Clinical, genetic, and pathologic characterization of FKRP Mexican founder mutation c.1387A>G

Objective

To characterize the clinical phenotype, genetic origin, and muscle pathology of patients with the FKRP c.1387A>G mutation.

Methods

Standardized clinical data were collected for all patients known to the authors with c.1387A>G mutations in FKRP. Muscle biopsies were reviewed and used for histopathology, immunostaining, Western blotting, and DNA extraction. Genetic analysis was performed on extracted DNA.

Results

We report the clinical phenotypes of 6 patients homozygous for the c.1387A>G mutation in FKRP. Onset of symptoms was <2 years, and 5 of the 6 patients never learned to walk. Brain MRIs were normal. Cognition was normal to mildly impaired. Microarray analysis of 5 homozygous FKRP c.1387A>G patients revealed a 500-kb region of shared homozygosity at 19q13.32, including FKRP. All 4 muscle biopsies available for review showed end-stage dystrophic pathology, near absence of glycosylated α-dystroglycan (α-DG) by immunofluorescence, and reduced molecular weight of α-DG compared with controls and patients with homozygous FKRP c.826C>A limb-girdle muscular dystrophy.

Conclusions

The clinical features and muscle pathology in these newly reported patients homozygous for FKRP c.1387A>G confirm that this mutation causes congenital muscular dystrophy. The clinical severity might be explained by the greater reduction in α-DG glycosylation compared with that seen with the c.826C>A mutation. The shared region of homozygosity at 19q13.32 indicates that FKRP c.1387A>G is a founder mutation with an estimated age of 60 generations (∼1,200–1,500 years).

Feasibility and Reproducibility of Echocardiographic Measures in Children with Muscular Dystrophies

BACKGROUND

Cardiac disease is a major cause of death in patients with muscular dystrophies. The use of feasible and reproducible echocardiographic measures of cardiac function is critical to advance the field of therapeutics for dystrophic cardiomyopathy.

METHODS

Participants aged 8 to 18 years with genetically confirmed Duchenne muscular dystrophy (DMD), Becker muscular dystrophy, or limb-girdle muscular dystrophy were enrolled at five centers, and standardized echocardiographic examinations were performed. Measures of systolic and diastolic function and speckle-tracking echocardiography-derived cardiac strain were reviewed independently by two central readers. Furthermore, echocardiographic measures from participants with DMD were compared with those from retrospective age-matched control subjects from a single site to assess measures of myocardial function.

RESULTS

Forty-eight participants (mean age, 13.3 ± 2.7 years) were enrolled. Shortening fraction had a greater interobserver correlation (intraclass correlation coefficient [ICC] = 0.63) compared with ejection fraction (ICC = 0.49). One reader could measure ejection fraction in only 53% of participants. Myocardial performance index measured by pulse-wave Doppler and Doppler tissue imaging showed similar ICCs (0.55 and 0.54). Speckle-tracking echocardiography showed a high ICC (0.96). Focusing on participants with DMD (n = 33), significantly increased mitral A-wave velocities, lower E/A ratios, and lower Doppler tissue imaging mitral lateral E' velocities were observed compared with age-matched control subjects. Speckle-tracking echocardiography demonstrated subclinical myocardial dysfunction with decreased average circumferential and longitudinal strain in three distinct subgroups: participants with DMD with normal shortening fractions, participants with DMD aged < 13 years, and participants with DMD with myocardial performance index scores < 0.40 compared with control subjects.

CONCLUSIONS

In a muscular dystrophy cohort, assessment of cardiac function is feasible and reproducible using shortening fraction, diastolic measures, and myocardial performance index. Cardiac strain measures identified early myocardial disease in patients with DMD.

Pentoxifylline as a rescue treatment for DMD: a randomized double-blind clinical trial

OBJECTIVE

To determine whether pentoxifylline (PTX) slows the decline of muscle strength and function in ambulatory boys with Duchenne muscular dystrophy (DMD).

METHODS

This was a multicenter, randomized, double-blinded, controlled trial comparing 12 months of daily treatment with PTX or placebo in corticosteroid-treated boys with DMD using a slow-release PTX formulation (~20 mg/kg/day). The primary outcome was the change in mean total quantitative muscle testing (QMT) score. Secondary outcomes included changes in QMT subscales, manual muscle strength, pulmonary function, and timed function tests. Outcomes were compared using Student t tests and a linear mixed-effects model. Adverse events (AEs) were compared using the Fisher exact test.

RESULTS

A total of 64 boys with DMD with a mean age of 9.9 ± 2.9 years were randomly assigned to PTX or placebo in 11 participating Cooperative International Neuromuscular Research Group centers. There was no significant difference between PTX and the placebo group in total QMT scores (p = 0.14) or in most of the secondary outcomes after a 12-month treatment. The use of PTX was associated with mild to moderate gastrointestinal or hematologic AEs.

CONCLUSION

The addition of PTX to corticosteroid-treated boys with DMD at a moderate to late ambulatory stage of disease did not improve or halt the deterioration of muscle strength and function over a 12-month study period.

CLASSIFICATION OF EVIDENCE

This study provides Class I evidence that treatment with PTX does not prevent deterioration in muscle function or strength in corticosteroid-treated boys with DMD.

The quick motor function test: a new tool to rate clinical severity and motor function in Pompe patients

Pompe disease is a lysosomal storage disorder characterized by progressive muscle weakness. With the emergence of new treatment options, psychometrically robust outcome measures are needed to monitor patients' clinical status. We constructed a motor function test that is easy and quick to use. The Quick Motor Function Test (QMFT) was constructed on the basis of the clinical expertise of several physicians involved in the care of Pompe patients; the Gross Motor Function Measure and the IPA/Erasmus MC Pompe survey. The test comprises 16 items. Validity and test reliability were determined in a cohort of 91 Pompe patients (5 to 76 years of age). In addition, responsiveness of the scale to changes in clinical condition over time was examined in a subgroup of 18 patients receiving treatment and 23 untreated patients. Interrater and intrarater reliabilities were good (intraclass correlation coefficients: 0.78 to 0.98 and 0.76 to 0.98). The test correlated strongly with proximal muscle strength assessed by hand held dynamometry and manual muscle testing (rs= 0.81, rs=0.89), and showed significant differences between patient groups with different disease severities. A clinical-empirical exploration to assess responsiveness showed promising results, albeit it should be repeated in a larger group of patients. In conclusion, the Quick Motor Function Test can reliably rate clinical severity and motor function in children and adults with Pompe disease.

Consensus treatment recommendations for late-onset Pompe disease

INTRODUCTION

Pompe disease is a rare, autosomal recessive disorder caused by deficiency of the glycogen-degrading lysosomal enzyme acid alpha-glucosidase. Late-onset Pompe disease is a multisystem condition, with a heterogeneous clinical presentation that mimics other neuromuscular disorders.

METHODS

Objective is to propose consensus-based treatment and management recommendations for late-onset Pompe disease.

METHODS

A systematic review of the literature by a panel of specialists with expertise in Pompe disease was undertaken.

CONCLUSIONS

A multidisciplinary team should be involved to properly treat the pulmonary, neuromuscular, orthopedic, and gastrointestinal elements of late-onset Pompe disease. Presymptomatic patients with subtle objective signs of Pompe disease (and patients symptomatic at diagnosis) should begin treatment with enzyme replacement therapy (ERT) immediately; presymptomatic patients without symptoms or signs should be observed without use of ERT. After 1 year of ERT, patients' condition should be reevaluated to determine whether ERT should be continued.

Antiretroviral therapy-associated acute motor and sensory axonal neuropathy

Guillain-Barré syndrome (GBS) has been reported in HIV-infected patients in association with the immune reconstitution syndrome whose symptoms can be mimicked by highly active antiretroviral therapy (HAART)-mediated mitochondrial toxicity. We report a case of a 17-year-old, HIV-infected patient on HAART with a normal CD4 count and undetectable viral load, presenting with acute lower extremity weakness associated with lactatemia. Electromyography/nerve conduction studies revealed absent sensory potentials and decreased compound muscle action potentials, consistent with a diagnosis of acute motor and sensory axonal neuropathy. Lactatemia resolved following cessation of HAART; however, neurological deficits minimally improved over several months in spite of immune modulatory therapy. This case highlights the potential association between HAART, mitochondrial toxicity and acute axonal neuropathies in HIV-infected patients, distinct from the immune reconstitution syndrome.

A randomized study of alglucosidase alfa in late-onset Pompe's disease

BACKGROUND

Pompe's disease is a metabolic myopathy caused by a deficiency of acid alpha glucosidase (GAA), an enzyme that degrades lysosomal glycogen. Late-onset Pompe's disease is characterized by progressive muscle weakness and loss of respiratory function, leading to early death. We conducted a randomized, placebo-controlled trial of alglucosidase alfa, a recombinant human GAA, for the treatment of late-onset Pompe's disease.

METHODS

Ninety patients who were 8 years of age or older, ambulatory, and free of invasive ventilation were randomly assigned to receive biweekly intravenous alglucosidase alfa (20 mg per kilogram of body weight) or placebo for 78 weeks at eight centers in the United States and Europe. The two primary end points were distance walked during a 6-minute walk test and percentage of predicted forced vital capacity (FVC).

RESULTS

At 78 weeks, the estimated mean changes from baseline in the primary end points favored alglucosidase alfa (an increase of 28.1+/-13.1 m on the 6-minute walk test and an absolute increase of 3.4+/-1.2 percentage points in FVC; P=0.03 and P=0.006, respectively). Similar proportions of patients in the two groups had adverse events, serious adverse events, and infusion-associated reactions; events that occurred only in patients who received the active study drug included anaphylactic reactions and infusion-associated reactions of urticaria, flushing, hyperhidrosis, chest discomfort, vomiting, and increased blood pressure (each of which occurred in 5 to 8% of the patients).

CONCLUSIONS

In this study population, treatment with alglucosidase alfa was associated with improved walking distance and stabilization of pulmonary function over an 18-month period. (ClinicalTrials.gov number, NCT00158600.)

Isolated cranial nerve enhancement in metachromatic leukodystrophy

Metachromatic leukodystrophy is a lysosomal storage disorder with an estimated incidence of 1:40,000. Magnetic resonance imaging at time of diagnosis often shows symmetric white matter involvement, sparing the arcuate fibers. A 25-month-old female child presented with a cranial neuropathy, a spastic gait, decreased leukocyte arylsulfatase-A activity, and elevated urinary sulfatides. Magnetic resonance imaging revealed multiple cranial nerve enhancement, without intraparenchymal white matter involvement.

Reliable surrogate outcome measures in multicenter clinical trials of Duchenne muscular dystrophy

We studied the reliability of a series of endpoints in an evaluation of subjects with Duchenne muscular dystrophy (DMD). The endpoints included quantitative muscle tests (QMTs), timed function tests, forced vital capacity (FVC), and manual muscle tests (MMT). Thirty-one ambulatory subjects with DMD (mean age 8.9 years; range 5-16 years) were evaluated at eight sites by 15 newly trained evaluators as a test of interrater reliability of outcome measures. Both total QMT score [intraclass correlation coefficient (ICC) 0.96] and individual QMT assessments (ICC 0.85-0.96) were highly reliable. Forced vital capacity and all timed function tests were also highly reliable (ICC 0.97-0.99). MMT was the least reliable assessment method (ICC 0.61). These data suggest that primary surrogate outcome measures in large multicenter clinical trials in DMD should use QMT, FVC, or time function tests to obtain maximum power and greatest sensitivity.

Respiratory failure as a first presentation of myasthenia gravis

BACKGROUND

Although respiratory failure commonly occurs during the course of myasthenia gravis (MG), it is rarely described at presentation in patients with previously unrecognized MG.

MATERIAL/METHODS

We determined the prevalence and clinical characteristics of patients with respiratory failure associated with undiagnosed MG by review of the medical records of all patients who were diagnosed with MG related respiratory failure at four University hospitals. Respiratory failure was defined on the basis of a forced vital capacity < or =1 liter, negative inspiratory force < or =20 cm H2O, or requirement of mechanical ventilation.

RESULTS

Out of 51 MG patients with respiratory failure, 7(14%) patients had no previous diagnosis of MG. Another patient was identified after the review. The mean age of these 8 patients was 56 years (range 23-76 years); six were women. Five had previous episodes of unexplained respiratory failure. On initial evaluation, ocular or bulbar signs were present in 7 patients. The diagnosis of MG was made by edrophonium test (n=3), edrophonium test with positive acetylcholine antibody levels or repetitive nerve stimulation (n=2), repetitive nerve stimulation with positive acetylcholine antibody levels (n=2), and positive acetylcholine antibody levels alone (n=1). Seven patients required mechanical ventilation. Plasma exchange (n=7) or intravenous immunoglobulins (n=1) resulted in successful extubation or resolution of symptoms in all patients.

CONCLUSIONS

Respiratory failure can occur at presentation in MG. A high index of suspicion should be maintained in patients with previous history of unexplained respiratory failures.

Intraoperative pediatric laryngeal electromyography: experience and caveats with monopolar electrodes

We report our experience with intraoperative laryngeal electromyography (L-EMG) using direct laryngoscopy and placement of monopolar electrodes under general anesthesia in the evaluation and management of laryngeal dysfunction in pediatric patients. In this series of case studies, we present clinical data on 30 pediatric patients with known or suspected anatomic or neurologic laryngotracheal disorders evaluated with placement of shielded monopolar electrodes into the thyroarytenoid muscles during direct laryngoscopy under general anesthesia. Diagnoses included congenital vocal fold paralysis (VFP), laryngotracheal stenosis, cerebral palsy, laryngeal tumors, traumatic vocal fold dysfunction, and postsurgical VFP. The impact of L-EMG on patient management was assessed. We found that L-EMG objectively supported clinical findings, but provided new objective data relevant toward management recommendations in only a few selected pediatric patients with new-onset vocal fold paralysis or paresis or infiltrative laryngeal tumors, and in selected postsurgical cases involving decannulation decisions. The prognostic utility of L-EMG in newborns with congenital VFP has not been established. A normal L-EMG recording indicates an intact neuromuscular axis, but does not guarantee vocal fold mobility or guarantee muscle function in a partially denervated or deconditioned muscle. The potential for false-negative recordings is the major limitation of this technique.

Charcot-Marie-Tooth disease type I diagnosed in a 5-year-old boy after vincristine neurotoxicity, resulting in maternal diagnosis

Charcot-Marie-Tooth disease type 1, also known as hereditary motor sensory neuropathy type 1, is an uncommon autosomal dominant disease that causes destruction of peripheral nerves with a varied clinical course, but often leads to muscle weakness. If the peroneal muscle is involved, the patient may develop a characteristic slapping gait. The dose-limiting side effect of the chemotherapeutic agent vincristine is usually its neurotoxicity. We report the case of a 5-year-old patient with leukemia who developed an acute polyneuropathy after treatment with vincristine. Charcot-Marie-Tooth disease type 1 was diagnosed in the patient and, subsequently, in his mother only after vincristine toxicity was observed.

Plasma exchange versus intravenous immunoglobulin treatment in myasthenic crisis

We performed a retrospective multicenter chart review to compare the efficacy and tolerance of plasma exchange (PE) and intravenous immunoglobulin (i.v.Ig) in treatment of 54 episodes of myasthenic crisis. After adjustment for other variables, PE (compared with i.v.Ig) was associated with a superior ventilatory status at 2 weeks (partial F = 6.2, p = 0.02) and 1 month functional outcome (partial F = 4.5, p = 0.04). However, the complication rate was higher with PE compared with i.v.Ig (13 versus 5 episodes, p = 0.07).

Neutropenia in a patient receiving intravenous immune globulin

A child with Guillain-Barre syndrome treated with intravenous immune globulin (IVIG) developed neutropenia (absolute neutrophil count = 390), which resolved 3 days after completion of the therapy. Potential mechanisms for the development of neutropenia during the use of IVIG therapy are discussed. In this case, testing of the IVIG used revealed the presence of a high concentration of anti-neutrophil antibodies compared to other samples. It is recommended that white blood cell and neutrophil counts be monitored daily during the use of such therapy.

Possible radiation-induced dural fibrosarcoma with an unusually short latent period: case report

We report a case of radiation-induced dural fibrosarcoma in a 9.5-year-old male patient who was treated with radiation for medulloblastoma. He received a total dose of 53.2-Gy radiation, delivered at 1.6 and 1.8 Gy per fraction with a 6 MV linear accelerator using the standard cranial-spinal technique. A sequential magnetic resonance image at 15 months after the completion of radiation therapy showed a mass above the cerebral convexity that increased two-fold in size within a period of 4 months. The tumor showed characteristics of a low-grade fibrosarcoma. This case emphasizes the potential risk of early development of a second neoplasm after therapeutic radiation, especially in children, and also documents what is to our knowledge the shortest latent period between the administration of radiation therapy and the development of an intracranial fibrosarcoma that has been reported.

Stroke in purine nucleoside phosphorylase deficiency

The first documented case of cerebrovascular disease occurring in a 13-year-old girl with purine nucleoside phosphorylase deficiency is reported. This patient, the oldest known survivor with purine nucleoside phosphorylase deficiency, had previously experienced multiple sequential neurologic problems. She presented with episodes of transient left hemiparesis, followed shortly thereafter by dense left hemiplegia. Magnetic resonance imaging revealed a right internal capsule infarct; cerebral angiography revealed vasculopathy of the proximal vessels. Proposed mechanisms for neurologic dysfunction and cerebrovascular disease in purine nucleoside phosphorylase deficiency are discussed.

Dietary erucic acid therapy for X-linked adrenoleukodystrophy

We investigated the biochemical and clinical efficacy of dietary erucic acid (C22:1) therapy for X-linked adrenoleukodystrophy (ALD). In a double-blind crossover study of patients who were on chronic oleic acid (C18:1) therapy, addition of erucic acid to the diet led to a further reduction in plasma hexacosanoic acid (C26:0) concentration. We treated 12 newly diagnosed ALD patients with a diet enriched with erucic acid and oleic acid for 2 to 19 months. Mean plasma C26:0 concentration decreased to normal by 4 weeks, and the C26:0 composition of plasma sphingomyelin and phosphatidylcholine became normal by 4 months on therapy. Fatty acid analysis of postmortem tissues from 1 boy treated for 10 months suggested that dietary erucic acid entered the heart, liver, adrenal gland, and brain. Eight patients remained on treatment long enough (mean, 12 +/- 3 months) to evaluate their clinical response; 6 of these patients with moderate to advanced disease deteriorated neurologically or showed progression of white matter disease on brain magnetic resonance imaging whereas 2 mildly affected patients remained clinically stable after 10 and 19 months. No adverse effects of the diet occurred. We conclude that dietary erucic acid therapy is effective in lowering plasma C26:0 to normal in ALD patients, and may prevent further demyelination in some mildly affected boys.

Remyelination in the human central nervous system

Remyelination, albeit incomplete, has been demonstrated in human central nervous system (CNS). However, information about the initial stage and the final extent of such remyelination is not available. We describe the morphologic findings of a demyelinating lesion with evidence of early remyelination in a biopsy obtained from a 15-year-old boy about two weeks after the onset of neurologic symptoms. The demyelinated area appeared hypercellular with a relatively large number of oligodendrocytes frequently seen in the process of new myelin formation. In addition to the usual reactive changes, the astrocytes were often seen to contain otherwise normal-looking oligodendrocytes within their cytoplasm. In the ensuing months, the patient made apparently total functional recovery accompanied by nearly complete resolution of the white matter lesions demonstrated by the subsequent magnetic resonance studies. These observations suggested that the initial remyelination seen in the biopsy eventually succeeded in producing extensive remyelination in the lesion. Although the exact nature of the demyelinating disorder in our patient remains undetermined, this study indicates that clinically significant remyelination is possible in human CNS. Also, our findings appeared strikingly similar to those described in certain experimental animal models in which widespread remyelination is known to occur.

Use of DNA probes in detecting carriers of Duchenne muscular dystrophy: selected case studies

Detection of Duchenne muscular dystrophy carriers by genetic analysis is illustrated by four case studies. The technique is most useful in obligate families, in excluding carrier status in isolated cases, and in families in which the affected child demonstrates a molecular deletion. A major limitation of this technique is that the accuracy of carrier status in isolated (i.e., no family history) cases is limited by the probability that the affected child may represent a new mutation. To improve the carrier risk estimate generated by the DNA data, particularly in isolated cases, we suggest that measuring creatine kinase activities in the serum and performing the genetic analysis on the nonaffected males may be helpful.

Use of DNA probes in detecting carriers of Duchenne muscular dystrophy: selected case studies

Detection of Duchenne muscular dystrophy carriers by genetic analysis is illustrated by four case studies. The technique is most useful in obligate families, in excluding carrier status in isolated cases, and in families in which the affected child demonstrates a molecular deletion. A major limitation of this technique is that the accuracy of carrier status in isolated (i.e., no family history) cases is limited by the probability that the affected child may represent a new mutation. To improve the carrier risk estimate generated by the DNA data, particularly in isolated cases, we suggest that measuring creatine kinase activities in the serum and performing the genetic analysis on the nonaffected males may be helpful.

Intraoperative electroneurography: management of ulnar neuropathy at the elbow

At the elbow the ulnar nerve may be compressed either in the retrocondylar groove or at the cubital tunnel. Optimal surgical therapy should be directed at the specific site of involvement. Intraoperative electroneurography performed in conjunction with 19 ulnar nerve explorations helped localize the precise site of compression. Of the primary procedures, abnormality was at the retrocondylar groove in 9, cubital tunnel in 4, both locations in 3, and at an unusual distal point in 1; 12 anterior subcutaneous transpositions, 4 cubital tunnel releases, and 1 distal decompression resulted. Intraoperative studies helped identify residual compression in two patients undergoing reexploration. Although routine electrodiagnosis may localize an ulnar neuropathy to the elbow, reliably separating retrocondylar from cubital tunnel compression is more difficult. Preoperatively, percutaneous serial short increment studies were more accurate than simple "inching" in predicting the site of compression.

Adrenoleukodystrophy: dietary oleic acid lowers hexacosanoate levels

Adrenoleukodystrophy (ALD) is an X-linked disorder characterized by demyelination, adrenal insufficiency, and accumulation of saturated very-long-chain fatty acids (VLFA), particularly hexacosanoate (C26:0). We treated 5 patients with adrenoleukodystrophy (3 males and 2 symptomatic female carriers) for 6 months with a diet enriched in oleic acid (C18:1) and moderately restricted in C26:0. Elevated plasma and erythrocyte levels of C26:0 decreased in a time-dependent manner during treatment. Total plasma C26:0 concentration was lowered by 50 +/- 9% (p less than 0.01); it became normal in the female carriers. The total erythrocyte level of C26:0 decreased (44 +/- 5%; p less than 0.001) into the normal range in all patients. Significant decreases were noted in the saturated VLFA composition of plasma and erythrocyte sphingomyelin and erythrocyte phosphatidylcholine during dietary treatment. In general, decreases in saturated VLFA levels were accompanied by increases in monounsaturated VLFA levels, while total VLFA values did not change. This novel approach to the treatment of adrenoleukodystrophy, in which there is an exchange of monounsaturated VLFA for the more toxic saturated VLFA, may prove clinically beneficial in this disorder.

CT-guided stereotactic biopsies of lesions in the medulla and a case of Leigh's disease

CT-guided stereotactic biopsy of lower brain stem lesions in 7 consecutive cases is discussed. A frontal transincisural approach was used. Five patients had astrocytomas histologically. The single patient who had undergone empirical radiation therapy prior to tissue diagnosis revealed only necrosis. One patient was found to have pathology suggestive of Leigh's disease. This patient was not radiated and is the first alive adult to have this diagnosis confirmed. Although controversy still exists in the management of brain stem lesions, we intend to demonstrate the value of tissue diagnosis in the management of such lesions.

Malignant thymoma with dysautonomia and disordered neuromuscular transmission

A 42-year-old man had prominent dysautonomia accompanied by clinical and electrophysiological features of both myasthenia gravis and the Lambert-Eaton myasthenic syndrome. Antiacetylcholine receptor antibodies were present in high titer. Invasive thymoma was found at thymectomy; later, a solitary metastasis to the spleen required a splenectomy. Complete remission followed surgery. There was evidence of antibody activity directed against postsynaptic acetylcholine receptors, presynaptic somatic motor terminals, and autonomic effector junctions. To our knowledge, the association of thymoma with a myasthenia gravis-Lambert-Eaton overlap syndrome has not been reported previously.

Autosomal dominant humeroperoneal myopathy

Emery-Dreifuss muscular dystrophy is a syndrome with five salient features: early and unusual contractures; humeroperoneal muscle wasting; the slow progression of weakness, beginning in childhood; cardiac conduction defects; and X-linked inheritance. We present two cases and detail other reports with a similar constellation of findings with apparent autosomal dominant inheritance. We postulate separate genetic disorders with similar phenotypic expression.

Information processing speed of children with Friedreich's ataxia

Two children with Friedreich's ataxia and six controls matched for age and Verbal IQ were administered a measure of short-term memory scanning and tests of attention, memory, language and abstraction. The patients demonstrated a deficit in information processing speed, decreased sustained attention and variable memory performance. The findings suggest that a deficit in information processing speed occurs early in the clinical course of Friedreich's ataxia and progresses as neurological status deteriorates.

Nocardia asteroides brain abscess following mastoidectomy

Nocardia asteroides brain abscess occurred after mastoidectomy and tympanoplasty in a previously healthy 10-year-old boy. Combined surgical excision and trimethoprim/sulfamethoxazole therapy resulted in significant improvement.

Hypertrophia musculorum vera in familial ataxia

A kindred with dominantly inherited ataxia demonstrated hypertrophia musculorum vera as a phenotypic feature of the disease. The proband had fasciculations, cramps, absent sensory nerve action potentials, an increased creatine kinase level, dramatic enlargement of calf muscles, and a muscle biopsy specimen showing denervation accompanied by true muscle fiber hypertrophy; ataxia and other clinical signs of spinocerebellar degeneration were also present. Other family members displayed progressive ataxia and calf muscle enlargement to varying degrees. Though peroneal atrophy is a more common feature of the familial ataxias, some kindreds may have muscle enlargement simulating the pseudohypertrophy of muscular dystrophy that is due instead to denervation-induced compensatory individual fiber hypertrophy.

Biotinidase deficiency: initial clinical features and rapid diagnosis

Biotinidase deficiency is the primary defect in most individuals with late-onset multiple carboxylase deficiency. We have reviewed the presenting clinical features of 31 children with the disorder. Seizures, either alone or with other neurological or cutaneous findings, are the most frequent initial symptom observed. Other neurological symptoms, such as hypotonia, ataxia, hearing loss, optic atrophy, and developmental delay, are seen, in addition to skin rash and alopecia. The disorder is also characterized by ketolactic acidosis and organic aciduria. Biotinidase activity may be diagnosed using a simple, rapid, semiquantitative colorimetric procedure. Samples of whole blood spotted on the same filter paper used by most states to screen for phenylketonuria and other inborn errors of metabolism may be sent to an appropriate reference laboratory. None of the common anticonvulsants or sedatives used to treat newborns and children interfere with the test. Because biotinidase deficiency can be treated readily with biotin, this disorder should be considered in children with infantile seizures, especially in the presence of other characteristic neurological or cutaneous features.

Prediction of carrier status in Duchenne dystrophy by creatine kinase measurement

Serum creatine kinase (CK) was measured in 515 healthy white women and 28 obligate carriers for Duchenne muscular dystrophy. There was substantial overlap between the control and carrier populations. To analyze the impact of the degree of overlap, the predictive value of a CK result was determined by (1) using sensitivity and specificity analysis, which assumes dichotomization into a positive or negative result based on a particular cut-off value; and (2) using likelihood ratio analysis, which evaluates an individual result based on the continuum observed for control and carrier populations. There was no clinically important difference whether an observed 57% or a hypothetical 33% overlap between control and carrier results was used. Because of the substantial overlap, the CK test utility is limited to those suspected carriers whose results fall above the healthy population interval. A low CK result does not provide sufficient assurance of noncarrier status.

Information processing speed in Friedreich's ataxia

Three patients with Friedreich's ataxia and six controls matched by age and vocabulary and information scores on the Wechsler Adult Intelligence Scale-Revised were administered a measure of short-term memory scanning. Patients with Friedreich's ataxia demonstrated a deficit in information processing speed in the relative absence of impairment in attention, memory, language, judgment, reasoning, and other cognitive functions. The short-term memory scanning procedure may be useful in documenting cognitive slowing and in distinguishing this impairment from the motor abnormality often associated with a subcortical brain disorder.

Are reference limits for serum creatine kinase valid in detection of the carrier state for Duchenne muscular dystrophy?

We evaluated serum creatine kinase (CK) as an index to heterozygosity in Duchenne muscular dystrophy. When the 97.5th percentile of the CK normal reference interval was selected as the cutoff point, only 31% of 28 obligate carrier mothers and 24% of 43 mothers of simplex cases (those with only one occurrence of dystrophy in the kindred) exceeded this cutoff value. The outcome depended to some degree on the method used for establishing the reference limit for 379 presumably non-carrier, ambulatory women. The considerable overlap of CK activities between the control and carrier population as well as the non-gaussian distribution of the data permitted no satisfactory approach for differentiating these two populations. Neither the application of likelihood ratios, which evaluates a continuum of results without the dichotomy of a cutoff point, nor the application of predictive value based on sensitivity and specificity, which involves use of a cutoff value for decision making, provided a reliable estimate of carrier status. There was no significant difference (2 alpha = .19) between the median CK activity of obligate carrier mothers and mothers of simplex cases. The serum CK test does not provide data that either support or reject the Haldane hypothesis.

Are reference limits for serum creatine kinase valid in detection of the carrier state for Duchenne muscular dystrophy?

We evaluated serum creatine kinase (CK) as an index to heterozygosity in Duchenne muscular dystrophy. When the 97.5th percentile of the CK normal reference interval was selected as the cutoff point, only 31% of 28 obligate carrier mothers and 24% of 43 mothers of simplex cases (those with only one occurrence of dystrophy in the kindred) exceeded this cutoff value. The outcome depended to some degree on the method used for establishing the reference limit for 379 presumably non-carrier, ambulatory women. The considerable overlap of CK activities between the control and carrier population as well as the non-gaussian distribution of the data permitted no satisfactory approach for differentiating these two populations. Neither the application of likelihood ratios, which evaluates a continuum of results without the dichotomy of a cutoff point, nor the application of predictive value based on sensitivity and specificity, which involves use of a cutoff value for decision making, provided a reliable estimate of carrier status. There was no significant difference (2 alpha = .19) between the median CK activity of obligate carrier mothers and mothers of simplex cases. The serum CK test does not provide data that either support or reject the Haldane hypothesis.

Myasthenia gravis immunoglobulin augments motor neuron survival without producing muscle paralysis

Effects of sera or immunoglobulins from patients with acquired myasthenia gravis on motor neuron survival during critical stages of embryonic development were investigated in the trochlear nucleus-superior oblique muscle system of white Peking duck embryos. A significant increase in motor neuron survival occurred following application of myasthenia gravis sera or myasthenic immunoglobulin during the period of embryonic death of motor neurons. There was no reduction in limb or extraocular muscle movement in treated embryos. Trochlear motor neuron survival persisted after sera or immunoglobulin treatment was discontinued. The total number of muscle fibers and acetylcholine receptors were unchanged following immunoglobulin treatment. Myasthenic immunoglobulin is therefore unique in preventing motor neuron death without producing muscle paralysis and in promoting a prolonged augmentation of motor neuron survival. It is concluded that factors other than muscle activity may also control neuron survival during embryogenesis. Previous studies of myasthenic sera in muscle have shown effects only postsynaptically. This is the first demonstration that myasthenic immunoglobulin affects structures in the central nervous system.

Plasma exchange in myasthenia gravis: electrophysiological studies

Electrophysiological recordings of evoked muscle action potentials during repetitive stimulation were performed in four female patients undergoing plasmapheresis for myasthenia gravis. Studies were done immediately before and after each exchange and were repeated daily during a series of exchanges and at intervals thereafter. Electrophysiological improvement was seen but was delayed for at least seven days from the start of plasmapheresis therapy. No sudden and substantial improvements were encountered, though anti-receptor antibody titers dropped precipitously. A reversible neuromuscular blocking effect of anti-receptor antibody could not be demonstrated in these patients.

Intractable hiccups. (singultus)

Intractable hiccups (singultus) is an uncommon disorder with various etiologies. The majority of reported studies of intractable hiccups has claimed ipsilateral spasm of the hemidiaphragm based solely on clinical or radiographic evidence. A case of intractable hiccups is presented. Documentation of normal phrenic nerve latencies with bilateral synchronous firing of anterior scalene, intercostal muscles and bilateral hemidiaphragm involvement is presented. This combination of muscle group involvement supports the concept of a "supraspinal hiccup center." A systematic trial of chemotherapeutic agents described as effective against hiccups was employed. Relief lasting for three to four week periods has been obtained by the intravenous administration of a specially prepared sterile solution of methylphenidate. The nerve pathways pertinent to hiccup are discussed. The etiology of intractable hiccups and the various treatment modalities are presented.

Myelopathy in mucopolysaccharidosis type II (Hunter syndrome)

A 24-year-old man with Hunter syndrome had spastic quadriparesis due to impingement of thickened meninges upon the cervical spinal cord. Tracheal narrowing due to submucosal deposits (presumably mucopolysaccharide) produced serious ventilatory complications during induction of anesthesia and necessitated tracheostomy before surgical decompression of the spinal cord could be attempted. Recognition of compressive myelopathy and tracheal compromise as late complications of Hunter syndrome may promote early therapy and prevent respiratory catastrophe.

Arm-diaphragm synkinesis: electrodiagnostic studies of aberrant regeneration of phrenic motor neurons

Arm-diaphragm synkinesis may occur after injury to the proximal portion of the brachial plexus or cervical nerve roots. Regenerating axons of phrenic motor neurons are misdirected to supply limb muscles. Electrodiagnostic investigations of three patients with symptoms referable to upper brachial plexus or cervical roots revealed motor units in either biceps or triceps muscles that discharged during inspiration. These units did not fire during forced or passive expiration or Valsalva maneuver. Activation of these units could not be achieved by volitional contraction of the appropriate arm muscles. The synkinetic motor units were of increased amplitude and duration. Some units contained late components that demonstrated jitter and blocking, as is characteristic of reinnervated motor units. The unwary electromyographer may misinterpret these synkinetic units as incomplete muscle relaxation or some form of abnormal repetitive discharge. Correct identification of these units provides objective evidence of antecedent nerve root or brachial plexus injury.