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.

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.

Angiographic film subtraction using a laser digitizer and computer processing.

Digital subtraction angiography has been accepted as an invaluable clinical tool over the past decade; however, film-screen-based angiography is still performed routinely when high-resolution or large field-of-view angiograms are needed. A technique is presented whereby two films from an angiographic sequence are digitized using a high-resolution laser digitizer, and the digitized images are aligned, subtracted, and displayed using the computer. To accommodate for some types of patient motion, an image warping algorithm is presented and discussed in detail. The warping algorithm is piecewise linear, using triangular regions for warping, resulting in a global nonlinear transform across triangle elements. An algorithm describing optimal triangle selection also is discussed. The results show that subtraction images of excellent quality can be produced by the proposed technique, and suggest that, in some settings, digitized subtraction films may be preferred over conventional film subtraction.

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.

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.

Transient paralysis associated with epidural steroid injection.

Epidural steroid therapy is a commonly applied "conservative" therapy, but it is not inherently benign. Although arachnoiditis, infection, and meningitis have been reported, acute paraplegia has not been reported as a complication of either caudal or spinal epidural steroid injection. A unique case of transient, profound paralysis after epidural steroid injection is reported here. The procedure was carried out without fluoroscopic control and was complicated by a puncture of the thecal sack. Radiographic studies demonstrated a focal, space-occupying lesion in the spinal canal at the level corresponding to the neurologic deficit, which spontaneously resolved over the next 2-3 h. Surgical decompression was initially considered and then deferred in favor of observation. The patient recovered motor, sensory, and bowel and bladder function over the next 48 h. The period of recovery was consistent with an acute but brief compressive injury and inconsistent with an anesthetic effect. Radiographic studies suggest three possible explanations: (a) inadvertent thecal penetration during injection may have produced an atypical anesthetic block; (b) loculation of the injected fluid may have caused a transient compressive lesion; or (c) intrathecal injection may have produced an iatrogenic arachnoid cyst. Although pathologic confirmation of the cause was not possible, the potential for this alarming complication should be recognized by physicians prescribing epidural steroid therapy. We do not suggest that epidural steroid therapy is the treatment of choice for patients with multiple back operations or that it is efficacious for these patients. Our purpose is to alert surgeons and therapists to a rare but potentially devastating complication and to provide our experience in treating it.

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.

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.

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.

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.

Spinal arteriovenous malformation presenting as meningitis.

An 8-month-old boy presented with a two-day history of lethargy. Meningitis was suspected, and cerebrospinal fluid examination demonstrated pleocytosis and elevated protein. After initial improvement with antibiotic and steroid therapy, progressive lower extremity weakness developed, and a midthoracic spinal cord arteriovenous malformation (AVM) was diagnosed. These lesions present rarely in infancy; the classification and pathophysiology of spinal cord AVMs are reviewed.

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.

Palliative embolization of fibrosarcoma for control of tumor-induced hypoglycemia.

A 77-year-old woman with prior long-standing insulin-dependent diabetes presented with malignant hypoglycemia secondary to insulin-like substances excreted from a large unresectable fibrosarcoma of the left thigh. Partial embolization of the tumor supply from the deep femoral artery was performed using 150-250 microns polyvinyl alcohol foam particles. After embolization, the patient's serum glucose levels reverted to normal and she could be discharged from the hospital.

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.

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.

Digital subtraction lumbar diskography: technical note.

A simple technique is described for increasing the conspicuousness of radiographic contrast media injection during lumbar diskography. Injections are monitored with a digital C-arm unit using digital subtraction technique, rather than conventional fluoroscopic technique. Fourteen disk levels in six patients have so far been imaged with digital subtraction lumbar diskography. The technique permits more precise monitoring of contrast injections, and may be particularly useful for detecting minute test injections in spaces other than the nucleus pulposus, as well as for diskography on large and overweight patients.