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INTRODUCTION

The clinician caring for pts with neurologic symptoms is faced with an expanding number of imaging options. MRI is more sensitive than CT for detection of many lesions affecting the nervous system, particularly those of the spinal cord, cranial nerves, and posterior fossa structures. Diffusion MR, a sequence that detects reduction of microscopic motion of water, is the most sensitive technique for detecting acute ischemic stroke and is useful in the detection of encephalitis, abscesses, and prion diseases. CT, however, can be quickly obtained and is widely available, making it a pragmatic choice for initial evaluation of pts with suspected acute stroke (especially when coupled with CT angiography and perfusion CT), hemorrhage, and intracranial or spinal trauma. CT is also more sensitive than MRI for visualizing fine osseous detail and is indicated in the initial evaluation of conductive hearing loss as well as lesions affecting the skull base and calvarium. MRI and CT-myelography have replaced conventional myelography for evaluation of disease of the spinal cord and canal. An increasing number of interventional neuroradiologic techniques are available including embolization, coiling, and stenting of vascular structures as well as spine interventions such as discography, selective nerve root injection, and epidural injection. Conventional angiography is now reserved for pts in whom small-vessel detail is essential for diagnosis or for whom interventional therapies are planned. Guidelines for initial selection of neuroimaging studies are shown in Table 192-1.

TABLE 192-1GUIDELINES FOR THE USE OF CT, ULTRASOUND, AND MRI

For a more detailed discussion, see Dillon WP: Neuroimaging in Neurologic Disorders, Chap. 368, p. 3240, in HPIM-18.

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