Highlights of the 26th Annual Meeting of the American Society of Neuroimaging

Rohit Bakshi, MD

Disclosures

March 26, 2003

In This Article

Introduction

The Annual Meeting of the American Society of Neuroimaging (ASN) showcases the applications of neuroimaging to a wide variety of disorders. This year's meeting highlighted advances in the neuroimaging of cerebrovascular diseases, lupus, epilepsy, autism, multiple sclerosis, neuro-oncology, and epilepsy. Abstracts from the 26th Annual Meeting of the ASN are published in the April issue of the Journal of Neuroimaging

Vasomotor Reactivity. Cerebral vasomotor reactivity (CVR) can be assessed by transcranial Doppler (TCD) using various stimuli, such as acetazolamide challenge and breath-holding. Tests of CVR are valuable in the assessment of vascular reserve and the effect of injury to the brain or the intracranial vessels. Breath-holding has the advantages of ease of use and noninvasiveness.

Tegler and colleagues[1] from the Karolinska Institute in Stockholm, Sweden, tested CVR using TCD in 91 amateur athletes, 8 of whom had experienced sports-related concussions. The athletes participated in organized football (n = 86) or soccer (n = 4). TCD was performed at rest and with continuous bilateral middle cerebral artery monitoring during a variety of challenges including hyperventilation, breath-holding, and leg-up tilt. Neuropsychological testing revealed significant impairment in those who had concussions. TCD showed abnormally reduced CVR to breath-holding as compared with baseline in all of these postconcussive patients. This pilot study shows the feasibility of using TCD to assess brain injury after concussion. TCD may provide a sensitive tool to objectively assess concussive brain injury and assist in evaluation and treatment of these patients.

Cerebral Circulatory Arrest in Brain Death. The diagnosis of brain death requires clinical examination and, when necessary, appropriate laboratory confirmation. The accurate diagnosis of brain death is important for guiding decision making in the critically ill patient, including assessing the need for continued mechanical support and identifying candidates for organ donation. There is wide consensus that a person is dead when the brain is dead. However, brain death must be differentiated from severe brain injury with residual brain function. The most common causes of brain death are trauma, subarachnoid hemorrhage, anoxia, and infection.

Laboratory measures of brain function, such as electroencephalography, angiography, and nuclear imaging, are often useful adjuncts to clinical examination in the diagnosis of brain death. TCD can also be used to document a lack of intracranial blood flow, a sign known as reverberating flow. Garami and colleagues[2] developed a specialized TCD protocol for assessing brain death and correlated such findings with neurologic examination and nuclear medicine studies in 22 patients. The diagnosis of cerebral circulatory arrest by TCD required the demonstration of no arterial or venous intracranial blood flow in the setting of reverberating flow and normal systemic hemodynamic status. Accuracy of TCD was 100% compared against nuclear medicine studies.

TCD requires the presence of clear windows and is best implemented in this setting by experienced operators. This study shows the feasibility of using a relatively inexpensive, rapid, bedside laboratory test to confirm the diagnosis of brain death.

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