134th ENMC International Workshop: Outcome Measures and Treatment of Spinal Muscular Atrophy, 11-13 February 2005, Naarden, The Netherlands.
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Biomedical subjects
Publications and source records attributed to B Reitter.
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After atraumatic birth, three neonates presented with muscle hypotonia and weakness. Flaccid paresis of the upper extremities, spasticity of the lower extremities, dissociate sensory loss and autonomic dysfunction developed later. This ruled out the initial, tentative diagnoses of cerebral palsy, spinal muscular atrophy or hereditary neuropathy. Diagnostic imaging revealed marked thinning of the cervical spinal cord in all patients. The possible aetiology of these lesions is considered. In all cases, an antenatal or perinatal infarction is thought to be the most probable cause. Different clinical pictures following intrauterine spinal cord ischemia are discussed. Spinal cord lesion must be considered even after atraumatic birth.
Central sleep apnea is a common respiratory pattern in healthy neonates. Nevertheless, frequent central sleep apnea associated with drops in oxygen saturation may contribute to infantile morbidity. Recently, low-dose acetazolamide was shown to reduce symptomatic central sleep apnea in adults. We treated 12 infants, median conceptional age 42 weeks (range, 40-44 weeks), with central sleep apnea. In all cases, the central apnea index was >40/h total sleeping time (apnea > or = 3 sec). The cumulative duration of drops in oxygen saturation below 90% was more than 3 min/h total sleeping time. All individuals received acetazolamide 7 mg/kg/day (orally, divided in three doses) for 11 weeks. Polysomnography was begun 10 hours before the first dose and continued for 10 hours after the third dose. Polysomnography was repeated after 6 weeks of treatment and 1 week after acetazolamide therapy was discontinued. Comparison of the respiratory patterns before and after treatment (10-hour recording after the third dose) showed a decrease in the median central apnea index from 74/h (range, 42-152/h) to 13/h (range, 6-49/h). The median of the cumulative duration of drops in oxygen saturation below 90% decreased from 3.6 min/h (range, 3.1-9.2 min/h) to 0.07 min/h (range, 0-0.5 min/h). Basal oxygen saturation increased from 95 (92-97%) to 98% (96-99%). This improvement was maintained in the final polysomnography (12 weeks after therapy was begun and 1 week after completion of the 11-week course). No adverse effects were noted. We conclude that low-dose acetazolamide treatment may be useful for the treatment of central infantile sleep apnea associated with hypoxemia.
Recently, a congenital myasthenic syndrome (CMS) with end-plate acetylcholine receptor (AChR) deficiency due to missense mutations in the genes for the AChR subunit was described. The first observed patient with this CMS was heteroallelic for the two epsilon-AChR subunit mutations epsilon1101insT and epsilon1293insG. This patient had only a moderate phenotype with mild muscle weakness and abnormal fatigue. We have now found homozygosity for the epsilon1293insG mutation in a severely affected CMS patient, who lost the ability to walk in midchildhood and shows profound weakness and muscle wasting. Our observation allows a genotype-phenotype correlation illustrating how differences in the AChR mutation haplotype can profoundly influence disease severity.
Although migraine is an accepted cause of cerebral infarction in adults, this association is less well recognized in children. We present two children with migraine and cerebral infarction, which we regard as migrainous stroke, though neither patient fulfills all criteria of the International Headache Society for the diagnosis of migrainous infarction. Review of the literature concerning examples of migraine-associated stroke in childhood suggests that these criteria are too restrictive to comprise the majority of migrainous strokes, especially in this age group.
A 9-year-old, otherwise healthy girl presented with a 5-year history of pain in her right calf with retarded growth and development of an equinus contracture of her right leg. Magnetic resonance imaging showed an irregular mass with heterogeneous enhancement after contrast in her right triceps surae muscles, especially the soleus. Histological studies of this triceps surae muscle tissue revealed a haphazard distribution of adipose and connective tissue, striated and smooth muscle cells, vessels and lymphoid follicles, as well as nerve bundles which, together, were considered components of a hamartoma.
The parasitic protozoan Trypanosoma congolense exhibits a dense surface coat which is pivotal for immunoevasion of the parasite. This dense surface coat is made of a single protein species, the variant surface glycoprotein, which is present in a high copy number. The protein is anchored to the plasma membrane by a glycosyl-phosphatidylinositol membrane anchor. A detailed study of the structure of T. congolense strain 423 (clone BENat 1.3) variant surface glycoprotein glycosyl-phosphatidylinositol membrane anchor was performed. Radioactively labelled core-glycan prepared by dephosphorylation, deamination and reduction was analysed by high-pH anion-exchange chromatography, size-exclusion and lectin affinity chromatography. Additionally the glycosyl-phosphatidylinositol membrane anchor core-glycan was purified from a bulk preparation of variant surface glycoprotein and subjected to mass spectrometry and methylation analysis. Using these methods we could identify a novel galactose-beta 1,6-N-acetyl-glucosamine-beta 1,4-branch modifying the mannose adjacent to the glucosamine of the mannose-alpha 1,2-mannose-alpha 1,6-mannose-alpha 1,4-glucosamine core-glycan of the variant surface glycoprotein glycosyl-phosphatidylinositol membrane anchor. Furthermore the biosynthetic pathway leading to this novel structure was investigated. Two putative glycosyl-phosphatidylinositol anchor precursors were identified having structures identical to the previously characterized Trypanosoma brucei brucei glycolipids P2 and P3 (also designated glycolipid A and C) consistent with a trimannosyl core and a dimyristoyl-glycerol. Both glycosyl-phosphatidylinositol anchor precursors of T. congolense do not possess the side-branch modification found on the mature protein membrane anchor, implying that the sugar side-chain is added to the anchor during its passage through the Golgi-apparatus.
The discovery of the subsarcolemmal muscle fiber protein dystrophin has, to a certain extent, replaced former nosological terms of Duchenne (DMD) and Becker (BMD) muscular dystrophies by the term dystrophinopathies. The immunohistochemical and Western blot analysis of dystrophin has not only enlarged the clinical spectrum of dystrophinopathies, but has also made carrier detection of DMD more reliable, particularly in manifesting carriers without family history. Moreover, prenatal muscle biopsy, under selected circumstances, can show presence or absence of dystrophin, ie, in the latter case an affected male fetus. Molecular genetics have provided a wealth of genetic details in the dystrophinopathies, but therapy has not yet succeeded to a similar extent, on the contrary, myoblast transplantation has not resulted in any clinical improvement.
Several studies have demonstrated the slowing effect of corticosteroids on the decline of muscle strength in Duchenne muscular dystrophy (DMD). Deflazacort (DFC) is supposed to have fewer side effects than prednisone (PRED). An ongoing double blind multicenter study is comparing the effects and side effects of deflazacort (0.9 mg/kg/day) and prednisone (0.75 mg/kg/day) in DMD. This interim report includes data for 67 boys between age 5 years and loss of ambulation. Besides the common clinical and laboratory data for chronic corticoid treatment, motor performance has been tested. Interim results, 3-15 months after starting the medication, show some scattering but no grouping of data for all the functions tested: timed motor functions, sum of the strength of 20 muscles according to a 10-point scale on manual testing, weight gain, osteocalcin and alkaline phosphatase. Only the changes in CK activity after 3 months medication might reflect two equal groups without any correlation with the initial activity or with other parameters. On average, there was no clear-cut loss of muscle strength or performance. Except for in 4 patients, who were excluded due to unacceptable weight gain and/or loss of ambulation, there were no side effects considered to be serious. The results suggest that (i) DFC and PRED in equal anti-inflammatory dosage are similarly or equally efficient in slowing down the decline of muscle strength in DMD; (ii) benefits outweigh the side effects. This allows the study to continue as designed.
Progressive neurological deterioration may occur after meningomyelocele repair. Magnetic resonance imaging almost invariably demonstrates a conus medullaris in an abnormally low position, whether neurological symptoms develop or not. Surgery of a secondary tethered cord is indicated when progression of neurological symptoms is documented. We performed a longitudinal study of posterior tibial nerve somatosensory evoked potentials (SSEPs) in children and adolescents after neonatal meningomyelocele repair. All patients were able to walk. Declining or negative posterior tibial nerve SSEPs were recorded in 15 patients; 14 of these had clinical signs of a secondary tethered cord. After surgery of the tethered cord, the SSEPs improved in 8 of 10 patients. Posterior tibial nerve SSEPs may contribute to the diagnosis of secondary tethered cord. After untethering, the evoked potentials demonstrate recovery of spinal cord function and might help to delineate prognosis.
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A newborn male with mitochondrial complex I deficiency suffered from neonatal epileptic seizures, which later developed into infantile spasms. The infant was blind due to aplasia of the retinal vessels and hypoplasia of the optic nerve. There was congenital lactic acidosis, which persisted in later life. The boy was microcephalic and retarded. Muscular hypotonia later shifted to spasticity. Succinic acid was increased in urine. We assume that the aplasia of the retinal vessels is due to damage of the retinal ganglion cells caused by the mitochondrial disease in the first 3 to 4 months of pregnancy.
UNLABELLED: Patients who are homozygous for an atypical pseudocholinesterase enzyme (PCHE) suffer a prolonged neuromuscular block after succinylcholine application. In order to determine which patients have atypical PCHE preoperatively, an automated method using the Greiner G450 analyzer was developed. PATIENTS AND METHODS: The contribution of blocked and unblocked PCHE by dibucaine hydrochloride (optimal concentration 10(-4) mol/l;) was determined in 113 patients (ASA groups 1-2) and the dibucaine number (DN) was evaluated. RESULTS: According to the DN, the patients were subdivided into three groups: group A (PCHE 5.01 +/- 1.64 kU/l, DN 74.47 +/- 0.87); group B (PCHE 4.28 +/- 3.41 kU/l, DN 64.95 +/- 3.41); group C (PCHE 1.33 +/- 0.54 kU/l, DN 13.08 +/- 2.19;). PCHE and DN of group A corresponded with normal standard values, whereas the patients in groups B and C could be considered to be patients with heterozygous and homozygous atypical PCHE, respectively. CONCLUSIONS: Our data indicate that an automated analysis of blocked and unblocked PCHE with the Greiner G450 can be easily done in a routine laboratory. By interpreting the DN, the possible risks of delayed succinylcholine degradation can probably be prevented.
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Reevaluation of neonatal EEGs and polygraphic tracings of 40 infants with infantile spasms and/or hypsarrhythmia resulted in the constitution of a compound score for the identification of infants at risk for infantile spasms by neonatal EEG. The score comprises 8 distinct items: 2 concern behavioral characteristics, 6 abnormality of EEG background activity and paroxysmal events. A tracing registered at conceptional age 36 to 44 weeks (eventually up to 50 weeks) presenting at least 4 of these 8 items is scored positive for the risk of evolving hypsarrhythmia. In a prospective study the polygraphic tracings of 941 newborn infants were evaluated for risk: 18 infants suffering from perinatal distress and 7 newborns with malformations of the brain were scored positive and all 25 developed infantile spasms and/or hypsarrhythmia. One infant with later infantile spasms was missed by the scoring system. None of the remaining infants scored negative manifested infantile spasms. Thus, correct positive prognostication was 100% and false negative 0.1%. By conventional EEG 5 out of 8 patients with infantile spasms were correctly predicted. The high validity of the risk-score based on polygraphic tracing between conceptional age 36 to 44 weeks may allow pre-onset treatment preventing secondary mental deterioration due to hypsarrhythmia and infantile spasms.
The analysis of 57 cases of Duchenne muscular dystrophy (DMD) from W.-Germany outlined an average delay in motor development with an extended period of time between learning to stand and to walk. 33 patients could not walk when they were 16 months old. At the age of 27 months people without medical training generally noticed first symptoms. Unexpectedly often quantitative deficiencies in movements became evident. On average 26 months passed until DMD was diagnosed. To improve the situation, the authors propose a selective screening of boys who are not able to walk without help when they are 16 months old (90th percentile for healthy children).
On the basis of electrophoretic and enzyme inhibition studies it was postulated that an aberrant adenylate kinase occurs in muscle and serum of patients with Duchenne muscular dystrophy (Schirmer, R.H. and Thuma, E. (1972) Biochim. Biophys. Acta 268, 92-97; Hamada, M. et al. (1981) Biochim. Biophys. Acta 660, 227-237; Hamada et al. (1985) J. Biol. Chem. 260, 11595-11602). On the basis of the following results we conclude that Duchenne muscular dystrophy patients do not possess an unusual adenylate kinase isoenzyme. In muscle biopsies from five Duchenne patients, the electrophoretic mobility of adenylate kinase and the inhibition of the enzyme by P1, P5-di(adenosine-5')pentaphosphate (Ap5A) was normal. Because of the high SH-group content of the extracts from Duchenne muscle, high concentrations of Ellman's reagent were needed to inhibit adenylate kinase activity in these samples. In Duchenne plasma the adenylate kinase activity was elevated. Like in muscle specimens, the DTNB inhibition curves were shifted to higher reagent concentrations; this was due to a high SH-group content of Duchenne plasma when compared with normal plasma. With respect to inhibition by Ap5A and electrophoretic mobility, Duchenne adenylate kinase in Duchenne plasma behaved like normal muscle adenylate kinase in normal plasma. It was noted that normal muscle adenylate kinase changes its electrophoretic behaviour when mixed with normal or Duchenne plasma. This finding had been considered previously as evidence for the presence of an aberrant adenylate kinase in Duchenne plasma.