Reply:

We would like to thank Drs Aralasmak and Karaali for their interest in our report of extraventricular neurocytomas (EVNs) published in the March 2009 issue of the American Journal of Neuroradiology¹ and their excellent comments. We also read with interest their article,² in which they present a case of EVN, which showed nonenhancing and hypovascular features, which are uncommon imaging findings and much different from ours and other authors’ cases.^1,3,4 Their presentation of CT perfusion data is unique in the literature.

In our article, we did mention that EVN should be considered in the differential diagnosis when a large cerebral parenchymal mass with cystic necrosis, calcification and/or hemorrhagic foci, and extensive enhancement is encountered in younger patients, on the basis of our cases and other reports. We described EVNs as variably enhancing masses¹ at the time of the submission of our article, before the case presented by Aralasmak et al² had been published on-line. The conclusion can now be drawn that marked enhancement is not always necessary for EVNs.² We appreciate Aralasmak et al for broadening our knowledge in the diagnosis of EVNs.

After reviewing seriously the case of Aralasmak et al,² we agree that dysembryoplastic neuroepithelial tumor should also be in the differential diagnosis of some EVNs due to the unique imaging features and histologic similarity. However, we regard the imaging findings that Aralasmak et al described as uncommon ones in EVN. Most EVNs appear as a large parenchymal mass with cystic necrosis, calcification, and/or hemorrhagic foci and extensive enhancement, whereas few EVNs are hypovascular with no or mild enhancement. We believe a future investigation with a larger series is required to evaluate the usefulness of CT and/or MR perfusion data in the differential diagnosis of suspected EVNs.

• Copyright © American Society of Neuroradiology