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Sixteen patients with suspected cerebral metastases were studied with magnetic resonance (MR) imaging before and after the intravenous administration of 0.1 mmol/kg of gadolinium diethylenetriaminepenta-acetic acid. The images were interpreted blindly by two neuroradiologists; all clinical, radiologic (computed tomographic and MR imaging), and pathologic data were reviewed to arrive at a final "best diagnosis," which was then compared with the prior blinded interpretations. Of seven patients found to have multiple metastases, six (86%) had at least one tumor nodule depicted by postinfusion MR imaging that was missed by one or both observers on review of preinfusion images alone. Lesions missed on preinfusion studies were usually small nodules hidden by or not detected next to regions of high-signal edema thought to be related to the adjacent tumor nodule. The authors believe that contrast enhancement improves detection of metastatic foci with MR imaging and that the findings indicate broader implications for the detection of multiple lesions from other causes.

These days, with a surge in skull base surgery and increased aggressiveness in resection of tumors earlier considered inoperable, the need for reliable means of brain monitoring becomes quite clear. This is especially true in cases involving major alteration of cerebral blood flow, as happens in resection, ligation, or occlusion of the internal carotid artery (ICA). I The possibility of preoperative assessment of brain circulatory reserves may allow the neurosurgeon to predict the necessity of shunting or bypassing the arterial flow to the brain. Although there is a commonly used way to simulate flow interruption-a temporary occlusion of ICA, prior to the operation-by itself it does not provide any quantitative data about brain circulation. For this reason, it was proposed that combining temporary occlusion with various imaging techniques such as positron emission tomography and single photon emission computed tomography, electroencephalography, transcranial Doppler ultrasonography, and others might meet this need. However, these methods do not give direct information about the sufficiency of brain respiration-its oxygen supply.For several years our group has been working with near-infrared spectroscopic evaluation of brain oxygenation-transcranial cerebral oximetry (TCCO). This technique is a useful, real-time, and reliable source of information about brain oxygenation in various neurosurgical situations, such as intraoperative monitoring of carotid endarterectomies and various intracranial procedures, evaluation of brain ischemia and vasospasm, and monitoring of endovascular procedures.In this article we report our preliminary experience using TCCO for preoperative assessment of patients undergoing surgery that may compromise ICA patency. 117Skull