State of the art epilepsy imaging: an update.

Drug-resistant epilepsy is a chronic debilitating disorder, but many cases are potentially curable by surgery. The key to the successful epilepsy surgery with complete postoperative seizure-free status is precise localization of the epileptic zone that must be resected and the adjacent eloquent areas of gray and white matter that must be preserved to avoid neurological defects. This article reviews the current state of the art epilepsy imaging techniques facilitating successful epilepsy surgery. The overview of the imaging appearances of the most common epileptogenic etiologies that are amenable to surgical resection is also included in this review.

Evaluation of rare choroid plexus metastasis from papillary thyroid carcinoma with multimodality imaging.

Papillary thyroid carcinoma (PTC) is the most common malignancy of thyroid gland. Though it metastasizes primarily through lymphatics, hematogenous spread is not infrequent. We report the case of a 62-year-old male patient with intraventricular choroid plexus metastasis from PTC, incidentally detected on post-high-dose radioiodine therapy whole-body I scan, which is an extremely rare presentation. Only 3 cases of choroid plexus metastasis from thyroid carcinoma have been reported. Further multimodality radiological investigations confirmed diagnosis and helped in assessing treatment response. The patient received gamma-knife stereotactic radiosurgery, and follow-up radiological imaging suggested improvement of intracranial metastasis.

Radiation necrosis in the brain: imaging features and differentiation from tumor recurrence.

Radiation necrosis in the brain commonly occurs in three distinct clinical scenarios, namely, radiation therapy for head and neck malignancy or intracranial extraaxial tumor, stereotactic radiation therapy (including radiosurgery) for brain metastasis, and radiation therapy for primary brain tumors. Knowledge of the radiation treatment plan, amount of brain tissue included in the radiation port, type of radiation, location of the primary malignancy, and amount of time elapsed since radiation therapy is extremely important in determining whether the imaging abnormality represents radiation necrosis or recurrent tumor. Conventional magnetic resonance (MR) imaging findings of these two entities overlap considerably, and even at histopathologic analysis, tumor mixed with radiation necrosis is a common finding. Advanced imaging modalities such as diffusion tensor imaging and perfusion MR imaging (with calculation of certain specific parameters such as apparent diffusion coefficient ratios, relative peak height, and percentage of signal recovery), MR spectroscopy, and positron emission tomography can be useful in differentiating between recurrent tumor and radiation necrosis. In everyday practice, the visual assessment of diffusion-weighted and perfusion images may also be helpful by favoring one diagnosis over the other, with restricted diffusion and an elevated relative cerebral blood volume being seen much more frequently in recurrent tumor than in radiation necrosis.