Clinical
Presentation: Patient is a 20-month-old child with right-side generalized seizures.
Imaging Findings: Non-contrast CT images show a well-defined hypodense lesion in left temporal lobe with peripheral rim of calcification. The lesion shows hypointense signal on T1W MR images, hyperintense signal on T2W images, with minimal perilesional edema. A small enhancing nodule is seen in the superior aspect of the lesion.
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Figures 1A-B: Hypodense lesion with peripheral calcification is seen in left temporal lobe.
Figures 2A-B: On T1W images, the lesion has hypointense signal with a slightly hyperattenuating peripheral rim due to calcification.
Figures 3A-B: The lesion has hyperintense signal on T2W images, with minimal perilesional edema.
Figures 4A-B: Contrast-enhanced images show a small enhancing component in the superior aspect of the lesion. No significant peripheral enhancement is seen.
Diagnosis: Ganglioglioma, left temporal lobe
Discussion: Pure neuronal and mixed neuronal-glial tumors of the central nervous system are uncommon and make up approximately 1% of all brain tumors. Distinguishing these from the more common glial tumors is important because neuronal tumors are less aggressive and their prognosis is excellent. Neuronal tumors have favorable clinical outcomes and are generally cured with surgery alone, whereas gliomas typically require radiation therapy or chemotherapy depending on their histologic grade. Neurologic manifestations are varied and include seizures, symptoms of increased intracranial pressure, and neurologic deficits according to tumor location [1].
At histopathologic analysis, neuronal tumors are usually classified as pure neuronal cell tumors (gangliocytoma, Lhermitte-Duclos disease [dysplastic cerebellar gangliocytoma], central neurocytoma) and mixed neuronal-glial tumors (ganglioglioma, desmoplastic infantile ganglioglioma, dysembryoplastic neuroepithelial tumor, ganglioneuroma).
The term gangliocytoma denotes a spectrum of rare tumors in which neuronal cell lineages are the sole neoplastic constituents. In addition to the neuronal population, there is a highly variable normocellular network of nonneoplastic glial cells. This distinguishes gangliocytomas from gangliogliomas, which also contain anaplastic glial cells. But clear-cut separation of gangliocytomas from gangliogliomas is difficult. They represent opposite ends of a spectrum of differentiated ganglion cell tumors. Since these two entities are not always distinct, the term ganglion cell tumor is a useful compromise in which the neoplastic nature of the glial component remains in doubt [1].
Gangliogliomas are the most common of the neuronal-glial neoplasms arising within the central nervous system. These tumors comprise 0.4%–6.25% of all primary brain tumors in adults and approximately 10% of all primary brain tumors in children. Most of these tumors are found either in infants or young individuals aged 8–31 years [2].
Although any site within the central nervous system may be affected, most tumors develop in the temporal lobe. Gangliogliomas of the temporal lobe are commonly associated with the clinical presentation of medically refractory seizures, particularly those of the partial complex type. When they arise in the cerebellum, ataxia and headaches secondary to compression of the fourth ventricle and hydrocephalus are common [3].
Classically, ganglioglioma is described as a cystic mass with a mural nodule in approximately 40% of diagnosed cases. The solid portion of the tumor appears as varying degrees of attenuation on non-enhanced CT images. Calcification has been noted in about 30% of cases. Peripherally located gangliogliomas may cause scalloped pressure erosion of the overlying calvaria due to their slow-growing nature. At MR imaging, a well-defined cystic mass with a solid mural nodule is typically seen. However, a solid mass showing nonspecific low to intermediate signal intensity on T1-weighted images and high signal intensity on T2-weighted images is also not uncommon. Enhancement of the solid portion is highly variable, ranging from non-enhancing to ring-like to intense homogeneity. There is usually little associated mass effect or surrounding vasogenic edema [1].
Surgery continues to be the only therapy that can offer a “cure” in these patients. Complete resection leads to a good long-term prognosis [3]
References:
Shin JH, Lee HK, Khang SK, et al. Neuronal tumors of the central nervous system: radiologic findings and pathologic correlation.Radiographics. 2002 Sep-Oct;22(5):1177-89. PMID: 12235346 [PubMed]
Hamburger C, Büttner A, Weis S. Ganglioglioma of the spinal cord: report of two rare cases and review of the literature. Neurosurgery. 1997 Dec;41(6):1410-5; discussion 1415-6. PMID: 9402595 [PubMed]
Castillo M. Gangliogliomas: ubiquitous or not? AJNR Am J Neuroradiol. 1998 May;19(5):807-9. PMID: 9613490 [PubMed]
