Relationship between foot strength and motor function in preschool-age children

Foot weakness occurs in many paediatric neuromuscular disorders, which overtime can cause considerable functional motor difficulties. Measuring foot strength with hand-held dynamometry is reliable in preschool-age children, but its validity in this age group is unknown. If foot strength measures are collected as endpoints in clinical trials, they should represent functionally meaningful outcomes. We evaluated the foot strength-motor function relationship in 60 healthy children aged 2–4 years. Foot strength measures included inversion, eversion, dorsiflexion and plantarflexion using hand-held dynamometry. Motor function parameters included time to run 10-m, standing long jump distance and vertical jump height. Measures of foot strength showed significant correlations with all measures of motor function (r = 0.40–0.57, p < 0.001). Hand-held dynamometry may be used as a valid and functionally meaningful measure of foot strength in very young children.     

Muscle ultrasound measurements and functional muscle parameters in non-dystrophic myotonias suggest structural muscle changes

Patients with non-dystrophic myotonias, including chloride (myotonia congenita) and sodium channelopathies (paramyotonia congenita/potassium aggravated myotonias), may show muscular hypertrophy in combination with some histopathological abnormalities. However, the extent of muscle changes has never been assessed objectively in a large group genetically confirmed patients. This study quantitatively determines echo intensities, thicknesses, ranges-of-motion and force of four skeletal muscles in 63 genetically confirmed patients. The main findings revealed elevated echo intensities in all muscles except the rectus femoris (+1.3–2.2 SD, p < 0.0001), and hypertrophy in the arms (+0.5–0.9 SD, p < 0.01). Muscle echo intensities were inversely correlated to the corresponding ranges-of-motion (biceps brachii: r = ?0.43; p < 0.001, forearm flexors: r = ?0.47; p < 0.001, rectus femoris: r = ?0.40; p = 0.001, and tibial anterior: r = ?0.27; p = 0.04) and correlated positively to age (r = 0.22; p = 0.05). The echo intensity of the forearm flexors was inversely correlated to their muscles’ force (r = ?0.30; p = 0.02). Together, these data suggest that non-dystrophic myotonias may lead to structural muscle changes.     

The relation between spasticity and muscle behavior during the swing phase of gait in children with cerebral palsy

There is much debate about how spasticity contributes to the movement abnormalities seen in children with spastic cerebral palsy (CP). This study explored the relation between stretch reflex characteristics in passive muscles and markers of spasticity during gait. Twenty-four children with CP underwent 3D gait analysis at three walking velocity conditions (self-selected, faster and fastest). The gastrocnemius (GAS) and medial hamstrings (MEHs) were assessed at rest using an instrumented spasticity assessment that determined the stretch-reflex threshold, expressed in terms of muscle lengthening velocity. Muscle activation was quantified with root mean square electromyography (RMS-EMG) during passive muscle stretch and during the muscle lengthening periods in the swing phase of gait. Parameters from passive stretch were compared to those from gait analysis.In about half the children, GAS peak muscle lengthening velocity during the swing phase of gait did not exceed its stretch reflex threshold. In contrast, in the MEHs the threshold was always exceeded. In the GAS, stretch reflex thresholds were positively correlated to peak muscle lengthening velocity during the swing phase of gait at the faster (r = 0.46) and fastest (r = 0.54) walking conditions. In the MEHs, a similar relation was found, but only at the faster walking condition (r = 0.43). RMS-EMG during passive stretch showed moderate correlations to RMS-EMG during the swing phase of gait in the GAS (r = 0.46–0.56) and good correlations in the MEHs (r = 0.69–0.77) at all walking conditions. RMS-EMG during passive stretch showed no correlations to peak muscle lengthening velocity during gait.We conclude that a reduced stretch reflex threshold in the GAS and MEHs constrains peak muscle lengthening velocity during gait in children with CP. With increasing walking velocity, this constraint is more marked in the GAS, but not in the MEHs. Hyper-activation of stretch reflexes during passive stretch is related to muscle activation during the swing phase of gait, but has a limited contribution to reduced muscle lengthening velocity during swing. Larger studies are required to confirm these results, and to investigate the contribution of other impairments such as passive stiffness and weakness to reduced muscle lengthening velocity during the swing phase of gait.     

Reliability and validity of the Japanese version of the Modified Checklist for autism in toddlers (M-CHAT)

Early detection and intervention is essential for children with autism spectrum disorders (ASD). Therefore, we examined the reliability and validity of the Japanese version of the Modified Checklist for autism in toddlers (M-CHAT), a 23-item, yes–no questionnaire regarding early autistic symptoms completed by parents of children at 18–24 months of age. Herein, the reliability of the M-CHAT was investigated for children 4–20 months of age. The M-CHAT score (the number of failed items) was found to be significantly correlated among 24 mother–father pairs (Pearson's r = .933), representing good inter-rater reliability. The test–retest reliability was satisfactory, with 22 mothers providing almost equal M-CHAT scores on two different occasions (r = .990). Significant correlations were observed between the M-CHAT score and the Childhood Autism Rating Scale-Tokyo version score in 25 two-year-old children (r = .581), indicating good concurrent validity. The M-CHAT score was significantly higher in 20 children later diagnosed with ASD compared with reference children (n = 1167), revealing sufficient discriminant validity. A short version of the M-CHAT using 9 items was proposed and effectively differentiated children with ASD from reference children. The efficacy of the Japanese version of the M-CHAT was demonstrated for first-level screening in the general population.     

Potential predictors of changes in gross motor function during various tasks for children with cerebral palsy: A follow-up study

Very few studies have investigated predictors of change in various gross motor outcomes in ambulatory children with cerebral palsy (CP). The aim of this study was to identify potential predictors for change in gross motor outcomes measured during various tasks in children with CP. A group of 45 children (age, 6–15 years) with CP and 7 potential predictors were identified, including age, gender, CP subtypes, gross motor function classification system (GMFCS) levels, abdominal muscle endurance, and muscles strength of knee extensor and knee flexor measured by isokinetic dynanometer. Motor outcome was assessed by means of the gross motor composite (GMC) of Bruininks–Oseretsky Test of Motor Proficiency (BOTMP), including four gross motor subtests: running speed and agility (RSA), balance (BAL), bilateral coordination (BCO), and strength (STR). The outcomes were measured at baseline and 12-week later (follow-up). The regression analyses showed that knee extensor strength was a robust predictor of change in BAL, BCO, and GMC (adjusted R² = 0.07–0.19, P < 0.05). Additionally, abdominal muscle strength was a negative predictor for the changes in the RSA (adjusted R² = 0.08, P < 0.05). However, STR model revealed no significant predictors. These findings suggest that ambulatory children with greater knee muscle strength may benefit more from therapy than those with lower strength. The knee muscle strength can be used as a biomarker to predict the changes in the gross motor functions.     

Growth hormone combined with child-specific motor training improves motor development in infants with Prader-Willi syndrome: A randomized controlled trial

Although severe motor problems in infants with Prader-Willi syndrome (PWS) are striking, motor development has never been studied longitudinally and the results of growth hormone (GH) treatment on motor development are contradictory. The authors studied whether GH treatment can enhance the effect of physical training on motor development in infants with PWS. Twenty-two infants were followed for two years during a randomized controlled trial. The treatment and control groups began GH after baseline or following a control period, respectively. Both groups followed a child-specific physical training program. Motor performance was measured every three months. Multi-level regression analysis revealed that motor development differed significantly between infants (p < .001), and this could be partially explained by baseline motor developmental level (p < .01). GH treatment enhanced the effects of child-specific physical training on both motor developmental rate and motor developmental potential. Moreover, this effect was more pronounced when GH treatment was initiated at a younger age.     

A randomized controlled trial of clinic-based and home-based interventions in comparison with usual care for preterm infants: Effects and mediators

This study examined the effects and mediators of a clinic-based intervention program (CBIP) and a home-based intervention program (HBIP) compared with usual care in very-low-birth-weight (VLBW) preterm infants on developmental and behavioral outcomes at 24 months of age (corrected for prematurity). In this randomized controlled trial, VLBW preterm infants received either CBIP (n = 57), HBIP (n = 63), or usual care (n = 58) from hospitalization to 12 months. At 12 months, infant emotional regulation was assessed using the toy-behind-barrier procedure and dyadic interaction was observed during free play. At 24 months, infant developmental and behavioral outcomes were assessed using the Bayley Scales of Infant and Toddler Development- 3rd edition and the Child Behavior Checklist for Ages 1.5–5, respectively. Compared with infants under usual care, the CBIP-group infants showed higher cognitive composite scores (difference, 95% confidence interval (CI) = 4.4, 0.8–7.9) and a lower rate of motor delay (odds ratio (OR), 95% CI = 0.29, 0.08–0.99); the HBIP-group infants had lower sleep problem scores (difference, 95% CI = −1.4, −2.5 to −0.3) and a lower rate of internalizing problems at 24 months (OR, 95% CI = 0.51, 0.28–0.93) (all p < .05). The CBIP's effect on cognitive outcome was attenuated when maternal or dyadic interactive behavior was considered; whereas the HBIP's effect on sleep and internalizing behavior was attenuated when duration of orientation to a toy or object was considered. In conclusions, interventions enhanced the cognitive, motor, and behavioral outcomes of VLBW preterm infants. The effects on cognitive and behavioral outcomes might be mediated by early-improved mother–infant interaction and infant emotional regulation, respectively.     

Motor competence assessment in children: Convergent and discriminant validity between the BOT-2 Short Form and KTK testing batteries

This study investigated convergent and discriminant validity between two motor competence assessment instruments in 2485 Flemish children: the Bruininks-Oseretsky Test of Motor Proficiency 2 Short Form (BOT-2 Short Form) and the KörperKoördinationsTest für Kinder (KTK). A Pearson correlation assessed the relationship between BOT-2 Short Form total, gross and fine motor composite scores and KTK Motor Quotient in three age cohorts (6–7, 8–9, 10–11 years). Crosstabs were used to measure agreement in classification in children scoring below percentile 5 and 15 and above percentile 85 and 95. Moderately strong positive (r = 0.44–0.64) associations between BOT-2 total and gross motor composite scores and KTK Motor Quotient and weak positive correlations between BOT-2 Short Form fine motor composite and KTK Motor Quotient scores (r = 0.25–0.37) were found. Levels of agreement were fair to moderate. Therefore, some proof of convergent and discriminant validity between BOT-2 Short Form and KTK was established in this study, underlining the notion that the evaluation of motor competence should not be based upon a single assessment instrument.     

Age-related variables in childhood epilepsy: How do they relate to each other and to quality of life?

How do age of onset and duration of epilepsy correlate with each other and with patient-reported outcomes? To address this question, we explored whether age of onset, duration, and proportion of life with epilepsy are either similar or relatively independent variables that can be used as markers on how children experience the complexity of epilepsy and adjustment.Three hundred ninety-one Canadian and 266 Hong Kong youth with epilepsy completed the childhood epilepsy-specific quality of life (QOL) measure (CHEQOL-25). Each cohort was separately stratified by tertiles for age of onset, life proportion with epilepsy, and duration of epilepsy. Pearson's r was used for correlation analysis.The epilepsy age-related variables correlated strongly with each other among children with epilepsy onset ≤ 4 years (r = 0.53–0.66). The correlation between these variables was weaker with an onset ≥ 9 years (r = 0.22–0.35). Correlation with QOL was clinically non-significant.These variables appear to measure the same phenomenon only in children with early epilepsy onset (< 4 years) and explain little variance in QOL.     

Impaired theory of mind and symptoms of Autism Spectrum Disorder in children with Prader–Willi syndrome

In order to evaluate the social cognitive functioning in children with Prader–Willi syndrome (PWS), Theory of Mind (ToM) and symptoms of Autism Spectrum Disorder were evaluated. Sixty-six children with PWS aged 7–17 years were tested using the Theory of Mind test-R and the Diagnostic Interview for Social Communication disorders. We tested the correlation between Total ToM Standard Deviation Score (Total ToM SDS) and genetic subtype of paternal deletion or maternal uniparental disomy, and total IQ, verbal IQ and performal IQ. Prevalence and symptoms of Autism Spectrum Disorder were assessed. Median (interquartile range) of total ToM SDS of those aged 7–17 years was ?3.84 (?5.73, ?1.57). Their Total ToM SDS correlated with total IQ (β = 0.662, p < 0.001, adj.R² = 0.407), in particular with verbal IQ (β = 0.502, p = 0.001, adj.R² = 0.409), but not with performal IQ (β = 0.241, p > 0.05, adj.R² = 0.259). No difference in Total ToM SDS was found between children with deletion and maternal uniparental disomy (β = ?0.143, p > 0.05, adj.R² = ?0.016). Compared to the reference group of healthy children aged 7–12 years, children with PWS in the same age group had a median ToM developmental delay of 4 (3–5) years. One third of children with PWS scored positive for Autism Spectrum Disorder. Most prominent aberrations in Autism Spectrum Disorder were focused on maladaptive behavior. Our findings demonstrate a markedly reduced level of social cognitive functioning, which has consequences for the approach of children with PWS, i.e. adjustment to the child's level of social cognitive functioning.     

Assessment of intramuscular lipid and metabolites of the lower leg using magnetic resonance spectroscopy in boys with Duchenne muscular dystrophy

The purpose of this study was to use proton magnetic resonance spectroscopy to assess intramuscular lipid and metabolites of lower leg muscles in boys with Duchenne muscular dystrophy (DMD) and determine its relationship with strength and functional ability. Spectroscopic measurements were obtained from four muscles of the lower leg in 25 boys with DMD (9.2 ± 3.1 years) and 10 healthy boys (10.2 ± 2.6 years). Lipid fractions and metabolite concentrations were also determined. Muscle strength, a timed functional test, and the Modified Brooke Lower Extremity Functional Scale were also determined. Lipid fractions were higher (p < 0.01) for the DMD group than healthy subjects for all muscles, and lipid fraction was found to be greater in the older DMD boys. The peroneal muscle demonstrated a significant difference in lipid fraction in all DMD age groups. Lipid fractions in all muscles correlated with functional measures (r = 0.52–0.70, p < 0.001), with smaller inverse correlations with the strength measure (r = −0.36 to −0.56, p < 0.05). These findings provide quantifiable information regarding intramuscular lipid and metabolite levels of different muscles across various age groups in boys with DMD and may be used in determining the effect of interventions in future clinical trials.     

Psychometric properties of the DCD-Q-07 in children ages to 4–6

It is important to identify Developmental Coordination Disorder (DCD) early in a child's life to allow for proper and timely intervention and support, and to reduce the negative secondary consequences associated with this condition. In this study we assessed the psychometric properties (construct validity, concurrent validity, reliability and test accuracy) of the Developmental Coordination Disorder Questionnaire (DCD-Q-07) in preschool children. A community-based sample of children ages 4–6 (n = 181) were screened for motor difficulties using the Movement Assessment Battery for Children (M-ABC-2). Use of the M-ABC-2 resulted in the identification of 29 children below the 15th percentile, which we classified as probable DCD. Parents of these children concurrently completed the DCD-Q-07 to report their child's motor performance. The DCD-Q-07 demonstrated high internal consistency for both the full scale (alpha = 0.881) and each subscale: control during movement (alpha = 0.813), fine motor and handwriting (alpha = 0.869) and general coordination (alpha = 0.728). Moderate correlations (r = 0.47–0.63) were also seen between the subscales on the DCD-Q-07, the strongest correlation being between control during movement and general coordination (r = 0.63). Based on published age and sex cut points, the DCD-Q-07 showed poor sensitivity (20.7%) but high specificity (92.1%) against the M-ABC-2. Overall agreement with the M-ABC-2 was low using ROC analysis (area under the curve = 0.654). Although it is important to screen for DCD in young children, the DCD-Q-07 may not be the best choice as a screening tool for DCD in preschool children ages 4–6 due to its low test accuracy.     

Pulmonary function in patients with hereditary motor and sensory neuropathy: A comparison of patients with and without spinal deformity

We assessed pulmonary function in hereditary motor and sensory neuropathy. Fourteen neuropathy patients without spinal deformity (group 1), 14 with spinal deformity (group 2), and 16 individuals with idiopathic spinal deformity (group 3) matched to group 2 for age, height and Cobb angle, were included. Hereditary motor and sensory neuropathy severity was measured with Charcot–Marie–Tooth Neuropathy Score. All participants exhibited mild decrease in maximal inspiratory pressure at the mouth. One-way analysis of variance yielded significant main effects for lung volumes – slow vital capacity, forced expiratory volume in 1 s, and total lung capacity (p’s < .01), attributable to greater volumes in group 1 compared to groups with spinal deformity – and transfer factor for carbon monoxide (p = .013), reflecting differences between groups 1 vs. 2. Slow vital capacity and total lung capacity correlated with maximal inspiratory pressure at the mouth in group 2, whereas slow vital capacity correlated with muscle work in group 3 (p’s < .05). Decreased lung volume may be due to impaired respiratory muscle strength in hereditary motor and sensory neuropathy with spinal deformity and due to spinal deformity in idiopathic patients.     

Treadmill walking effects on grip strength in young men with Down syndrome

This study was aimed at investigating the relation between grip strength and anthropometric factors and the impact of an aerobic exercise on grip strength in young men with Down syndrome (DS). This study was a pre-post design. Twelve males with DS were assigned to an exercise group, who walked using an incremental protocol on a treadmill for 20 min at aerobic levels. Eight additional persons with DS were assigned to an attentional control group, who watched a video. Measure of grip strength was tested pre- and post-interventions. The results showed positively significant relationship among grip strength and age (r = .74, p < .01), weight (r = .52, p = .02), body mass index (r = .61, p = .01) and waist circumference (r = .54, p = .02). In addition, Grip strength was slightly improved after exercise (p = .03) but decreased after control condition. The results showed that anthropometric factors, such as age, weight, body mass index and waist circumference, were positively correlated with grip strength in young men with DS. Further, improvement in grip strength can be found even after a single exercise session. This finding emphasizes the importance of maintaining an active lifestyle in persons with DS for performing activities of daily living.     

Linguistic validation of the Sleep Disturbance Scale for Children (SDSC) in Iranian children with Persian language

ObjectiveThe aim of this study was to have a linguistic validation of the Sleep Disturbance Scale for Children (SDSC) in Iranian children with Persian language.MethodsThe study included a randomly selected sample of children, aged 6–15 years, from three primary and secondary schools located in Isfahan City, Iran. Following the forward–backward translation method, parents completed the SDSC as well as the Pediatric Quality of Life Inventory (PedsQL™). Reliability (Cronbach’s α) and convergent validity (item–subscale and subscale–total correlations) were assessed. The association of SDSC scores with PedsQL scores was evaluated for construct validity.ResultsOne hundred children were studied; mean age, 9.36 ± 2.58 years, 68 girls. Scale Cronbach’s α was 0.82, ranging from 0.40 for ‘disorder of arousal’ to 0.86 for ‘sleep hyperhidrosis’ subscales. Convergent validity was acceptable according to the corrected item–subscale correlations (r = 0.22–0.76) and corrected subscale–total correlations (r = 0.30–0.50). The SDSC total score as well as its subscales, except the ‘disorder of arousal’, were associated with the total PedsQL score and its factors (r = −0.20 to −0.64).ConclusionThe overall psychometric properties of the Persian version of the SDSC seem to be appropriate in Iranian children.     

Motor cortex dysfunction in complex regional pain syndrome

ObjectiveMost patients with complex regional pain syndrome (CRPS) exhibit debilitating motor symptoms. The effect of continuous pain on motor system in CRPS, however, is not well known. We searched for signs of motor cortex dysfunction in chronic CRPS type 1 patients with motor impairment.MethodsWe recorded rhythmic brain activity with magnetoencephalography (MEG) during noxious thulium–laser stimulation of both hands in eight CRPS patients and eight control subjects. We measured excitability of the motor cortex by monitoring the reactivity of the ∼20-Hz motor cortex rhythm to laser stimuli. The reactivity was defined as a sum of the stimulus-induced suppression and the subsequent rebound of the ∼20-Hz rhythm.ResultsIn CRPS, the reactivity of the ∼20-Hz rhythm in the hemisphere contralateral to the painful hand was significantly weaker than in control subjects. The reactivity correlated with the mean level of the spontaneous pain (r = −0.64, P = 0.04). Suppression of the ∼20-Hz rhythm correlated with the grip strength in the painful hand (r = 0.66, P = 0.04).ConclusionContinuous pain in CRPS is associated with attenuated motor cortex reactivity.SignificanceAbnormal motor cortex reactivity may be linked with motor dysfunction of the affected hand in CRPS.     

A psychometric study of the Bayley Scales of Infant and Toddler Development – 3rd Edition for term and preterm Taiwanese infants

The Bayley Scales of Infant and Toddler Development – 3rd Edition (Bayley-III) was updated to enhance its usefulness for contemporary child developmental assessment. However, recent data in Western countries have implicated the overestimation of child development by the new instrument. This study aimed to investigate the psychometric features of the Bayley-III for term and preterm infants in Taiwan. Forty-seven term infants and 167 preterm infants were prospectively examined with the Bayley Scales of Infant Development – 2nd Edition (BSID-II) and the Bayley-III at 6, 12, 18, and 24 months of age (corrected for prematurity). The psychometric properties examined included reliability, construct validity, and known-group validity. The intra- and inter-rater reliabilities of the Bayley-III were good to excellent. The correlations between the BSID-II and Bayley-III raw scores were good to excellent for the cognitive and motor items and low to excellent for the language items. Term infants achieved higher composite scores than preterm infants on all of the Bayley-III scales (p < 0.05). However, their rates of developmental delay were lower than the previously established prevalence estimates. The Bayley-III cut-off composite score was adjusted 10–20, 1–13, and 12–24 points higher than 70 for optimal prediction of cognitive, language, and motor delay, respectively, as defined by the BSID-II index score < 70. The Bayley-III is a reliable instrument that extends its previous edition, especially in early language assessment. However, the upward adjustment of its cut-off score is recommended for the accurate identification of developmental delay in term and preterm Taiwanese infants.     

Predictors for changes in various developmental outcomes of children with cerebral palsy—A longitudinal study

We aimed to identify predictors for the changes of various developmental outcomes in preschool children with cerebral palsy (CP). Participants were 78 children (49 boys, 29 girls) with CP (mean age: 3 years, 8 months; SD: 1 year, 7 months; range: 1 year to 5 years, 6 months). We examined eight potential predictors: age, sex, CP subtype, Gross Motor Function Classification System (GMFCS) level, selective motor control, Modified Ashworth Scale, and the spinal alignment (SA) and range of motion subscales of the Spinal Alignment and Range of Motion Measure (SAROMM). Developmental outcomes for cognition, language, self-help, and social and motor functions were measured at baseline and a 6-month follow-up with the Comprehensive Developmental Inventory for Infants and Toddlers. Regression model showed GMFCS level was a negative predictor for change of language (adjusted r² = 0.30, p < .001), motor function (adjusted r² = 0.26, p < .001), social function (adjusted r² = 0.07, p = 0.014), and self-help (adjusted r² = 0.26, p < .001). Age was a negative predictor for change of cognition (adjusted r² = 0.21, p < .001) and language functions (adjusted r² = 0.26, p < .001). SAROMM-SA was a negative predictor for cognitive change (adjusted r² = 0.30, p < .001). The GMFCS levels and age are robust negative predictors for change of most developmental domains in these children.     

Mastery motivation in adolescents with cerebral palsy

The aim of this study is to describe motivation in adolescents with cerebral palsy (CP) and factors associated with motivation level. The Dimensions of Mastery Questionnaire (DMQ) measures motivation in mastering challenging tasks and expressive elements. It was completed by 153 parents and 112 adolescents with CP. Adolescents (GMFCS in n = 146 – I:50, II:43, III:13, IV:15, V:25) were assessed using the Leiter IQ and Gross Motor Function Measure. Parents completed the Vineland Adaptive Behavior Scale and the Strengths and Difficulties Questionnaire. Motivation scores were highest for mastery pleasure and social persistence with adults and lowest for gross motor and object-oriented persistence. Socio-demographic factors were not strongly correlated with DMQ. Higher gross motor ability (r = 0.24–0.52) and fewer activity limitations (r = 0.30–0.64, p < .001) were associated with persistence in cognitive, motor and social tasks, but not mastery pleasure. Higher IQ was associated with persistence in object-oriented tasks (r = 0.42, p < .001). Prosocial behaviors correlated with high motivation (r = 0.39–0.53, p < .001). Adolescents’ motivation scores were higher than parents’ scores. Adolescents with CP express high mastery pleasure, not related to abilities. High motivation was associated with fewer activity limitations and prosocial behaviors and aspects of family environment. Findings elucidate those at-risk for low motivation, which can influence treatment adherence and participation in challenging but meaningful activities.     

Decreased processing speed might account for working memory span deficit in schizophrenia,and might mediate the associations between working memory span and clinical symptoms

ObjectiveVerbal working memory span is decreased in patients with schizophrenia, and this might contribute to impairment in higher cognitive functions as well as to the formation of certain clinical symptoms. Processing speed has been identified as a crucial factor in cognitive efficiency in this population. We tested the hypothesis that decreased processing speed underlies the verbal working memory deficit in patients and mediates the associations between working memory span and clinical symptoms.MethodForty-nine schizophrenia inpatients recruited from units for chronic and acute patients, and forty-five healthy participants, were involved in the study. Verbal working memory span was assessed by means of the letter-number span. The Digit Copy test was used to assess motor speed, and the Digit Symbol Substitution Test to assess cognitive speed.ResultsThe working memory span was significantly impaired in patients (F(1,90) = 4.6, P < 0.05). However, the group difference was eliminated when either the motor or the cognitive speed measure was controlled (F(1,89) = 0.03, P = 0.86, and F(1,89) = 0.03, P = 0.88). In the patient group, working memory span was significantly correlated with negative symptoms (r = –0.52, P < 0.0001) and thought disorganisation (r = –0.34, P < 0.025) scores. Regression analyses showed that the association with negative symptoms was no longer significant when the motor speed measure was controlled (β = –0.12, P = 0.20), while the association with thought disorganisation was no longer significant when the cognitive speed measure was controlled (β = –0.10, P = 0.26).ConclusionsDecrement in motor and cognitive speed plays a significant role in both the verbal working memory impairment observed in patients and the associations between verbal working memory impairment and clinical symptoms.