Spatial neglect in parietal glioma patients: what do we know? a systematic review

Abstract

Background

Spatial neglect—a multifaceted neuropsychological (NP) syndrome—has been studied extensively after stroke. Yet its prevalence, trajectory, and anatomical underpinnings in parietal glioma remain poorly defined. We performed a systematic literature review to synthesize current evidence on neglect in this population, highlighting its temporal course, the white-matter networks implicated, and the NP assessment.

Methods

A systematic literature search was conducted following PRISMA guidelines, using keywords related to parietal gliomas and visuospatial deficits. Eligible studies included adult patients with parietal gliomas assessed with NP assessment.

Results

Only nine heterogeneous studies met inclusion criteria. Overall, across 86 parietal glioma cases, neglect was documented in 12% pre-operatively and in 23% post-operatively. Long-term follow-up (reported for just five patients) suggested an 80% recovery rate. Most cases recovered within five days, indicating that neglect may be transient or under-detected. Low-grade gliomas (LGGs) were associated with a lower risk then high-grade gliomas (HGGs), despite the limited sample size. Diffusion-tensor imaging (DTI) and direct electrical stimulation (DES) consistently implicated the second branch of the superior longitudinal fasciculus (SLF II), while pointing to a broader fronto-parietal network involved in both onset and recovery. Comprehensive NP batteries proved critical for delineating neglect occurrence and evolution, and co-existing visuospatial or global cognitive deficits.

Conclusions

Neglect frequency rises after resection of parietal gliomas, though current evidence is limited by small, heterogeneous samples. While most patients recover within three months, these findings rely on low-quality data often limited to single-task assessments. Multimodal evaluation via DTI, DES, and comprehensive NP batteries is essential for tracking recovery. Larger, prospective studies are needed to clarify the network dynamics that govern neglect emergence and resolution, and to refine evidence-based management strategies.

Introduction

In contemporary glioma surgery the guiding principle is “maximal safe resection”: excising the greatest possible volume of tumour while sparing eloquent cortex and subcortical pathways so that core neurological functions are preserved [7]. Central to the functional integrity of the parietal lobe is the management of spatial neglect, a multifaceted neuropsychological syndrome where patients fail to detect or respond to stimuli on the side of space opposite a brain lesion, despite intact primary sensation and movement [20]. Some authors defined neglect as a collection of symptoms rather than a single syndrome [29]. For this reason, neglect is considered a weak syndrome because it is open to dissociation in its various manifestations [37]. It frequently results in a loss of patient autonomy and significantly impacts the performance of daily activities, often compounded by anosognosia, where the patient is completely unaware of their deficit [59].

Surgical planning concentrates heavily on motor and language networks, whose integrity can be mapped and monitored with well-validated tests before, during, and after the operation [27]. Conversely, assessing complex cognitive functions, such as visuospatial abilities (VSAs), requires specialised NP evaluation and therefore comparatively receives less emphasis in routine neurosurgical practice [38]. It should be noted that many cognitive functions have a major impact on the quality of life and should therefore be considered during the preoperative and postoperative management of the patient [57]. A further obstacle is that the neuroanatomy of many complex cognitive functions remains only partly clarified, hampering the prediction of functional outcomes and the adoption of preventive strategies [38].

VSAs comprise the perception of visual stimuli and the subsequent analysis of an object’s orientation or location in space [28]. This implies a complex functional and anatomical interaction with the attentional process and its neural correlates [4]. VSAs impairments, whether caused by vascular lesions or brain tumours, may manifest as visuospatial judgement errors, topographical disorientation, Balint’s syndrome, or unilateral spatial neglect [11]. Among these, neglect is a particularly striking disorder. At a clinical level, neglect patients may lose their autonomy and have consequences on the performance of daily activities, sometimes being completely unaware of their deficit [23]. Even if neglect can be classified into subtypes according to spatial, clinical and personal manifestation of the deficit [61], in clinical practice, subtypes usually overlap, and patients present mixed symptoms [52]. These subtypes include egocentric (space-based) neglect, where the deficit is relative to the patient's body midline, and allocentric (object-based) neglect, where the patient fails to attend to the contralesional side of individual objects regardless of their position in space [19]. Other manifestations include personal neglect, involving the patient's own body, and motor neglect, characterized by underutilization of a limb despite the absence of primary motor deficits [8, 9].

The incidence and recovery trajectory of neglect vary significantly across neurological disorders. In the stroke population, neglect is a well-established consequence of acute vascular disruption, with recovery rates estimated at approximately 42% within the first three months [2]. A meta-analysis by Overman et al. showed 42% recovery in the first three months and 53% by six months, with over 40% showing persistent symptoms [41]. Recent studies reported an overall incidence of 30–40% in unselected acute stroke patients, with approximate rate of 60% in right hemisphere strokes and 20% in left hemisphere strokes [12, 37]. In rehabilitation settings with right hemisphere stroke patients, personal neglect occurs in approximately 1% of cases, while motor neglect occurs in 17% [8]. Conversely, in neuro-oncology, the progressive growth of gliomas induces functional reorganization and brain plasticity, which may mask deficits preoperatively. Nevertheless, the occurrence of neglect within parietal glioma surgery has been scarcely investigated by the literature. This deficit generally develops as a consequence of surgery in case of lesions affecting the posterior inferior-parietal region, mostly of the right hemisphere [51].

The neuroanatomical basis of spatial neglect has been a subject of intense investigation, historically centred on the right posterior parietal cortex. Extensive research in stroke populations has established neglect as a disconnection syndrome involving large-scale frontoparietal networks, specifically the dorsal attentional network (DAN) and ventral attentional network (VAN) [8, 9]. While these vascular models provide a foundational framework, their direct applicability to neuro-oncology is limited by the unique biological behaviour of gliomas [25]. Unlike the acute disruption seen in stroke and occurring on a normal anatomy, gliomas are characterized by slower growth patterns that allow for functional reorganization and metaplasticity, potentially modifying the white matter organization [21]. Thus, surgery determines the acute presentation of the deficit on a modified underling white matter structure, possibly altering the clinical presentation of neglect.

While systematic reviews on post-stroke neglect are abundant, there is a lack of systematic evidence synthesizing the prevalence, trajectory, and anatomical underpinnings specifically in parietal glioma patients. Existing studies are frequently limited to case reports or small cohorts, often failing to use standardized multimodal assessments. By consolidating these sparse data, this review aims to bridge the gap between stroke-derived models and the specific clinical reality of surgical neuro-oncology.

This review synthesises current evidence on the incidence, mechanisms, and prognosis of neglect in patients undergoing resection of parietal gliomas. We place particular emphasis on (i) the value of systematic NP testing for VSAs and neglect across the peri-operative timeline, and (ii) emerging data on white-matter involvement and functional reorganisation that may underlie neglect onset and recovery.

Methods

Search strategy

A systematic review was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. We searched MEDLINE/PubMed and Embase databases using the following keywords and MeSH terms: "parietal”, “glioma", “glioblastoma”, "neglect", “hemineglect”, "visuospatial deficit", “neurosurgery”, “resection”, "functional reorganization" and "white matter”. Boolean operators (AND, OR, NOR) were applied to refine the search. The search covered articles published between January 2000 and December 2024. Additional studies were identified through a manual search of reference lists from relevant articles.

Inclusion and exclusion criteria

Studies meeting inclusion criteria have been selected according to PRISMA guidelines as reported in the PRISMA flowchart (Fig. 1). Studies were included if they met the following criteria:

Fig. 1.

PRISMA flow chart of study selection

1. Patients diagnosed with parietal gliomas including both low-grade gliomas (LGGs) and high-grade gliomas (HGGs). LGGs typically include grade 2 gliomas according to WHO classification while HGGs are referred to as grade 3 and 4 gliomas.

2. Visuospatial performance assessed with NP tests.

3. Available imaging (MRI including T1 c.e. and T2-Flair), possibly including diffusion tensor imaging (DTI).

4. Reported preoperative and/or postoperative neglect NP assessments.

Exclusion criteria included reviews, animal studies, paediatric patients (< 18 years), articles without full-text availability in English.

Study selection

The initial search resulted in a total of 307 papers. After excluding the duplicates, 26 papers published before 2002 and 15 non-English language papers, the titles and abstracts of 201 studies were evaluated. An additional 151 studies were excluded, and 32 reports were not retrieved, yielding 18 studies for the full-text evaluation. Of these 18 papers, 9 were excluded as they did not fulfil the inclusion criteria (Fig. 1). Considering that neglect requires to be recognized, classified and followed through specific NP tests and not with standard clinical evaluation, some studies have been excluded by this review despite their focus on parietal glioma related deficits. Finally, 9 papers including 4 prospective studies and 5 case reports were collected. Considering the limited number and the nature of the studies, the overall level of evidence is low. Furthermore, the studies show significant heterogeneity in NP assessment for both timing and included tests. The characteristics of the selected studies are highlighted in Table 1, including clinic and demographic data. Considering the 9 analysed studies, 86 patients have been considered including 37 LGGs and 45 HGGs. The study by Emanuele et al. [23] included 4 cases with different histological diagnosis (metastasis and meningioma). The studies included 63 cases of right-side glioma and 23 cases of left-side glioma. Prospective studies by Liouta et al. [34] and Emanuele et al. [23] focused specifically on right parietal gliomas. Moreover, patient right-handedness has been reported except for one case report [18].

Table 1.

Demographic and clinical characteristics

Author	Year	Study	n	Age	Sex	Histology			Side		Handedness
						LGG	HGG	Other	Right	Left	Right	Left
Bartolomeo et al. [3]	2007	Case report	2	28	n.r	2	0	0	2	0	0	2
Emanuele et al. [23]	2012	Prospective	14	57	5–9	1	9	4	14	0	14	0
Talacchi et al. [49]	2013	Case report	2	46	1–1	2	0	0	2	0	2	0
Vallar et al. [55]	2014	Prospective	7	35	0–7	5	2	0	6	1	5	2
Charras et al. [13]	2015	Prospective	20	39	14–6	19	1	0	20	0	18	2
DeDios-Stern et al. [18]	2019	Case report	1	67	0–1	1	0	0	0	1	n.r	n.r
Liouta et al. [34]	2019	Prospective	38	60	20–18	6	32	0	17	21	38	0
Laksmidewi et al. [32]	2020	Case report	1	45	0–1	0	1	0	1	0	1	0
Tamás et al. [51]	2021	Case report	1	30	1–0	1	0	0	1	0	1	0

n number of patients, sex: female-male, LGG Low-grade glioma, HGG High-grade glioma, n.r.” not reported

Data extraction and quality assessment

Two independent reviewers screened titles and abstracts for eligibility. Full-text articles were reviewed for final inclusion. Extracted data included study design, sample size, glioma characteristics (location, side, grade), NP assessment for neglect and visuospatial deficits, imaging findings on MRI and DTI, surgical strategy and outcome. Risk of bias was evaluated using the Newcastle–Ottawa Scale for cohort studies and the Cochrane Risk of Bias Tool for randomized controlled trials (Fig. 2). The included studies show considerable heterogeneity in clinical presentation, the timing of neuropsychological evaluations (ranging from immediate postoperative to long-term follow-up), and the specific testing batteries used to detect neglect. Furthermore, differences in surgical management, such as the use of awake versus asleep protocols and the extent of intraoperative monitoring, contribute to the variability in reported outcomes.

Fig. 2.

Risk of bias assessment according to the Newcastle–Ottawa scale and the cochrane risk of bias tool for the included studies: Bartolomeo [3], Emanuele [23], Talacchi [49], Vallar [56], Charras [9], DeDios-Stern [18], Liouta [34], Laksmidewi [32], Tamas [51]

Outcome measures

The primary outcome was the presence and severity of spatial neglect, assessed with standard NP tools, including the line-bisection task, bells/stars/letters cancellation tests, and complementary visuospatial measures. The timing of these evaluations, especially the postoperative assessments, was analysed alongside neglect severity.

Secondary outcomes comprised pre- and post-operative MRI findings, documenting cortical involvement, tumour grade, side, and location. Where available, we also recorded (i) pre-operative indices of white-matter integrity and (ii) post-operative evidence of structural change or reorganisation. White-matter tracts of interest were the superior longitudinal fasciculus (SLF), inferior fronto-occipital fasciculus (IFOF), and optic radiation (OR).

Additional variables included surgical strategy (awake vs general-anaesthesia resection), the use of intra-operative NP testing, and histopathology, with tumour grade classified according to the WHO classification.

Results

Incidence of neglect

All the studies included analyzed the prevalence of neglect in the preoperative setting using standardized NP tests. Among the total sample of 86 patients, 10 cases (12%) demonstrated evidence of preoperative neglect. Notably, only seven studies conducted postoperative follow-up evaluations for VSAs [3, 13, 18, 23, 49, 51, 55], encompassing 47 patients; of these, 11 patients (23%) exhibited neglect in the immediate post-operative period. Results for neglect occurrence were reported in Table 2.

Table 2.

Results for neglect occurrence and recovery

Author	Year	Study	n	Neglect
				Preop (n)	Preop (%)	Postop (n)	Postop (%)	Recovery (%)	Recovery (t)	Type (e/a/p)
Bartolomeo et al. [3]	2007	Case report	2	0	0%	1	50%	100%	5d	e
Emanuele et al. [23]	2012	Prospective	14	2	14%	6	43%	100%	n.r	ep
Talacchi et al. [49]	2013	Case report	2	0	0%	1	50%	100%	3d	e
Vallar et al. [55]	2014	Prospective	7	0	0%	0	0%	n.r	n.r	ep
Charras et al. [13]	2015	Prospective	20	0	0%	1	5%	100%	3 m	e
DeDios-Stern et al. [18]	2019	Case report	1	1	100%	1	100%	0%	n.r	e
Liouta et al. [34]	2019	Prospective	38	6	16%	n.r	n.r	n.r	n.r	e
Laksmidewi et al. [32]	2020	Case report	1	1	100%	n.r	n.r	n.r	n.r	e
Tamás et al. [51]	2021	Case report	1	0	0%	1	100%	100%	5d	e

n number of patients, %: percentage of patients, t timing, d days, m months, e egocentric, a allocentric, p personal, n.r. not recorded

Follow-up of neglect

Results concerning long-term follow-up of neglect symptoms were reported by 5 studies [3, 13, 18, 49] with NP tests performed at different timepoints between 3 weeks and 3 months after surgery. The results show an almost complete rate of recovery from neglect within the 3 months assessment which occurred in 4 patients (80%), as reported in Table 2. Nevertheless, the latter data is based on a very limited number of patients (5). Moreover, the single case presenting persistent neglect at 3 months assessment was affected by cognitive impairment [18]. Interestingly, some studies reported a very fast recovery from neglect occurring within the 5 days after surgery and, thus, requiring far less than three months [4, 49, 51]. The indication for a further recovery to perform rehabilitation after discharge from the neurosurgery department was reported in 6 studies [3, 13, 23, 49, 51, 55], but this treatment was unnecessary for the analysed cases.

Tumor grade

The analysed studies reported 37 cases of LGGs and 45 cases of HGGs. LGGs include grade 2 gliomas, while HGGs include grade 3 and 4 gliomas. Only two studies reported the specific WHO classification adopted for glioma classification, respectively WHO 2007 [55] and WHO 2016 [34]. Although the limited number of cases (79 patients) and the different inclusion criteria, prospective studies [13, 23, 34, 55] suggest a relatively lower incidence of neglect in LGGs then in HGGs. In fact, the two studies reporting the lower incidence of pre-operative and post-operative neglect present with a prevalence of LGGs, respectively 5/7 cases (71%) by Vallar et al. [55] and 19/21 cases (95%) by Charras et al. [13]. Indeed, studies including HGGs presented higher rates of neglect both preoperatively and postoperatively [23, 34]. Conversely, the only case described without neglect recovery presented a histological diagnosis of grade 2 glioma [18].

White matter tracts analysis

Radiological assessment with MRI was routinely performed in each study included in this review. Indeed, only a few studies included within the radiological DTI assessment [13, 51, 55]. The white matter bundles that were reconstructed included the SLF, IFOF and the OR. Vallar et al. [55] examined DTI for SLF, considering its three branches, and IFOF. They suggest SLF II being the tract most related to neglect occurrence, basing their results on DES. In fact, they could not relate neglect with DTI analysis because no patients experienced preoperative or postoperative neglect. Similarly, Charras et al. [13] experienced intra-operative deficit at line-bisection test while stimulating the SLF II. They performed DTI only on a single patient that experienced postoperative neglect and reconstructed SLF, IFOF, OR and Middle Longitudinal Fasciculus. For this case, they demonstrated complete cortical resection of the right angular gyrus with preservation of these fasciculi according to DTI. Tamas et al. [51] performed a preoperative DTI demonstrating the integrity of SLF but postoperative assessment was not repeated despite the occurrence of neglect.

Surgical strategy

Glioma resection has been performed with NP intraoperative monitoring in 5 studies with line bisection test, while the other 4 performed surgery under general anaesthesia. Intraoperative monitoring in awake surgery was performed in 32 cases, mainly with histological results of LGGs (29 cases, 90%). Generally, a higher frequency of postoperative neglect occurrence was observed in case of asleep surgery rather than awake surgery. Particularly, prospective studies by Vallar et al. [55] and Charras et al. [13] reported very low rates of postoperative neglect in patients operated with an awake protocol, respectively in 0/7 cases (0%) and 1/2 0 cases (5%). Nevertheless, patients operated within intraoperative NP assessment generally present a higher performance status and prevalently harbour a histological diagnosis of LGG. Interestingly, Talacchi et al. [49] discussed the surgical strategy adopting different approaches to intraoperative NP monitoring in two patients with right parietal LGGs. The first patient underwent awake surgery with the preservation of essential visuospatial areas (supramarginal and angular gyri) and did not report postoperative neglect. Meanwhile, in the second case, an essential visuospatial area (superior temporal, angular, supramarginal, infraparietal, and postrolandic gyri) within the tumor was resected. The latter patient displayed transient neglect symptoms immediately after surgery, which then resolved within three days. A significant limitation of the intraoperative data is the reliance on a single assessment tool; the line-bisection test was the only task performed intraoperatively in 100% of the monitored cases. This narrow focus may fail to capture the full spectrum of neglect subtypes, potentially leading to an underestimation of the true incidence of the deficit.

Preoperative neuropsychological assessment

NP assessment has been analysed particularly considering the different tests performed and the timing of administration. Some studies focused exclusively on preoperative evaluations [32, 34], while the others.

conducted both preoperative and postoperative assessments to monitor the evolution of neglect. The authors mainly focused on egocentric neglect, which was addressed in all the studies, while two studies tested and reported also personal neglect [4, 25]. Interestingly, no studies reported data on allocentric neglect (Table 2).

All the selected studies performed a preoperative NP assessment, reported in Table 3. Except for the studies by Vallar et al. [55], global cognitive functioning was assessed by all the included studies, through specific tests such as the Montreal Cognitive Assessment (MoCA) [40], the repeatable Neuropsychological Status Assessment Battery—Update (RBANS) [44], the Yes/No Western Aphasia Comprehension Subtest (WAB) [54], the Token Test subtest and the Multilingual Aphasia Examination (MAE) [6] or by the Mini Mental State Examination (MMSE) [23]. Regarding the neglect-related assessment, the line bisection test and the line/letter/star/apple cancellation tests were assessed preoperative by all the authors, except one study where the latter was not performed [18]. Some studies focused on reading, writing, copying, and spontaneous drawing to assess preoperative visuospatial functions [32, 55]. Charras et al. [13] used the “Letters” and “Cube analysis” subtests of the Visual and Object Space Perception battery (VOSP) [60], to assess the visual-perceptive abilities. On the contrary, Emanuele et al. [23] used a collection of tests, and not a single battery able to provide a single score to evaluate the global performance of the patients, including the Clock Drawing test, the Map of Italy, the constructional apraxia test, the Card sorting task (subtest of the behavioural inattention test–BIT), the Spontaneous gaze and head orientation test and tests for personal or motor neglect. Notably, they also administered the Catherine Bergego scale both to the caregiver and the patient to evaluate patient’s awareness of the deficit. A discrepancy between the evaluations of both was taken as evidence of anosognosia for the deficit.

Table 3.

NP pre-operative assessment of the selected studies

VOSP Visual and Object Space Perception Battery. *Line/letter/star/apple/bell cancellation test

Postoperative neuropsychological assessment

Regarding the post-operative NP assessment, which is summarized in Table 4, follow-up of neglect symptoms was assessed by 7 studies performed at different timepoints between 1–5 days after surgery [4, 23, 51] and 3 months after surgery [4, 13, 49]. Post-operative global cognitive functioning was not assessed in two studies [4, 55], while both the line bisection test and the line/letter/star/apple cancellation test were assessed by all the authors, except for one study [18] where the latter was not performed, in alignment with the pre-operative NP assessment. Generally, all the authors used the same NP assessment both for the pre-operative and the post-operative evaluation of neglect manifestation.

Table 4.

NP post-operative assessment of the selected studies

VOSP Visual and Object Space Perception Battery. *Line/letter/star/apple/bell cancellation test

Discussion

Neglect occurrence and time evolution

The primary pattern emerging from the nine included studies is a significant doubling of neglect incidence immediately following surgery. This acute postoperative presentation is generally followed by rapid improvement and a high rate of recovery at three months. Despite the limits related to the number and heterogeneity of the studies included, the available data suggest that neglect may emerge or worsen after surgery, likely due to intraoperative disruption of critical white matter pathways or cortical hubs. Nevertheless, the transient nature of the deficit indicates a remarkable capacity for rapid functional compensation, often occurring within the first postoperative days [4, 49, 51]. This highlights the difference between stroke-related neglect and tumor-related neglect. In fact, the progressive tumor growth induces functional reshaping of brain networks before surgery, explaining why most patients present without deficits despite invasion of eloquent structures. This preoperative plasticity creates a foundation for rapid postoperative recovery. Especially for low-grade gliomas, a hierarchical model of reorganization has been described three levels: intrinsic reorganization within injured areas, recruitment of remote ipsilateral regions, and solicitation of contralateral homologous regions [22]. Indeed, in stroke, neglect recovery is more variable and often incomplete. This rapid and dynamic course in glioma underscores the importance of early and specific NP assessment to enhance tumor plasticity with rehabilitative strategies. In fact, long-term follow-up, although infrequently reported, suggests that persistent neglect is rare, but may be associated with broader cognitive impairment or, possibly, with failure of compensatory mechanisms [18, 45].

The identification of predictive factors for neglect occurrence remains challenging due to the small number and heterogeneity of available studies. Tumor grade appears to influence neglect risk: LGGs, often associated with slower growth and increased neuroplasticity, may pose a lower risk compared to HGGs, which tend to cause more abrupt disruption [21]. In fact, studies including majorly LGGs reported a lower rate of neglect occurrence [4, 13, 55]. Lesion laterality also plays a role, as right parietal tumors more frequently result in neglect, reflecting the lateralization of attentional networks [4]. Nevertheless, patients with left brain damage may also present signs of right hemineglect, albeit it happens more rarely and usually in a less severe form [5]. This knowledge comes from studies concerning ischemic events, but also in case of left parietal glioma this phenomenon was described [18].

Other factors such as tumor size, patient age, and preoperative cognitive status warrant further investigation, as they may modulate the onset and resolution of symptoms [45]. In fact, previous studies on post-stroke neglect supported the notion that larger lesion volume is a risk factor for severe neglect [1, 29, 33]. Large lesions may damage multiple pathways and hamper compensation, resulting in more severe neglect and reduced recovery. Overall, larger prospective studies are needed to refine our understanding of risk stratification and to guide clinical decision-making.

Neuroanatomical correlates

Another consistent finding across the analysed studies is the critical role of the SLF II as the anatomical substrate for spatial neglect. Our review confirms that damage or stimulation of the subcortical white matter, rather than the parietal cortex alone, is the most reliable predictor of neglect symptoms. This aligns with the "disconnection" theory of neglect, which identifies the SLF II as the bridge between the dorsal and ventral attentional networks.

Neglect in the context of parietal glioma represents a complex and multifactorial phenomenon that challenges the traditional lesion-deficit model. Rather than resulting solely from focal cortical lesions, neglect increasingly appears to stem from disruptions within large-scale attentional networks. The mechanisms underlying the phenomenon of neglect remain an area of active research, with focus on functional reorganization and compensatory mechanisms. Anatomically, visuospatial attention relies on two large fronto-parietal interconnected networks [4, 14]. A dorsal attentional network (DAN) includes the superior parietal lobule and the dorsolateral prefrontal cortex controlling the spatial orienting of attention [14, 17]. Indeed, the ventral attentional network (VAN) includes the right temporo-parietal junction and the right ventral frontal cortex and seems to be crucial for non-lateralized attentional functions, such as visual and temporal orientation, saliency detection and attention recall [15, 42].

The superior longitudinal fasciculus (SLF), especially its second branch (SLF II), serves as a key anatomical connector between these networks, and its disruption has been repeatedly associated with neglect symptoms in the stroke literature [48]. Stimulation of SLF II within the analysed studies has been shown to induce neglect-like deficits, particularly in line-bisection tasks, underlining its functional importance in visuospatial processing [13, 55]. Moreover, the anatomical configuration of the SLF branches helps explain the lateralization of neglect to the right hemisphere. SLF III, which connects VAN regions, is typically more prominent in the right hemisphere, whereas SLF II links the VAN to the prefrontal DAN, thus representing a critical site of network integration [15, 53]. Thus, an important damage within the inferior parietal lobule (IPL) may lead to severe, lasting neglect [39, 58]. However, less extensive damage sparing SLF II may allow intra-hemispheric compensation, maintaining VAN-DAN communication and thus supporting recovery. Initially, this could cause an imbalance favouring the left DAN activation, which may normalize after the post-acute phase with consequently improving symptoms [16].

Although SLF II is most frequently implicated, other tracts such as the IFOF may contribute to neglect, potentially through their role in integrating visual and attentional information across [29, 30]. Involvement of OR may also mimic neglect symptoms by producing visual field deficits, which underscores the importance of differential diagnosis with other VSAs and comprehensive assessment [13, 31].

Despite the theoretical appeal of these models, the reviewed studies provided limited direct evidence for neuroanatomical correlates, primarily due to the scarce and heterogeneous use of advanced imaging techniques. DTI was used in only a few cases, yet it holds substantial potential for mapping white matter integrity and tracking changes over time [13, 26, 51, 55]. Longitudinal DTI assessments, particularly when combined with standardized NP testing, could yield important insights into neglect pathophysiology and prognosis.

A third result pattern from the analysed studies shows a lower incidence of permanent neglect in patients operated on via awake surgery with DES compared to resections under general anaesthesia. Nevertheless, the evidence remains highly biased and the role of DES in intraoperative neglect mapping remains debated. In fact, awake surgery is more frequently offered to LGG patients with higher plastic potential and better preoperative cognitive status [13, 46, 55]. Furthermore, the only intraoperative task consistently applied across studies was line bisection test, which, although feasible, may not fully capture the spectrum of attentional deficits [47].

In the future, the integration of DTI, DES, and rigorous NP testing is essential to move beyond a focal lesion approach and toward a network-based model of visuospatial deficits. Also emerging strategies, such as transcranial magnetic stimulation (nTMS), have been recently proposed [43]. Future prospective studies should standardize these tools to refine our understanding of neglect mechanisms.

Neuropsychological assessment

A crucial pattern identified in our review is the heavy reliance on egocentric assessment tools, which may lead to an underestimation of the true incidence of neglect. Our systematic analysis shows a total lack of specific testing for allocentric (object-based) neglect in current neurosurgical literature. While stroke studies frequently report dissociations between egocentric and allocentric deficits, glioma research remains focused on space-centered symptoms [19]. This methodological gap suggests that current "normal" postoperative results might overlook subtle but disabling object-based attentional deficits that impact patients' daily lives and quality of survival.

In the examined studies, a pre- and post-operative cognitive global functioning assessment, in addition to VSAs evaluation was generally performed, except in two cases [9, 51]. Previous studies reported that a prospective NP approach is an essential tool in neuro-oncology for comprehensive clinical assessment [50]. In fact, parietal lobe dysfunctions are often subtle and may be missed at bedside. Particularly in the postoperative phase, clinical evaluation is complicated by transient and heterogeneous deficits including cognitive deficit. For this reason, standardized NP assessment, performed both before and after surgery, offers a reliable framework to detect deficits occurrence within the perioperative period, to monitor their evolution, and to support rehabilitation planning [45].

Within the scenario of intraoperative NP monitoring, the only test performed was the line bisection [49] This choice is fundamentally driven by the need to balance diagnostic accuracy with the unique requirements of the surgical setting, such as time efficiency, limited patient mobility, and the need for repeated testing during resection. While the Line Bisection is admittedly limited in capturing the full spectrum of neglect (failing to detect allocentric or personal subtypes), its combination of reasonable sensitivity (60%) and high specificity (90%) makes it the most feasible 'stress test' for the attentional network intraoperatively [47]. In this task, patients are asked to mark the perceived midpoint of a horizontal line; a consistent displacement of the mark toward the side of the brain lesion indicates a failure to attend to the contralateral space.

Further analysis of neglect subtype and additional tests have been rarely performed. The differentiation of neglect from visual field deficits such as homonymous hemianopia was scarcely investigated, even if these conditions may lead to similar clinical presentation at bedside examination [31]. Tests like line bisection can support this differential diagnosis as patients with combined neglect and hemianopia typically result in more pronounced errors due to absent visual input and lack of corrective eye movements [10]. The Brentano Illusion Test (BRIT) is another useful tool to identify visual hemifield deficits in the context of neglect, by assessing implicit processing of contralesional stimuli [24].

Moreover, additional tasks can help characterize neglect subtypes but this also was poorly investigated. For example, the Apple Cancellation Test distinguishes egocentric (space-based) from allocentric (object-based) neglect by analysing which stimuli are omitted [35]. The task requires the patient to search for and cross out specific targets distributed across a sheet of paper, thus measuring the efficiency of visual scanning in the neglected hemispace and object part. Similarly, figure-copying tasks (e.g., the Gainotti Figure) and drawing-from-memory tests like the Clock Drawing Test provide insight into the spatial and imaginative components of neglect. Patients with egocentric neglect omit elements on the contralesional side of space, whereas allocentric neglect affects the contralesional part of the perceived object [19, 56].

Finally, qualitative tools like the Catherine Bergego Scale assess neglect in real-life contexts and provide valuable information on anosognosia and functional impact [36]. By combining caregiver and patient perspectives, this scale supports both diagnostic accuracy and the design of personalized rehabilitation strategies [36].

Limitations and future perspectives

Despite the increasing attention on visuospatial deficits in glioma patients, the literature on spatial neglect in parietal gliomas remains scarce and methodologically inconsistent. Most of the available studies are limited by small sample sizes, heterogeneous patient populations, and variable NP assessments. For these reasons, the findings of this review must be interpreted with caution due to the inherent weaknesses of the included primary studies and the resulting low level of evidence. This lack of methodological rigor likely contributes to the high variability in reported neglect incidence and underscores the need for a more robust, multi-task approach in future neuro-oncological research. According to our risk of bias assessment, four out of the nine included studies presented a significant risk of bias, primarily due to retrospective designs or lack of standardized assessment protocols.

Second, considerable uncertainty arises from the histological classification used across the reports. Only two of the selected studies explicitly utilized the WHO classification for glioma grading. The remaining studies either used older grading systems or did not provide granular data on molecular and histological subtypes.

Moreover, the use of non-standardized testing protocols, which are often limited to a single cancellation or bisection task, hampers reliable comparisons across studies and reduces the overall generalizability of findings.

Future research should focus on prospective multicentric studies incorporating advanced imaging (e.g., DTI), intraoperative mapping (e.g., DES), and comprehensive NP testing. A multimodal approach is essential not only for evaluating spatial attention, but also for capturing higher-order cognitive functions such as working memory, executive function, and self-awareness—domains that are often underexplored in neurosurgical studies but crucial for functional independence.

Importantly, while neglect symptoms are apparently transient in glioma patients, the opportunity to identify these deficits preoperatively and to inform patients accordingly should not be underestimated. Early detection through standardized, sensitive protocols allows clinicians to better understand the functional anatomy involved and may facilitate a more personalized surgical and rehabilitative plan. Ultimately, future efforts should aim to move from a purely lesion-deficit model toward a network-based, integrative framework that reflects the multifaceted nature of brain function and recovery.

Conclusion

In conclusion, while parietal gliomas can induce spatial neglect, particularly when involving the right hemisphere, the current body of evidence remains limited by small sample sizes and significant methodological heterogeneity. Our synthesis suggests that although neglect may emerge or worsen immediately following surgical resection, most patients experience a favourable trajectory with substantial recovery typically documented within three months. However, these findings must be interpreted with caution as they often rely on low-quality studies and single-task assessments, such as the line-bisection test, which may fail to capture the full complexity of the syndrome. To move beyond these limitations, future study should implement standardized, comprehensive NP batteries alongside advanced multimodal tools like DTI and DES. Such an integrated approach is essential not only for accurate perioperative tracking but also for refining our understanding of the network-based mechanisms of recovery. Ultimately, large-scale prospective and multicentric studies are required to establish robust evidence-based protocols for the management of visuospatial deficits in the neuro-oncological population.

Abbreviations

ADL

Activities of Daily Living

BIT

Behavioral Inattention Test

DAN

Dorsal Attentional Network

DES

Direct Electrical Stimulation

DTI

Diffusion Tensor Imaging

HGG

High-Grade Glioma

IFOF

Inferior Fronto-Occipital Fasciculus

LGG

Low-Grade Glioma

MAE

Multilingual Aphasia Examination

MMSE

Mini Mental State Examination

MoCA

Montreal Cognitive Assessment

MRI

Magnetic Resonance Imaging

NP

Neuropsychological

OR

Optic Radiations

PRISMA

Preferred Reporting Items for Systematic Reviews and Meta-Analyses

RBANS

Repeatable Neuropsychological Status Assessment Battery

SLF

Superior Longitudinal Fasciculus

VAN

Ventral Attentional Network

VNF

Ventral Non-spatial Network

VSA

Visuo-Spatial Abilities

WAB

Western Aphasia Comprehension Subtest

Authors contributions

Conceptualization: M.B., C.C. Data curation and formal analysis: C.C., G.A., F.M.D. Methodology: M.B. Prepared manuscript text and tables: M.B., C.C., L.B. Supervision: M.D.B., F.D.M., F.M.D. Edited manuscript text, and/or tables: all authors. All authors have read and agreed to the published version of the manuscript.

Funding

This work was partially supported by the Italian Ministry of Health (RRC).

Data availability

All data generated or analyzed during this study are included in this published article. Further datasets are available from the corresponding author on reasonable request.

Declarations

Ethics approval and consent to participate

Not applicable. This study is a systematic review and does not involve primary data collection.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.