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• Thalamic strokes in 62 patients selected from the Stroke Data Bank were studied to determine differences among 18 infarctions (INF), 23 localized hemorrhages (ICH), and 21 hematomas with ventricular extension (IVH). Stupor or coma at onset occurred more frequently in the IVH (62%) than in the INF (6%) or ICH (13%) groups and was reflected in significantly lower median Glasgow Coma Scores in the IVH group (7) than in the INF (15) and ICH (14) groups. Although ocular movements were more frequently abnormal in the IVH group compared with the ICH and INF groups, no significant differences were found in the frequency of motor or sensory deficits. Among the 62 strokes, 32 had restricted lesions of the posterolateral (n=9), anterior (n=3), paramedian (n=7), and dorsal (n=13) portions of the thalamus. Differences in consciousness and in motor, sensory, and oculomotor deficits were found among the topographic subgroups. Stroke-related deaths occurred in 52% of IVH cases, 13% of ICH cases, and no cases of INF. Median lesion volume as detected with computed tomography was greater in hemorrhages (INF, 2 cm3; ICH, 10 cm3; IVH, 16 cm3), with mortality related to increasing hematoma size. Coma, Glasgow Coma Score lower than 9, weakness score greater than 15 of a possible 30, abnormal ocular movements, and fixed pupils were also associated with stroke-related mortality. We conclude that the initial neurologic syndrome does not discriminate infarcts from intrathalamic hemorrhages. Ventricular extension, however, causes significantly more severe deficits and higher mortality.

• Interobserver reliability in interpretation of computed tomographic images was studied by six senior neurologists who independently evaluated on a standardized Stroke Data Bank form the brain lesions of 17 patients. The results analyzed with k statistics yielded moderate to substantial agreement on most items of interest including the stroke pathology and anatomy. In general, the levels of agreement were as high as previously reported for the diagnosis of the mechanism of the stroke, and much higher than on many stroke history items and items of neurologic examination. Excellent agreement was obtained for the detection of infarcts and intracerebral hemorrhage, and substantial agreement was obtained on whether the computed tomographic images were normal or indicative of small deep infarcts, superficial and deep infarcts, and aneurysms. The level of agreement on anatomy of the lesions was best for the frontal, parietal, and temporal lobes, putamen, cerebellum, and subarachnoid space. Implications for clinical research and diagnosis are discussed.

• Interobserver agreement is essential to the reliability of clinical data from cooperative studies and provides the foundation for applying research results to clinical practice. In the Stroke Data Bank, a large cooperative study of stroke, we sought to establish the reliability of a key aspect of stroke diagnosis: the mechanism of stroke. Seventeen patients were evaluated by six neurologists. Interobserver agreement was measured when diagnosis was based on patient history and neurologic examination only, as well as when it was based on results of a completed workup, including a computed tomographic scan. Initial clinical impressions, based solely on history and one neurologic examination, were fairly reliable in establishing the mechanism of stroke (ie, distinguishing among infarcts, subarachnoid hemorrhages, and parenchymatous hemorrhages). Classification into one of nine stroke subtypes was substantially reliable when diagnoses were based on a completed workup. Compared with previous findings for the same physicians and patients, the diagnosis of stroke type was generally more reliable than individual signs and symptoms. These results suggest that multicentered studies can rely on the independent diagnostic choices of several physicians when common definitions are employed and data from a completed workup are available. Furthermore, reliability may be less for individual measurements such as signs or symptoms than for more-complex judgments such as diagnoses.

• Interobserver reliability in obtaining neurologic histories and examinations was investigated among neurologists collaborating in the Stroke Data Bank (SDB). Seventeen in-hospital stroke patients were examined by six neurologists experienced in stroke over the course of three days. Patients were examined twice a day for two successive days, with each patient seen by four different neurologists. Data were recorded on SDB forms, according to definitions and procedures established for the SDB. Percent agreement and κ coefficients were calculated to assess the levels of agreement for each item. Important differences in levels of agreement were found among items on both neurologic history and examination. Agreement among neurologists was higher for neurologic examination than for history. Patterns of agreement for items with low prevalence or with numerous unknown ratings are discussed. Improvement in interobserver agreement due to data editing for intra-observer consistency was shown.