Presentation
Complex partial seizures
Patient Data
There is a focal, cortically based lesion in the posterior aspect of the left inferior temporal gyrus. In this region, there is abnormal increased FLAIR signal with apparent mild cortical thickening/disorganization. There are some areas of low T1 signal on this region. The left hippocampus has minimally increased FLAIR signal but normal size and internal architecture. No pathological contrast enhancement detected. Spectroscopy through the lesion shows reduced NAA and increased myoinositol within the lesion, as well as a small lactate peak. The findings in the posterior aspect of the left inferior temporal gyrus may represent an area of cortical dysplasia or a cortically based tumor such as DNET, oligodendroglioma or ganglioglioma.
The patient’s seizures were managed with levetiracetam, primidone and lacosamide and she subsequently underwent a stereotactic left temporal craniotomy and resection of the lesion.
Histopathology
Macroscopic description:
Oval-shaped rubbery fawn tissue consistent with low grade astrocytoma/ganglioglioma.
Microscopic description:
The sections show a moderately cellular glioneuronal tumor involving both the cortex and white matter. There is tumor in the subpial region. Increased numbers of abnormal ganglion cells are present. They are unevenly distributed with crowding. They have enlarged nuclei and prominent nucleoli. Bi-nucleated forms are occasionally seen. A second neoplastic astrocytic proliferation is identified. The astrocytes form diffuse sheets in a fibrillary background. They have elongated hyperchromatic nuclei and scanty ill-defined cytoplasm. Eosinophilic granular bodies are not seen. Mitoses are inconspicuous. There is no endothelial cell hyperplasia or necrosis. A small amount of perivascular lymphocytes is seen. The adjacent cerebral cortex shows distortion of the architecture with malorientation of the neurons, in keeping with focal cortical dysplasia. The overall features are those of ganglioglioma. The Ki-67 index is less than 1%. Ganglioglioma with no anaplastic features is considered as Grade I in the 2007 WHO classification.
Diagnosis: Brain tumor: Ganglioglioma (WHO grade I).
Six years post-diagnosis the patient remains seizure-free and with no evidence of disease recurrence.
Left-sided craniotomy again noted together with the small area of left posterior temporal FLAIR hyperintensity at the site of resection. No suspicious enhancement elsewhere. No new findings. Stable disease with no evidence of recurrence.
Case Discussion
This is an example of left temporal ganglioglioma. Gangliogliomas are slow-growing CNS neoplasms comprising of a mixture of neoplastic glial cells (primarily astrocytes) and neoplastic ganglion cells (differentiated nerve cells), in variable proportions 1-5.
Gangliogliomas account for 0.4 to 7-6% of pediatric CNS neoplasms and approximately 1-3% of those in adults 2. These tumors can occur anywhere in the neuraxis but are much more common in the brain than in the spinal cord 1,2. The temporal lobe is the most common location of gangliogliomas, followed by - in order of descending frequency - cerebellum, parieto-occipital lobe, frontal lobe, and spinal cord 6. These tumors have also been reported in the brainstem, thalamus, hypothalamus, third and fourth ventricles, trigone of the lateral ventricle, pineal region, intrasellar region, and optic nerve 4.
The most common clinical presentation is seizures, in particular, complex partial seizures, most likely a result of the high frequency of the temporal lobe location of these neoplasms 1.
Although neuroradiological findings are not specific for gangliogliomas, the ability to diagnose this type of tumor greatly improved with the advent of CT and MRI. Common imaging findings of ganglioglioma on CT include1-6:
- Calcification with an amorphous appearance
- Subtle bony changes such as thinning of the calvaria
- Isodensity, hypodensity, or a cystic appearance of the lesion
- Contrast-enhancement of the solid non-calcified component of the lesion
Reported imaging characteristics on MRI include 1-6:
- Cystic appearance of the lesion
- Hypointense on T1-weighted images
- Hyperintense solid component on T2-weighted images, with variable signal in the cystic component
The principal form of treatment of ganglioglioma is surgical excision, with most lesions being amenable to complete resection 1-6. Current literature suggests that radiation therapy is of minimal and/or questionable benefit, even in tumors which involve eloquent areas 4. Most patients with preoperative seizures are seizure-free following total surgical resection 1.
Case courtesy of Assoc Prof Pramit Phal
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