Contrast material enhancement for cross-sectional imaging has been used since the mid 1970s for computed tomography and the mid 1980s for magnetic resonance imaging. Knowledge of the patterns and mechanisms of contrast enhancement facilitate radiologic differential diagnosis. Brain and spinal cord enhancement is related to both intravascular and extravascular contrast material. Extraaxial enhancing lesions include primary neoplasms (meningioma), granulomatous disease (sarcoid), and metastases (which often manifest as mass lesions). Linear pachymeningeal (dura-arachnoid) enhancement occurs after surgery and with spontaneous intracranial hypotension. Leptomeningeal (pia-arachnoid) enhancement is present in meningitis and meningoencephalitis. Superficial gyral enhancement is seen after reperfusion in cerebral ischemia, during the healing phase of cerebral infarction, and with encephalitis. Nodular subcortical lesions are typical for hematogenous dissemination and may be neoplastic (metastases) or infectious (septic emboli). Deeper lesions may form rings or affect the ventricular margins. Ring enhancement that is smooth and thin is typical of an organizing abscess, whereas thick irregular rings suggest a necrotic neoplasm. Some low-grade neoplasms are "fluid-secreting," and they may form heterogeneously enhancing lesions with an incomplete ring sign as well as the classic "cyst-with-nodule" morphology. Demyelinating lesions, including both classic multiple sclerosis and tumefactive demyelination, may also create an open ring or incomplete ring sign. Thick and irregular periventricular enhancement is typical for primary central nervous system lymphoma. Thin enhancement of the ventricular margin occurs with infectious ependymitis. Understanding the classic patterns of lesion enhancement--and the radiologic-pathologic mechanisms that produce them--can improve image assessment and differential diagnosis.

The authors estimated the prevalence of post-traumatic stress disorder (PTSD) and illness resembling chronic fatigue syndrome (CFS) in the entire population of Gulf War and non-Gulf-War veterans. They also evaluated the relation between the extent of deployment-related stress and the risk of either PTSD or CFS. In 1995-1997, the authors conducted a health survey in which these two symptom-based medical diagnoses in a population-based sample of 15,000 Gulf War veterans representing four military branches and three unit components (active, reserve, and National Guard) were compared with those of 15,000 non-Gulf veteran controls. Gulf War veterans, compared with non-Gulf veteran controls, reported significantly higher rates of PTSD (adjusted odds ratio = 3.1, 95% confidence interval: 2.7, 3.4) and CFS (adjusted odds ratio = 4.8, 95% confidence interval: 3.9, 5.9). The prevalence of PTSD increased monotonically across six levels of deployment-related stress intensity (test for trend: p < 0.01), while the prevalence of CFS rose only at the low end of the stress spectrum. While deployment-related stress could account for the higher risks of both PTSD and CFS, additional factor(s) unique to the Gulf environment may have contributed to the risk of CFS among Gulf War veterans.

Despite numerous studies on veterans of the 1990 to 1991 Gulf War, the fundamental questions of how healthy they are and how their health compares with that of their military peers who were not deployed to the Gulf have not been fully answered. We conducted a health survey in which the health outcomes of a population-based sample of 15,000 Gulf veterans representing various military branches and unit components (regular, reserve, National Guard) were compared with those of 15,000 non-Gulf veterans who were randomly sampled to mirror the number in the same military strata in the Gulf veteran group. In comparison with their peers, Gulf veterans had a higher prevalence of functional impairment, health care utilization, symptoms, and medical conditions and a higher rate of low general health perceptions. A longitudinal follow-up of the health of these veterans will be needed to detect changes in health status and to detect diseases with a long latency period.

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