‘The anatomy underlying acute versus chronic spatial neglect’ also depends on clinical tests

Abstract

Sir,We would like to make a few comments on the interesting paper recently published in Brain by Karnath et al. (2011). We were impressed by the careful assessment of spatial neglect during acute and chronic phase, which was combined with a solid voxel-wise lesion symptom mapping technique in a series of 54 patients with right-hemisphere stroke. Anatomical data indicated that lesions in the superior and middle temporal gyri, the basal ganglia, as well as the inferior occipitofrontal fasciculus are responsible for spatial neglect in both acute and chronic phases.We also had the opportunity to evaluate 69 patients with right brain lesions longitudinally. Our patients were admitted after a first right-hemisphere stroke (mean delay: 7.5 AE 14.6 days), at a mean age of 64.95 AE 14.6 years. Mean delay between the acute and chronic phase was 350.21 AE 184.7 days. These demographic data are comparable with the patients of Karnath et al. (2011). Neglect was considered as present when patients failed at least two out of eight tests (Table 1)-unlike diagnoses based on two out three tests in Karnath et al. (2011). In the acute phase, 31 patients had neglect (45%). In the chronic phase, 17 of these 31 neglect patients still showed a significant impairment (55%). Using the same voxel-wise lesion mapping as Karnath et al. (2011), we found partly different results, particularly in the acute phase (detailed below). However, we believe that major differences in the findings may depend on the clinical measures used to define neglect, since this syndrome may include heterogeneous symptoms.

Apraxia and spatial inattention dissociate in left hemisphere stroke

“…To avoid these prevalent intrinsic associations we refrain from using the term neglect in the present study; instead we use the term spatial inattention. To comprehensively assess (spatial) inattention, it is important to use multiple attention tests (Saj, Verdon, Vocat, & Vuilleumier, 2012;Verdon, Schwartz, Lovblad, Hauert, & Vuilleumier, 2010). Therefore, we used the line bisection test that is supposed to be sensitive to posterior lesions (at least for contralesional inattention: (Rorden, FuhrmannBerger, & Karnath, 2006;Weiss et al, 2000) as well as cancellation tests that are also affected by frontal lesions (Vossel et al, 2011).…”

Incidence, Risk Factors and Anatomy of Peripersonal Visuospatial Neglect in Acute Stroke

“…Previous studies on the association between lesion side and incidence of PVN have yielded contradictory results [8,21,22,23]. This might be explained by the heterogeneity of assessment methods [18]. Indeed, studies using discriminative cancellation tasks - known to be more sensitive - frequently report lack of significant difference in the incidence of PVN in patients with right versus left brain damage [22].…”

“…First, the small sample size could have limited the possibility to identify associations using VLSM analysis (decreased power of statistical tests). Second, the statistical approach aiming to identify a single lesion focus underlying PVN does not account for the fact that visuospatial awareness is mostly supported by a network rather than a single right or left hemisphere region [6,18,24,25]. Hence, VLSM analysis, though interesting, could also be sometimes misleading.…”

“…We used a procedure previously reported in the analysis of brain lesion-behavior relationships [15,18,19]. The location and the extent of brain damage were delineated in each patient, based on their MRI scan obtained with a 3T apparatus.…”

Posterior parietal cortex and visuospatial control in near and far space

“…Parietalfrontal white matter damage, involving the anterior fascicle or the superior longitudinal fascicle, can disconnect large portions of the parietal, parietal-temporal and temporal cortex from frontal areas, and thus can be involved in the pathogenesis of neglect [7]. Moreover, lesions in white matter are particularly associated with chronic neglect [8].…”