The tectum, the dorsal (roof) part of the midbrain, is primarily responsible for integrating visual and auditory reflexes and coordinating eye and head movements. Tectal gliomas (Tectal Plate Gliomas, TPGs) are tumors localized within the tectal plate, typically benign, and classified as low-grade (WHO Grade I) gliomas. Due to their low-grade nature, they are known to grow slowly.
Tectal gliomas most commonly develop during childhood (ages 3–16). Despite being located in the tectal plate, which is adjacent to critical brainstem structures, these tumors generally have a favorable prognosis.
Pathological Features
Tectal gliomas are generally characterized by pilocytic astrocytoma (WHO Grade I) histology. However, in some cases, high-grade gliomas can be observed. For instance, certain tectal gliomas may display diffuse astrocytoma (WHO Grade II) features. In these cases, the infiltrative growth pattern and histological characteristics resemble those of diffuse astrocytomas. Nonetheless, these occurrences are rare, and the majority of tectal gliomas exhibit pilocytic astrocytoma features with a favorable prognosis.
Molecular profiling further differentiates tectal gliomas from other low-grade gliomas. DNA methylation profiling is particularly useful in distinguishing tectal gliomas as a distinct clinicopathologic entity.
Symptoms
Due to their proximity to major motor and sensory pathways of the brainstem, tectal gliomas may cause a range of neurological symptoms:
Headache: Slowly progressive, often more pronounced in the morning.
Parinaud Syndrome: Impaired upward gaze and diplopia (double vision).
Obstructive Hydrocephalus: Blockage of cerebrospinal fluid flow can lead to headache, nausea, vomiting, and balance disturbances.
Gait and Balance Impairment: Motor pathway involvement may result in walking difficulties and coordination problems.
Cognitive Changes: Particularly in children, learning difficulties and attention deficits may be observed.
Diagnostic Methods
Key diagnostic tools for tectal gliomas include:
Neurological Examination: Comprehensive assessment of motor, sensory, and cranial nerve functions.
Magnetic Resonance Imaging (MRI): Typically reveals iso- to hypointense lesions in the tectum; contrast enhancement is minimal or absent.
Treatment Approaches
Management of tectal gliomas depends on symptomatology and tumor growth rate:
1. Surgical Intervention
Gross total resection may often be unfeasible due to anatomical challenges and the critical location within the brainstem. Typically, microscopic resection (subtotal/near-total) is performed under neuronavigation and neuromonitoring.
If surgery is not feasible, a stereotactic biopsy can be performed to establish a pathological diagnosis and guide treatment planning.
2. Shunt Placement
In cases of obstructive hydrocephalus, a ventriculoperitoneal (VP) shunt can relieve intracranial pressure and alleviate neurological symptoms.
3. Chemotherapy and Radiotherapy:
Reserved for treatment-resistant or progressive cases (high-grade gliomas).
4. Targeted Therapy
In pediatric cases, molecular-targeted therapies may be considered depending on tumor pathology (e.g., BRAF mutation or KIAA1549::BRAF fusion).
Prognosis
Tectal gliomas are typically slow-growing and benign. With appropriate monitoring and symptom management, the tectal glioma survival rate is favorable. Patients can often maintain a normal quality of life over the long term. Understanding the molecular and histopathological characteristics of these tumors is essential for prognosis and treatment planning.
For patients and families, learning about living with a tectal glioma includes understanding the potential neurological impacts, the importance of regular imaging follow-up, and collaborative care from a multidisciplinary team.