Association of meningiomas with dural "tails"; surgical significance.

Intracranial meningiomas are characteristically benign tumours with a tendency to recur following surgical resection. Our group is investigating the pathogenesis of meningioma recurrence. In our initial studies we identified two cases of dural "tails" associated with intracranial meningiomas. Gadolinium-enhanced magnetic resonance images were utilized to identify the dural "tails" preoperatively. These images aided us in performing a more complete surgical resection of the meningiomas. Histopathological confirmation of meningotheliomatous cell infiltration into the dural "tails" demonstrates their surgical significance.

Radiographic evaluation of the skull base.

The anatomic complexities of the skull base and the variable clinical presentation of skull base tumors often precludes accurate determination of tumor boundaries by history and physical alone. Imaging, employing computed tomography (CT) and magnetic resonance imaging (MR) allows for accurate tumor mapping and planning of appropriate therapeutic intervention. Calvarium floor involvement and extracranial lesions are well delineated by CT. While multiplanar MR is unparalleled in demonstrating tumor boundaries and extension through the skull base. In order to employ these imaging modalities in an efficient way, it is important to understand the limitations and capabilities of these modalities as well as the imaging characteristics of common skull base lesions.

Lumbar disc disease and stenosis.

In recent years MR has been the major advancement in the imaging of lumbar disc disease. Its advantages include multiplanar imaging, excellent resolution, and absence of ionizing radiation. Although CT remains an efficient and accurate method of evaluating the spine, we currently recommend MR imaging as the best initial examination. Myelography with follow-up CT scans should be reserved for specific patients in whom additional information is needed after MR images or CT scans.

Hyperdense middle cerebral artery sign on CT: efficacy in detecting middle cerebral artery thrombosis.

The hyperdense middle cerebral artery sign is a CT predictor of the development of a large cerebral infarct. The limits of detectability were tested in a blinded, then unblinded analysis of CT scans from 25 acute stroke patients. In the initial blinded analysis, sign detection exhibited the following mean values: sensitivity, 78.5%; specificity, 93.4%; positive predictive value, 66%; negative predictive value, 96.4%; accuracy, 91.3%. Kappa statistics analysis indicated poor interobserver agreement (k = .38). Results of unblinded analysis were as follows: sensitivity, 69%; specificity, 94.4%; positive predictive value, 82.8%; negative predictive value, 88.7%; accuracy, 87.3%. There was fair unblinded interobserver agreement (k = .53). Unblinded analysis had a lower false-positive frequency and did not increase the number of true-positive determinations. We conclude that detection of the hyperdense middle cerebral artery sign on CT scans by multiple observers is a sensitive, accurate, and predictive indicator of middle cerebral artery thromboembolism.

Diagnosis and treatment of vascular brain-stem malformations.

Vascular malformations are a common cause of spontaneous brain-stem hemorrhage in young normotensive individuals. These lesions are no longer cryptic. Magnetic resonance (MR) imaging has renewed interest in the treatment of this disorder because of the precise accuracy in diagnosis and localization of these lesions that it affords. The MR image demonstrates characteristic findings of multiple hemorrhages of varying ages surrounded by a hypointense peripheral zone of hemosiderin. Five cases of vascular brain-stem malformation diagnosed with MR imaging are described. The vascular malformations could be demonstrated as "flow void" areas in three cases. Three patients were treated surgically and vascular malformations were confirmed: all three patients improved postoperatively. Two patients were treated nonsurgically; one of these recovered from a second hemorrhage and the other experienced neurological deterioration after a single hemorrhage. High-energy radiotherapy was not effective for the one vascular malformation treated by this method. This experience suggests that surgical exploration should be considered for vascular brain-stem malformations when the diagnosis is confirmed by MR criteria and the clinical course and lesion are both progressive in character.