Unilateral Neglect

Original Editor - Emily Wood, Kathy Bueckert, Alexandra Dansereau, Cassandra Schilling as part of the Queen's University Neuromotor Function Project, adapted by Céline Gueissaz

Top Contributors - Emily Wood, Céline Gueissaz, Cassandra Schilling, Kathy Bueckert, Alexandra Dansereau, Redisha Jakibanjar, Kim Jackson, Kalyani Yajnanarayan, 127.0.0.1, Alexandra Stead, Vidya Acharya, WikiSysop, Wout Van Hees, Candace Goh and Dinu Dixon

Page Summary

• Unilateral spatial neglect (USN) is a common post-stroke disorder where people fail to report, respond or orient to stimuli contralateral to the brain lesion.
• Right-hemisphere stroke produces USN in 61% of cases, compared with 22% for left-hemisphere stroke, because the right hemisphere directs visuospatial attention.
• Cancellation tasks are the recommended first-choice test for USN, while the Catherine Bergego Scale assesses personal, peripersonal and extrapersonal neglect during everyday tasks.
• Visual scanning training and prism adaptation are the best-supported USN interventions, though confidence in the evidence is low to moderate and most treatment effects are short term.

Introduction

Unilateral spatial neglect (USN) is one of the most common behavioural and cognitive disorders following a stroke. It typically results from damage to brain networks involving most of the time the inferior parietal lobe, temporo-parietal-occipital junction, or superior temporal gyrus of the temporal lobe. USN is also commonly known as hemineglect, hemispatial neglect, spatial neglect, visuo-spatial neglect, or inattention.

In USN, individuals fail to report, respond or orient to meaningful stimuli presented on the contralesional side (i.e. the side opposite to the brain lesion). Most commonly, damage occurs in the right cerebral hemisphere, leading to a loss of awareness and attention and/or a lack of motor activation for the left hemispace.

Epidemiology

USN is suggested to affect up to 70% of stroke survivors. However, its prevalence varies by lesion location, as well as the timing of assessment following stroke and and the methods used to assess USN. When the right hemisphere is damaged, USN occurs in 61% of cases, while that rate drops to 22% when the left hemisphere is affected. The reason for this difference is that the right hemisphere plays the dominant role in directing visual spatial attention, making USN more likely to occur.

It also becomes less common over time: about 45% of right-hemisphere stroke patients show USN in the first week, 40% between one week and three months, 29% between six months and a year, and 20% after one year.

Pathophysiology

Brain scans of two USN patients with right-hemisphere lesions. (A) MRI: hemorrhagic lesion, fronto-temporo-parietal regions. (B) CT: ischemic lesion, fronto-insulo-temporal cortico-subcortical regions, with a small secondary hemorrhage.

Although USN can stem from various origin, vascular lesions represent the most frequent cause of this syndrome. Several key characteristics describe the etiology of USN:

Several key characteristics describe the aetiology of USN:

• As mentioned previously, USN can result from damage to either hemisphere, though it is more common and more severe following right-hemisphere stroke
• It is not caused by damage to a single brain region but results from disruption of broader attention networks in the brain
• These networks involve several cortical and subcortical structures, and the white matter connections between them
• Damage limited to the frontal lobe alone is often linked to shorter-lasting, less disabling USN
• Larger strokes involving both frontal and parietal regions are often linked to longer-lasting, more disabling USN

Clinical Presentation

USN is a heterogeneous condition, meaning different individuals present with different clinical features. It can affect multiple sensory and motor modalities, including visual, auditory, somatosensory and motor/kinetic. Therefore, because USN varies so widely, it can be broken down along multiple dimensions:

• The region of space involved
• The stage of processing affected
• The frame of reference used

The following lists displays symptoms associated with the acute phase of USN:

• Head, eyes, and trunk turn toward the unaffected side
• Severe cases: may not recognise their own affected limbs or people on that side
• Often bump into things, groom, or eat food only on the unaffected side
• Pay less attention to conversations/tasks on the neglected side
• May feel sensations from the neglected side as if from the other side

Other impairments frequently described with USN are:

• Neglect dyslexia and neglect dysgraphia (reading and writing difficulties linked to USN)
• Overuse or repetition of responses on the unaffected side, possibly compensating for reduced responses on the neglected side
• Frequent overlap with hemianopia (partial vision loss) and hemianaesthesia (partial loss of sensation), which can worsen symptoms
• Anosognosia (lack of awareness of one's own deficits) is common and serious; and it raises safety concerns and complicates rehabilitation.
• Extinction: failure to notice a stimulus on the neglected side when presented at the same time as one on the unaffected side, even though it's detected when presented alone; can affect vision, hearing, or touch, sometimes just one sense
• Allochiria: a stimulus on the neglected side is felt, but mislocated to the unaffected side
  

Diagnosis

Clock drawing neglect test

Assessing USN is challenging because it can affect any or all three spatial dimensions, as severity is shaped by factors such as lesion site, cognitive reserve (the brain's capacity to compensate for damage), and the rehabilitation setting.

Diagnosis typically relies on clinical observations and standardised neuropsychological tests.

The following table summarises the main diagnostic tests used to assess USN:

Category	Test	Description	Advantages	Disadvantages
Pen-and-paper	Line bisection	Patient marks what they judge to be the midpoint of a horizontal line	Quick and simple. Larger deviation size tends to reflect greater neglect severity.	Doesn't reflect daily functioning. Doesn't reliably show which side is affected.
	Clock drawing	Patient draws a clock face from memory or copies one, placing all numbers	Quick and simple	Doesn't reflect daily functioning
	Cancellation task	Patient scans a page and marks out target shapes or letters among distractors	Recommended as the first-choice test when only one assessment is feasible	Doesn't reflect daily functioning
	Baking tray task	Patient arranges small objects across a tray, revealing any bias toward one side	Recommended as a secondary test when more time is available	Doesn't reflect day-to-day functioning
	Figure copying	Patient copies a drawing or scene, with neglect shown by omissions on one side	Recommended as a secondary test when more time is available	Doesn't reflect day-to-day functioning
Performance-based	Catherine Bergego Scale (SBS)	Clinician observes the patient performing everyday tasks to detect signs of neglect	Only test covering personal, peripersonal, and extrapersonal neglect. Captures real-world functional impact. Best used once the patient's condition has improved	Not widely used. Can be hard to apply in practice.

A key gap remains: no current tool combines standard neuropsychological tests with how patients actually perform in daily life. Many patients score well on formal tests but still struggle with everyday tasks.

Management / Interventions

The interventions to treat USN may include the following methods:

• Visual scanning training
• Prism adaptation
• Neck muscle vibration
• Non-invasive brain stimulation, such:
  • transcranial magnetic stimulation
  • transcranial direct current stimulation
• Optokinetic stimulation
• Vestibular stimulation, including:
  • Caloric vestibular stimulation
  • Galvanic-vestibular stimulation
• Limb activation training
• Mental imagery training
• Eye patching
• Virtual reality training
• Transcutaneous electrical nerve stimulation
• Mirror therapy

Visual Scanning Training

Visual scanning training (VST) is a common approach for treating USN, guiding patients to consciously shift attention toward their neglected side. It depends on patients engaging directly with the task, helping them build skill and awareness of their deficit. Typical VST tasks include:

• Searching for letters or images
• Copying drawings
• Reading text

Therapist feedback plays a central role, though in conventional VST it typically relies on the therapist's personal judgment rather than objective measures.

Along with prism adaptation, VST is among the best-supported interventions for USN, though variability in study design limits confidence in the findings to a low-to-moderate level. VST is very often used in clinical settings.

Prism Adaptation

Prism Adaptation (PA) is another frequently used therapy in clinical setting. It requires patients to wear optical prisms that will shift the visual field toward the affected side. With repetitive use, it will prompt the brain to recalibrate the connection between visual perception and motor output. However, recent systematic reviews and meta-analysis have demonstrated that PA effects are limited to a short-term time frame.

Neck Muscle Vibration

Neck muscle vibration (NMV) stimulates the left posterior neck muscles, shifting patients' visual attention and body orientation leftward to help correct the rightward bias in USN. This leftward shift persists after the vibration stops and appears specific to the left neck muscles. Applying stimulation to the right posterior neck muscles, to the hand, or using transcutaneous electrical stimulation was shown not to produce the same result.

However, several limitations with this intervention remain:

• Effects are often short term
• Evidence supporting its use as a standalone treatment is limited
• Functional benefits remain unclear

Non-Invasive Brain Stimulation

Recent evidence points toward the efficacy of non-invasive brain stimulation (NIBS) for the treatment of USN. NIBS include, but is not limited to:

• Transcranial magnetic stimulation (TMS)
• Transcranial direct currect stimulation (tDCS)

TMS and tDCS are both painless, noninvasive techniques, but they work differently. TMS uses a magnetic coil to directly activate brain cells, while tDCS uses a weak electrical current through the scalp to make brain cells more or less active.

Both methods are shown to produce small gains in neglect test scores, with TMS somewhat more consistent than tDCS, though real-world functional benefits remain uncertain and study protocols vary considerably. For the same reasons, those two interventions are typically paired with other rehabilitation methods rather than used on their own.

Optokinetic Stimulation

Optokinetic stimulation works by showing patients moving visual patterns, such as dots or lines, which trigger reflexive eye movements that help shift attention toward the neglected side. When paired with standard therapy, this approach has been linked to short-term gains, most notably on paper-based assessments.

A recent review found that how well it works depends on several factors:

• the specific task being measured
• the intensity of the stimulation
• and whether it is combined with other treatments

Vestibular Stimulation

Vestibular stimulation comes in two forms:

• Caloric: water is introduced into the ear canal
• Galvanic: a weak electric current is passed through the vestibular nerves

Both techniques work by briefly altering inner ear signals, which can temporarily ease USN symptoms and affect spatial orientation. Caloric stimulation, especially on the unaffected ear, tends to show more reliable short-term benefits, including some improvement in motor symptoms, while galvanic stimulation has produced more mixed, limited evidence. Overall, both may offer short-term attention gains, but inconsistent methods and unclear long-term benefits limit their clinical use.

Limb Activation Training

Limb activation is a common movement-based treatment for USN. The idea is that moving or stimulating the affected-side limb helps shift attention toward the neglected side. This can happen through:

• Active movement (voluntary)
• Passive movement (joint-position input)

Studies show limb activation can temporarily improve spatial task performance, likely by encouraging exploratory movement rather than fixing the underlying deficit, using both active and passive movement. However, Benefits tend to fade quickly and vary between patients, so it's usually paired with other treatments like visual scanning training or prism adaptation rather than used alone. Still, it offers a simple, inexpensive addition to standard clinical care.

Mental Imagery Training

Mental imagery is a technique that involves imagining an experience, whether visual, tactile, auditory, or physical, that is not actually occurring. This means mentally rehearsing actions without any real movement.

Mental imagery can take two forms:

• Visual: picturing shapes, colors, or brightness
• Motor: mentally simulating physical movement without actually moving

It's also been linked to improved memory, and may offer therapeutic value for treating USN.

Eye Patching

Eye patching can be done in two ways:

• covering one eye entirely (monocular) or
• covering half the visual field (hemifield).

It's thought to work by rebalancing activity between the two brain hemispheres and influencing visual orienting responses through the superior colliculus pathway.

Some studies have shown improvement on neuropsychological tests, though results are inconsistent and depend on several factors:

• Type of patching used
• Where the stroke occurred
• How long ago it happened

Its long-term, real-world benefits remain unclear, as confirmed by systematic reviews and meta-analysis specifically looking at rehabilitation approaches for USN and at eye patching.

Virtual Reality Training

Virtual reality creates computer-generated environments that feel like real life. It helps patients pay attention and move toward their neglected side. VR is safe and easy to use, and can both detect and treat USN, with many studies showing improved attention and scanning. There are three types of VR:

• Immersive: uses a headset for full 3D immersion
• Semi-immersive: uses a large screen with devices like gloves or cameras, while still seeing the real world
• Non-immersive: uses a standard screen with a keyboard or mouse, the least interactive form

Side effects like nausea or motion sickness can occur, and while using VR is straightforward for patients, developing and equipping these systems is costly.

Transcutaneous Electrical Nerve Stimulation

Transcutaneous electrical nerve stimulation (TENS), is a form of electrical stimulation through the skin that may influence spatial attention. Early studies found that applying TENS to the left side of the neck could:

• Briefly reduce neglect symptoms
• Improve mental visualisation of objects and space
• Support postural control

TENS combined with visual scanning training has also been shown to help with daily activities. One study found this combination led to short-term gains on neglect tests, lasting less than a week, alongside longer-lasting improvements in reading and writing that lasted more than a week.

Mirror Therapy

Mirror therapy is a promising treatment for USN after stroke, though evidence is mixed and limited by small study sizes. Patients watch the reflection of their unaffected limb, creating the illusion of movement on the neglected side, which may help redirect attention there.

Ramachandran and Roger-Ramachandran first developed it to treat phantom limb pain. A mirror is placed between the limbs so the affected side appears to move normally, sometimes while handling objects like balls or cloth. Larger mirrors tend to work better, and the technique has also shown moderate to large benefits for upper limb recovery.

Overall, it's a simple, accessible option for use alongside other rehabilitation methods.

Prognosis

USN predicts worse outcomes after stroke. Patients with USN tend to experience:

• More severe strokes
• Longer hospital stays
• Greater disability
• Higher mortality
• Greater need for institutional care
• Disrupted daily activities and balance
• Increased fall risk

Despite this, USN is often missed early and undertreated relative to its impact, even though targeted training could support broader rehabilitation.

Many patients recover somewhat on their own, but around 40% still have symptoms a year later. Recovery, when it happens, usually occurs within the first few months and varies by neglect type. Factors linked to faster recovery include:

• Smaller lesions
• Hemorrhagic (versus ischemic) strokes
• Younger age

Summary

USN is a common post-stroke condition, mostly after right-hemisphere damage, in which people fail to notice stimuli on the side opposite to their brain lesion (usually the left side). It affects up to 70% of stroke survivors, most often in the acute phase. It is assessed through clinical observation and standardised tests. A wide range of treatments exists, from behavioural training to sensory and brain stimulation techniques, but most effects are limited to the short term. Spontaneous recovery is frequent, with most patients recovering within a year.