Medical Excellence - Issue 2

Discussion Aim of the present study was to find determinants to identify those with subtle TIAs among patients with isolated transient vertigo, and to identify risk factors for future stroke or TIA during follow-up. Our sample of 339 persons was a high-risk population with multiple VRFs and a high proportion of vas- cular organ damage. Usually, patients are referred to this unit because the referring physician believes there is a problem with the cervical or cerebral arteries. A somewhat comparable population may be patients pre- senting with acute onset vertigo, although there are important differences: their vertigo episode may be singular (all recurrent in our cohort), possibly more severe (as acute patients called an ambulance immediately, whereas our patients consulted their physician days or weeks later), and presumably longer (in acute patients, the symptoms are mostly still present on arrival at the hospital emergency department). In comparison with the literature data on acute vertigo, absolute follow-up stroke rates were higher in our cohort (any stroke in 4% of the cohort per year) as compared to 1.4% per year in patients who presented with ‘non-stroke dizziness’ to an emergency department in Texas, U.S.A. [10], and 1.7% per year in patients hospitalized for vertigo in Taiwan [11]. This discrep- ancy may be largely explained by the high risk factor load in our cohort: a subgroup of Taiwanese patients hospitalized for vertigo with the most VRFs had a 3.5% annual stroke rate [11], which is very similar to our results. The proportion of patients with stroke as the cause of the initial episode was 0.7% in the Texas cohort [9], whereas in our cohort stroke or TIA was the definite cause in 5.6% and the probable or definite cause of vertigo in 14.2% of our cohort. Again, the main reason for this discrepancy is most likely the large number of VRFs among our patients. In the search for determinants of the diagnosis cerebrovas- cular vertigo , we identified age and precerebral artery stenosis, which were both expected. Unexpectedly, both these determi- nants were inconsistent for the stroke endpoints: here age was not identified at all as a predictor, and stenosis of any cervical or cerebral vessel was even negatively associated with future stroke. For the diagnosis on initial presentation, these two ‘obvious’ risk factors may have influenced the neurologist’s judgment. The fre- quency of vertigo attacks was predictive for the diagnosis ‘defi- nite or probable cerebrovascular vertigo’, where lower frequency was associated with cerebrovascular origin. As many uniform episodes are difficult to explain as TIAs, this factor may also have influenced the judgment of the diagnosing neurologist. ‘Reason for presentation’ was the only determinant that was consistently and significantly associated with the diagnosis ‘cerebrovascular vertigo’ and with future posterior circulation stroke and TIA. It is possible that vertigo, which is due to a subtle brainstem or cerebellar TIA, may be more intense or impressive than vertigo of other causes, thus persuading the patient or his primary care physician to make an urgent clinic appointment. A very interesting influential factor was identified only in the endpoint analysis: the provocation factor ‘changes in body position’, which was associated with lower stroke risk. This as- sociation may tell us that in our cohort peripheral positional vertigo (for example BPPV or benign disabling vertigo [22]) may be more frequent than (ischemic) central positional vertigo (e.g. pseudo-BPPV in vermis stroke/TIA [23]). The lack of an association between ‘head rotation’ as a trigger of vertigo and future stroke can mean either that vertigo caused by functional vertebral artery compression [22] is rare in our patients or – if it occurs – that it rarely causes stroke. The most surprising result of our work is that the judgment of the vascular neurologist was not correlated with future stroke risk. At first glance, this challenges our view of the world: are our sophisticated pathophysiological considerations out of sync with reality? A more comfortable explanation may be that the origi- nally elevated stroke risk for patients correctly classified as ‘subtle vertigo TIA’ was counteracted by the risk factor management we subsequently recommended. Such a hypothetical treatment bias might even explain the inverse association between ‘any stenosis’ and future stroke, as escalations of risk factor management (e.g. tightening low-density lipoprotein cholesterol [LDLc] goals) may be triggered by finding stenoses. What can we learn from these data for the management of our patients? First, we must be careful not to overinterpret these results, as they are explorative and require external vali- dation. Given our sparse and somewhat inconsistent findings, we refrained from constructing an originally planned predictive model. On the basis of the risk factor ‘reason for presentation’ we may consider doing an MRI in patients with isolated transient vertigo, who are worried enough to see the doctor because of this symptom. A clinical benefit of this measure has yet to be proven. Replication of this study in a prospective design may yield the necessary information for constructing a predictive model and developing a refined clinical algorithm. Limitations Some limitations of this study arise from the retrospective design. For example, some important variables characterizing the vertigo (frequency and duration) were incompletely docu- mented (33% and 44%, respectively). A complete documen- tation of these variables in a prospective setting may yield in- teresting results. Furthermore, in only 60% of the patients was a pathologic finding detected with vessel imaging, which is Issue-2  |  17 MEDICAL EXCELLENCE