Perspectives on Neuroradiology Medical Expert Testimony: Fact and Fiction.

There are numerous misconceptions about serving as a medical malpractice expert witness. By maintaining an objective perspective based in the unbiased interpretation of the images provided (for both sides of the conflict), one can best serve society as a whole. Most cases for which a neuroradiology expert is recruited are the following: 1) not with the radiologist as a defendant, 2) resolved without court testimony, and 3) short-lived if frivolous. One can learn much about medicine, our nonradiology colleagues, and the litigation process by participating as an expert witness.

Safety of unilateral endovascular occlusion of the cervical segment of the vertebral artery without antecedent balloon test occlusion.

BACKGROUND AND PURPOSE: Antecedent balloon test occlusion is often performed prior to vertebral artery sacrifice, but there is limited data to suggest this adds a significant clinical benefit, especially in the setting of trauma. Furthermore, balloon test occlusion can be time-consuming, add to the technical complexity of the procedure, and increase the overall cost of treatment. The purpose of this study was to determine the safety of unilateral vertebral artery occlusion without antecedent balloon test occlusion as part of the treatment regimen in patients with traumatic vertebral artery dissection, cervical tumor, or intracranial aneurysm. MATERIALS AND METHODS: The medical records and imaging studies of 59 patients in whom unilateral endovascular cervical vertebral artery occlusion was performed were retrospectively reviewed. Procedure-related stroke was defined as imaging evidence of acute infarct in the vascular territories supplied by the occluded vertebral artery or new focal neurologic deficit developing in the first 30 days after vertebral artery occlusion attributable to infarction in the posterior circulation. RESULTS: Fifty-nine patients underwent unilateral endovascular cervical vertebral artery occlusion to prevent potential thromboembolic complications of vertebral artery injury, for treatment of intracranial aneurysms, or for presurgical embolization of a cervical vertebral tumor. Unilateral occlusion was performed when endovascular reconstruction was considered impossible or deemed more risky than deconstruction. Fifty-eight of the 59 patients underwent vertebral artery occlusion without antecedent balloon test occlusion. None of the 59 patients had clinical or imaging evidence of a postprocedural infarct. CONCLUSIONS: In this series, endovascular occlusion of a cervical segment of 1 vertebral artery was safely performed without antecedent balloon test occlusion. As long as both vertebral arteries were patent and converged at the vertebrobasilar junction, there was anatomic potential for retrograde filling of the distal intracranial vertebral artery to the level of the posterior inferior cerebellar artery origin, and there was no major vascular supply to the spinal cord arising from the target segment of the affected vessel. Dominant and nondominant vertebral arteries were safely occluded, and no infarcts were attributed to the treatment.

Endovascular repair of traumatic cervical internal carotid artery injuries: a safe and effective treatment option.

BACKGROUND AND PURPOSE: The appropriate choice of treatment for traumatic extracranial carotid artery injury is still debated. The purpose of this study was to evaluate outcomes of endovascular carotid repair with regard to vessel patency and retreatment rates. METHODS AND METHODS: We retrospectively reviewed records of patients who underwent endovascular treatment for acute traumatic internal carotid artery dissection with or without pseudoaneurysm formation. The Biffl classification of blunt carotid arterial injuries with an additional modification to stratify grade 2 and 3 injuries into no-flow-limiting (2a/3a) and flow-limiting (2b/3b) was used to classify injuries. RESULTS: Forty-seven patients underwent 50 endovascular interventions. Forty-four were treated with stents alone, 4 required both stent and coil treatments, and 2 were treated with coils alone. Initial treatment resulted in complete restoration of the normal vessel lumen diameter in 25 (50%) treated vessels and good-to-acceptable restoration in 25 (50%) vessels. A single patient had complete stent occlusion. Three patients required stent and/or coil retreatment. There was no mortality or permanent morbidity relating to endovascular carotid artery repair. Twenty-one patients initially treated with medical management ultimately required endovascular treatment. Eighteen (87.5%) of these injuries were initially classified as grade 3a and 3 (14.3%) were initially grade 2a. Injury progression necessitating treatment was identified, on average, within 5 weeks of the initial injury. CONCLUSIONS: In our series, endovascular therapy was a safe and effective option for restoring luminal caliber and eliminating flow within pseudoaneurysms related to traumatic injuries. Imaging follow-up of all cervicocerebral vascular injuries is especially important within the first 45 days, a critical interval during which most lesions demonstrate healing or progression.

Embolization of a Cavernous Sinus Dural Arteriovenous Fistula with Onyx via Direct Puncture of the Cavernous Sinus through the Superior Orbital Fissure: Asystole Resulting from the Trigeminocardiac Reflex. A Case Report.

SUMMARY: Treatment of cavernous sinus dural arteriovenous fistula (CSDAVF) may be challenging.We describe a patient who had presented with progressive ocular symptoms due to CSDAVF requiring urgent interventional therapy. Initial attempts to embolize the fistula utilizing a transvenous approach through the inferior petrosal sinus failed because of difficult anatomy. Successful occlusion of the fistula was subsequently achieved with injection of ethylene vinyl alcohol copolymer, Onyx (EV3 Neurovascular, Irvine, CA, USA), via direct percutaneous puncture of the cavernous sinus through the superior orbital fissure.A brief period of asystole during the initial injection of Onyx may be the result of the trigeminocardiac reflex.

An intracranial aspergilloma with low signal on T2-weighted images corresponding to iron accumulation.

We present a case of cerebral aspergillosis in an immunocompetent patient. The MRI signal characteristics were compared with the histologic findings. Irregular low-signal zones were demonstrated between the wall of the abscess and the central necrosis on T2-weighted images; the pathology specimen revealed concentrated iron in these transitional zones but no hemosiderin. Iron is an essential element for the growth of fungal hyphae. The low-signal zones may represent the areas where there was active proliferation of aspergillus, and the unique location of the low signal may be a helpful imaging characteristic for the diagnosis of an aspergillus abscess.

Vertebral artery pseudoaneurysm complicating posterior C1-2 transarticular screw fixation: case report.

BACKGROUND: Vertebral artery injury during posterior C1-2 transarticular screw fixation occurs in approximately 3% of patients and may remain asymptomatic or result in arteriovenous fistulae, occlusion, narrowing, or dissection of the vertebral artery, and lead to transient ischemic attacks, stroke, or death. CASE DESCRIPTION: This is the first report of a pseudoaneurysm resulting from damage to the vertebral artery during the procedure. This 31-year-old male underwent posterior C1-2 transarticular screw fixation for unstable os odontoideum. Injury to the left vertebral artery occurred while the hole for the left screw was being drilled. Temporary control of bleeding with local pressure was followed by immediate postoperative angiography that revealed a left vertebral artery pseudoaneurysm. Although the patient remained asymptomatic, therapeutic anticoagulation was instituted 6 hours postoperatively. Increasing size of the pseudoaneurysm was noted on routine follow-up angiography 4 weeks later. Endovascular occlusion of the pseudoaneurysm and left vertebral artery, with preservation of vertebrobasilar flow through the right vertebral artery, was accomplished without neurological consequence. CONCLUSIONS: Vertebral artery pseudoaneurysm complicating posterior C1-2 transarticular screw fixation may be effectively treated with endovascular approaches.

A clinical comparison of the safety and efficacy of MultiHance (gadobenate dimeglumine) and Omniscan (Gadodiamide) in magnetic resonance imaging in patients with central nervous system pathology.

RATIONALE AND OBJECTIVES: The safety and diagnostic efficacy of MultiHance (gadobenate dimeglumine) in the central nervous system (CNS) were evaluated in a double-blind, multicenter, phase III clinical trial. METHODS: Two hundred five patients highly suspected of having a CNS lesion (by previous imaging exam) were enrolled at 16 sites in the United States. Patients were randomized to one of three incremental dosing regimens. Magnetic resonance imaging with Omniscan (gadodiamide) at doses of 0.1 and 0.3 mmol/kg was compared with MultiHance (gadobenate dimeglumine) at doses of 0.05 and 0.15 mmol/kg and at 0.1 and 0.2 mmol/kg. RESULTS: Compared with predose images alone, efficacy was demonstrated in each of the gadobenate dimeglumine and gadodiamide groups (single and cumulative doses) as indicated by the level of diagnostic information, number of lesions detected, and contrast-to-noise ratio measurements. The level of diagnostic information from gadobenate dimeglumine at 0.1 mmol/kg was equivalent to that with gadodiamide at the same dose. One of the two blinded reviewers found equivalence between the gadobenate dimeglumine 0.05 mmol/kg dose and gadodiamide at 0.1 mmol/kg. Both reviewers found the level of diagnostic information to be equivalent after the second dose of contrast for all three dosing regimens. The cumulative doses of gadobenate dimeglumine were well tolerated and as safe as gadodiamide. CONCLUSIONS: Gadobenate dimeglumine is comparable to gadodiamide in terms of safety and efficacy for imaging of CNS lesions, with a possible advantage in imaging applications owing to enhanced T1 relaxivity.

Temporal lobe injury in temporal bone fractures.

OBJECTIVE: To determine the incidence of intracranial injury, specifically in the temporal lobe, in patients with longitudinal fractures of the temporal bone. DESIGN: Prospective inception cohort. SETTING: University of Maryland Division of Otolaryngology-Head and Neck Surgery and the Maryland Shock Trauma Center, Baltimore. PATIENTS: Twenty-seven consecutive patients with unilateral or bilateral temporal bone fractures. MAIN OUTCOME MEASURES: Evaluation of temporal bone and intracranial trauma using computed tomography (CT) and magnetic resonance imaging (MRI). RESULTS: Of the 27 patients enrolled in the study, 12 had the complete battery of MRI, CT, and physical and audiological examinations. In all 12 patients, MRI demonstrated adjacent middle cranial fossa meningeal enhancement. Results of non-contrast-enhanced CT and MRI demonstrated ipsilateral temporal lobe contusions in 6 of the 13 fractures for an overall incidence of 46%. In addition, MRI demonstrated 4 cerebral contusions not seen in the results of non-contrast-enhanced CT. CONCLUSIONS: While high-resolution CT remains the criterion standard for evaluation of temporal bone fractures, MRI revealed a higher incidence of related temporal lobe injuries. Magnetic resonance imaging data may be valuable in preoperative evaluation of patients who require surgical intervention through a middle cranial fossa approach to document pre-existing injury and potential morbidity before retraction of the middle cranial fossa dura mater and temporal lobe.

Surgically confirmed incorporation of a chronically retained neurointerventional microcatheter in the carotid artery.

A woman reported painful thrombosis of the superficial femoral artery 16 months after a transfemoral microcatheter was glued into a cerebral arteriovenous malformation and transected at the groin. When the catheter was removed, a portion was found to be incorporated into the wall of the carotid artery. This case demonstrates that portions of a retained microcatheter may be incorporated into the arterial wall while other portions may remain mobile and cause late peripheral arterial symptoms.

Superior blowout fracture of the orbit: the blowup fracture.

We describe a patient who sustained a blowout fracture of the superior orbital roof without an orbital rim fracture. The initial CT study (obtained with 10-mm-thick sections) did not show herniation of the intraorbital fat into the anterior cranial fossa; however, thin (3-mm-thick) direct orbital sections showed a fracture of the midportion of the superomedial orbital roof with displacement of the fracture fragment into the anterior cranial fossa.

Performance characteristics of microcatheter systems in a standardized tortuous pathway.

BACKGROUND AND PURPOSE: Published reports of controlled experiments designed to evaluate the performance of over-the-wire microcatheter systems are rare and have often been based on subjective impressions from small clinical series. This investigation was designed to compare the load forces required to propel state-of-the-art, hydrophilically coated microcatheters from each of four manufacturers through a standardized tortuous pathway constructed of polytetrafluoroethylene tubing. METHODS: Currently available hydrophilically coated microcatheters were provided by four manufacturers. A 20-cm long, three-dimensional pathway simulating the intracranial carotid circulation was constructed of 0.065-in. (inner diameter) polytetrafluoroethylene tubing and immersed in a water bath at 37 degrees C. Testing was performed using an Instron tabletop load frame fitted with a 2-lb load cell. Durability and load force tests were conducted using a 0.014-in. stainless steel noncoated guidewire, with the wire tip protruding 1 cm beyond the catheter tip. At least four samples of microcatheters from each manufacturer were tested. RESULTS: Extensive trackability testing of the guidewire alone established reproducible performance with maximum load forces of less than 8 g. Maximum gram forces for the four reinforced microcatheters were not greatly different, measuring between 9 and 14 g. Excessive buckling of the only nonreinforced catheter was initially overcome early in the pathway in a staccato, stepwise fashion. After reaching a critical load, however, the catheter and guidewire prolapsed. CONCLUSION: All reinforced microcatheters tested established good and reproducible performance in our model. Reinforced microcatheters provided superior trackability over the one nonreinforced device tested.

Radiologic and pathologic findings of intracerebral schwannoma.

We report the radiologic and pathologic findings of an intracerebral schwannoma. MR imaging studies showed a superficially located cystic mass with an enhancing nodule and evidence of peritumoral edema or gliosis.

Subdural grid implantation for intracranial EEG recording: CT and MR appearance.

PURPOSE: Subdural grid arrays are used when seizure activity cannot be located by ictal scalp recordings and when functional cortical mapping is required before surgery. This study was performed to determine and compare the CT and MR imaging appearance of subdural EEG grids and to identify the types and frequency of associated complications. METHODS: We retrospectively reviewed the medical records and imaging studies of 51 consecutive patients who underwent 54 craniotomies for subdural EEG grid implantation with either stainless steel or platinum alloy contacts between June 1988 and September 1993. Twenty-two patients had both CT and MR examinations, 27 patients had CT only, and five patients had MR imaging only. All studies were assessed for image quality and degradation by the implanted EEG grids, for intra- and extraaxial collections, and for mass effect, with differences of opinion resolved by consensus. RESULTS: Subdural EEG grids caused extensive streak artifacts on all CT scans (corresponding directly to grid composition) and mild to moderate magnetic susceptibility artifacts on MR images. Sixteen associated complications were detected among the 54 patients imaged, including four significant extraaxial hematomas, four subfalcine or transtentorial herniations, two tension pneumocephali, two extraaxial CSF collections, two intraparenchymal hemorrhages, and one case each of cerebritis and brain abscess. In all but four cases, the detected complications were not clinically apparent and did not require specific treatment. There were no residual sequelae. CONCLUSION: Because of extensive streak artifacts, CT showed only gross complications, such as herniation and grid displacement by extraaxial collections. MR imaging artifacts were more localized, allowing superior evaluation of subdural EEG grid placement and associated complications.

Use of a guide catheter as a temporary stent during microcatheter intervention.

Placement of a guiding catheter through a tortuous, narrowed, or intrinsically small vessel may result in severe reduction or occlusion of blood flow. However, nonbraided guiding catheters can be simply modified with a catheter hole punch to create a temporary stent. The stent reestablishes blood flow, which is routed through the distal segment of the guiding catheter while maintaining the guide platform for the introduction of microcatheters and devices necessary to perform intervention.

Intra-arterial papaverine treatment for cerebral vasospasm: our experience and review of the literature.

We described the techniques and efficacy of intra-arterial papaverine hydrochloride infusion (IA-PAP) for symptomatic vasospasm due to aneurysmal subarachnoid hemorrhage based on our experience and review of the literature. Angiographic improvement occurred almost always, but only 50% of patients who presented with acute symptoms showed remarkable clinical improvement after the first, second, or third IA-PAP. Recurrent vasospasm after IA-PAP frequently occurred and this seems to be an apparent source of controversy regarding its efficacy. Review of the literature indicates that IA-PAP may be most effective in combination with percutaneous transluminal angioplasty. Further controlled studies should be conducted regarding papaverine's true efficacy including most effective papaverine concentration and rate of infusion, maximum total dose, site of infusion, timing of treatment, and selection of patients.

Systemic sarcoidosis with bilateral orbital involvement: MR findings.

A 43-year-old woman with diplopia had a disconjugate gaze on physical examination. MR images revealed enlarged, abnormally enhancing extraocular muscles and lacrimal glands bilaterally. Biopsy results were consistent with sarcoidosis. Chest radiographs and CT scans were normal. Clinical and MR findings improved after appropriate medical therapy.

Rhombencephalitis caused by adenovirus: MR imaging appearance.

Encephalitis is a rare manifestation of adenovirus infection. We report the MR imaging findings of a patient with rhombencephalitis caused by adenovirus. Imaging findings included T2 signal abnormalities in the brain stem and cerebellum with mild patchy enhancement and mass effect.

Repeat intra-arterial papaverine for recurrent cerebral vasospasm after subarachnoid haemorrhage.

We assessed the prevalence of recurrent vasospasm following failure of intra-arterial papaverine and the efficacy of repeat intra-arterial infusions of papaverine for control of recurrent vasospasm. Of 24 patients treated with intra-arterial papaverine for vasospasm following aneurysm surgery, 12 did not improve clinically after the initial treatment; 9 received second or third infusions on consecutive days; 6 received only a second infusion; and 3 received a third. Superselective infusion into the intracranial arteries was performed in all nine cases. Despite angiographic improvement after the initial or second infusions, all nine patients showed varying degrees of recurrent vasospasm at the time of the second or third treatment. Within 24 h of a second infusion, three of the six patients had significant clinical improvement, and one of these showed marked improvement soon after a third infusion. Our preliminary results suggest that repeat papaverine infusion may be a way of controlling recurrent or recalcitrant vasospasm.

Granulomatous amebic encephalitis caused by leptomyxid amebae in an HIV-infected patient.

MR images of granulomatous amebic encephalitis caused by leptomyxid amebae in an HIV-infected patient showed both heterogeneous and ring-enhancing hemorrhagic lesions. The brain was diffusely involved, including the brain stem, deep gray matter nuclei, and corticomedullary junction regions of all lobes.

Endovascular extraction of malpositioned fibered platinum microcoils from the aneurysm sac during endovascular therapy.

We describe two cases of coil malpositioning that occurred during endovascular occlusion of saccular basilar tip aneurysms with fibered platinum microcoils. The technique of endovascular coil extraction, accomplished successfully and without complication in both cases, is described and may be applicable to recently available controlled-detachment coil systems.