Ganglioglioma
A ganglioglioma is an uncommon CNS tumour which accounts for around 2% (from 0.4% to 3.8%) of all primary intracranial tumours; and up to 10% of primary cerebral tumours in children. There are however the most frequent of the neuronal-glial CNS neoplasms 6.
They are of low grade (WHO Grade I or II). Typical occurrence is in the temporal lobes, although they have been described in all parts of the central nervous system.
Epidemiology
Children and young patients are usually affected, and no gender predominance is recognised.
Clinical presentation
The most common presentation is with temporal lobe epilepsy, presumably due to the temporal lobes being a favoured location.
Pathology
Gangliogliomas are composed of two cell populations:
- ganglion cells (large mature neuronal elements) : ganglio-
- neoplastic glial elements (primarily astrocytic) : -glioma
It is the grade of the glial component that determines biological behaviour. Dedifferentiation into high grade tumours does occasionally occur, and it is usually the glial component (into a GBM). Only rarely is it the neuronal component (into a neuroblastoma)
They are closely related to gangliocytomas, which contains essentially only mature neural ganglion cells, and ganglioneurocytoma which in addition have small mature neoplastic neurons.
Markers
Neuronal origin is demonstrated by positivity to neuronal markers such as
- synaptophysin
- neuronal specific enolase
May also show positivity to the GFAP marker
Variants
Desmoplastic infantile ganglioglioma
Location
There is predilection towards the temporal lobes 6.
Radiographic features
Imaging findings mirror the various patterns of growth which these tumours may demonstrate, and unfortunately their appearance is very variable. Partially cystic mass with an enhanging mural nodule is seen in 35 - 55% 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
Non specific findings of a mass which is:
- iso or hypodense
- frequently calcified ~ 35 %
- bony remodeling 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
- T1 : iso to hypo intense
- C+ (GAD) : variable contrast enhancement
- T2 : hyper intense solid component, with variable signal in the cystic component depending on amount of proteinaceous material or presence of blood products ; peri tumoural FLAIR / T2 oedema is distinctly uncommon
- GE / SWI : calcified areas will show blooming
Treatment and prognosis
Local resection is the treatment of choice and determines prognosis. In the brain where a reasonable resection margin can be achieved, prognosis is good. In the spinal cord where this is not possible without devastating deficits local recurrence is very common.
If only incomplete resection is achievable, or tumour recurrence occurs then radiotherapy may be of some benefit.
Differential diagnoses
The differential diagnosis is very broad and should be restricted by location.
Temporal lobe
- pleomorphic xanthoastrocytoma (PXA)
- ganglioneuroma
- pilocytic astrocytoma
- dysembyoplastic neuroepithelial tumour (DNET)
See temporal lobe tumour Differential diagnosis
