Central Nervous System Complications of Oncologic Therapy.

Traditional and newer agents used to treat cancer can cause significant toxicity to the central nervous system. MRI of the brain and spine is the imaging modality of choice for patients with cancer who develop neurologic symptoms. It is important to be aware of the agents that can cause neurotoxicity and their associated imaging findings so that patients are properly diagnosed and treated. In some instances conventional MRI may not be able to differentiate posttreatment effects from disease progression. In these instances advanced imaging techniques may be helpful, although further research is still needed.

Stroke risk stratification in acute dizziness presentations: A prospective imaging-based study.

OBJECTIVE: To estimate the ability of bedside information to risk stratify stroke in acute dizziness presentations. METHODS: Surveillance methods were used to identify patients with acute dizziness and nystagmus or imbalance, excluding those with benign paroxysmal positional vertigo, medical causes, or moderate to severe neurologic deficits. Stroke was defined as acute infarction or intracerebral hemorrhage on a clinical or research MRI performed within 14 days of dizziness onset. Bedside information comprised history of stroke, the ABCD(2) score (age, blood pressure, clinical features, duration, and diabetes), an ocular motor (OM)-based assessment (head impulse test, nystagmus pattern [central vs other], test of skew), and a general neurologic examination for other CNS features. Multivariable logistic regression was used to determine the association of the bedside information with stroke. Model calibration was assessed using low (<5%), intermediate (5% to <10%), and high (≥10%) predicted probability risk categories. RESULTS: Acute stroke was identified in 29 of 272 patients (10.7%). Associations with stroke were as follows: ABCD(2) score (continuous) (odds ratio [OR] 1.74; 95% confidence interval [CI] 1.20-2.51), any other CNS features (OR 2.54; 95% CI 1.06-6.08), OM assessment (OR 2.82; 95% CI 0.96-8.30), and prior stroke (OR 0.48; 95% CI 0.05-4.57). No stroke cases were in the model's low-risk probability category (0/86, 0%), whereas 9 were in the moderate-risk category (9/94, 9.6%) and 20 were in the high-risk category (20/92, 21.7%). CONCLUSION: In acute dizziness presentations, the combination of ABCD(2) score, general neurologic examination, and a specialized OM examination has the capacity to risk-stratify acute stroke on MRI.

Safety of intravenous thrombolytic use in four emergency departments without acute stroke teams.

OBJECTIVES: The objective was to evaluate safety of intravenous (IV) tissue plasminogen activator (tPA) delivered without dedicated thrombolytic stroke teams. METHODS: This was a retrospective, observational study of patients treated between 1996 and 2005 at four southeastern Michigan hospital emergency departments (EDs) with a prospectively defined comparison to the National Institute of Neurological Disorders and Stroke (NINDS) tPA stroke study cohort. Main outcome measures were mortality, intracerebral hemorrhage (ICH), systemic hemorrhage, neurologic recovery, and guideline violations. RESULTS: A total of 273 consecutive stroke patients were treated by 95 emergency physicians (EPs) using guidelines and local neurology resources. One-year mortality was 27.8%. Unadjusted Cox model relative risk (RR) of mortality compared to the NINDS tPA treatment and placebo groups was 1.20 (95% confidence interval [CI] = 0.87 to 1.64) and 1.04 (95% CI = 0.76 to 1.41), respectively. The rate of significant ICH by computed tomography (CT) criteria was 6.6% (odds ratio [OR] = 1.03, 95% CI = 0.56 to 1.90 compared to the NINDS tPA treatment group). The proportions of symptomatic ICH by two other prespecified sets of clinical criteria were 4.8 and 7.0%. The rate of any ICH within 36 hours of treatment was 9.9% (RR = 0.94, 95% CI = 0.58 to 1.51 compared to the NINDS tPA group). The occurrence of major systemic hemorrhage (requiring transfusion) was 1.1%. Functional recovery by the modified Rankin Scale score (mRS = 0 to 2) at discharge occurred in 38% of patients with a premorbid disability mRS < 2. Guideline deviations occurred in the ED in 26% of patients and in 25% of patients following admission. CONCLUSIONS: In these EDs there was no evidence of increased risk with respect to mortality, ICH, systemic hemorrhage, or worsened functional outcome when tPA was administered without dedicated thrombolytic stroke teams. Additional effort is needed to improve guideline compliance.

Feasibility of superficial temporal artery as the input artery for cerebral perfusion CT.

OBJECTIVE: The purpose of this study was to determine whether the superficial temporal artery as a surrogate arterial input function, compared with the anterior cerebral artery as the arterial input function, generates accurate perfusion CT maps with significant correlates for cerebral blood flow, cerebral blood volume, and mean transit time. MATERIALS AND METHODS: One hundred perfusion CT examinations performed on 90 patients (51 women and girls, 39 men and boys) were retrospectively reviewed and postprocessed by one investigator using CT perfusion software at a workstation. Color-coded cerebral blood flow, cerebral blood volume, and mean transit time maps were constructed with the superficial temporal artery as a surrogate arterial input function and the anterior cerebral artery as the arterial input function. The effect of input artery choice on mean cerebral blood flow, cerebral blood volume, and mean transit time values in six regions of interest (one region of interest in each anterior cerebral artery, middle cerebral artery, and posterior cerebral artery territory) was assessed. RESULTS: All graphs of correlation between the anterior cerebral artery as the arterial input function and the superficial temporal artery as a surrogate arterial input function produced significant results (p < 0.0001). Excellent correlation existed between the cerebral blood flow (r = 0.96 [Pearson correlation coefficient]; rho(c) = 0.96 [concordance correlation coefficient]), cerebral blood volume (r = 0.97; rho(c) = 0.97), and mean transit time (r = 0.97; rho(c) = 0.97) values obtained with the anterior cerebral artery and the values obtained with the superficial temporal artery. Linear regression lines produced strong agreement between use of the anterior cerebral artery and use of the superficial temporal artery (cerebral blood flow, y = 1.03x + 0.65; cerebral blood volume, y = 1.05x - 0.09; mean transit time, y = 0.92x + 0.21). CONCLUSION: The preliminary results show that using an extracranial vessel such as the superficial temporal artery as a surrogate input artery can generate perfusion maps comparable with those generated with an intracranial vessel such as the anterior cerebral artery. This knowledge can be useful if the proximal intracranial vessels typically used for arterial input are not visible owing to diffuse disease, such as diffuse vasospasm and atherosclerosis, or are not included in the field of view of perfusion CT.

Cerebral perfusion imaging.

There are multiple imaging techniques available to assess cerebral perfusion, including positron emission tomography (PET), xenon computed tomography (XeCT), single photon emission computed tomography (SPECT), perfusion-weighted MRI (PWI), and perfusion computed tomography (PCT). Current interest has focused mainly on their use in the setting of acute brain ischemia. Perfusion imaging may be able to distinguish infarcted from salvageable ischemic tissue as a guide to treatment. Perfusion techniques may also be helpful in cases of chronic ischemia, post-subarachnoid hemorrhage vasospasm, trauma, and contemplated therapeutic carotid artery occlusion.

Delineation of lateral tentorial sinus with contrast-enhanced MR imaging and its surgical implications.

BACKGROUND AND PURPOSE: The lateral tentorial sinus (LTS) has not been well described in the imaging literature. The aim of this study was to investigate the value of MR imaging in assessing the LTS, which may provide guidance for preoperative planning. METHODS: Fifty-five adult patients underwent MR imaging of the brain. Four neuroradiologists evaluated the studies for delineation of the LTS and its branches. Presence of arachnoid granulation and dominance of the venous drainage also were reported. RESULTS: An LTS was detected in 104 of 110 lobes. The LTS in each lobe was classified as type I (candelabra) in 30 (28.8%), type II (independent veins) in 22 (21.1%), and type III (venous lakes) in 37 (35.5%); in 15 (14.4%) of the lobes, the LTS was indeterminate. LTS branches were inconsistently detected, with the exception of the vein of Labbé (VL). Five of eight branches were seen in approximately half of the cases. The VL was identified in 94 (85.4%) lobes. Among these, 53 (56.4%) were draining into the LTS and 22 (23.4%) into the transverse sinus; in 19 (20.2%) cases, the terminal portion was not visualized. The right transverse sinus was dominant in 19 (34.5%) patients and the left in 18 (32.7%); codomination was present in 18 (32.7%) cases. At least one arachnoid granulation was seen in the transverse sinus in 27 (49.1%) patients. CONCLUSION: In many instances, the LTS and VL drainage patterns were well delineated on routine MR images. For selected cases, this information may be crucial during lateral skull base surgery to avoid venous infarct.

Cerebral perfusion CT: technique and clinical applications.

Perfusion computed tomography (CT) is a relatively new technique that allows rapid qualitative and quantitative evaluation of cerebral perfusion by generating maps of cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT). The technique is based on the central volume principle (CBF = CBV/MTT) and requires the use of commercially available software employing complex deconvolution algorithms to produce the perfusion maps. Some controversies exist regarding this technique, including which artery to use as input vessel, the accuracy of quantitative results, and the reproducibility of results. Despite these controversies, perfusion CT has been found to be useful for noninvasive diagnosis of cerebral ischemia and infarction and for evaluation of vasospasm after subarachnoid hemorrhage. Perfusion CT has also been used for assessment of cerebrovascular reserve by using acetazolamide challenge in patients with intracranial vascular stenoses who are potential candidates for bypass surgery or neuroendovascular treatment, for the evaluation of patients undergoing temporary balloon occlusion to assess collateral flow and cerebrovascular reserve, and for the assessment of microvascular permeability in patients with intracranial neoplasms. This article is a review of the technique, clinical applications, and controversies surrounding perfusion CT.

Carotid perfusion CT with balloon occlusion and acetazolamide challenge test: feasibility.

Carotid balloon test occlusion (BTO) is used to assess the collateral circulation and cerebrovascular reserve in patients in whom carotid artery occlusion is contemplated. Eight patients in whom the test was successful were evaluated with perfusion computed tomography (CT) in the resting state and after acetazolamide challenge. Three of the patients showed symmetric blood flow and normal response to acetazolamide. One of them underwent permanent carotid occlusion and did not develop any delayed ischemic stroke. The remaining five patients showed asymmetric blood flow. One of them had markedly low blood flow and abnormal response to acetazolamide. The patient developed ipsilateral hemispheric stroke following permanent carotid occlusion after the superficial temporal artery to middle cerebral artery bypass graft occluded. In the other four patients, the steal phenomenon was seen in ipsilateral and contralateral hemispheres. Although definitive quantitative values for perfusion CT are not yet standardized, it may be feasible to predict that the patients with symmetric blood flow and normal acetazolamide-enhanced challenge test results will do well after permanent carotid occlusion. Patients with asymmetric blood flow and abnormal response to the acetazolamide challenge test may require a revascularization procedure to protect them from delayed ischemic stroke.

Computed tomography perfusion of squamous cell carcinoma of the upper aerodigestive tract. Initial results.

OBJECTIVE: To define the computed tomography (CT) perfusion characteristics of head and neck squamous cell carcinoma. METHODS: Fourteen consecutive patients with untreated squamous cell cancers of head and neck underwent CT of the head and neck along with CT perfusion imaging through the primary site. For the perfusion studies, CT density changes in blood and tissues were kinetically analyzed using the commercially available CT Perfusion 2 software (General Electric Medical Systems. Milwaukee, WI) on a GE Advantage Windows workstation. This yielded parameter maps of fractional tissue blood volume (mL/100 g), blood flow (mL x 100 g(-1) x min(-1)), mean transit time (s), and microvascular permeability surface area product (mL x 100 g(-1) x min(-1)). One head and neck radiologist analyzed perfusion data. Regions of interest (ROI) were placed over the primary tumor site, tongue base, and adjacent muscle groups. The average values of tissue blood volume (BV), blood flow (BF), mean transit time (MTT), and capillary permeability surface area product (CP) were then calculated for the tumor and compared with the average values for the tongue base and adjacent musculature. To determine a statistically significant difference between the tumor and muscle parameters, the Wilcoxon sign test, a nonparametric test for paired data, was employed. RESULTS: The average values of CP, BF, and BV were higher in primary tumor (41.9, 132.9, 6.2, respectively) than in tongue base or adjacent muscular structures. The MTT was reduced in primary tumors (4.0) compared with adjacent normal structures. The above differences were statistically significant (P<0.05). CONCLUSIONS: We obtained baseline perfusion data for head and neck squamous cell cancers and compared it with adjacent normal structures. Our initial results suggest that CT perfusion parameters (CP, BF, BV, and MTT) can be used to help differentiate head and neck squamous cell carcinoma (SCCA) from adjacent normal tissue.