomusjugular tumors originate from the paraganglia in the pit of the temporal bone (fossa jugularis). Brain metastases are daughter tumors, the primary tumors are often lung cancer, breast cancer, renal cell cancer and black skin cancer.
