Functional assessment tools in children with Pompe disease: A pilot comparative study to identify suitable outcome measures for the standard of care

Arginine:glycine amidinotransferase (AGAT) deficiency: an easy-to-miss treatable adult-onset myopathy

Arginine:glycine amidinotransferase (AGAT) deficiency is an ultrarare disorder of creatine metabolism, presenting with developmental delay, characteristic biochemical findings and muscle weakness. Most known cases have been identified and treated in early childhood. We describe a 27-year-old woman with learning difficulties and significant myopathy who was diagnosed through genetic investigation in adulthood. Treatment with creatine (10-15 g/day) led to a significant and rapid improvement of muscle strength. A literature review of the few reported adult cases confirms that progressive myopathy is a prominent feature that responds well to creatine supplementation. AGAT deficiency, a partially treatable condition, should be considered in the differential diagnosis of a genetic myopathy, particularly in people with developmental delay and progressive myopathy.

Quantitative Motion Measurements Based on Markerless 3D Full-Body Tracking in Children with SMA Highly Correlate with Standardized Motor Assessments

BACKGROUND

Spinal Muscular Atrophy (SMA) is the most common neurodegenerative disease in childhood. New therapeutic interventions have been developed to interrupt rapid motor deterioration. The current standard of clinical evaluation for severely weak infants is the Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders (CHOP INTEND), originally developed for SMA type 1. This test however, remains subjective and requires extensive training to be performed reliably.

OBJECTIVE

Proof of principle of the motion tracking method for capturing complex movement patterns in ten children with SMA.

METHODS

We have developed a system for tracking full-body motion in infants (KineMAT) using a commercially available, low-cost RGB-depth sensor. Ten patients with SMA (2-46 months of age; CHOP INTEND score 10-50) were recorded for 2 minutes during unperturbed spontaneous whole-body activity. Five predefined motion parameters representing 56 degrees of freedom of upper, lower extremities and trunk joints were correlated with CHOP INTEND scores using Pearson product momentum correlation (r). Test-retest analysis in two patients used descriptive statistics.

RESULTS

4/5 preselected motion parameters highly correlated with CHOP INTEND: 1. Standard deviation of joint angles (r = 0.959, test-retest range 1.3-1.9%), 2. Standard deviation of joint position (r = 0.933, test-retest range 2.9%), 3. Absolute distance of hand/foot travelled (r = 0.937, test-retest range 6-10.5%), 4. Absolute distance of hand/foot travelled against gravity (r = 0.923; test-retest range 4.8-8.5%).

CONCLUSIONS

Markerless whole-body motion capture using the KineMAT proved to objectively capture motor performance in infants and children with SMA across different severity and ages.

Spinal Muscular Atrophy: The Use of Functional Motor Scales in the Era of Disease-Modifying Treatment

Spinal muscular atrophy (SMA) is a genetic condition characterized by progressive motoneuron loss. Infants affected by SMA type 1 do not gain developmental milestones and acutely decline, requiring ventilatory support. Several scales are used to assess motor disability and its progression in SMA. Recently, 3 disease-modifying therapies have been approved for SMA patients: nusinersen, an intrathecal antisense oligonucleotide enhancing SMN protein production by the SMN2 gene, risdiplam, also influencing the SMN2 gene to stimulate SMN production but administered orally, and onasemnogene abeparvovec-xioi, an SMN1 gene replacement therapy. Thus, the functional scales should now be applicable for patients improving their motor function over time to assess treatment efficacy. In this paper, we compare different functional scales used in SMA patients. Their usefulness in different SMA types, age groups, and feasibility in daily clinical practice is described below. Some changes in motor function assessments in SMA are also suggested.