Table of Contents
Intracranial ganglioglioma
Epidemiology
Children and young patients are usually affected, and no gender predominance is recognised. It accounts for around 2% (from 0.4-3.8%) of all primary intracranial tumors, and up to 10% of primary cerebral tumors in children.
Because of their rarity, large-scale, population-based studies focusing on epidemiology and outcomes are lacking.
Classification
Ganglioglioma is a benign slow-growing neoplasm that most frequently occurs at the supratentorial region. Nevertheless, there are occasional reports of ganglioglioma occurring in thebrainstem and spinal cord.
see Intraventricular ganglioglioma
Pathogenesis
Molecular pathogenesis, risk factors for malignant progression, and their frequent association with drug-resistant focal seizures remain poorly understood. This contrasts recent progress in understanding the molecular-genetic basis and targeted treatment options in diffuse gliomas. The Neuropathology Task Force of the International League against Epilepsy examined available literature to identify common obstacles in diagnosis and research of LEAT. Analysis of 10 published tumour series from epilepsy surgery pointed to poor interrater agreement for the histopathology diagnosis. The Task Force tested this hypothesis using a web-based microscopy agreement study. In a series of 30 LEAT, 25 raters from 18 countries agreed in only 40% of cases. Highest discordance in microscopic diagnosis occurred between GG and DNT variants, when oligodendroglial-like cell patterns prevail, or ganglion cells were difficult to discriminate from pre-existing neurons. Suggesting new terminology or major histopathological criteria did not satisfactorily increase the yield of histopathology agreement in 4 consecutive trials. To this end, the Task Force applied the WHO 2016 strategy of integrating phenotype analysis with molecular-genetic data obtained from panel sequencing and 450k methylation arrays. This strategy was helpful to distinguish DNT from GG variants in all cases. The Task Force recommends, therefore, to further develop diagnostic panels for the integration of phenotype-genotype analysis in order to reliably classify the spectrum of LEAT, carefully characterize clinically meaningful entities and make better use of published literature 1).
Pathology
Clinical features
The most common presentation is with temporal lobe epilepsy, presumably due to the temporal lobes being a favoured location.
Diagnosis
Radiographic features
Tumor calcification are best appreciated on CT and are seen in 30%. Frequently appears cystic on CT, but still may be found to be solid at operation.
MRI: T1WI low to iso-intense, variable enhancement. T2 weighted image hyperintense. Calcifications appear as low signal on both.
CT & MRI: the temporal lobe is favored. Mass effect rare (suggests slow growth). Enhancement varies from none to intense.
Plain skull X-ray: calcification may be noted.
Imaging findings mirror the various patterns of growth which these tumours may demonstrate and thus their appearance is very variable. Partially cystic mass with an enhancing mural nodule is seen in ~45% of cases. They may also simply present as a solid mass expanding the overlying gyrus. An infiltrating mass is uncommon and may reflect higher grade.
CT
Findings are of a mass which is often non-specific. General features include:
iso- or hypodense
frequently calcified ~35%
bony remodelling or thinning can indicate the slow growing nature of the tumour
enhancement is seen in approximately 50% of cases (involving the solid non-calcified component)
MRI
Reported MR signal characteristics include:
T1 Solid component isointense to hypointense.
T1 C+ (Gd) solid component variable contrast enhancement
T2 hyperintense solid component variable signal in the cystic component depending on the amount of proteinaceous material or the presence of blood products peritumoural FLAIR/T2 oedema is distinctly uncommon
T2* (GE/SWI) calcified areas (common) will show blooming signal loss
Differential diagnosis
Treatment
Outcome
Gangliogliomas and ganglioneuromas are slow growing benign tumors.
In the largest retrospective study of adult low-grade GGs till 2020. Younger age, female gender, temporal lobe location, and GTR indicated better survival. Adjuvant RT and/or chemotherapy should not be considered after whatever surgery in adult patients with low-grade GGs, unless the malignant transformation has been confirmed 2)
Local resection is the treatment of choice and determines prognosis. In the brain, where a reasonable resection margin can be achieved, the prognosis is good, with recurrence-free survival reported to be 97% at 7.5-year follow-up 3).
In contrast, in the spinal cord where complete resection is often not possible without devastating deficits, local recurrence is very common.
Although the majority of patients have an excellent prognosis, infants and patients with brainstem tumors have worse survival rates.