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Thalamic gliomas are very rare, deep-seated, generally high-grade glial neoplasms that form in the thalamus, representing 1–5% of all pediatric brain tumors.[1] Because of their difficult to reach position, they are a unique and difficult challenge for neuro-oncologists and neurosurgeons.
| Thalamic glioma | |
|---|---|
| Specialty | Neuro-oncology, neurosurgery |
| Causes | Unknown |
| Prevention | Unknown |
| Treatment | Watchful waiting, radiation therapy, chemotherapy, resection |
| Prognosis | Two year survival rate 19.7% (adults), pediatric five year survival rate 15-25% (high grade astrocytoma) or 40% (low grade astroyctoma) |
Thalamic gliomas are most often discovered on magnetic resonance imaging following symptoms, with the most common presenting symptom being motor deficit.[2] While a definitive diagnosis of the neoplasm cannot be made without a biopsy of the tumor, biopsies have historically been avoided due to the extreme sensitivity of the region.
Bithalamic glioma
A notable variant of thalamic gliomas are bithalamic gliomas. Bithalamic gliomas cross the interthalamic adhesion and occupy space in both thalami. These have poorer outcomes than unilateral thalamic gliomas.[3]
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Unless a thalamic glioma shows aggressive behavior, they are often treated with a "watch and wait" approach until signs of growth occur.[4] Thalamic gliomas can be treated with radiotherapy, chemotherapy, and/or resection.[5]
Resection
Thalamic gliomas are among the most difficult challenges a neurosurgeon faces today. Historically, thalamic gliomas were considered inoperable.[6] Advances in neurosurgical technology have opened up the thalamic area to resection, but conservative approaches remain popular.[7] Microsurgical approaches are well suited for thalamic gliomas.[8]
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Thalamic gliomas have a poor prognosis. In adult patients, the overall two-year survival rate is 19.7%, with low grade tumors holding a two-year survival rate of 31.0% and high-grade tumors holding a two-year survival rate of 16.5%.[2] In pedtiatric patients, low-grade astrocytomas held a five-year survival rate of 40% while high-grade astrocyte tumors held a five-year survival rate that varies between 15% and 25%.[9] Strangely, pediatric thalamic oligodendrogliomas appear to have a far worse prognosis than thalamic astrocytomas, with a three-year survival rate of 14% in one series.[9]
Higher Karnovsky performance status and CSF diversion[10] are good prognostic markers in cases that match the criteria for glioblastoma.
While the H3K27m mutation that is the distinct marker of a diffuse midline glioma is generally a very poor prognostic factor, it is unusually associated with slightly higher rates of survival in adult thalalmic glioma patients.[11]
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Thalamic gliomas are often but not exclusively diffuse midline gliomas; other varieties of glial tumor can develop in this region.[2]
- Tammi Terrell (1945–1970), Motown singer that died from an "acorn size" tumor in her thalamus[12]
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