Br Ir Orthopt J 2012; 9: 17–22 Prism adaptation: is this an effective means of rehabilitating neglect? KIRSTY LAVERY BSc Hons (Orth) AND FIONA J ROWE PhD, DBO Directorate of Orthoptics and Vision Science, University of Liverpool, Liverpool Abstract parietal lobe, although it may be caused by a left sided lesion and involvement of any one of various brain Aim: Controversy exists as to whether prism adapta- structures.3 It results in the patient being unaware of one tion improves the symptoms of neglect. The purpose side of their environment, the side contralateral to the of this review is to investigate the efficacy of prism lesion. Neglect has a huge impact not only on patients adaptation techniques in the rehabilitation of neglect. but also on their families and carers,4 and as the presence Methods: A literature review was conducted using the of neglect adversely affects patients’ overall rehabilita- search engines Pubmed, Medline, Embase, Ovid, tion, effective treatment of this debilitating condition is Google scholar and http://pcwww.liv.ac.uk/~rowef/ an important aim.5 The syndrome has been reported to index_files/Page646.htm. Study and review abstracts show spontaneous partial recovery,6 with the most from the literature search were analysed and marked evident manifestations of neglect usually vanishing for inclusion if they contained the following terms in within 1 month after a stroke.7 One study has reported reference to visual neglect: ‘visual inattention’, a 43% partial recovery of patients during a 2-week ‘visual neglect’, ‘stroke’, ‘cerebro-vascular accident’, period and furthermore a complete recovery was ‘rehabilitation’ and ‘prism adaptation’. Only jour- observed in 9% of patients.8 nals written in English with full text access were included in this review. Results: Neglect is now known as a multi-component Domains of space disorder and recent studies have suggested using a combination therapy approach for the rehabilitation There are a number of different aspects of neglect: of neglect. There have been promising reports when personal space (a patient failing to notice their own prism adaptation has been used in combination with contralesional body parts), peri-personal space (within other methods of rehabilitation. However, there is not arm’s reach) and extra-personal space (beyond arm’s yet an adequate amount of evidence to definitively reach).9–11 The careful assessment of each component of guide rehabilitation and thus additional research is neglect rather than the condition as a whole is essential advocated. for the expansion of research on rehabilitation. Conclusion: Although negative results have been reported, the majority of studies advocate the use of prism adaptation. However, there is not yet enough Multi-component disorder evidence to incorporate prism adaptation into the Visual neglect may be a multi-component disorder clinical rehabilitation programme for neglect characterised by at least three separate deficits. These patients. Further studies need to concentrate on the deficits include an initial automatic orienting of attention clinical significance of improvements in neglect towards the ipsilesional side, an impairment in dis- symptoms and the extent to which improvements engaging attention from the ipsilesional side and extend to the everyday lives of patients. reorienting attention towards the contralesional side, and a generalised reduction in attentional processing Key words: Neglect, Prism adaptation; Rehabilitation, 12–18 Stroke, Visual inattention capacity. A study by Mark et al.19 aimed to test the hypothesis that left neglect patients cannot disengage attention from, or over-attend to, stimuli on the right side of space. Introduction The patients were given the standard line cancellation Visual inattention, also known as neglect, has been test as well as a modified version where they had to erase reported to be one of the most common visual the lines rather than draw through them. Interestingly the difficulties caused by stroke. The incidence has been patients’ performance significantly improved on the reported to be as high as 90%1 and as low as 8%.2 This modified test compared with the standard test. Mark et condition usually follows a right-sided lesion of the al.’s results imply that lines in the right hemispace inhibit the patient from exploring the left hemispace. Once the lines on the right side are erased, the patient Correspondence and offprint requests to: Kirsty Lavery, Orthoptic becomes aware of and can attend to those on the left. Department, Wycombe General Hospital, Queen Alexandra Road, High Wycombe, Bucks HP11 2TT. e-mail: kirsty.lavery@ Therefore the authors suggest neglect is related to the buckshealthcare.nhs.uk presence or absence of stimuli in the right hemispace. 18 K. Lavery and F. J. Rowe Lesion site system. This proposal is supported by Serino et al.21 who stated that low-order visuomotor reorganisation is Lesion site is routinely considered in relation to clinical stimulated by prism adaptation. They conclude that it findings. It may also influence recovery and response to is error reduction and not the after-effect that may play a treatment, although research to date has been conflicting. role in ameliorating characteristics of neglect. A 2002 MRI (magnetic resonance imaging) study of patients with persisting neglect20 revealed extensive lesions involving three or more cortical lobes or Prism adaptation procedures subcortical regions in all patients. Areas included the Prism adaptation procedures classically involve ocular parietal lobe, basal ganglia, frontal lobe, temporal lobe rotation (eye shift with prisms) and manual correction and thalamus, but the occipital lobe was intact in all (hand shift with prisms). It is difficult to establish which patients. of these is involved in the underlying mechanisms that In contrast, one study has found that severe occipital contribute to the amelioration of neglect. Newport et lesions negatively affect neglect rehabilitation by prism al.30 dissociated the contributions of ocular rotation and adaptation.21 manual correction to SSA realignment in normal subjects by shifting the eye alone, hand alone and both Visual rehabilitation together. Shifting the eye alone did not contribute to SSA realignment whereas shifting the hand alone or the Various rehabilitation therapies are reported in the hand and eyes together did. It was proposed that limb literature. Top-down approaches rely on the patient error has greater central nervous system input when eye being aware of their disorder and voluntarily compensat- and limb shift are in attendance at the same time. The ing as a consequence. Rather than focusing on the 5,22 authors also propose that error reduction may be the impairment they focus at the level of disability. fundamental prism adaptation component that modifies Methods include scanning therapy, hemianopic patching SSA. It was suggested that if oculomotor resetting is and mental imagery training. The top-down approach responsible for neglect amelioration then it may occur has drawbacks for treatment of neglect. Feedback is after prism exposure and not during it as suggested by usually provided as the majority of neglect patients are Serino et al.21,30 It was concluded that should oculo- not aware of their disorder and therefore need frequent motor resetting occur, it cannot be as a direct result of prompting to look left or right. In day-to-day life 22 prism exposure but must be a by-product of propriocep- situations, this is unrealistic. tive realignment of the limb.30 Bottom-up approaches do not require subjective awareness of the disorder, but involve passive stimula- Inconsistency in methods of assessment tion such as caloric stimulation, contralesional limb activation, neck muscle vibration and prism adapta- The majority of studies have used SSA (pointing with tion.23 In most cases an automatic change in behaviour eyes closed) or visual open-loop pointing (VOL), i.e. occurs,5,22 with patients able to perform tasks during or pointing to a visual target without seeing the hand, to after stimulation, rather than learning to actively assess the after-effects of prism adaptation. In 2008, compensate for their deficit.24 Sarri et al.31 directly compared these two measures in The main objective of this review is to determine the same group of neglect patients and also a control whether prism adaptation is an effective means of group. They found the SSA after-effect was pathologi- rehabilitating visual neglect following stroke. cally large in left neglect patients compared with normal subjects, while the VOL after-effect was similar in the Prism adaptation therapy as a bottom-up approach patients and the normal subjects. It was suggested that SSA may not provide a ‘pure’ measure of prism Prism adaptation was first described as a rehabilitation adaptation, as the post-prism shift in SSA may also method for neglect by Rossetti et al.23 It is a bottom-up reflect one aspect of neglect improvement. approach to rehabilitation5,25,26 where the method Therefore SSA and VOL should not be considered typically involves a short exposure period to a prismatic interchangeable when assessing prism adaptation in optical shift of approximately 10–15° to the right in left neglect.31 It is essential that further research is carried neglect, combined with a task such as pointing to visual out to discern the best methodology in order for studies targets in free vision whilst wearing the prisms. to be comparable. This will not only