Supratentorial lesion and Epilepsy

Clinical History

The patient had a cranioencephalic trauma when he was younger and his patient history was consistent with epileptic seizures some years ago. He suffered from persisting and increasing of seizure attacks. EEG findings were localizing, so neuro-imaging studies were done.

Imaging Findings

The patient had a cranioencephalic trauma when he was younger, followed by seizures (the first one reported type tonic-clonic generalized; others seemed to be simple partial seizures- without loss of consciousness). Because of variable but increasing frequency of attacks, he went to doctor. Reported seizures were consistent with simple partial seizures. Neurological examination was normal. Scalp EEG showed slow right parieto-occipital activity, without paroxistic activity. He underwent non-invasive prolonged video-EEG monitoring that revealed interictal paroxistic activity in the right frontal and anterior temporal lobe and also occurrence of an electro-clinic seizure: stop of initial activity followed by left hemiclonic seizure- ictal EEG pattern in right temporal lobe and inferior temporal. So, the focal nature and lateralized seizures were demonstrated clinically and also by the electroencephalogram, displaying localized epileptic activity over the seizure focus. Neuroimaging studies (Brain CT and MR) were done and showed a superficial cystic-appearance lesion in the right temporal lobe, considered to be the epileptic seizure focus (tumour-related chronic epilepsy). The imaging findings were not pathognomonic for the type of glial tumour.
As in other reported cases, the preoperative interictal EEG lateralized the tumour side but not localized to the correct lobe. The abnormalities on the ictal EEG allowed the identification of the correct region of the tumour.
Antiepileptic drugs were introduced, without longstanding seizure-free result.
Later, complete resection of the identified tumour was done and seizure control was achieved.

Discussion

The differential diagnosis of a superficial located supratentorial lesion in a young adult presenting with seizures/epilepsy includes: dysembryoplastic neuroepithelial tumour (DNET), ganglioglioma, low-grade astrocytoma, pleomorphic xanthoastrocytoma (PXA), tubers in tuberous sclerosis and neurocysticercosis. gangliogliomas are well-differentiated tumours containing both neuronal and glial components. It is slow-growing tumours (WHO grade I) that affects mostly children and young adults. Most gangliogliomas are supratentorial, mostly located in the superficial hemispheres, in a cortical/ subcortical location. They most commonly arise in the temporal lobe, followed by the frontal lobe, parietal lobe, occipital lobe and region of the hypothalamus and third ventricle. They may also be infratentorial (arising within the cerebellum or brainstem) and appear in the spinal cord. The diagnosis should be considered in a young patient (80% occur in patients under 30 years; peak incidence of 10-20 years), with a cortically based cystic appearing or solid lesion. They are variable in size and can be cystic with a mural nodule (classic description), solid or infiltrating (rare). Calcification is common (up to 50%) as well as heterogeneous enhancement. Gangliogliomas are the most common cause of chronic temporal lobe epilepsy, unresponsive to anti-epileptic drugs. Clinical prognosis is excellent following complete resection, with resolution of seizures in the majority of cases. The usual appearance of DNET is a homogeneously high signal lesion on long TR sequences, pseudocystic, typically well-demarcated "bubbly" intracortical wedge-shaped lesion pointing towards the ventricle.
Low-grade astrocytoma can resemble the more typical T2 hyperintense wedge-shaped appearance of the DNET. Both typically don't enhance after gadolinium.
PXA is histologically pleomorphic, so imaging findings are also variable. The classic appearance is a mural nodule (with strong enhancing) at the margin of a large cyst, adjacent to the peripheral leptomeninges in supratentorial brain. Peripheral location is the most consistent imaging finding. Surrounding oedema is usually modest relative to the size of the mass. PXA is associated with long-standing epilepsy. Cortical-subcortical tubers in Tuberous Sclerosis are usually multifocal and associated with other features of TS such as subependymal nodules.
The superficial cerebral gliomas, involving the cortical gray matter, are noteworthy because of they tend to manifest in younger patients with refractory seizures, of their amenability to surgical resection - often curative, their generally favourable prognosis, and their characteristic imaging features, which facilitate diagnosis before surgery. They are all classified as WHO grade I tumours, except the PXA (considered a WHO grade II. The smaller lesions include ganglioglioma and DNET.
It is important to recognize early the structural lesions (in particular low-grade glial neoplasms) associated with intractable epilepsy because they have a better and favorable outcome following early complete resection.
In this case, CT and MRI findings are not specific for ganglioglioma, making the final diagnosis difficult - absense of calcifications on CT scan; no contrast enhancement. Both can be associated with cortical dysplasia, not seen in present case. Because of the imaging findings, ganglioglioma or DNET seem to be the more probably lesion, being gangliogliomas more frequent.

Differential Diagnosis List

Final Diagnosis

Ganglioglioma (histopathology showed presence of glial and ganglion cells)

URL:	https://www.eurorad.org/case/7231
DOI:	10.1594/EURORAD/CASE.7231
ISSN:	1563-4086