Gangliogliomas of the optic pathway

Rare Neuronal, Glial and Glioneuronal Tumours in Adults

Rare glial, neuronal and glioneuronal tumours in adults form a heterogeneous group of rare, primary central nervous system tumours. These tumours, with a glial and/or neuronal component, are challenging in terms of diagnosis and therapeutic management. The novel classification of primary brain tumours published by the WHO in 2021 has significantly improved the diagnostic criteria of these entities. Indeed, diagnostic criteria are nowadays multimodal, including histological, immunohistochemical and molecular (i.e., genetic and methylomic). These integrated parameters have allowed the specification of already known tumours but also the identification of novel tumours for a better diagnosis.

Suprasellar Ganglioglioma Arising from the Third Ventricle Floor: A Case Report and Review of the Literature

Gangliogliomas are uncommon intracranial tumors that include neoplastic and abnormal ganglion cells, and show positive immunohistochemical staining for GFAP and syn. This type of lesion occurs more frequently in the temporal lobe than in other areas; they are extremely rare in the suprasellar region. To the best of our knowledge, including our case, 19 cases of GGs have been found in the suprasellar region. Among them, five tumors invaded the optic nerve, nine tumors invaded the optic chiasm, one tumor invaded the optic tract, and two tumors invaded the entire optic chiasmal hypothalamic pathway. In the present study, we describe the first case of suprasellar GGs arising from the third ventricle floor that was removed through the endoscopic endonasal approach. In addition, we summarize the clinical characteristics of GGs, such as age of onset, gender distribution, MRI signs, main clinical symptoms, and treatment methods for GG cases.

[Chiasmatic syndrome]

The optic chiasm is an essential anatomical structure in neuro-ophthalmology. The systematization of the visual pathways results from the arrangement of the retinal ganglion cell fibers. It explains the signs of chiasmal syndrome. A good knowledge of the anatomy permits to correlate visual field defects with imaging results. It is now possible to map the organization of the ganglion cell fibers within the chiasm. Their hemidecussation allows for stereoscopic vision in humans. The causes of chiasmal syndrome are multiple, but tumors and compressive causes predominate. The proximity of the pituitary region to the chiasm accounts for the frequency of chiasmal syndrome, which involves ophthalmologists not only through dysfunction of the visual pathway, which may be the presenting sign, but also through possible complications throughout the course of the disease. This review aims to synthesize the embryology, anatomy and principles of work-up for chiasmal syndrome as well as its many possible causes.

Pediatric Optic Pathway/Hypothalamic Glioma

Optic pathway/hypothalamic gliomas (OP/HGs) are rare astrocytic tumors that appear more commonly among young children and often are unresectable. They comprise approximately 2% of all central nervous system tumors and account for 3–5% of pediatric intracranial tumors. Initial manifestations are often visual disturbances, endocrinopathies and hypothalamic dysfunction such as the diencephalic syndrome, and sometimes hydrocephalus due to cerebrospinal fluid (CSF) outflow obstruction. In many cases, the tumors are diagnosed late in the clinical course because they silently enlarge. These tumors consist mostly of histologically benign, World Health Organization (WHO) grade I tumors represented by pilocytic astrocytomas (PA), the rest being pilomyxoid astrocytomas (PXA) – WHO grade II tumors. In young pediatric patients, however, can be seen PXA that show aggressive clinical course such as CSF dissemination. Our small series of 14 non-Neurofibromatosis type 1 (NF-1) OP/HGs PA patients underwent extended resection without any adjuvant treatments. The median age at initial treatment was 11.5 ± 6.90 years (range, 1–25 years) and median follow up 85.5 ± 25.0 months. Surgical resection for OP/HGs results in acceptable middle-term survival, tumor control and functional outcome equivalent to chemotherapy. There is, however, no longer doubt that chemotherapy with or without biopsy and as-needed debulking surgery remains the golden standard in management of OP/H. Clinical conditions and treatment plans for OP/HGs vary depending on their structure of origin.

Discrepancy between radiological and histological findings in ganglioglioma of the optic chasm: Case report

BACKGROUND

Gangliogliomas involving the optic nerve or chiasm are extremely rare tumors, which can be confused radiologically with other neoplasms. α-[N-methyl-¹¹C]-methylaminoisobutyric acid (¹¹C-MeAIB) is a new artificial amino acid positron emission tomography (PET) tracer, which is metabolically more stable in vivo and may be more specific for tumors than ¹¹C-methionine. However, the utility of ¹¹C-MeAIB PET in the diagnosis of brain tumors has not yet been reported.

CASE DESCRIPTION

A 26-year-old man presented with visual field defects and headache, and magnetic resonance imaging demonstrated a suprasellar mass involving the optic chiasm. A biopsy and partial tumor resection were performed via an interhemispheric approach. We diagnosed the tumor as ganglioglioma (WHO grade I) involving the optic chiasm. Although this lesion was histologically benign, ¹¹C-MeAIB PET, 2-deoxy-2-[¹⁸F] fluoro-D-glucose (¹⁸F-FDG) PET and proton magnetic resonance spectroscopy indicated malignant features.

CONCLUSION

The discrepancy between radiological and histological findings implies that this new amino acid tracer PET may have a limitation in the diagnosis of gangliogliomas. Although further study is necessary, gangliogliomas should be included in the differential diagnosis of suprasellar tumors, even if PET findings show malignant features.

Bilateral Optic Pathway Ganglioglioma: The Fifth Case in the Literature

Gangliogliomas are mixed tumors which contain both glial and neuronal elements. The optic pathway is a very rare location for gangliogliomas, with less than 23 cases reported in the literature. Bilateral involvement of the entire optic pathway was reported in only 4 cases before. Because of similar radiological appearance of other pathological entities such as gliomas and craniopharyngiomas, histopathological diagnosis is essential. We report a ganglioglioma case that involved both optic pathways. A 12-year-old patient suffering from visual deterioration for 6 months was evaluated. After a visual field test and radiological examinations, a microsurgical biopsy procedure was performed. Pathological examination revealed dysplastic/neoplastic ganglion cells and neoplastic glial cells, and the diagnosis was a World Health Organization (WHO) grade 1 ganglioglioma. The patient is scheduled for adjuvant radiotherapy with the hope of prevention of progression.