Lysosomal glycogen accumulation in Pompe disease results in disturbed cytoplasmic glycogen metabolism.

Pompe disease is an inherited metabolic myopathy caused by deficiency of acid alpha-glucosidase (GAA), resulting in lysosomal glycogen accumulation. Residual GAA enzyme activity affects disease onset and severity, although other factors, including dysregulation of cytoplasmic glycogen metabolism, are suspected to modulate the disease course. In this study, performed in mice and patient biopsies, we found elevated protein levels of enzymes involved in glucose uptake and cytoplasmic glycogen synthesis in skeletal muscle from mice with Pompe disease, including glycogenin (GYG1), glycogen synthase (GYS1), glucose transporter 4 (GLUT4), glycogen branching enzyme 1 (GBE1), and UDP-glucose pyrophosphorylase (UGP2). Expression levels were elevated before the loss of muscle mass and function. For first time, quantitative mass spectrometry in skeletal muscle biopsies from five adult patients with Pompe disease showed increased expression of GBE1 protein relative to healthy controls at the group level. Paired analysis of individual patients who responded well to treatment with enzyme replacement therapy (ERT) showed reduction of GYS1, GYG1, and GBE1 in all patients after start of ERT compared to baseline. These results indicate that metabolic changes precede muscle wasting in Pompe disease, and imply a positive feedforward loop in Pompe disease, in which lysosomal glycogen accumulation promotes cytoplasmic glycogen synthesis and glucose uptake, resulting in aggravation of the disease phenotype.

MRI changes in diaphragmatic motion and curvature in Pompe disease over time.

OBJECTIVES: To evaluate changes in diaphragmatic function in Pompe disease using MRI over time, both during natural disease course and during treatment with enzyme replacement therapy (ERT). METHODS: In this prospective study, 30 adult Pompe patients and 10 healthy controls underwent pulmonary function tests and spirometry-controlled MRI twice, with an interval of 1 year. In the sagittal view of 3D gradient echo breath-hold acquisitions, diaphragmatic motion (cranial-caudal ratio between end-inspiration and end-expiration) and curvature (diaphragm height and area ratio) were calculated using a machine learning algorithm based on convolutional neural networks. Changes in outcomes after 1 year were compared between Pompe patients and healthy controls using the Mann-Whitney test. RESULTS: Pulmonary function outcomes and cranial-caudal ratio in Pompe patients did not change significantly over time compared to healthy controls. Diaphragm height ratio increased by 0.04 (-0.38 to 1.79) in Pompe patients compared to -0.02 (-0.18 to 0.25) in healthy controls (p = 0.02). An increased diaphragmatic curvature over time was observed in particular in untreated Pompe patients (p = 0.03), in those receiving ERT already for over 3 years (p = 0.03), and when severe diaphragmatic weakness was found on the initial MRI (p = 0.01); no progression was observed in Pompe patients who started ERT less than 3 years ago and in Pompe patients with mild diaphragmatic weakness on their initial MRI. CONCLUSIONS: MRI enables to detect small changes in diaphragmatic curvature over 1-year time in Pompe patients. It also showed that once severe diaphragmatic weakness has occurred, improvement of diaphragmatic muscle function seems unlikely. KEY POINTS: • Changes in diaphragmatic curvature in Pompe patients over time assessed with 3D MRI may serve as an outcome measure to evaluate the effect of treatment on diaphragmatic function. • Diaphragmatic curvature showed a significant deterioration after 1 year in Pompe patients compared to healthy controls, but the curvature seems to remain stable over this period in patients who were treated with enzyme replacement therapy for less than 3 years, possibly indicating a positive effect of ERT. • Improvement of diaphragmatic curvature over time is rarely seen in Pompe patients once diaphragmatic motion shows severe impairment (cranial-caudal inspiratory/expiratory ratio < 1.4).

Diaphragmatic dysfunction in neuromuscular disease, an MRI study.

The aim of this exploratory study was to evaluate diaphragmatic function across various neuromuscular diseases using spirometry-controlled MRI. We measured motion of the diaphragm relative to that of the thoracic wall (cranial-caudal ratio vs. anterior posterior ratio; CC-AP ratio), and changes in the diaphragmatic curvature (diaphragm height and area ratio) during inspiration in 12 adults with a neuromuscular disease having signs of respiratory muscle weakness, 18 healthy controls, and 35 adult Pompe patients - a group with prominent diaphragmatic weakness. CC-AP ratio was lower in patients with myopathies (n=7, 1.25±0.30) and motor neuron diseases (n=5, 1.30±0.10) than in healthy controls (1.37±0.14; p=0.001 and p=0.008), but not as abnormal as in Pompe patients (1.12±0.18; p=0.011 and p=0.024). The mean diaphragm height ratio was 1.17±0.33 in patients with myopathies, pointing at an insufficient diaphragmatic contraction. This was also seen in patients with Pompe disease (1.28±0.36), but not in healthy controls (0.82±0.33) or patients with motor neuron disease (0.82±0.24). We conclude that spirometry-controlled MRI enables us to investigate respiratory dysfunction across neuromuscular diseases, suggesting that the diaphragm is affected in a different way in myopathies and motor neuron diseases. Whether MRI can also be used to evaluate progression of diaphragmatic dysfunction requires additional studies.

Chest MRI to diagnose early diaphragmatic weakness in Pompe disease.

BACKGROUND: In Pompe disease, an inherited metabolic muscle disorder, severe diaphragmatic weakness often occurs. Enzyme replacement treatment is relatively ineffective for respiratory function, possibly because of irreversible damage to the diaphragm early in the disease course. Mildly impaired diaphragmatic function may not be recognized by spirometry, which is commonly used to study respiratory function. In this cross-sectional study, we aimed to identify early signs of diaphragmatic weakness in Pompe patients using chest MRI. METHODS: Pompe patients covering the spectrum of disease severity, and sex and age matched healthy controls were prospectively included and studied using spirometry-controlled sagittal MR images of both mid-hemidiaphragms during forced inspiration. The motions of the diaphragm and thoracic wall were evaluated by measuring thoracic cranial-caudal and anterior-posterior distance ratios between inspiration and expiration. The diaphragm shape was evaluated by measuring the height of the diaphragm curvature. We used multiple linear regression analysis to compare different groups. RESULTS: We included 22 Pompe patients with decreased spirometry results (forced vital capacity in supine position < 80% predicted); 13 Pompe patients with normal spirometry results (forced vital capacity in supine position ≥ 80% predicted) and 18 healthy controls. The mean cranial-caudal ratio was only 1.32 in patients with decreased spirometry results, 1.60 in patients with normal spirometry results and 1.72 in healthy controls (p < 0.001). Anterior-posterior ratios showed no significant differences. The mean height ratios of the diaphragm curvature were 1.41 in patients with decreased spirometry results, 1.08 in patients with normal spirometry results and 0.82 in healthy controls (p = 0.001), indicating an increased curvature of the diaphragm during inspiration in Pompe patients. CONCLUSIONS: Even in early-stage Pompe disease, when spirometry results are still within normal range, the motion of the diaphragm is already reduced and the shape is more curved during inspiration. MRI can be used to detect early signs of diaphragmatic weakness in patients with Pompe disease, which might help to select patients for early intervention to prevent possible irreversible damage to the diaphragm.

Positive association between physical outcomes and patient-reported outcomes in late-onset Pompe disease: a cross sectional study.

BACKGROUND: Pompe disease is a rare, progressive metabolic myopathy. The aim of this study is to investigate the associations of physical outcomes with patient-reported outcome measures (PROMs) in late-onset Pompe disease. METHODS: We included 121 Dutch adult patients with Pompe disease. Physical outcomes comprised muscle strength (manual muscle testing using Medical Research Council [MRC] grading, hand-held dynamometry [HHD]), walking ability (6-min walk test [6MWT]), and pulmonary function (forced vital capacity [FVC] in upright and supine positions). PROMs comprised quality of life (Short Form 36 health survey [SF-36]), participation (Rotterdam Handicap Scale [RHS]) and daily-life activities (Rasch-Built Pompe-Specific Activity [R-PAct] Scale). Analyses were cross-sectional: the time-point before, and closest to, start of Enzyme Replacement Therapy was chosen. Associations between PROMs and physical outcomes were investigated using linear regression models. RESULTS: RHS and R-PAct scores were better in patients with higher FVC supine and upright, HHD, MRC and 6MWT scores, accounting for the effect of sex, disease duration, use of wheelchair and ventilator support. While the SF-36 Physical Component Summary (PCS) was correlated positively with FVC upright, HHD, MRC and 6MWT scores, there was no significant relationship between the SF-36 Mental Component Summary (MCS) and any of the physical outcomes. CONCLUSIONS: Participation, daily-life activities, and the physical component of quality of life of adult Pompe patients are positively correlated to physical outcomes. This work serves as a first step towards assessing how changes over time in physical outcomes are related to changes in PROMs, and to define the minimal change in physical outcomes required to make an important difference for the patient.

Large variation in effects during 10 years of enzyme therapy in adults with Pompe disease.

OBJECTIVE: To determine the effects of 10 years of enzyme replacement therapy (ERT) in adult patients with Pompe disease, focusing on individual variability in treatment response. METHODS: In this prospective, multicenter cohort study, we studied 30 patients from the Netherlands and France who had started ERT during the only randomized placebo-controlled clinical trial with ERT in late-onset Pompe disease (NCT00158600) or its extension (NCT00455195) in 2005 to 2008. Main outcomes were walking ability (6-minute walk test [6MWT]), muscle strength (manual muscle testing using Medical Research Council [MRC] grading), and pulmonary function (forced vital capacity [FVC] in the upright and supine positions), assessed at 3- to 6-month intervals before and after the start of ERT. Data were analyzed with linear mixed-effects models for repeated measurements. RESULTS: Median follow-up duration on ERT was 9.8 years (interquartile range [IQR] 8.3-10.2 years). At the group level, baseline 6MWT was 49% of predicted (IQR 41%-60%) and had deteriorated by 22.2 percentage points (pp) at the 10-year treatment point (p < 0.001). Baseline FVC upright was 54% of predicted (IQR 47%-68%) and decreased by 11 pp over 10 years (p < 0.001). Effects of ERT on MRC sum score and FVC supine were similar. At the individual level, 93% of patients had initial benefit of ERT. Depending on the outcome measured, 35% to 63% of patients had a secondary decline after ≈3 to 5 years. Still, at 10 years of ERT, 52% had equal or better 6MWT and/or FVC upright compared to baseline. CONCLUSIONS: The majority of patients with Pompe disease benefit from long-term ERT, but many patients experience some secondary decline after ≈3 to 5 years. Individual variation, however, is considerable. CLASSIFICATION OF EVIDENCE: This study provides Class IV evidence that for the majority of adults with Pompe disease, long-term ERT positively affects, or slows deterioration in, muscle strength, walking ability, and/or pulmonary function.

Long-term follow-up of 17 patients with childhood Pompe disease treated with enzyme replacement therapy.

OBJECTIVES: Pompe disease is a progressive metabolic myopathy for which enzyme replacement therapy (ERT) was approved in 2006. While various publications have examined the effects of ERT in classic-infantile patients and in adults, little has been published on ERT in children with non-classic presentations. STUDY DESIGN: This prospective study was conducted from June 1999 to May 2015. Seventeen patients from various countries participated. Outcome measures comprised muscle function (6-minute walk test, quick motor-function test (QMFT)), muscle strength (hand-held dynamometry; manual muscle testing), and lung function (FVC sitting and supine). For each outcome measure, we used linear mixed-effects models to calculate the difference at group level between the start of therapy and 7 years of ERT. Patients' individual responses over time were also evaluated. RESULTS: Eleven males and six females started ERT at ages between 1.1 and 16.4 years (median 11.9 years); 82% of them carried the common c.-32-13T > G GAA gene variant on one allele. At group level, distance walked increased by 7.4 percentage points (p < 0.001) and QMFT scores increased by 9.2 percentage points (p = 0.006). Muscle strength scores seemed to remain stable. Results on lung function were more variable. Patients' individual data show that the proportion of patients who stabilized or improved during treatment ranged between 56 and 69% for lung function outcomes and between 71 and 93% for muscle strength and muscle function outcomes. CONCLUSIONS: We report a positive effect of ERT in patients with childhood Pompe disease at group level. For some patients, new or personalized treatments should be considered.

Language comprehension in nonspeaking children with severe cerebral palsy: Neuroanatomical substrate?

BACKGROUND AND AIMS: To identify relations between brain abnormalities and spoken language comprehension, MRI characteristics of 80 nonspeaking children with severe CP were examined. METHODS: MRI scans were analysed for patterns of brain abnormalities and scored for specific MRI measures: white matter (WM) areas; size of lateral ventricles, WM abnormality/reduction, cysts, subarachnoid space, corpus callosum thinning and grey matter (GM) areas; cortical GM abnormalities, thalamus, putamen, globus pallidus and nucleus caudatus and cerebellar abnormalities. Language comprehension was assessed with a new validated instrument (C-BiLLT). RESULTS: MRI scans of 35 children were classified as a basal ganglia necrosis (BGN) pattern, with damage to central GM areas; in 60% of these children damage to WM areas was also found. MRI scans of 13 children were classified as periventricular leukomalacia (PVL) with little concomitant damage to central GM areas, 13 as malformations and 19 as miscellaneous. Language comprehension was best in children with BGN, followed by malformations and miscellaneous, and was poorest in PVL. Linear regression modelling per pattern group (malformations excluded), with MRI measures as independent variables, revealed that corpus callosum thinning in BGN and parieto-occipital WM reduction in PVL were the most important explanatory factors for poor language comprehension. No MRI measures explained outcomes in language comprehension in the miscellaneous group. CONCLUSIONS: Comprehension of spoken language differs between MRI patterns of severe CP. In children with BGN and PVL differences in language comprehension performance is attributed to damage in the WM areas. Language comprehension was most affected in children with WM lesions in the subcortical and then periventricular areas, most characteristic for children with PVL.

CT within 6 hours of headache onset to rule out subarachnoid hemorrhage in nonacademic hospitals.

OBJECTIVE: To investigate whether staff radiologists working in nonacademic hospitals can adequately rule out subarachnoid hemorrhage (SAH) on head CT <6 hours after headache onset. METHODS: In a multicenter, retrospective study, we studied a consecutive series of patients presenting with acute headache to 11 nonacademic hospitals. Inclusion criteria were (1) normal level of consciousness without focal deficits, (2) head CT <6 hours after headache onset and reported negative for the presence of SAH by a staff radiologist, and (3) subsequent CSF spectrophotometry. Two neuroradiologists and one stroke neurologist from 2 academic tertiary care centers independently reviewed admission CTs of patients with CSF results that were considered positive for presence of bilirubin according to local criteria. We investigated the negative predictive value for detection of SAH by staff radiologists in nonacademic hospitals on head CT in patients scanned <6 hours after onset of acute headache. RESULTS: Of 760 included patients, CSF analysis was considered positive for bilirubin in 52 patients (7%). Independent review of these patients' CTs identified one patient (1/52; 2%) with a perimesencephalic nonaneurysmal SAH. Negative predictive value for detection of subarachnoid blood by staff radiologists working in a nonacademic hospital was 99.9% (95% confidence interval 99.3%-100.0%). CONCLUSIONS: Our results support a change of practice wherein a lumbar puncture can be withheld in patients with a head CT scan performed <6 hours after headache onset and reported negative for the presence of SAH by a staff radiologist in the described nonacademic setting.

Language comprehension in young people with severe cerebral palsy in relation to language tracts: a diffusion tensor imaging study.

Patients with severe cerebral palsy (CP) often have poor speech ability but potentially better language comprehension. The arcuate fasciculus and the extreme capsule are two important language tracts between the Wernicke and Broca areas. Using diffusion tensor imaging, we visualized language tracts and pyramidal tracts in both hemispheres in 10 controls (5 to 18 years) and 5 patients (5 to 23 years) with severe CP. Language comprehension was assessed with a recently designed instrument (the Computer-Based instrument for Low motor Language Testing [C-BiLLT]). The language tracts were visualized in all control children and in four CP patients. In one CP patient without any objective language comprehension skills, no language tract could be visualized. Both language and pyramidal tracts were smaller in patients than in controls. These preliminary data indicate a relation between language tracts and language skills. Further research is necessary to study the value of structural integrity of language tracts in predicting language comprehension in CP patients.

Utility of language comprehension tests for unintelligible or non-speaking children with cerebral palsy: a systematic review.

AIM: to identify the use and utility of language comprehension tests for unintelligible or non-speaking children with severe cerebral palsy (CP). METHOD: severe CP was defined as severe dysarthria (unintelligible speech) or anarthria (absence of speech) combined with severe limited mobility, corresponding to Gross Motor Function Classification System levels IV to V. An electronic search in the databases of PubMed, PsychInfo, Embase, and CINAHL was made of studies published between January 1965 and December 2008. Indexing terms and free-text terms for 'cerebral palsy', 'language', and 'instrumentation' were used. Studies were included when (1) the focus was to investigate comprehension of spoken language of children (0-18 y) with severe CP, and (2) language tests were described. RESULTS: twelve standardized tests and five experimental instruments were identified. All standardized tests were developed for children without limited mobility. Only the Peabody Picture Vocabulary Test - Revised was frequently used and feasible for older children with severe CP (> 9y). The other tests were used occasionally. To establish utility, adaptations of standardized test procedures were necessary. INTERPRETATION: language comprehension tests for children with severe CP are scarce. A language comprehension test specifically designed for these children is warranted. Cite this as: Dev Med Child Neurol 52: e267-e277.

Utility of language comprehension tests for unintelligible or non-speaking children with cerebral palsy: a systematic review.

AIM: to identify the use and utility of language comprehension tests for unintelligible or non-speaking children with severe cerebral palsy (CP). METHOD: severe CP was defined as severe dysarthria (unintelligible speech) or anarthria (absence of speech) combined with severe limited mobility, corresponding to Gross Motor Function Classification System levels IV to V. An electronic search in the databases of PubMed, PsychInfo, Embase, and CINAHL was made of studies published between January 1965 and December 2008. Indexing terms and free-text terms for 'cerebral palsy', 'language', and 'instrumentation' were used. Studies were included when (1) the focus was to investigate comprehension of spoken language of children (0-18 y) with severe CP, and (2) language tests were described. RESULTS: twelve standardized tests and five experimental instruments were identified. All standardized tests were developed for children without limited mobility. Only the Peabody Picture Vocabulary Test - Revised was frequently used and feasible for older children with severe CP (> 9 y). The other tests were used occasionally. To establish utility, adaptations of standardized test procedures were necessary. INTERPRETATION: language comprehension tests for children with severe CP are scarce. A language comprehension test specifically designed for these children is warranted.