Spontaneous calcific embolization to the supraclinoid internal carotid artery from a regurgitant bicuspid aortic valve.

Calcific brain embolization leading to stroke is rarely recognized. We report a case of spontaneous embolization to the right cerebral circulation from a severely regurgitant, calcified bicuspid valve. Bicuspid aortic valves constitute the most common congenital heart abnormality, and have a tendency to become stenosed, regurgitant, calcified, or infected. The presence of heavy calcification in a noninfected bicuspid valve may lead to dislodgement of calcific embolic material which is not necessarily heralded by acute valvular rupture. Accurate localization of the calcific embolus to the right supraclinoid internal carotid artery was provided by spiral CT imaging in this case.

Spiral CT scanning of the paranasal sinuses.

Because of the interest in reducing the time and radiation required for screening sinuses with CT, we compared the quality of conventional coronal CT images with coronally reconstructed, axially acquired spiral CT images. The spiral reconstructions compared favorably with the conventional images and had significantly less motion and dental amalgam artifacts.

Spiral CT of the larynx.

PURPOSE: To compare conventional and spiral CT studies of the larynx. METHODS: Ten patients had both conventional and spiral CT studies of the neck using 5-mm section collimation and 5-mm increments. The spiral scans also were reconstructed at 2-mm increments. Five patients had two spiral CT larynx studies with 5-mm and 2-mm collimation. Two observers independently rated the visibility of laryngeal structures and absence of motion artifact in the studies and assigned values from 1 (poor) to 4 (excellent). RESULTS: The spiral scan images showed less motion artifact (1.9 versus 3.6) and better anatomic detail (2.3 versus approximately 2.6). Thinner reconstruction intervals and sections gave better anatomic detail (2.3 versus approximately 3.3). Interobserver kappa was 0.65. CONCLUSION: Spiral is better than conventional CT scanning when studying the larynx.

Cocaine- and methamphetamine-induced acute cerebral vasospasm: an angiographic study in rabbits.

Stroke is a frequently reported, though uncommon, complication of drug abuse, primarily cocaine. The pathogenesis is uncertain, although such cerebrovascular events may result from sympathetically mediated vasoconstriction of cerebral vessels. Amphetamine, another sympathomimetic amine that is commonly abused, may also cause strokes by producing cerebral vasospasm and/or vasculitis. Amphetamine and its derivatives are frequent adulterants of illegally obtained cocaine and may also be used concurrently; the effect(s) of this combination of drugs upon the cerebral vasculature is not known. Our aim was to develop an animal model that would enable us to study the ability of these drugs to produce acute cerebral vasospasm and to observe the response to IV administration of amphetamine and cocaine, either alone or together. Magnified basilar artery arteriograms were obtained in 12 New Zealand white rabbits before and after IV administration of cocaine, methamphetamine, or both, at various dosages. Low doses produced mild vasodilatation. At higher doses, the animals who received cocaine and methamphetamine alone showed little or no basilar artery spasm, but coadministration produced definite basilar artery vasospasm, reflecting a synergistic vasoconstrictive effect. If a similar response exists in the human cerebral vasculature, then this could help explain the cause of strokes associated with drug abuse.

Reversible visual deficit following debulking of a Rathke's cleft cyst: a tethered chiasm?

Delayed chiasmal syndromes after emptying of a Rathke's cleft cyst have not been reported previously. When these deficits occur following the treatment of parasellar lesions they are usually associated with the descent of a scarred optic system into an empty sella, and vision often improves promptly when the optic system is elevated. Two months after transsphenoidal surgery with emptying of a large intrasellar cyst, a 22-year-old man developed recurrent bitemporal visual field deficits over a 3-day period. Sagittal magnetic resonance images demonstrated an enhancing band of tissue extending anteriorly from the normally placed chiasm down to the anterior portion of the sella turcica. At craniotomy the enhancing tissue was found to be scar extending from the anterior border of the chiasm to the diaphragma sellae. The anterior portion of the diaphragm was resected as widely as possible without dissecting the scar itself from the chiasm. A membrane consistent with the wall of a Rathke's cleft cyst was found attached to the resected tissue. The patient's vision was improved 2 days after surgery. This case illustrates that traction by scar extending from the chiasm to the diaphragm, even when the chiasm is in its normal anatomical location, may cause progressive visual loss; and that untethering of the chiasm by resecting the diaphragm while leaving the scar intact can result in improved vision.

Spinal cord compression secondary to ossified ligamentum flavum.

A case of spinal cord compression arising from ossification of the ligamentum flavum in an African-American is presented. Myelography and computed tomography were used to delineate the anatomy.

Cocaine-induced changes in time course of regional cerebral blood volume and transit time as determined by dynamic MR imaging.

We examined cocaine-mediated change in regional cerebral blood volume (rCBV) and mean transit time (MTT) in central brain structures of rats using functional MR imaging techniques. Changes in MTT and rCBV in animals who had previously been given cocaine depended on the length of time between the last pretreatment injection and the acute injection and seemed to parallel cocaine-mediated changes in extracellular dopamine concentrations.

Thrombus on indwelling central venous catheters: the histopathology of "Fibrin sheaths".

PURPOSE: Central venous catheters (CVC) may fail for many reasons, though "fibrin sheaths" blocking catheter ports are usually implicated. We examined the sheaths removed from dialysis catheters to determine their histopathology. METHODS: Ten catheter strippings were performed and the removed material was studied grossly and microscopically. RESULTS: The histologic specimens showed thrombus both with and without a proteinaceous sheath. CONCLUSION: Dialysis catheters fail because of thrombus formation. This can occur in either the absence or presence of a protein coating on the catheter, the so-called "fibrin sheath."

Spiral CT in evaluation of head and neck lesions: work in progress.

Spiral computed tomography (CT) was used in the evaluation of 21 patients with head and neck lesions. Scanning time ranged from 24 to 36 seconds, and high-quality diagnostic scans with excellent anatomic resolution and minimal motion artifact were produced. Vascular opacification was optimized with substantially less contrast medium than used in conventional studies. These preliminary results show spiral CT to be at least comparable with conventional CT in the evaluation of the head and neck.

Transfemoral repositioning of malpositioned central venous catheters.

PURPOSE: To determine the efficacy of the transfemoral vein approach to repositioning malpositioned central venous catheters. METHODS: During a 4(1/2)-year period, malpositioned central venous catheters were repositioned 91 times in 83 patients via the transfemoral vein approach. All repositioning was initially attempted with a Grollman catheter or other pigtail catheter and a tip-deflecting wire. If these techniques failed or the venous anatomy was unfavorable, gooseneck or long loop snares were used. RESULTS: During 48 repositionings, rotating a pigtail-type catheter alone was used successfully in 39 (81%). In 6 of 9 failures, the addition of a tip-deflecting wire also failed. A Grollman catheter and tip-deflecting wire were used initially in 39 repositionings (6 failures; 85% success). Successful repositioning required a snare in 8 (4 as the primary repositioning technique) and a long-loop technique in 5. All repositionings were ultimately successful and there were no complications. CONCLUSION: Central venous catheters can be repositioned consistently by the transfemoral route. Pigtail catheters or tip-deflecting wires alone are successful in over 80% of cases.

Complete MR angiography and Doppler ultrasound as the sole imaging modalities prior to carotid endarterectomy.

OBJECTIVE: To assess the combination of duplex Doppler ultrasound (DUS) and complete carotid magnetic resonance angiography (MRA) for the non-invasive imaging of carotid disease and their effect on outcomes. Determine inter-reader agreement of carotid MRA. MATERIALS AND METHODS: One-hundred and ten carotid bifurcations were evaluated using DUS, 2D and 3D time-of-flight MRA from the aortic arch to the Circle of Willis in 55 patients. Percentage stenoses were determined by two blinded readers using standardized criteria. Clinical follow-up was by chart review. RESULTS: Correlation of Doppler and MRA was excellent (r=0.903, P<0.001). Inter-reader agreement (K) for MRA was good: internal carotid artery (ICA) (0.750), external carotid artery (ECA) (0.674) and common carotid artery (CCA) (0.410). Differences in CCA readings were due to minor differences in categorizing lesions as CCA versus ICA or ECA. MRA and Doppler detected nine occluded ICAs. Two DUS occlusions had ICA flow by MRA; one due to a reconstituted precavernous ICA, one a near occluded vessel. Five patients (9%) had surgical management modified by MRA with four not having surgery: three distal ICA/Siphon occlusions and one less severe stenosis by MRA. One tandem lesion not visualized by DUS was surgically significant. Nine aortic arch abnormalities had no surgical impact, possibly due to small sample size. Of 41 endarterectomies, there were no complications from errors of diagnosis. CONCLUSION: Carotid MRA correlates well with DUS with good inter-reader agreement. MRA confirms Doppler findings, expands anatomical information and identifies tandem lesions from the aortic arch to the Circle of Willis which can affect surgical management. This approach to carotid artery imaging appears to have no negative effect on surgical outcome.

MR imaging of myxopapillary ependymoma: findings and value to determine extent of tumor and its relation to intraspinal structures.

OBJECTIVE: Myxopapillary ependymomas are highly vascular tumors that arise almost exclusively in the thoracolumbar region and produce symptoms that may mimic discogenic pathology. The purpose of our study was to define the typical MR features of myxopapillary ependymoma and to determine the value of MR imaging in identifying the tumor, establishing its extent, and defining its relationship to intraspinal structures. MATERIALS AND METHODS: MR studies performed on 20 patients (13 men and seven women; mean age, 35 years) with 24 pathologically proven myxopapillary ependymomas were evaluated retrospectively for size and location of lesions, expansion of the central spinal canal and neural foramina, and MR signal characteristics and enhancement patterns. T1-weighted (16 patients), proton density-weighted (15 patients), T2-weighted (14 patients), and enhanced T1-weighted (nine patients) sequences were examined. RESULTS: In all patients, masses were detected on MR images. MR imaging defined solitary masses in 17 patients and multiple lesions in three. Of the 24 tumors, MR imaging characterized 21 as predominately intradural extramedullary, two as intramedullary and intradural extramedullary, and one as extradural postsacral. Two lesions had associated syrinxes. Lesions occurred most often at the level of the L2 vertebral body, and no tumor extended above T9. Tumors spanned an average of four vertebral segments. MR imaging showed expansion of the spinal canal in five of eight tumors that extended over five or more vertebral segments. Two tumors extended into the neural foramina. The T1-weighted signal of the tumor was isointense in 12 patients, hypointense in three patients, and hyperintense in one patient. The T2-weighted signal was always hyperintense. All tumors imaged after administration of IV contrast material showed enhancement. CONCLUSION: MR imaging was valuable in identifying the extent of tumors and in defining their relationship to the intraspinal structures. Although the MR findings in myxopapillary ependymoma are nonspecific, the diagnosis can be suggested by a large, intensely enhancing, intradural extramedullary thoracolumbar mass that extends for several vertebral levels. Imaging protocols should examine the entire thoracolumbar region and include IV contrast.