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We measured biochemical markers of excitability in brain excised for neurosurgical therapy of epilepsy. Intraoperative electrocorticography was used to identify and compare samples from regions of persistent interictal spike discharges and areas of the cerebral convexity which were free of interictal piking. We found that interictal spiking was associated with elevated tissue levels of the excitatory amino acids glutamic acid (26%, p < 0.001) and aspartic acid (25%, p < 0.05). There was also a significant increase in the activity of the enzymes glutamic acid dehydrogenase (20%, p < 0.01) and aspartate acid aminotransferase (18%, p < 0.01) which are involved in their formation. There was no change in the levels of the inhibitory neurotransmitters GABA or taurine. We also found a significant increase in the activity of tyrosine hydroxylase (52%, p < 0.001), the rate controlling enzyme in catecholamine biosynthesis. There was a reduction in the density (Bmax) of cortical alpha-1 adrenoceptors (26%, p < 0.01) and a concommitant diminution of receptor coupled phosphatidylinositide metabolism (21%, p < 0.01). This blunting of inhibitory noradrenergic transmembrane signaling may contribute to a relative imbalance between excitatory and inhibitory mechanisms in epileptogenic neocortex.
Ependymomas usually arise from the ventricular surface.
We report an 11-year-old female who presented with a supratentorial ectopic ependymoma.
The patient presented with a two-month-history of progressive headache, nausea and vomiting. Examination revealed papilledema, horizontal nystagmus, diplopia on upward gaze, and right pronator drift. CT scan showed an enhancing left precentral subcortical lesion measuring 3 cm in diameter with associated edema and mass effect. Its medial border was located 3 cm from the ependymal surface of the ventricle. A firm tumour was dissected from the centrum semiovale white matter, and removed in toto as confirmed on MRI. Pathological examination revealed histological, immuno-histochemical and electron microscopic features consistent with an ependymoma. Spine MRI and bone marrow aspirate, as well as lumbar puncture of cytology failed to show any dissemination.
From the literature review, this represents an exceptional ependymoma located at the distance from the ventricular system or cisterns. Different pathogenic alternatives are discussed.
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