A glioma is a tumor that originates from the glial (connective/supporting) cells of the brain. Since glial cells are present throughout the central nervous system, gliomas can occur in various places in the brain or spinal cord. A thalamic glioma, as its name implies, is a glial tumor characterized by a primary growth center within or very near the thalamus, a structure located in the center of the brain. These tumors are very rare and account for a small minority of brain tumors in children and young adults.
The thalamus, a paired structure that is positioned just above the brainstem in the center of the brain, is a major processing and relaying center for sensory information traveling between the body and the cerebral cortex (the brain surface). It also plays a role in movement, and in regulating sleep states, consciousness, and awareness. The thalamus sits in close proximity to the lateral and third ventricles (chambers in which cerebrospinal fluid, or CSF, flows). The two thalami are interconnected through fibers that travel across the brain’s midline. It is through these connections that thalamic gliomas can frequently cross over to involve both sides of the brain (bilateral thalamic glioma).
While any glial cell (astrocyte, oligodendrocyte, or gangliocyte) can give rise to a thalamic glioma, the overwhelming majority are derived from astrocytes and are referred to as astrocytomas. Astrocytomas are further subdivided based degree of aggressiveness:
Grading a Glioma
Grade 1 tumors are benign and have the best prognoses. For the most part they are focal tumors, meaning they have well-defined borders, though some can be diffuse, with less defined borders.
Grade 2 tumors are also considered benign, but they can be more aggressive or infiltrative than grade 1 tumors. Even though Grade 1 and 2 tumors are both referred to as “low-grade tumors,” Grade 2 tumors are expected to eventually transition into Grade 3 astrocytomas.
Grades 3 (anaplastic astrocytoma and oligodendrogliomas) and 4 (astrocytomas including glioblastoma multiforme) tumors are more aggressive and are grouped together as malignant tumors.
Treatment options and prognosis depends on the grade and molecular characteristics of the tumor, so tissue diagnosis is crucial (find out more about Diagnosing and Treating a Thalamic Glioma).
Since thalamic gliomas are complicated tumors in a delicate area, they are best diagnosed and treated at a specialized medical center. Many doctors have never seen a thalamic glioma – at Weill Cornell Medicine Pediatric Neurosurgery, we see some of the most challenging brain tumors from around the country, and around the world.
Reviewed by Umberto Tosi, MD
Last reviewed/last updated: September 2024
Illustration by Thom Graves, CMI
