Jack, Clifford R.

BackgroundThe promise of Alzheimer's disease biomarkers has led to their incorporation in new diagnostic criteria and in therapeutic trials; however, significant barriers exist to widespread use. Chief among these is the lack of internationally accepted standards for quantitative metrics. Hippocampal volumetry is the most widely studied quantitative magnetic resonance imaging measure in Alzheimer's disease and thus represents the most rational target for an initial effort at standardization.Methods and ResultsThe authors of this position paper propose a path toward this goal. The steps include the following: (1) Establish and empower an oversight board to manage and assess the effort, (2) adopt the standardized definition of anatomic hippocampal boundaries on magnetic resonance imaging arising from the European Alzheimer's Disease Centers–Alzheimer's Disease Neuroimaging Initiative hippocampal harmonization effort as a reference standard, (3) establish a scientifically appropriate, publicly available reference standard data set based on manual delineation of the hippocampus in an appropriate sample of subjects (Alzheimer's Disease Neuroimaging Initiative), and (4) define minimum technical and prognostic performance metrics for validation of new measurement techniques using the reference standard data set as a benchmark.ConclusionsAlthough manual delineation of the hippocampus is the best available reference standard, practical application of hippocampal volumetry will require automated methods. Our intent was to establish a mechanism for credentialing automated software applications to achieve internationally recognized accuracy and prognostic performance standards that lead to the systematic evaluation and then widespread acceptance and use of hippocampal volumetry. The standardization and assay validation process outlined for hippocampal volumetry was envisioned as a template that could be applied to other imaging biomarkers.

BackgroundCerebral vasogenic edema (VE) has been reported to occur during antiamyloid immunotherapy. VE may be associated with central nervous system pathology with blood–brain barrier disruptions; however, less is known about the prevalence of naturally occurring VE in patients with Alzheimer's disease (AD).MethodsFluid‐attenuated inversion recovery imaging sequences were obtained from four ongoing multicenter, randomized, double‐blind, placebo‐controlled, phase 3 trials in patients with mild‐to‐moderate AD. The first set of baseline scans was from patients in volumetric magnetic resonance imaging addenda in the Interrupting Alzheimer's Dementia by EvaluatiNg Treatment of Amyloid PaThologY (IDENTITY) studies examining semagacestat, a γ‐secretase inhibitor (cohort 1, n = 621). The second set of baseline scans was from the EXPanding Alzheimer's Disease InvestigaTIONs (EXPEDITION) studies examining solanezumab, an anti‐Aβ monoclonal antibody (cohort 2, n = 2141). Readers were blinded to patient‐identifying information and future treatment. A third set of baseline scans was from the first 700 patients who underwent protocol‐specified magnetic resonance imaging before randomization in the EXPEDITION studies (cohort 3). The analysis used three neuroradiologists: two performed independent primary interpretations and the third was the adjudicator. Readers were blinded to patient information, treatment, protocol, and time point.ResultsFour cases of asymptomatic VE were detected at baseline/screening. Two VE cases were due to underlying extra‐axial mass lesions. The third VE case was associated with numerous microhemorrhages in keeping with cerebral amyloid angiopathy‐related inflammation or Aβ‐related angiitis. The final VE case demonstrated localized sulcal fluid‐attenuated inversion recovery imaging hyperintensity. No VE was detected in cohort 3 by readers blinded to patient baseline status.ConclusionsVE seems to be rare at baseline in patients with AD in clinical trials, 2 of 2762 associated with AD. Additional cohorts should be evaluated to support these findings.

Intracerebral hematoma may complicate treatment of acute myocardial infarction in patients treated with fibrinolytic agents. We studied the clinical presentation and computed tomographic characteristics. We studied eight patients with lobar intracerebral hematomas after fibrinolytic treatment of acute coronary occlusion. All patients had electrocardiographic and laboratory evidence of acute myocardial infarction and were treated with tissue plasminogen activator or streptokinase followed by heparin infusion to prevent reocclusion. Computed tomography scans of 17 patients with cerebral hemorrhage from other causes were used for comparison. For most patients, outcome was fatal within hours of the ictus. Computed tomography scans showed superficially large lobar hematomas in six patients. One patient had a putaminal hemorrhage, and one had a vermis hemorrhage. Multiple sites of intracerebral hemorrhage were noted in three patients. Fluid levels inside the hematoma suggesting continuing hemorrhage into multiple compartments were common. Radiologically, fluid levels in hematomas, multiple hematomas, and blood in multiple compartments served to differentiate fibrinolysis-induced hemorrhage from hemorrhage of other causes. Severe amyloid angiopathy was found in one patient who was operated on. Hemorrhages in multiple compartments and the presence of fluid levels inside the hematoma suggest fibrinolysis-associated cerebral hematomas. Severe amyloid angiopathy may be a crucial factor in this clinical entity. Outcome is poor, and a high proportion of patients have rapid progression to brain death. Therefore, emergency neurosurgical evacuation will probably be unsuccessful.

Antiphospholipid antibodies are known to be associated with increased risk of venous and arterial thrombotic events, including cerebral venous thromboses. Pseudotumor syndrome can be produced by cerebral venous thrombosis. A patient with cerebral venous thrombosis associated with antiphospholipid antibodies who exhibited pseudotumor syndrome is reported. A 49-year-old man who noted visual blurring and persistent vertical wavy lines in his fields of vision was found to have papilledema. Cerebrospinal fluid values were normal except for an opening pressure increase to 510 mm of fluid. His visual symptoms improved with lumbar puncture and the use of acetazolamide. Imaging studies showed that the transverse sinus was occluded completely on the left and partially on the right and that there was a small left cerebellar cortical venous infarction. Antiphospholipid syndrome should be considered in the differential diagnosis of pseudotumor syndrome related to cerebral venous thrombosis.