Tentorium cerebelli is the second largest extension or fold of the dura mater after falx cerebri. In Latin, tentorium cerebelli means the ‘tent of the cerebellum’, which splits the cerebellum from the occipital (posterior) lobes of the cerebrum. Tentorium cerebelli comprises of attached and free margins that are related to several structures and cavities of the brain. It covers the cerebellum and supports the occipital lobes from below. To its anterior, midbrain and cerebral aqueduct are present.
Tentorium cerebelli is an important tool of diagnosing type of tumor in the nearby regions to it. Brain tumors are commonly referred to as supratentorial, if present above the tentorium cerebelli, or infratentorial, if found below it. It should be mentioned here that most juvenile tumors occur above the tentorium cerebelli, while adult brain tumors most often occur above it.
Clinical Importance – Associated Diseases/Conditions
Ascending Transtentorial Herniation: It is a condition in which upper parts of cerebellum herniate through the tentorial notch due to a lesion or tumor or any other growth in the posterior part of cranium such as an infarct or perhaps due to increased cerebrospinal fluid as in hydrocephalus, thus putting pressure on cerebellar contents. Patient may experience nausea and/or vomiting, progressive decrease in consciousness and may ultimately lead to death.
Uncal Transtentorial Herniation: It is a common type of transtentorial herniation in which the uncus (deepest part of temporal lobe) is pushed towards the tentorium, thereby compressing the brainstem. This can result in the pressing of oculomotor nerve thus causing pupillary dilation and oculomotor nerve palsy (third nerve palsy) in which several muscles of eye are paralysed. Uncal herniation can seriously impair blood supply of some structures and may lead to ischemia and possibly tissue death (infarction).
Normal Intracranial Calcification: It is an age-related process that does not produce any signs or symptoms and apparently poses no risk to the quality of life of the patient. This process has been observed in other parts of the brain, but the folds of the dura mater are significant since it occurs in approximately 10% of the elderly population.
Hematoma of Tentorium Cerebelli: Rarely though, a hematoma of the tentorium cerebelli has occurred in some cases of trauma to the back of the head (occiput). Typically, a subdural hematoma can collect in the potential spaces in and around the tentorium due to tearing of adjacent blood vessels as a result of back head trauma. Surgery may be considered in cases of large bleeds or in rapid progression of mental deterioration.