Continuum: Lifelong Learning in Neurology®

Neuroimaging plays a pivotal role in the evaluation and management of patients with ischemia and cerebrovascular disorders. Multimodal CT and MRI, as well as ultrasound and angiography, detail the extent and severity of blood flow abnormalities, vascular lesions, and resultant tissue injury. From acute stroke to chronic phases of cerebral ischemia, neuroimaging techniques complement the clinical examination and enable the neurologist to improve patient outcomes.(C) 2008 American Academy of Neurology

Imaging of intracranial vascular structures and pathology has become more complex in the recent decade and involves multiple modalities, including conventional endovascular techniques (catheter angiography), magnetic resonance angiography (MRA), and computed tomographic angiography (CTA). Vascular malformations may be characterized physiologically as high or low flow, a determination that can dramatically affect treatment plans. Further characterization of high-flow vascular malformations in the brain is made based on complexity and drainage patterns of the malformation itself. Imaging of aneurysms has been shown with MRA, CTA, and conventional angiography, but the controversy still exists as to when and how to use these modalities in various clinical settings. The purpose of this chapter is to briefly review the types of intracranial vascular malformations, discuss the preferred methods of imaging in each case, and attempt to provide a rational approach to imaging the intracranial vascular structure and pathology with techniques available in 2007.(C) 2008 American Academy of Neurology

Imaging for headaches is one of the most frequent and at times challenging decisions a neurologist has to make in the clinical practice of neurology and is complicated by today's medical-legal milieu and overseeing regulatory organizations. Although the final decision should always be made by the treating physician, the American Academy of Neurology has developed practice parameters for the imaging of headaches. One strong criticism of the overzealous use of neuroimaging in patients with headache is the frequency of incidental findings, which may in turn increase a patient's anxiety and potentially cause an exacerbation of symptoms. This may subsequently lead to unnecessary testing as well as neurosurgical intervention. The clinical interpretation of incidental findings and headaches is best made by a neurologist who is able to correlate the imaging findings with the patient's symptoms and examination. One of the principal precepts in medicine, "primum nil nocere" or "first, do no harm" to patients, should be considered in the interpretation of these so-called abnormalities. The development of programs to certify competence in physicians who have completed accredited training programs in neuroimaging as well as headache medicine by the United Council for Neurologic Subspecialties is an important advancement that allows clinicians the opportunity to enhance quality of patient care.(C) 2008 American Academy of Neurology

Structural brain imaging with CT or MRI should be performed in any patient with progressive cognitive impairment to rule out a reversible cause, such as a benign brain tumor, a subdural hematoma, or hydrocephalus. But imaging can also help separate the various types of degenerative dementia and facilitates the prognosis of these disorders. Medial temporal atrophy is an early finding in Alzheimer disease (AD). Early in AD, metabolism is decreased in the parietotemporal association cortex and retrosplenial region. When these imaging findings are present in mild cognitive impairment, it is more likely to evolve to AD. Amyloid deposition in AD and Lewy body dementia can now be imaged, differentiating these disorders from dementias without amyloid deposition, such as frontotemporal dementia and corticobasal degeneration. Atrophy or the decrease in brain metabolic activity associated with the dementias could be used as surrogate markers of response to new therapies in clinical trials.(C) 2008 American Academy of Neurology

Neuroimaging has become as important as the use of EEG in the diagnosis and classification of epilepsy. Although functional techniques such as SPECT and PET have played important roles in the workup of patients prior to surgery, MRI remains the principal imaging technique used in epilepsy. Additionally, the multimodal use of imaging is becoming increasingly important in the evaluation of patients with epilepsy.(C) 2008 American Academy of Neurology

The practice of neurology presents a series of ethical challenges for the clinician. These rarely have simple or straightforward solutions, but require careful consideration by the neurologist. This section of CONTINUUM provides a case vignette that raises one or more ethical questions related to the subject area of this issue. The discussion that follows, written by colleague(s) with particular interest in bioethics, should help the reader understand and resolve the ethical dilemma.(C) 2008 American Academy of Neurology