Brain tumors are categorized in several ways, but one of the most fundamental classifications is based on their location. The distinction between supratentorial and infratentorial tumors arises from where they develop in relation to a specific anatomical landmark within the skull. This difference in location profoundly influences the type of tumor that is likely to develop, the symptoms a person might experience, and the approaches taken for treatment.
The Anatomical Divide
The brain is separated into upper and lower compartments by a durable sheet of tissue called the tentorium cerebelli. Any tumor that develops above this dividing line is classified as supratentorial. This upper region is the largest part of the cranial cavity and contains the cerebrum, which is divided into left and right hemispheres responsible for higher-level functions like thought, personality, speech, and voluntary movements.
Conversely, the area below this dural fold is the infratentorial region. This more compact space houses two structures: the cerebellum and the brainstem. The cerebellum, located at the back of the skull, is the control center for balance, coordination, and fine motor skills. The brainstem connects the brain to the spinal cord and manages autonomic functions necessary for survival, including breathing, heart rate, and consciousness.
Common Tumor Types by Location
The types of tumors that commonly arise in these two regions differ, with a notable divergence in their prevalence between adults and children. In adults, the majority of primary brain tumors are supratentorial. Among the most frequent are gliomas, a category that includes astrocytomas and the more aggressive glioblastomas. Meningiomas, which grow from the meninges (the layers of tissue covering the brain), are also a common type of supratentorial tumor in adults.
In children, the pattern is reversed, with most pediatric brain tumors being infratentorial, accounting for up to 60% of all brain tumors in this population. Common examples found in the posterior fossa (the space containing the cerebellum and brainstem) include medulloblastomas, ependymomas, and cerebellar astrocytomas.
Distinct Symptom Profiles
The symptoms of a brain tumor are directly linked to its location and the brain functions it disrupts. Since the supratentorial region governs cognition and voluntary actions, tumors here often manifest with symptoms like seizures. Patients may also experience personality or behavioral changes, difficulties with memory and concentration, or problems with speech and language. Because the cerebrum’s hemispheres control opposite sides of the body, a tumor in this area can cause weakness, numbness, or sensory changes isolated to one side.
Infratentorial tumors produce a different set of symptoms related to the functions of the cerebellum and brainstem. Problems with balance (ataxia) and a loss of coordination are hallmark signs. Patients might also experience dizziness, double vision, facial weakness, or difficulty swallowing due to pressure on cranial nerves. These tumors can also obstruct the flow of cerebrospinal fluid (CSF), leading to hydrocephalus, which increases pressure inside the skull and often causes severe headaches, nausea, and vomiting.
Treatment and Prognostic Factors
A tumor’s location adds a layer of complexity to treatment planning, alongside its type, grade, and the patient’s overall health. Surgical accessibility is heavily influenced by whether a tumor is supratentorial or infratentorial. For example, operating on a tumor located near the brainstem carries substantial risks due to the concentration of vital functions in that small area.
The prognosis depends on a combination of factors, and the ability to perform a complete surgical resection is a major prognostic indicator. For some supratentorial tumors, such as certain meningiomas near the brain’s surface, complete removal may be more achievable. In contrast, infratentorial tumors, particularly those that invade the brainstem, present greater surgical challenges, which can influence long-term outcomes.