This study primarily aims to compare, on a sample of 118 post-acute stroke patients, the results on extinction and inattention NIHSS subtest with a more accurate test for peripersonal hemineglect (OCS heart subtest, Ohs). Additionally, this study investigates the influence of the visual field NIHSS subtest on the results of extinction and inattention item, given that hemianopsia and neglect frequently coexist and that the two disturbances may be confused in the stroke population .
Our results showed a poor sensitivity of NIHSS detecting peripersonal neglect (56.8%). Dichotomising the results (normal/pathological), Cohen’s kappa test between the two tests was moderate and the accuracy was 72.9%. Compared to the Ohs, NHISS extinction and inattention subtest had 29 false negatives, and 3 false positives. Therefore, in the 24.6% of cases, NIHSS was unable to detect neglect and, unexpectedly, in the 2.5% of cases NIHSS classified as inattention symptoms signs that were not detected in Ohs test.
Among the false negatives, NIHSS showed a tendency in misclassification especially on those patients with mild forms of heminattention, where, as it is intuitive, clinical observation may not be enough (Fig. 1). Nevertheless, some other considerations could be done. NIHSS may fail in detecting neglect, also because the scale considers extinction as a crucial aspect. The lack of extinction in visual or somatic bilateral stimulation, does not unequivocally mean that patients do not present hemineglect. Neglect is a heterogeneous syndrome and extinction is not the determining factor for the diagnosis. Although both neglect and extinction are typical syndromes of acute right hemispheric stroke and frequently co-occur, they do not overlap [21,22,23]. Hence, the principle used by the NIHSS scale to guide the clinician towards the diagnosis, may not be the most appropriate.
Regarding the false positives, one out of three presented a normal Nvfs. After the analysis of the patient’s performance, it was found in the clinical folder that he was affected by a selective extrapersonal neglect, and consequently correctly diagnosed with respect to hemianopia. In the other two cases, a confounding effect of visual field task may be supposed. Hemianopia and neglect frequently coexist, and a differential diagnosis is often difficult. Hemianopia may be misattributed to hemineglect and, equally, neglect impairments may be misattributed to hemianopia. In fact, patients with heminattention may fall into the manual visual field test, because they do not pay attention to information coming from the neglected side, even if they perceive it .
The results of the influence of the NIHSS visual field subtest on NIHSS accuracy in detecting neglect showed that when the Nvfs score resulted impaired, the accuracy of the NIHSS dramatically dropped (61.1%). Therefore, a visual field impairment could be in some cases confounded with neglect symptoms. Nevertheless, another issue has to be considered. In fact, three subtypes of neglect disturbances were aforementioned described: personal, peripersonal and extrapersonal. These subtypes may dissociate and considered to be related to region-specific lesions . In the study of Spaccavento et al.  on 130 right stroke patients with neglect, 57% showed an overlap between two or three forms, 17% presented only the peripersonal form, 12% only the personal form and 11% only the extrapersonal form. In the absence of a clear definition of the exact distance in which NIHSS visual field task has to be performed, we cannot exclude an effect of a dissociation between peripersonal and extrapersonal neglect forms. Furthermore, the visual extinction test, that allows the clinician to score also the extinction and inattention test, is conducted at the end of the visual field examination, and therefore it could in the same way be affected by the bias described above.
Together with the probable influence of visual field subtest alterations, another aspect should also be considered. Indeed, in this study, we limited our analysis to the space asymmetry score, the measure on the heart test that is more informative concerning egocentric neglect [REF]. Nevertheless, the test includes two other measures (total omissions and object asymmetry scores), that allow for a more accurate interpretation of the results giving the information on the general attentional ability and the presence of allocentric neglect. However, by focussing solely on the latter two measures, misleading conclusions could be drafted concerning neglect diagnosis. In fact, a high number of total omissions could indicate both a very serious form of neglect (if concentrated in the omitted half-space), and more general attentional difficulties (if spread throughout the space). Similarly, a high object asymmetry score alone does not exclude the presence of additional global cognitive and attentive difficulties, besides the allocentric component of neglect. Therefore, we decided to focus on the asymmetry of space score exclusively, as a reliable measure of egocentric neglect, but we cannot exclude the presence in our sample of subjects without a “pure” syndromic pattern of neglect.