Functional magnetic resonance imaging depicts the brain in action.

In summary, FMRI is a new technique for discovering the organization and function of the brain. The ability rapidly and non-invasively to image regional cerebral blood flow, blood volume, and blood oxygenation may strengthen diagnoses in neurology, neurosurgery, and trauma medicine. The ability to localize specific functions in an individual's brain will have a large impact on the planning of therapeutic interventions, and in predicting outcomes after disease and injury. Substantial contributions to the diagnosis and treatment of psychiatric disorders are expected based on the ability to image subtle differences in a patient's response to auditory and visual stimuli of different emotional content.

Longitudinal MRI findings in pyridoxine-dependent seizures.

BACKGROUND: Pyridoxine dependency is an uncommon familial cause of intractable seizures in newborns and infants. Fewer than 100 patients have been reported, and only four reports have included examples of brain imaging findings. We report the first longitudinal MRI findings in two patients with this condition. METHODS: Six brain MR scans, three each from two patients with pyridoxine-dependent seizures, were reviewed. Morphometry of selected axial images was performed to calculate the ventricle-to-brain ratio (VBR). PATIENTS: A girl, followed for 5 years, presented with intrauterine fetal seizures and neonatal seizures, and pyridoxine dependency was confirmed at 3.5 months of age. This patient had a subsequent history of poor compliance with pyridoxine therapy and severe developmental disability. A boy, followed for 9 years, presented with neonatal seizures, and pyridoxine dependency was diagnosed at 8 months of age. RESULTS: The serial MR scans demonstrated progressive dilation of the ventricular system and atrophy of the cortex and subcortical white matter together with an increase in the VBR. These progressive abnormalities were greater in the 5-year-old girl. CONCLUSION: Pyridoxine-dependent seizures are due to an inborn abnormality in the pyridoxine-dependent synthesis of gamma-aminobutyric acid (GABA). The progressive MR changes may be due to chronic excitotoxicity caused by an imbalance of cerebral levels of GABA and glutamic acid.

Arteriovenous malformation model for training and research.

PURPOSE: To develop an arteriovenous malformation (AVM) model for teaching embolization techniques and for researching and developing new interventional devices. METHODS: Open pore cellulose sponges 2 to 5 cm in diameter were coated with a watertight elastomer. One to three afferent tubes (arteries) and one large efferent tube (vein) allowed insertion of the model into a circuit of pulsatile, flowing, non-Newtonian fluid. Using fluoroscopy and angiographic imaging, five neuroradiologists practiced occluding the AVM nidus with a variety of techniques and cyanoacrylate mixtures. RESULTS: The model appeared and behaved like a human brain AVM. Attempts to teach liquid adhesive techniques were successful, and though they were stressful for the trainee, failure had none of the disastrous sequelae that attend training with human subjects. CONCLUSION: The AVM training and research model is of value in introducing physicians to the techniques needed for endovascular cyanoacrylate therapy: it allows users to develop skills at their own rates, and permits safe "failure-mode" learning.

Blood pressure changes in feeders to cerebral arteriovenous malformations during therapeutic embolization.

We recorded blood pressures in feeding arteries of cerebral arteriovenous malformations with microcatheters before, during, and after embolization in awake patients. Our embolization results corroborate reports of intraoperative measurements that show an immediate increase in blood pressure after ligation. Demonstration of abrupt hemodynamic changes gives additional credence to the theory of normal perfusion pressure breakthrough and to theories of neurologic change based on vascular steal phenomena. Furthermore, pressure changes occurred earlier than visible slowing of flow during the embolization, suggesting that this is a more sensitive guide with which to monitor the progress of the embolization than is serial angiography.

Prediction of major vascular injury in patients with gunshot wounds to the neck.

PURPOSE: To determine whether plain film and CT findings help predict the presence and severity of vascular trauma. METHODS: The records of 65 patients with gunshot wounds of the neck were reviewed. There were 58 men and 7 women ranging in age from 2 to 72 years. All had angiography of the cervical vessels; in addition, 64 had plain radiography, 22 had CT, and 14 had a barium swallow. The results of plain films, barium swallow, and CT scans were correlated. RESULTS: Eighteen patients (28%) had major vascular injury, which included 10 pseudoaneurysms, six vascular occlusions, four intimal injuries, and one arteriovenous fistula. Ten patients had prevertebral soft-tissue swelling (sensitivity, 59%; specificity, 77%), 14 had a bullet fragment close to a vessel (sensitivity, 78%; specificity, 36%), and 13 had missile fragmentation (sensitivity, 72%; specificity, 45%). CONCLUSION: Prevertebral soft-tissue swelling, missile fragmentation, and missiles adjacent to major vessels are useful but nonspecific radiographic signs and are present in many patients with normal angiographic findings. A knowledge of the physical findings, including the entry and exit wounds, plus the results of plain radiography and CT can help define bullet trajectories and guide angiographic evaluation.

Flow dynamics in a fatal aneurysm of the basilar artery.

PURPOSE: To examine the flow dynamics in a fatal aneurysm of the basilar artery in humans. METHODS: We made transparent elastic replicas of the vertebrobasilar arteries of an elderly patient who died of a ruptured aneurysm in the basilar artery. Using non-Newtonian fluid, physiological pulsatile flow volumes and profiles, and isobaric dyes and particles, we observed and recorded the slipstreams as they entered the aneurysm while changing relative flow in the vertebral arteries. Finally, we placed clips on the aneurysm, leaving residuals (or dog-ears), and observed the slipstreams. RESULTS: The aneurysm originated laterally from the greater curvature of a tortuous basilar artery, measured 19 x 11 x 12 mm, and had a Murphy's teat at the apex, the rupture site. The neck measured 10 x 4 mm, about the diameter of the basilar artery. Slipstreams joined at the confluence of the vertebral arteries, formed helical flow patterns, and entered the aneurysm violently, striking the apex. They then passed proximally around the sac walls, then centrally, and finally reentered the basilar artery to pass distally. Altering the relative flows in the vertebral arteries could modify and prevent slipstream flow into the aneurysm. When a dog-ear was created by incorrect placement of an aneurysm clip, slipstreams entered only dog-ears that lay distal to the clip. Correctly placed clips excluded the aneurysm from the circulation, but did not return the flow dynamics to normal. CONCLUSION: High-velocity slipstreams strike aneurysms at their rupture site and have an impact on distal but not proximal dog-ears. Modifying relative flow may prevent aneurysmal filling. Further, a knowledge of flow dynamics may allow us to predict which aneurysms are at risk of enlarging and rupturing, and may help guide proper therapy.

Impaired cerebral vasoreactivity after embolization of arteriovenous malformations: assessment with serial acetazolamide challenge xenon CT.

Embolization of a portion of the nidus of an arteriovenous malformation not only may alter hemodynamics within the nidus, but also may change blood flow dynamics in adjacent normal vessels. Sequential acetazolamide-challenge xenon CT cerebral blood flow studies were performed in eight patients before and after embolization of arteriovenous malformations to assess the hemodynamic effects on the major vascular territories supplying the malformation. Acetazolamide is a potent cerebral vasodilator, and its administration combined with cerebral blood flow studies allows assessment of cerebral vasoreactivity. In seven of the eight patients, one or more parenchymal areas exhibited a normal cerebral blood flow augmentation response to acetazolamide before embolization, but diminished acetazolamide flow augmentation was seen after embolization, indicating abnormal vasoreactivity. We found that the decrease in vasoreactivity peaked 6-10 days after embolization. In one of the eight patients, a temporary delayed neurologic deficit developed during a period of impaired cerebral vasoreactivity following embolization. Our results suggest that embolization of an arteriovenous malformation can induce vasoreactivity changes in adjacent normal vessels. Because these changes appear to be somewhat time-dependent, an appropriate interval should be observed between embolization stages or before surgical resection of an arteriovenous malformation following embolization to allow hemodynamic equilibration to occur. Acetazolamide challenge combined with serial cerebral blood flow studies following embolization enables determination of this hemodynamic equilibration.

Imaging findings of the developing temporal bone in fetal specimens.

PURPOSE: To trace the development of the normal fetal temporal bone by means of plain radiography, MR, and CT. METHODS: Eighteen formalin-fixed fetal specimens, 13.5 to 24.4 weeks' gestational age, were examined with a mammographic plain film technique, CT, and MR imaging at 1.5 T. Temporal bone development and ossification were assessed. RESULTS: The membranous labyrinth grows with amazing rapidity and attains adult size by the middle of the gestation period. The cochlea, vestibule, and semicircular canals are very prominent and easily recognized on MR images. The otic capsule develops from a cartilage model. Ossification of the otic capsule proceeds rapidly between 18 and 24 weeks from multiple ossification centers that replace the cartilaginous framework. The mastoid, internal auditory canal, vestibular aqueduct, and external auditory canal continue to grow after birth. CONCLUSION: The study of fetal developmental anatomy may lead to a better understanding of congenital disorders of the ear. Faster MR scanning techniques may provide a method for in utero evaluation of the fetal temporal bone.

MR, CT, and plain film imaging of the developing skull base in fetal specimens.

BACKGROUND AND PURPOSE: The developing fetal skull base has previously been studied via dissection and low-resolution CT. Most of the central skull base develops from endochondral ossification through an intermediary chondrocranium. We traced the development of the normal fetal skull base by using plain radiography, MR imaging, and CT. METHODS: Twenty-nine formalin-fixed fetal specimens ranging from 9 to 24 weeks' gestational age were examined with mammographic plain radiography, CT, and MR imaging. Skull base development and ossification were assessed. RESULTS: The postsphenoid cartilages enclose the pituitary and fuse to form the basisphenoid, from which the sella turcica and the posterior body of the sphenoid bone originate. The presphenoid cartilages will form the anterior body of the sphenoid bone. Portions of the presphenoid cartilage give rise to the mesethmoid cartilage, which forms the central portion of the anterior skull base. Ossification begins in the occipital bone (12 weeks) and progresses anteriorly. The postsphenoid (14 weeks) and then the presphenoid portion (17 weeks) of the sphenoid bone ossify. Ossification is seen laterally (16 weeks) in the orbitosphenoid, which contributes to the lesser wing of the sphenoid, and the alisphenoid (15 weeks), which forms the greater wing. CONCLUSION: MR imaging can show early progressive ossification of the cartilaginous skull base and its relation to intracranial structures. The study of fetal developmental anatomy may lead to a better understanding of abnormalities of the skull base.

Treatment of arteriovenous malformations of the brain with combined embolization and stereotactic radiosurgery: results after 1 and 2 years.

Seven patients with large arteriovenous malformations (AVMs) of the brain were selected for combined therapy with particulate embolization, followed by radiosurgery of the residual nidus. The goal of embolization was to reduce the patient nidus to a size that facilitated successful stereotactic radiosurgery. Angiograms obtained 1 and 2 years after radiosurgery were evaluated for changes in nidus size, flow rate, and feeding and draining vessels. One year after stereotactic radiosurgery, one AVM was angiographically undetectable. Three other AVMs demonstrated a volume reduction of greater than 50%, in addition to decreased shunt speed and altered angioarchitecture at 1-year follow-up. At 2-year follow-ups, two of seven AVMs were cured, and an additional two of seven had a greater than 98% reduction in nidus volume. Although one patient experienced a transient deficit from embolotherapy, none of our patients suffered a new neurologic deficit or a hemorrhage during the follow-up period. Our data support the efficacy of combined embolotherapy and radiosurgery for definitive therapy of selected large AVMs of the brain.

Use of acetazolamide-challenge xenon CT in the assessment of cerebral blood flow dynamics in patients with arteriovenous malformations.

Arteriovenous malformations (AVMs) may cause symptoms related to a reduction of cerebral blood flow (CBF) to surrounding brain parenchyma. To evaluate this compromise of hemodynamic reserve (commonly referred to as steal phenomenon), we used acetazolamide challenge and stable-xenon CT (Xe/CT). Baseline Xe/CT studies in 13 patients with AVMs were followed by an acetazolamide challenge to the vascular reserve. Blood flow maps were quantitated by using region-of-interest (ROI) software. ROI findings were categorized into four groups on the basis of the presence or absence of normal baseline CBF and presence or absence of normal augmentation of CBF. ROIs were designated as near site (within the vascular territory supplying the AVM) or far site (outside the vascular territory supplying the AVM). One patient had a normal baseline and normal augmentation of CBF (group 1). The other patients had a combination of one or more of the other three categories. Ten patients had parenchymal areas that exhibited either a normal or low baseline CBF with decreased augmentation; both conditions were interpreted as decreased vascular reserve (groups 2 and 3). Eleven patients had parenchymal areas that showed a low baseline CBF and normal augmentation with acetazolamide (group 4), interpreted as having a decreased demand for CBF but having a normal vascular reserve. Decreased vascular reserve was found in 27% of the nearsite areas and 17% of the far-site areas. No patients had only far-site abnormal vascular reserve. We believe that compromised vascular reserve can best be evaluated with a challenge study, such as this acetazolamide-challenge Xe/CT study.(ABSTRACT TRUNCATED AT 250 WORDS)

Emergency embolectomy for embolic occlusion of the middle cerebral artery after internal carotid artery balloon test occlusion. Case report.

Balloon test occlusion of the internal carotid artery (ICA) is useful in preoperatively assessing the risk of temporary occlusion or permanent sacrifice of the carotid artery. The incidence of symptomatic complications from this procedure is 1.7%. The case is reported of a 57-year-old woman in whom a balloon test occlusion of the left ICA was attempted. She developed a left ICA dissection/occlusion with subsequent embolization to the left middle cerebral artery, leading to right-sided hemiplegia and expressive aphasia. She was successfully treated by an emergency embolectomy followed by surgical repair of the left ICA, with an excellent outcome. This case represents the most serious complication encountered by the authors in more than 300 balloon test occlusions. Means of avoiding this complication during balloon test occlusion as well as the important factors in managing this problem are emphasized.

The prophylactic use of transluminal balloon angioplasty in patients with Fisher Grade 3 subarachnoid hemorrhage: a pilot study.

OBJECT: Recent advances in neuroradiology have made it possible to dilate vasospastic human cerebral arteries after aneurysmal subarachnoid hemorrhage (SAH), but the time window is short and the success rate for reversal of delayed ischemic neurological deficits (DINDs) varies between 31% and 77%. In a dog model of vasospasm, transluminal balloon angioplasty (TBA) performed on Day 0 totally prevented the development of angiographically demonstrated narrowing on Day 7. Because the effect of preventive TBA in this animal model was better than any pharmacological treatment described previously for experimental vasospasm, the authors conducted a pilot trial in humans to assess the safety and efficacy of TBA performed within 3 days of SAH. METHODS: The study group consisted of 13 patients with Fisher Grade 3 SAH who had a very high probability of developing vasospasm. In all patients, regardless of the site of the ruptured aneurysm, target vessels for prophylactic TBA were as follows: the internal carotid artery, A1 segment, M1 segment, and P1 segment bilaterally; the basilar artery; and one vertebral artery. Prophylactic TBA was considered satisfactory when it could be performed in at least two of the three parts of the intracranial circulation (right and/or left carotid system and/or vertebrobasilar system), and included the aneurysm-bearing part of the circulation. Of the 13 patients, none developed a DIND or more than mild vasospasm according to transcranial Doppler ultrasonography criteria. At 3 months posttreatment eight patients had made a good recovery, two were moderately disabled, and three had died; one patient died because of a vessel rupture during TBA and two elderly individuals died of medical complications associated with poor clinical condition on admission. CONCLUSIONS: Compared with large series of patients with aneurysmal SAH reported in the literature, the results of this pilot study indicate an extremely low incidence of vasospasm and DIND after treatment with prophylactic TBA. A larger randomized study is required to determine whether prophylactic TBA is efficacious enough to justify the risks, and which vessels need to be dilated prophylactically.

Phase III clinical trial comparing iodixanol and iohexol in cerebral angiography.

RATIONALE AND OBJECTIVES: We report on our early clinical experience in the United States with the nonionic dimeric (6:1 ratio) contrast medium iodixanol in cerebral angiography. Iodixanol has an osmolality less than half that of monomeric, nonionic contrast media such as iohexol at equivalent iodine concentrations and is isosmotic to blood. METHODS: Forty-nine adult patients undergoing elective cerebral angiography were studied in a phase III, double-blind, randomized, parallel-design clinical trial comparing the safety and diagnostic efficacy of iodixanol at 320 mg I/ml (IOD-320) and iohexol 300 mg I/ml (IOH-300). Diagnostically adequate cerebral angiograms were routinely obtained with both contrast agents. RESULTS: A total of 37% of the patients experienced adverse events (48% in the IOD-320 group and 25% in the IOH-300 group). No statistically significant differences were noted between the two groups studied in the proportion of patients with one or more adverse events or in the intensity of the adverse events. The most common adverse event was headache. There were no deaths or serious complications related to either contrast medium in this study. CONCLUSION: The results of this phase III trial support the conclusion that iodixanol at a concentration of 320 mg I/ml is comparable to iohexol at 300 mg I/ml in terms of efficacy (overall radiographic diagnostic visualization) and safety.

Radiopaque markers facilitate intraoperative angiography: technical note.

Lead markers taped to patients' heads prior to surgery can facilitate positioning during intraoperative cerebral angiography. More rapid positioning reduces the duration of interruption of surgery required for angiography.

Safety and efficacy of transluminal balloon angioplasty in the prevention of vasospasm in patients with Fisher Grade 3 subarachnoid hemorrhage: a pilot study.

Recent advances in neuroradiology have made it possible to dilate human cerebral arteries that show vasospasm following aneurysmal subarachnoid hemorrhage (SAH), but the time window is short and the success rate for reversal of delayed ischemic neurological deficit (DIND) varies between 31% and 77%. In a canine model of vasospasm, transluminal balloon angioplasty (TBA) performed on Day 0 (the day of aneurysm rupture) has been shown to completely prevent the development of angiographically demonstrated narrowing by Day 7; this effect is better than any pharmacological treatment for vasospasm thus far described. The authors conducted a pilot trial to assess the safety and efficacy of TBA performed within 3 days post-SAH. Twelve patients with a very high probability of developing vasospasm (Fisher Grade 3) were included. Target vessels for prophylactic TBA were the internal carotid artery, A1 segment, M1 segment, and P1 segment bilaterally, the basilar artery, and the vertebral artery. No patient developed DIND or more than mild vasospasm, according to transcranial Doppler criteria. At 3 months, seven patients made a good recovery, two patients were moderately disabled, and three patients died; one patient died because of a vessel rupture during TBA and two older patients died of medical complications associated with an already poor clinical condition at admission. Compared with the results of large series reported in literature of patients with aneurysmal SAH, the results of this pilot study indicate an extremely low incidence of vasospasm and DIND after patients underwent prophylactic TBA. A larger, randomized study, however, is required to determine whether prophylactic TBA is efficacious enough to justify the risks.