van der Johannes Hoeven

Reference values of maximum isometric muscle force obtained in 270 children aged 4-16 years by hand-held dynamometry

Since muscle force and functional ability are not related linearly; maximum force can be reduced while functional ability is still maintained. For diagnostic and therapeutic reasons loss of muscle force should be detected as early and accurately as possible. Because of growth factors, maximum muscle force in children varies with age, which makes detection of force loss difficult. The purpose of this study was to establish reference values for muscle force in children aged 4-16 years, obtained by hand-held dynamometry in 11 muscle groups. In boys muscle force was predicted best by weight whereas in girls weight and age were best predictors. At age 14 boys become significantly stronger for nearly all tested muscle groups. These age-related reference values can be used to quantify muscle weakness in individual muscle groups in children aged 4-16 years and to evaluate the effects of therapy.

Predictors of Obstructive Sleep Apnea-Hypopnea Treatment Outcome

Oral appliance therapy is an alternative to continuous positive airway pressure (CPAP) for treating the obstructive sleep apnea-hypopnea syndrome. However, the ability to pre-select suitable candidates for either treatment is limited. The aim of this study was to assess the value of relevant variables that can predict the outcome of oral appliance and CPAP therapy. Fifty-one patients treated with oral appliance therapy and 52 patients treated with CPAP were included. Relevant clinical, polysomnographic, and cephalometric variables were determined at baseline. The predictive value of variables for treatment outcome was evaluated in univariate and multivariate analyses. The outcome of oral appliance therapy was favorable, especially in less obese patients with milder sleep apnea and with certain craniofacial characteristics (mandibular retrognathism in particular). Neither univariate nor multivariate analyses yielded variables that reliably predicted the outcome of CPAP. We conclude that the variables found in this study are valuable for pre-selecting suitable candidates for oral-appliance therapy.

Muscle fiber conduction abnormalities in early diabetic polyneuropathy

OBJECTIVE Diabetic polyneuropathy (PNP) has been proposed to be a primary disorder of sensory nerves. At an early stage motor nerve conduction velocity (MNCV) and muscle strength remain preserved due to compensatory mechanisms (axonal sprouting, reinnervation). We evaluated the use of invasive muscle fiber conduction velocity (MFCV) measurements as a method to detect muscle fiber denervation atrophy, as an early sign of motor axonal loss in diabetes mellitus (DM). METHODS Twelve selected male patients (8 type 1, 4 type 2; mean age 35.8 years, SD 10.6), without any sign of micro- or macroangiopathy, were studied by systematic clinical and neurophysiological testing including MFCV estimation. RESULTS Hand-held dynamometry was normal in all subjects. There were no signs of recent denervation by concentric needle EMG in any of the patients. Sensory nerve conduction velocity (SNCV) was abnormal in 6 subjects, MFCV in 6 subjects (5 had also low SNCV). The ratio of fastest/slowest muscle fibers in MFCV was correlated to SNCV of sural nerve (-.59, p < .05), but not to MNCV. CONCLUSIONS Half of the clinically asymptomatic DM subjects showed sensory involvement together with MFCV abnormalities, despite normal needle EMG and force. SIGNIFICANCE MFCV estimation offers a sensitive method in detecting early signs of motor axonal dysfunction in DM.

Can repetitive transcranial magnetic stimulation increase muscle strength in functional neurological paresis? A proof-of-principle study

Therapeutic options are limited in functional neurological paresis disorder. Earlier intervention studies did not control for a placebo effect, hampering assessment of effectivity. A proof‐of‐principle investigation was conducted into the therapeutic potential of repetitive transcranial magnetic stimulation (rTMS), using a single‐blind two‐period placebo‐controlled cross‐over design.

Quantitative assessment of calf circumference in Duchenne muscular dystrophy patients

Duchenne muscular dystrophy is clinically characterised by progressive muscle weakness and a gradual increase in the size of some affected muscles, especially calf muscles. The extent of calf enlargement is usually determined by subjective visual assessment. The purpose of this study was to determine the extent of calf muscle enlargement in Duchenne muscular dystrophy (DMD) patients compared with healthy age matched boys by quantifying calf circumference. Calf circumference in the group of DMD patients is significantly increased. However, in individual patients calf enlargement can be feigned by a discrepancy between calf circumference and circumference of the upper leg and arm muscles as part of a general muscle atrophy.

Muscle ultrasound density in human fetuses with spina bifida aperta

BACKGROUND In fetal spina bifida aperta (SBA), leg movements caudal to the meningomyelocele (MMC) are transiently present, but they disappear shortly after birth. Insight in the underlying mechanism could help to improve treatment strategies. In fetal SBA, the pathogenesis of neuromuscular damage prior to movement loss is still unknown. We reasoned that prenatal assessment of muscle ultrasound density (fetal-MUD) could help to reveal whether progressive neuromuscular damage is present in fetal SBA, or not. AIM To reveal whether prenatal neuromuscular damage is progressively present in SBA. PATIENTS/METHODS In SBA fetuses (n=6; 22-37 weeks gestational age), we assessed fetal-MUD in myotomes caudal to the MMC and compared measurements between myotomes cranial to the MMC and controls (n=11; 17-36 weeks gestational age). Furthermore, we intra-individually compared MUD and muscle histology between the pre- and postnatal period. RESULTS Despite persistently present fetal leg movements caudal to the MMC, fetal-MUD was higher caudal to the MMC than in controls (p<0.05). Fetal-MUD caudal to the MMC did not increase with gestational age, whereas fetal-MUD in controls and cranial to the MMC increased with gestational age (p<0.05). In 5 of 6 patients assessed, comparison between pre- and postnatal MUD and/or muscle histology indicated consistent findings. CONCLUSIONS In fetal SBA, persistent leg movements concur with stable, non-progressively increased fetal-MUD. These data may implicate that early postnatal loss of leg movements is associated with the impact of additional neuromuscular damage after the prenatal period.

128-Channel somatosensory evoked potentials in the differential diagnosis of parkinsonian disorders

PURPOSE The differential diagnosis of parkinsonian disorders can be very difficult, especially at an early stage. In this study, we investigated whether SEP amplitude recorded by 128-channel EEG is useful for diagnosis of parkinsonian disorders, and in particular whether SEP asymmetry can differentiate corticobasal degeneration (CBGD) from other parkinsonian disorders. METHODS We recorded median nerve SEPs in 47 patients suspected of CBGD, supranuclear palsy or definite Parkinsons disease at an early stage. We compared SEP asymmetry and parietal peak amplitudes of the patients after grouping them based on their clinical diagnosis after 1-5 years of follow-up. In nine subjects the diagnosis remained unclear. RESULTS Three of 13 patients with a clinical diagnosis of CBGD had an abnormal SEP asymmetry. Furthermore, we found extremely high N20 amplitudes in three other patients with CBGD. However, similar asymmetry abnormalities were found in patients with other Parkinsonian disorders. CONCLUSION Despite the use of 128-channel SEP recordings and analysis techniques, which are more accurate than conventional techniques, sensitivity and specificity of cortical median nerve SEP asymmetry and parietal amplitude for differentiating CBGD from other parkinsonian disorders were low at an early stage of the disease. A possible reason for this may be that the hand area of the primary somatosensory cortex was not yet affected in most CBGD patients.

Neurophysiological evaluation in children with Friedreich's ataxia

INTRODUCTION In children with Friedreichs ataxia (FRDA children), clinical ataxia outcomes are hardly substantiated by underlying neurophysiological parameters. In young FRDA children, some reports (based upon International Cooperative Ataxia Rating Scale scores (ICARS)) mention transient neurological improvement upon idebenone treatment. However, these outcomes are obtained with adult instead of pediatric reference values. It is unknown whether age-related neurophysiological parameters can really substantiate neurologic improvement. AIM In young FRDA children, we aimed to determine longitudinal neurophysiological parameters during idebenone treatment. METHODS During a two-year study period, 6 genetically proven FRDA children with cardiomyopathy (6-18years) were longitudinally assessed for neurophysiological parameters [sensory evoked potentials (SEPs), F response, peripheral nerve conduction and dynamometry] in association with age-matched ICARS-scores. RESULTS In all FRDA children, SEPs remained absent during the two-year study period. Peroneal nerve conduction velocity declined (from -1SD to -2SD; p<.05), whereas F responses remained essentially unaltered. Total muscle force and leg muscle force decreased (from -2 to -3SD and -2.5 to -3.5SD; both p<.05) and age-related ICARS-scores deteriorated (median increase +41%; p<.05). CONCLUSION In FRDA children, age-related neurophysiological and ataxia parameters deteriorate during idebenone treatment. Although we cannot exclude some (subjective) disease stabilization, age-related neurophysiological parameters do not substantiate neurologic improvement.

Pyridoxine induces non-specific EEG alterations in infants with therapy resistant seizures

PURPOSE In infants with frequent therapy resistant seizures (TRS-infants), clinical detection of pyridoxine-dependency (PD) or -responsiveness (PR) occurs by empirical intravenous (IV) pyridoxine administration during recording of the EEG. However, in undiagnosed TRS-infants it is still unclear to what extent EEG alterations by pyridoxine-IV are attributable to PD/PR or to non-specific responses. Before EEG alterations by pyridoxine-IV can be ascribed to PD/PR, these non-specific responses should be excluded first. METHODS In 10 TRS-infants under 1 year of age, we determined the EEG effect by pyridoxine-IV on the EEG-recording. RESULTS After pyridoxine-IV administration, our data indicate declined (10-15%; p<0.05) EEG-amplitudes and total power (magnitude/frequency-band) at frontal, central and centro-temporal electrodes. CONCLUSION In TRS-infants, pyridoxine-IV affects EEG-amplitude and -total power in a non-specific way, which does not identify PD/PR.

Abnormal surface EMG during clinically normal wrist movement in cervical dystonia

We investigated whether patients with cervical dystonia (CD) have abnormal muscle activation in non‐dystonic body parts. Eight healthy controls and eight CD patients performed a flexion‐extension movement of the right wrist. Movement execution was recorded by surface electromyography (EMG) from forearm muscles. Although patients had no complaints concerning wrist movement and had no apparent difficulty in executing the task, they demonstrated lower mean EMG amplitude (flexor: 0.32 mV and extensor: 0.61 mV) than controls (flexor: 0.67 mV; P = 0.021 and extensor: 1.18 mV; P = 0.068; borderline significant). Mean extensor muscle contraction was prolonged in patients (1860 ms) compared with controls (1334 ms; P = 0.026). Variation in mean EMG amplitude over movements tended to be higher in patients (flexor: 43% and extensor: 35%) than controls (flexor: 34%; P = 0.072 and extensor: 26%; P = 0.073). These results suggest that CD patients also have abnormal muscle activation in non‐dystonic body parts at a subclinical level. This would support the concept that in dystonia, non‐dystonic limbs are in a ‘pre‐dystonic state’.