Spatial neglect is defined as the inability to respond to sensory stimuli in the contralesional hemispace or body of a neurological patient (Kerkhoff 2001; Husain 2008). In addition to visual, auditory, or tactile neglect, motor neglect often co-occurs as a reduced use of contralesional extremities, i.e. during reaching, standing, or walking. Moreover, neglect patients show a lack of insight into their left-sided sensory and motor deficits termed anosognosia or unawareness. Anosognosia in patients with neglect delays recovery (Gialanella et al. 2005) and both are a major source of long-term disability and associated with an adverse rehabilitation outcome (Jehkonen et al. 2006a, b) and longer hospital stays (Kalra et al. 1997). Return to work seems almost impossible in chronic neglect, even after treatment.
Spontaneous recovery from neglect occurs mostly in the first 3 months after stroke (Nijboer et al. 2013). Some 30–40% of those patients presenting initially with neglect show chronic neglect at 1 year post-lesion (Karnath et al. 2011; Rengachary et al. 2011). The presence of an additional visual field defect reflects larger lesions and predicts chronic neglect as well as severe neglect dyslexia (Ptak et al. 2012). Spatial neglect is most often multimodal (visual, auditory, haptic, olfactory, Kerkhoff 2001). Behavioural recovery is task- and side-specific: while the conspicuous conjugate gaze deviation may be up to 30–40° ipsilesionally in the first weeks, this recovers continuously within 3 months, paralleled by a more symmetrical, wider visual exploration field of the patient (Aimola et al. 2014). Similarly, visual scanning and cancellation tests improve first on the ipsilesional side, later on the contralesional side (Nijboer et al. 2013). Directional hypokinesia (which designates the phenomenon that neglect patients do not reach far enough to their contralesional side with their intact, nonparetic limb/s) shows better spontaneous recovery than visuospatial inattention (Rengachary et al. 2011).
Moreover, left hemineglect is frequently associated with left hemianopia, which is often difficult to disentangle (pseudo-hemianopia). Left hemianopia worsens the severity of visual neglect. Furthermore, hemiparesis/-plegia and hemi-anaesthesia or hypaesthesia are also often present in patients with left neglect. All these associated deficiencies worsen neglect and reduce the functional effects of rehabilitation.
2.3. Description of Treatments for Neglect
While with exception of the Optokinetic/smooth pursuit therapy (SPT), the quality of evidence available is too low to give a weak or strong recommendation, there is nevertheless a variety of therapeutic options that are supported by clinical experience. The résumés presented below are therefore expert opinion.
In visual scanning training (VST or exploration training), patients typically look at a visual display (on a table, a computer screen, or a large projection wall) on which different classes of visual stimuli (i.e. stars, circles, numbers, photos from real objects) are shown, and the patient is required to look for a specific class of stimuli (“Search for all stars and point to them”, with a stick or laser pointer or on a touch screen). Patients are verbally instructed to look to the neglected side (“cueing of attention”), search systematically row by row as in reading in order to acquire a systematic search strategy. By this, the number of omissions and search time is reduced.
Résumé: VST is the most widely used treatment for neglect and improves selectively visual neglect in scanning and related tasks, but has no effect on non-visual neglect. It can easily be realized but requires many sessions to be effective (>40). It is difficult to implement in the early phase (first 2 months after stroke) because it requires some awareness and cooperation on the patient’s side.
Optokinetic/smooth pursuit therapy (OKS, SPT): Patients are instructed to make following (pursuit) eye movements to visual stimuli that move slowly towards the neglected field. The stimuli are usually presented on a computer screen or via beamer to a large projection wall via specific software. When the patient has reached with his eyes the neglected side of space, he is instructed to remain there with his eyes for some seconds, before the task is repeated. OKS/SPT can be performed early after stroke at the bedside, or later. Twenty or more sessions (á 30-min) are recommended.
Résumé: OKS/SPT is more effective than scanning therapy and can be implemented earlier. Improvements transfer to a wide variety of visual and non-visual neglect domains and reduce anosognosia.
Neck-muscle vibration (NMV): During NMV therapy, the patient’s contralesional neck muscles (hence left neck in left neglect) are vibrated with a conventional vibrator (either battery-driven or not; with a small vibration head, <2 cm diameter, and a vibration frequency >60–80 Hz). This induces activation of muscle spindles and leads to a relocation of gaze (eye and head position) towards a more symmetrical, midline position. The vibrator is usually held by the therapist, which can be demanding for the therapist as he/she will feel the vibration as well and has to do it for at least 20 sessions (á 30 min).
Résumé: NMV is easy to apply but is more demanding for the therapist holding the vibrator. On the other hand, a battery-driven vibrator makes therapy more flexible and mobile, thus therapy can be performed at the bedside, in physio or occupational therapy, or at home.
Prism adaptation (PA): This therapy requires a conventional spectacle on which two prism glasses are mounted inducing a gaze shift to the ipsilesional side (hence to the right in left neglect). This prism goggle is worn by the patient only for the period of the prism exposure (not during the day, especially not during walking!). The prism exposure lasts typically for 20–30 min per session, and this should be repeated (several times per week). While the patient wears the prism goggles, he/she carries out visuo-motor tasks. These can be pointing to marked locations on a table, or reaching for objects in daily life (i.e. cups or glasses on a table or in a bookshelf). After this exposure period, the goggles are taken off and the therapeutic after-effect occurs (re-orienting of spatial attention to the neglected side). This can be used for other subsequent therapies (i.e. motor, postural, reading, cognitive …). Twenty or more sessions (á 20–30 min) are recommended.
Résumé: PA is a widely used tool for neglect therapy that works best with a 10° prism (not smaller prism angle!) and is also mobile and relatively easy to apply.
Visuo-motor feedback (VF): The patient has to lift wooden or metal rods with his ipsilesional hand (index finger and thumb), so that their left and right half are balanced and the rod does not fall to one side. As the patient ignores initially the contralesional side of the rod (due to his neglect), he will grasp it more to the right side and consequently the bar will fall to the left side. This “natural” feedback leads to a subsequent adaptation of the patient’s lifting behaviour, thus lifting the rods more accurately in the middle part during the course of the therapy. Twenty or more sessions (á 20–30 min) recommended.
Résumé: VF is an easily applicable and low-cost treatment that can be implemented in different settings, including the patient’s home. This makes it flexible and mobile.
Mirror therapy (MT): MT is a well-established treatment for therapy of motor impairments (of the hemiparetic arm or leg). It requires a vertically oriented mirror which is placed in front of the patient’s breast so that he can view his ipsilesional hand/arm/leg performing different motor tasks. This action observation facilitates motor recovery of the impaired extremity behind the mirror. MT has shown therapeutic effects in patients with left-sided hemiparesis and left-sided visual neglect. Twenty or more sessions (á 20–30 min) recommended.
Résumé: MT is an easily applicable, low-cost therapy which can be used as an add-on treatment (not as a primary neglect therapy) for neglect.
Attention training: Alertness and sustained attention can be trained by various ways: by computer-based training and specific software, by table-top exercises, and also by motor (for instance treadmill) training. Improvements in attention lead to better performance in neglect-specific tasks, especially dual-tasks (i.e. looking and recollecting numbers heard, or looking and walking simultaneously).
Résumé: Attention training can be an element of neglect therapy. However, therapy should not rely solely on computerized training as such improvements are often not stable in the long term.
Hemifield Fresnel Prisms: Press-on (Fresnel) prism foils are attached on the contralesional side of the two glasses of a conventional spectacle sparing the central (macular) visual field region. This induces a gaze shift towards the neglected side (hence opposite to that in prism adaptation, see above).
Résumé: Easy-to-use technique, which should be used only during sitting and when the patient is not involved in transfers or other potentially dangerous activities, as the prism distorts the visual field. The central 10° of each glass should be free from foil to enable unimpaired central vision. Fresnel prisms reduce visual acuity by some 10–20%.
Repetitive transcranial magnetic stimulation (rTMS): During rTMS, a magnetic coil attached to a magnetic stimulator is hold by a medical doctor over the non-lesioned parietal cortex (hence the intact) hemisphere, to re-balance the attentional systems of both hemispheres. Left parietal attentional systems are typically hyperactive in patients with left neglect thus preventing the lesioned right-sided attentional systems from functional recovery. rTMS temporarily dampens the leftward hyperactive systems, thus improving functional recovery. This works without the patient being attentive, but care must be taken not to induce fits. Twenty or more sessions (á 20 min) are recommended.
Résumé: rTMS (or theta burst stimulation) is the most costliest neglect therapy to date and requires medical staff. It can be used earlier than other treatments as the mechanism of action does not require awareness or active cooperation from the patient. An optional add-on treatment when safety criteria are followed.
Transcranial direct current stimulation (tDCS): Similar principle of action as in rTMS, but instead of magnetic pulses, weak electrical currents are delivered via two electrodes over the two parietal lobes. Twenty or more sessions (of 20 min) are recommended.
Résumé: Less costly than rTMS, but often the technique cannot be applied due to exclusion criteria for safety reasons (fits, open scull) or is difficult to apply because of hairy skin thus preventing the flow of electric currents.
Transcutaneous electrical nerve stimulation (TENS): Application of weak electrical currents to the contralesional neck/upper back. Portable, low-cost technique, easily applicable, and no safety problems. Twenty or more sessions (á 20 min) recommended.
Résumé: Suitable as an add-on treatment, probably less suited as a primary and sole neglect therapy. It has good effects also on postural imbalance and non-lateralized attention.
Arm/hand activation with/without peripheral electrical stimulation: The method entails volitional movement of the contralesional limbs (i.e. opening and closing the hand). This can be facilitated by the additional application of electrodes to the neglected limb.
Résumé: Limb activation is often not applicable in the early phase of neglect because of severe hemiparesis or plegia. Later, with concurrent electrical stimulation, it is a useful, low-cost technique that particularly addresses neglect of the neglected extremities which is not targeted by the majority of other neglect treatments (except GVS, see below).
Galvanic vestibular stimulation (GVS): Application of weak electrical current via two electrodes attached behind both ears (over the mastoid bones) activates the vestibular system via the vestibular nerves. This has good therapeutic effects on body-related neglect (tactile extinction, sense of arm position for the neglected limb and visual neglect). Same limitations for safety reasons as in rTMS and tDCS (no fits). Twenty or more sessions (of 20 min) recommended.
Résumé: A suitable add-on treatment, especially for the body-related phenomena of neglect. The same electrical stimulators as used for tDCS can be used.
Drugs: The administration of attention-enhancing drugs is intended to improve non-lateralized attention (alertness), thereby reducing neglect. Moreover, antidepressant drugs can improve attention.
Résumé: Potentially, drugs may be helpful as an add-on treatment (not as a primary neglect therapy). Unfortunately, the therapeutic effects are inconsistent and many potential interactions with other drugs the patient must take have to be considered. Antidepressants given because of post-stroke depression may have an additional positive effect on neglect but should not be the primary reason for their prescription.