One in four adults in their lifetime will have a stroke (1). Stroke commonly results in spatial neglect, which can be defined as the neglect of any type of stimuli (such as visual, tactile, auditory or mental representations) from the side opposite the brain lesion or a lack of spontaneous movement of the contralesional side of the body (or any part of the body toward the contralesional side), despite the ability to do so (2, 3). Prevalence estimates of neglect range from 25 to 80% of stroke survivors (4–7), depending on the methods of assessment, stage of recovery and type of neglect (8, 9). Neglect is associated with poorer functional outcomes such as reduced independence in daily tasks, higher risk of falls, longer length of hospital stays, and reduced likelihood of home discharge (10, 11). It is essential to accurately identify the presence of neglect, to reduce the burden for individuals, their careers and the health system (12).

However, the identification of neglect can be challenging. Neglect manifestations are heterogeneous and no single test can accurately identify all types of neglect (13, 14). Additionally, neglect presents on a scale from very severe to mild (15), with mild neglect only becoming noticeable in certain situations (16) such as navigating a busy environment. Many current assessment tools can lack the sensitivity to detect mild or moderate neglect (14, 17–20) resulting in people with undiagnosed neglect.

Multiple taxonomies for how neglect is defined and categorized into subtypes have been proposed [for example, see (2, 21, 22)]. The taxonomy recently mentioned (21) to capture and classify the heterogenous behaviors of neglect into three dimensions will be used in this review. The three dimensions of neglect include: (1) reference frame (as either egocentric or allocentric); (2) processing stage which includes perceptual subtypes (visual, tactile or auditory), representational, and motor; and (3) spatial sector (as either personal, peripersonal, and extrapersonal) (21). Neglect can be multimodal and occur in any or all combinations of the three dimensions (12), which makes assessment so challenging.

It is important to identify the subtype(s) of neglect for several reasons. Firstly, clinicians will be able to predict which daily tasks are impacted by the neglect behavior if the subtype is known. For example, visual neglect present in the far extrapersonal space will impact the ability to cross a road safely, however tasks such as reading, shaving or putting on make-up will not be impacted. The clinician will therefore be able to educate the person to increase their awareness of the risks associated with specific tasks and target interventions to compensate for the symptoms of neglect and improve the person's independence. If neglect in a particular subtype is not detected, the person may remain unaware of the risks associated with returning to their daily routines, potentially putting themselves and others at risk when attempting particular activities such as cooking, driving or crossing a road (19, 23).

Secondly, recovery from neglect may depend on the subtype. More people recover completely after 6 months from personal and extrapersonal neglect in comparison to peripersonal neglect (24). Also, some interventions may be more effective for particular neglect subtypes in comparison to others. For example, visual scanning training in isolation has been shown to improve visual related tasks such as reading with minimal effect on non-visual neglect behavior (25). Prism adaptation has shown to improve motor neglect, with no effect on perceptual neglect (26), while monocular patching may have the opposite effect on the two subtypes (27). Also cold water caloric stimulation might be more effective for sensory neglect in comparison to motor neglect (28). Consequently, the results of intervention studies that do not assess neglect subtypes may be invalid, indicating a combination of improvement in one subtype and no change of another type (29).

Neglect subtypes are referred to inconsistently across the literature. There are five systematic reviews on the assessment of neglect according to our knowledge (8, 30–33), however, none of them have considered assessments for all neglect subtypes across the three dimensions proposed.

A gold standard tool to identify all types of neglect does not exist (8, 13). Therefore, there is a need to identify all the tools available for each neglect subtype; identify the most robust tools; and develop a consensus on the most appropriate battery of tools for the diagnosis of neglect. This scoping review is the first stage of this process. Scoping reviews are used to map the available evidence across multiple disciplines, clarify the conceptual boundaries of a topic, key concepts and working definitions (34–36). In accordance with these guidelines, the objectives of this scoping review are to capture the reported working definitions for the subtypes of neglect and map the range of tools employed for assessing each neglect subtype.

The questions and sub questions we will answer with this scoping review are:

This scoping review followed the guidelines for reporting outlined in the PRISMA extension for scoping reviews (PRISMA-Scr) (36). The study protocol is registered on the Open Science Framework (https://osf.io/bzv9q/). Any deviations from the protocol are described at the end of the paper.

The study selection criteria are outlined in Table 1. Inclusion criteria under each heading of Participants, Concept and Context were used to determine eligibility for inclusion in accordance with the guidelines for conducting scoping reviews (34, 35).

The following databases were searched on 17th July 2020 from database inception: EMBASE (EMBASE, RRID:SCR_001650), Emcare, Medline (MEDLINE, RRID:SCR_002185) and psychINFO. Additionally, AMED and CINAHL databases were searched in January 2018, however they were not accessible to the authors in 2020 when completing the updated search. The search strategy was developed in conjunction with a research librarian. Search terms included combinations of the following terms: Stroke, CVA, cerebrovascular accident; and unilateral spatial neglect, spatial neglect, visual neglect, visual inattention; and all allied terms of neglect, assessment, evaluation, measurement, screening tools, psychometric properties. Full details of the database search strategy are available in the Supplementary Table S1. The top 10 authors working in neglect based on number of publications were also searched according to their citation indexes using Scopus to confirm that all relevant publications were obtained. The reference lists of all secondary research identified by the search strategy and the final included studies were hand searched for any additional relevant studies. Refer to Figure 1 for the PRISMA flow diagram of included studies.

The references identified from each database were imported into Endnote X8.2 (EndNote, RRID:SCR_014001). The duplicates were removed in Endnote and the titles were screened by one author for the obviously irrelevant studies before the remaining studies were exported into Covidence (Covidence, RRID:SCR_016484) (37). Two authors independently screened the titles and abstracts for eligibility for inclusion. The full texts of potentially eligible studies were retrieved and assessed for eligibility independently by two authors. Any discrepancies over the eligibility of studies were resolved through discussion with a third author.

The following information was extracted from each study: neglect subtype(s) and definition(s); name of tool(s); abbreviated name; description of tool and protocols followed; purpose (what does each tool purport to measure)?; population; primary author; country of residence; and discipline according to the primary author's affiliation. If the discipline was not evident from the listed affiliation, then a google search was completed (primary author's name and affiliation) and the discipline was recorded as per their current work webpage if available. Extracting the data and documenting the results was an iterative process. The extraction form was trialed on ten studies with two independent researchers as recommended by The Joanna Briggs Institute (35). The extracted data from the ten studies was discussed with the research team and the form was refined to ensure that all the relevant information was extracted. (For example, the neglect subtypes were not explicitly stated for most tools. Therefore, all the documented protocols for each tool were collated in more detail so that the analysis of the underlying subtypes could be completed by the research team).

All the terms used within the studies to label neglect and each neglect subtype were collated and presented in figures to display the frequency of terms used for each discipline. The documented definitions for each neglect subtype were collated, grouped and summarized. All neglect tools with documented protocols used in the included studies were collated. The description of each neglect tool and the documented protocols were analyzed by two authors to determine the underlying subtypes of each tool. Disagreements were discussed with the authorship team until an agreement was determined.

The systematic search produced 2,168 articles to be screened. After reviewing the titles and abstracts, the full texts of 660 articles were further reviewed for eligibility, resulting in 371 articles in the final sample for this review (see Figure 1 for details and full list of exclusion reasons). The included studies were published by a cross section of disciplines as listed in Table 2.

To determine the reported definitions in the included studies, first the terms used to label neglect and the subtypes were collated, and summarized. There was no agreement on the terms used to refer to this disorder with 33 different terms used in the included studies (see Figure 2). The term neglect (excluded from Figure 2) was the most frequently used (174 studies, 47.3%). However, only 23 studies (6.2%) used the term neglect in isolation, with the majority of studies using it within the article as a shortened version of another, more descriptive term. There was variability across the disciplines with neurology having a clear preference for the term hemispatial neglect, however this was not consistent with other disciplines, such as neuropsychology preferring the term spatial neglect, while psychology was evenly split across the top four terms. The definitions for each neglect subtype were grouped according to the three dimensions of neglect (21).

The aim of this scoping review was to (1) collate the neglect subtypes and their definitions as reported in the literature and (2) to map the reported tools for assessing neglect and the identified subtypes.

It is evident from the results of this scoping review that there is a lot of variability with the terms used to label this syndrome as a whole and the individual subtypes. There is no consistency with the terms used for each subtype with some terms being used for multiple subtypes. For example, “extrapersonal” is sometimes used to refer to the reaching space (110), while many studies use this term to refer to the far space or outside of reaching (111–113). On the other hand, “extrapersonal” has also been used refer to neglect of the environment; encompassing both within and outside of reaching distance (80). Additionally, some subtypes are being described and grouped into different categories by different studies. For example, perceptual neglect is categorized as incorporating visual and representational neglect by some (41, 42), or visual, tactile and auditory by others (40). Some subtypes have multiple conflicting definitions such as personal neglect and allocentric neglect, which have both been challenged as legitimate neglect subtypes. This inconsistency with the terms and definitions used to refer to the neglect subtypes is creating confusion across the field and is a major barrier for clinicians to understand, compare and apply the literature to clinical practice.

Additionally, there is no agreement on the tools used for identifying neglect. This scoping review has revealed almost 300 neglect tools with documented protocols, and the development of new tools is not slowing down. The majority of tools are brief paper and pencil screening tools that are frequently used in combination with one or two other tools for screening, or as a suite of tools for the comprehensive diagnosis of neglect. Apart from a few validated batteries such as the Behavioral Inattention Test (114), many of the neglect batteries used in the included studies were made from different combinations of tools that have not been validated when used together as a diagnostic suite. This has resulted in high variability in the reported incidence of neglect and a plethora of research that cannot be effectively collated together.

It is important to identify the presenting neglect subtypes to assist with predicting and ameliorating the impact on daily life. Visual neglect in the peripersonal space is most commonly assessed, however the sheer number of tools available for these subtypes would be overwhelming for clinicians to navigate. Alternatively, very few standardized tools for tactile and representational neglect subtypes exist. Only one representational neglect tool (O'clock test) was identified in this review that is not dependent on knowledge of local landmarks and thus could be standardized for use in any country. However, this test has been found to be too difficult to complete for the majority of people with neglect (115). This may be due to the tool relying on other functions such as sustained attention and intact executive functions, which are often impaired after stroke. This can be said for many neglect tools, such as the mirror or pulley devices developed to dissociate motor and visual neglect [for example, see (71, 73, 116)], with impaired performance not necessarily reflecting true neglect behavior if executive functions are impaired. Gaps also exist for identifying motor or auditory neglect in clinical practice. Several tools exist for identifying both subtypes, however many of them are not feasible for use in clinical practice due to the individualized set up and equipment requirements.

Pen and paper tools are commonly used in clinical practice, however they only identify impairments in one spatial dimension—within peripersonal (reaching) space. The use of pen and paper tools may result in a person with undetected neglect in either personal or extrapersonal (outside of reaching) space. Another limitation with pen and paper tools is the inability to differentiate between motor and visual neglect as mentioned previously. Pen and paper tools may be useful to screen for neglect, however other methods of assessment need to be considered for the comprehensive diagnosis of all neglect behaviors.

Tools developed to tease apart the motor and perceptual aspects of neglect have not been able to categorize the two subtypes consistently (117, 118). It has been suggested that minor differences in task requirements such as reaching for a direct target vs. a spatial /delayed judgment may account for these discrepancies (119). Moreover, it is uncertain if neglect subtypes are transient or consistent over time. In the subacute phase post stroke, significant variability in the categorization of visual, motor and personal neglect was observed over three test sessions in 18 (86%) participants (120). The pattern of variability was not consistent with practice effects or spontaneous recovery. It is unclear whether these results can be explained by methodological limitations such as low test-retest reliability of the neglect tools, or actual fluctuations in the neglect behavior.

New tools for identifying neglect are continually being developed, possibly due to the existing tools not being able to detect milder forms of neglect, or an inability to detect the different neglect subtypes. The increasing number of virtual reality and computer-based tools being developed have the potential to increase the task demands, such as dual-task paradigms or speeded reaction time tests, in order to identify mild or subclinical neglect (121–123). However, many of these tools are not feasible to use in clinical settings due to the complex setup or cost requirements.

The following questions were raised by the research team during the process of mapping the subtypes identified with specific tools: (1) All tasks tap into eye movements—thus are all of them tapping into motor (oculomotor) aspects of neglect? It was decided that for the purpose of this review to indicate motor neglect only for the tasks that require a motor response, as opposed to a verbal response or the tracking of eye movements. And (2) If spatial neglect is due to an impairment of spatial representation (124, 125), then do all tasks that require a motor response also tap into representational neglect? For the purpose of this review only tasks that rely on visual memory, such as drawing objects from memory or completing tasks with the eyes closed, along with completing functional tasks in personal space were indicated as being influenced by representational neglect. However, these questions would benefit from further consideration in future studies.

There was no consistency with the terms used to refer to neglect and presenting subtypes. It is essential to unify the terminology and definition for each subtype of neglect. There are hundreds of neglect tools available, however many are not able to differentiate presenting subtypes. There have been multiple tools developed to dissociate different types of neglect such as egocentric and allocentric neglect; however, the responsiveness, validity and reliability of these tools has not been compared. It is important for clinicians and researchers to critically evaluate the neglect tools being used for the screening and diagnosis of neglect. The results of this scoping review will inform the scope of tools to be included in a full systematic review summarizing the reliability, validity, responsiveness and utility of neglect tools used in clinical practice. We recommend further work to develop consensus around neglect subtypes, definitions, and assessment.

This scoping review has not answered the following sub-questions as originally proposed in the protocol of (1) “what definitions have been used by different disciplines?”; and (2) “how have the definitions evolved over time?” There were relatively few studies that described each subtype so trends between the different disciplines or over time were unable to be made. The definitions for each subtype were analyzed collectively. Additionally, it was deemed outside the scope of this review to comment on “what tools are being used by different disciplines?” as originally proposed. It was decided that the included studies may not be representative of all the tools used across the disciplines as the criteria for inclusion were only studies that examined some aspect of validity or reliability of a tool.

The original contributions presented in the study are included in the article/Supplementary Material, further inquiries can be directed to the corresponding author.

LW completed the database searches and wrote the first draft of the manuscript. LW and TL contributed to the data extraction and analysis. All authors contributed to conception and design of the study, screening of abstracts and full texts, manuscript revision, and read and approved the submitted version.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.