CLINICAL STUDIES / ETUDES CLINIQUES
CLINICAL AND DEMOGRAPHIC CORRELATES OF UNILATERAL SPATIAL NEGLECT AMONG COMMUNITY-DWELLING NIGERIAN STROKE SURVIVORS
CORRÉLATIONS CLINIQUES ET DÉMOGRAPHIQUES DE LA NÉGLIGENCE SPATIALE UNILATÉRALE PARMI LES SURVIVANTS D'UNE COMMUNAUTE NIGÉRIANE POST-ACCIDENT VASCULAIRE CEREBRAL
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Keywords: Perceptual Disorder, Rehabilitation, Stroke, Unilateral Spatial Neglect
Unilateral Spatial Neglect (USN) is a common disorder after stroke (10). It is a failure to report, respond, or orient to stimuli in the space contralateral to a brain lesion, and the failure is not attributable to a primary sensory or motor deficit (6). Stroke patients with USN could experience impaired ability to detect sensory stimuli (sensory neglect), visualize or process mental representation of objects (memory or representational neglect), and move (motor neglect) in the space opposite the hemisphere affected by stroke (2, 4). These clinical features may account for the negative impact of USN on different functional activities of people who have suffered a stroke (4).
Attempts have been made to provide a reliable estimate of the incidence and prevalence of USN after stroke (3). A wide variation in the reported figures however makes conclusive deduction and generalization difficult. While the reported prevalence ranges from 12% to 100% in patients with right hemispheric stroke, figures among those with left hemispheric stroke vary from 0% to 76% (3). Although differences in the frequency of occurrence of USN has been linked to the side of brain damage, factors such as differences in research methodology and attributes of study population are also major contributors to the variations in the available data (3).
The influence of gender, age, stroke severity, marital status, handedness and post-stroke duration on the prevalence of USN (1, 3, 11) has been explored. Whereas there appears to be no consensus on the impact of these factors, nevertheless availability of information on factors associated with the frequency of USN may have implications for the successful post-stroke rehabilitation. This is especially more so that post-stroke patients with USN have been reported to require longer periods of rehabilitation and often end up with lesser functional recovery than those without the disorder (1), a situation affirming that USN often hinders response to therapy (3). Furthermore, negative consequences such as postural imbalance, frequent falls, poor autonomy, impaired mobility (2) and directional hypokinesia(4) which often accompany USN are known to result in poor functional outcome. Obtaining information about the correlates of USN among post-stroke individuals should then be considered as an important factor when designing rehabilitation programmes for this group of patients. The aim of this study was to investigate influence of age, gender, duration and motor function as correlates of USN among community-dwelling stroke survivors in Nigeria.
MATERIALS AND METHODS
Participants were 40 post-stroke patients receiving physiotherapy on out-patient basis at tertiary health facilities in south west Nigeria. Inclusion criteria for the participants were stroke onset within 12 months preceding this study, being community-dwelling, ability to hold a pencil to complete the USN screening tests and willingness to participate in the study by giving written informed consent. The protocol for this study was approved by the Health Research Ethics Committee of the University of Ibadan/University College Hospital, Nigeria.
Demographic and clinical data of age, gender, side of stroke and time since stroke were obtained from the patients and medical records as appropriate; motor function was assessed using the Modified Motor Assessment Scale (MMAS). The MMAS is a widely used 8-item scale that assesses motor function in stroke. Assessment entails patients carrying out functional movements rather than isolated patterns of movements. Supine to side lying; supine to sitting over the side of the bed; balanced sitting; sitting to standing; walking; upper-arm function; hand movements and advanced hand activities were assessed and performance of each movement was graded on a 1 to 6 scale. The total obtainable score on the scale ranges from 8 to 48 with higher score indicative of better motor function (9).
Participants were assessed for existence of USN using 2 paper and pencil cancellation tests namely the star and bell tests. The use of more than one cancellation tests to detect USN is in line with documented recommendations (13).
The second test was the bells cancellation test. The bells test consists of 35 bells surrounded by 280 distractors such as houses, keys, guitars arranged in 7 columns on an 11 x 8.5 inch paper . Patients circled the bells with a pencil. Maximum obtainable score is 35 and an omission of 6 bells or more indicates USN. A patient was diagnosed to have USN if he failed both cancellation tests. This is because no single test can effectively test for this dysfunction.
Descriptive statistics of frequency, mean and standard deviation were used to summarize the demographic and clinical data. Mann Whitney U test was used to determine difference in prevalence of USN by stroke severity while Chi square statistics was used to analyze difference by demographic and other categorical clinical variables at 0.05 alpha.
Majority (55.0%) of the 40 stroke patients who took part in the study were males, and had suffered left hemispheric stroke with 42.5% aged 60 years and above. Presence of unilateral spatial neglect was observed in 15 (37.5%) of the participants. Table 1 shows their demographic and clinical characteristics.
Among the categorical variables, only gender was significantly associated with neglect, with a greater proportion of females experiencing USN. The other variable with significant association with USN was motor function assessed using the Modified Motor Assessment scale (MMAS). The MMAS score was significantly better among stroke patients without neglect than those with neglect. Results obtained for test of association are presented in table 2.
Unilateral spatial neglect was observed in about a third of the participants in this study. Prevalence of USN across previous studies shows wide variations, ranging from 0% to as high as 100% (5). Reasons for the wide variability have been identified to include differences in methodology in the existing studies (3). The proportion of patients with USN observed in this study is within the range reported by the earlier cited studies.
As a result of some assumptions, many authors who had investigated USN involved only patients with right hemispheric stroke. These authors opine that the right hemisphere of the brain plays the primary role in spatial processing and therefore would be more affected by USN. Others exclude patients with left hemispheric stroke because of their higher likelihood to experience dysphasia and consequent difficulty in understanding and utilizing tools and instructions for assessment of USN (5). In spite of this trend among studies on USN, there are a number of studies that compared the occurrence of USN between stroke patients with right and left brain damage. Our present study included stroke patients with right and left brain damage and results showed that neglect was equal in proportions between right and left hemispheric stroke patients. our finding contrasts submissions from majority of similar studies as shown in the outcome of a systematic review of 17 stroke studies in which 16 out of the studies reported a higher rate of neglect after right brain damage than occurs following left brain damage (3). The other study in the review reported findings of almost equal incidence of USN following left and right brain damage (3), and this is similar to our findings in this study.
Our findings showed no significant influence of age and time since occurrence of stroke on USN. A previous study however reported a significantly positive relationship between age and frequency of USN (11). The documented influence of increasing age on increased frequency of neglect contrasts our findings in which a higher proportion of those aged 50 years and below presented with neglect. Spatial neglect was also not statistically associated with time after stroke. Our results however showed a trend that more people with longer duration had the disorder. Differences between the genders in performance of cognitive tasks have generated a lot of interest in research over the years. Gender differences have been reported in about 80% of studies that investigated performance of spatial tasks among apparently healthy individuals, with males performing better than females (12). Available studies on the influence of gender on the occurrence of USN after stroke however revealed no gender differences (8,11). In this present study however, a significantly higher proportion of females experienced USN. This observation could result from differences in stroke severity between the genders since the degree of severity has a relationship with occurrence of neglect.
Increased stroke severity in terms of high levels of motor impairment was associated with increased frequency of neglect among the stroke patients in this study. Previous studies have also observed association between the presence of USN with the severity of stroke (1,4). The relationship between stroke severity and neglect can be described as reciprocal since neglect may be seen to contribute to severity while on the other hand, occurrence of neglect depends on, and indicates the severity of stroke. Inclusion of assessment of neglect among other variables in determining the severity of stroke is therefore justified.
Increased frequency of USN was associated with female gender and lower motor function in this study. The proportion of participants with USN indicates that neglect is a fairly frequent disorder among stroke patients receiving physiotherapy hence the need for screening all stroke patients for the disorder especially as it adversely affects outcome of rehabilitation.
Table 1: Demographic and Clinical Characteristics of Participants (N=40)
Table 2: Distribution of neglect by demographic and clinical variables (N=40)
*= significant at p<0.05 X²=Chi-Square U=Mann Whitney U