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Patients who experience symptoms described as transient neurological attacks, such as temporary amnesia or confusion, may have a higher risk for stroke and dementia, according to a new study. Patients who experience symptoms described as transient neurological attacks, such as temporary amnesia or confusion, may have a higher risk for stroke and dementia, according to a study[1] in the December 26 issue of JAMA.

Transient neurological attacks (TNAs) are episodes involving temporary (less than 24 hours) neurological symptoms. These symptoms can be nonfocal (that can include nonlocalizing cerebral symptoms), focal (known as transient ischemic attacks [TIAs], similar to ischemic stroke, except for duration [commonly two to 15 minutes, maximum 24 hours]), or a mixture of both focal and nonfocal. Although it has been well-documented that patients with TIA are at high risk of major vascular disease, few studies have examined whether nonfocal TNAs are a serious health threat, according to background information in the article.

Michiel J. Bos, M.D., M.Sc., of Erasmus Medical Center, Rotterdam, the Netherlands, and colleagues studied the incidence and prognosis of focal, nonfocal and mixed TNAs. The study included 6,062 participants who were age 55 years or older and free from stroke, heart attack, and dementia when they entered the study (1990-1993), and were followed-up until January 2005.

During the study a TNA occurred in 548 participants; 282 of these were classified as focal, 228 as nonfocal, and 38 as mixed. In both men and women, the incidence rates for nonfocal TNAs were almost as frequent as focal TNAs, and for both types of events the incidence rates strongly increased with increasing age. Mixed TNAs were less frequent.

During follow-up, there were 619 cases of stroke, 848 cases of ischemic heart disease, 662 vascular deaths (also classified as having stroke [192] or ischemic heart disease [430]) and 609 cases of dementia. Compared with participants without TNA, participants with focal TNA had more than twice the risk of stroke and 2.6 times the risk of ischemic stroke; the risk of stroke within 90 days after focal TNA (TIA) was 3.5 per cent. Patients with nonfocal TNA had a 56 per cent higher risk of stroke and 59 per cent higher risk of dementia, than participants without TNA.

Patients with mixed TNA were at increased risk of stroke, especially ischemic stroke; ischemic heart disease, especially heart attack; and vascular death and dementia, compared with participants without TNA.

"Our findings challenge the strong but unfounded conviction that nonfocal TNAs are harmless. On the contrary, our findings suggest that nonfocal TNAs are not only a risk factor for stroke, but also for dementia," the authors write.

Editorial: Transient neurological attack - a useful concept?

In an accompanying editorial[2], S. Claiborne Johnston, M.D., Ph.D., of the University of California, San Francisco, writes that this study reports important new information.

"… this is the first large-scale study of TNAs, and the findings are intriguing for several reasons. Most patients with nonfocal TNAs are currently treated as though the condition were benign. For some etiologies, such as transient global amnesia, the evidence supports this, but for most of these events, there is no consistent evaluation, no guidelines for treatment, and no information on prognosis. This study argues that, whatever is causing these events, the prognosis justifies greater attention. More needs to be done to identify the TNA patients at greatest risk, to complete evaluations, to rule out important underlying disease, and to continue to study this heterogeneous group."


[1] JAMA. 2007;298(24):2877-2885.
[2] JAMA. 2007;298(24):2912-2913.