Well-differentiated, slowly growing neuroepithelial tumor composed of neoplastic ganglion cells and neoplastic glial cells
Most common cause of temporal lobe epilepsy (TLE)
Partially cystic, enhancing, cortically based mass in child/young adult with TLE
Can occur anywhere, but most commonly superficial hemispheres, temporal lobe (> 75%)
Circumscribed cyst + mural nodule most common
Calcification is common (up to 50%)
Superficial lesions may expand cortex, remodel bone
Approximately 50% enhance
May see associated cortical dysplasia
Pleomorphic xanthoastrocytoma (PXA)
Dysembryoplastic neuroepithelial tumor (DNET)
Astrocytoma
Oligodendroglioma
Neurocysticercosis
WHO grade I or II (80% grade I)
Uncommon: Anaplastic ganglioglioma (WHO III)
Rare: Malignant with GBM-like glial component (WHO IV)
Occurs at all ages, peak: 10-20 years
Most common mixed neuronal-glial tumor
Excellent prognosis if surgical resection complete
TERMINOLOGY
Ganglioglioma (GG)
Well-differentiated, slowly growing neuroepithelial tumor composed of neoplastic ganglion cells and neoplastic glial cells
Most common cause of temporal lobe epilepsy (TLE)
IMAGING
Best diagnostic clue: Partially cystic, enhancing, cortically based mass in child/young adult with TLE
Location
Can occur anywhere, but most commonly superficial hemispheres, temporal lobe (> 75%)
Frontal and parietal lobes next most common
Rare locations: Brainstem, cerebellum, pineal region, optic nerve/chiasm, intraventricular, pituitary axis, spinal cord, cranial nerves
Size
Variable, typically 2-3 cm in adults
Larger in children, typically > 4 cm
Up to 6 cm reported
Morphology
3 patterns
Most common: Circumscribed cyst + mural nodule
Solid tumor (often thickens, expands gyri)
Uncommon: Infiltrating, poorly delineated mass
Calcification is common (up to 50%)
In younger patients (< 10 years), gangliogliomas are larger and more cystic
NECT
Variable density
40% hypodense
30% mixed hypodense (cyst), isodense (nodule)
15% isodense or hyperdense
Ca++ common (35-50%)
Superficial lesions may expand cortex, remodel bone
CECT
Approximately 50% enhance
Varies from moderate, uniform to heterogeneous
Can be solid, rim, or nodular
Often shows cyst with enhancing nodule
T1WI
Mass is hypointense to isointense to gray matter
Rarely hyperintense
Ca++ has variable signal intensity
May see associated cortical dysplasia
T2WI
Hyperintense mass typical
May be heterogeneous
No surrounding edema
T2* GRE: May show Ca++ as areas of "blooming"
T1WI C+
Variable enhancement, usually moderate but heterogeneous
May be minimal, ring-like, homogeneous
Meningeal enhancement rarely seen
MRS: Elevated Cho has been described
PET
Typically decreased activity with FDG PET indicating tumor hypometabolism
May have some hypermetabolic foci
201Tl-SPECT: Increased activity in high-grade gangliogliomas (grade III, IV)
Typical gangliogliomas have decreased or normal SPECT activity
Best imaging tool: Multiplanar MR
Protocol advice: Contrast-enhanced MR to include coronal T2 images for better evaluation of temporal lobes
DIFFERENTIAL DIAGNOSIS
Pleomorphic Xanthoastrocytoma (PXA)
Supratentorial cortical mass, dural "tail" common
Often cyst and mural nodule, may be solid
Enhancing nodule abuts pial surface
Temporal lobe most common location
Dysembryoplastic Neuroepithelial Tumor (DNET)
Superficial cortical tumor, well demarcated
Multicystic "bubbly" appearance
T2 hyperintense mass with rare, mild enhancement
May remodel calvarium
Pilocytic Astrocytoma
Supratentorial location other than hypothalamus/chiasm rare
Typically solid and cystic or solid mass
Enhancement typical
Low-Grade Astrocytoma (Grade II)
Circumscribed but infiltrative white matter mass
No enhancement
Oligodendroglioma
Calcified, heterogeneous mass
Typically more diffuse than ganglioglioma
May remodel/erode calvarium
Neurocysticercosis
Cyst with "dot" inside
Often calcified
Multiple lesions common
Imaging varies with pathologic stage, host response
PATHOLOGY
Etiology
2 theories
Origin from dysplastic, malformative glioneuronal precursor lesion with glial element neoplastic transformation
Neoplastic transformation of glial hamartoma or subpial granule cells
Genetics
Gain of chromosome 7 reported
Sporadic
Tp53 mutations found in malignant degeneration
Syndromic
GG has been reported in Turcot syndrome, NF1, and NF2
Associated abnormalities
Gangliogliomas have been found in association with oligodendroglioma, DNET, tanycytic ependymoma
Malignant transformation into GBM, neuroblastoma has been reported
Cortical dysplasia is commonly associated
WHO grade I or II (80% WHO grade I)
Uncommon: Anaplastic ganglioglioma (WHO grade III)
Rare: Malignant with GBM-like glial component (WHO grade IV)
Solid or cystic mass with mural nodule
Firm, well-circumscribed mass, often expands cortex
Mix of mature but neoplastic ganglion cells and neoplastic glial cells (usually astrocytes)
Dysmorphic, occasionally binucleate neurons
Immunohistochemistry of neuronal cells
Synaptophysin and neurofilament protein are positive
Majority exhibit CD34 immunoreactivity (70-80% of gangliogliomas)
Electron microscopy shows dense core granules, variable synapses
Neoplastic glial cells are GFAP(+)
Mitoses rare (75% have Ki-67 < 1%, low MIB)
CLINICAL ISSUES
Most common signs/symptoms
Chronic temporal lobe epilepsy (approximately 90%)
Often partial complex seizures
Other signs/symptoms: Headache and signs of increased intracranial pressure
Age
Tumor of children, young adults
80% of patients < 30 years
Occurs at all ages, peak: 10-20 years
Gender: Slight male predominance
Epidemiology
1% of primary intracranial neoplasms
Most common mixed neuronal-glial tumor
Represents 1-4% of pediatric CNS neoplasms
Most common tumor to cause TLE (> 45%)
Ganglioglioma > DNET > pilocytic astrocytoma > low-grade astrocytoma > oligodendroglioma > PXA
Excellent prognosis if surgical resection complete
94% have 7.5-year recurrence-free survival
Vast majority of patients seizure-free after surgery (80%)
Well-differentiated tumor with slow growth pattern
Malignant degeneration is rare (approximately 5-10% glial component)
Surgical resection is treatment of choice
Radiation therapy &/or chemotherapy for aggressive or unresectable tumors
DIAGNOSTIC CHECKLIST
Ganglioglioma in young patient with history of temporal lobe epilepsy
In children under 10 years old, gangliogliomas are larger and more cystic
Cyst with enhancing mural nodule is classic, but not specific for ganglioglioma