Prospective analysis of strength in spinal muscular atrophy. DCN/Spinal Muscular Atrophy Group.

Spinal muscular atrophy is a genetic disorder of the motor neurons that causes profound hypotonia, severe weakness, and often fatal restrictive lung disease. Patients with spinal muscular atrophy present a spectrum of disease from the most severe infantile-onset type, called Werdnig-Hoffmann disease (type 1), associated with a mortality rate of up to 90%, to a late-onset mild form (type 3), wherein patients remain independently ambulatory throughout adult life. Although many clinicians agree that patients with spinal muscular atrophy lose motor abilities with age, it is unknown whether progressive weakness occurs in all patients with spinal muscular atrophy. We present here results of the first prospective study of muscle strength in patients with spinal muscular atrophy. There was no loss in muscle strength as determined by a quantitative muscle test during the observation period. However, motor function diminished dramatically in some patients with spinal muscular atrophy. Explanations for this loss of function could not be determined from our data. Decrease in motor function could be caused by factors other than loss of strength. Therefore, it is not clear from our results whether spinal muscular atrophy is a neurodegenerative disease. We conclude that treatment trials in spinal muscular atrophy should be designed with consideration of the natural history of strength and motor function in this disorder.

Muscle fatigue in spinal muscular atrophy.

We previously reported that patients with spinal muscular atrophy do not lose muscle strength over time as measured quantitatively. However, we noted that many patients with spinal muscular atrophy suffer from what they call fatigue. We wondered if we could measure fatigue during a single maximal voluntary contraction, whether fatigue might increase with time, independent of muscle strength, and whether increasing fatigue might correlate with loss of function in some patients. We measured fatigue during a single maximal voluntary contraction in a cohort of patients having spinal muscular atrophy using quantitative strength testing. We included only patients with spinal muscular atrophy aged 5 years or older, so they could follow instructions regarding muscle contraction, and who were followed for at least 2 years. Seventy-six children with spinal muscular atrophy and 24 untrained individuals, aged 5 to 57 years (mean, 16.8 years), were studied. There was no discernible abnormal fatigue in patients with spinal muscular atrophy compared to untrained controls using our methodology. Thus, spinal muscular atrophy may not be associated with fatiguability. Moreover, spinal muscular atrophy does not appear to cause progressive muscle fatigue with age or loss of function. It is possible that fatigue was undetectable by our methods. An alternative explanation is that what patients describe as fatigue may be caused by factors outside the neuromuscular system. Such factors may include chronic respiratory insufficiency with hypoventilation and carbon dioxide retention as well as chronic malnutrition and negative nitrogen balance.

A clinical study of end-to-end versus end-to-side techniques for microvascular anastomosis.

The choice of microvascular anastomotic technique, end-to-end versus end-to-side, is still an item of debate. A review of the literature reveals no difference in patency rates in animal models where there is no size discrepancy. The available clinical evidence stems from Godina's early experience, proclaiming a higher failure rate with end-to-end anastomoses. Factors such as size mismatch and use of injured vessels, rather than anastomotic technique, may have been responsible. This clinical study examines the fate of over 2000 microvascular anastomoses performed in more than 900 tissue transplants. Complications attributable to the anastomosis were considered failures of the anastomosis, were tabulated, and were compared between the two techniques. The end-to-end and end-to-side microvascular techniques were found to be equally effective when properly applied. The choice of technique therefore should be secondary to factors influencing the choice of recipient vessel, such as the condition of the vessel, its accessibility, and the preservation or augmentation of maximal distal flow to an extremity.

Function changes in spinal muscular atrophy II and III. The DCN/SMA Group.

The course of spinal muscular atrophy (SMA) is not well established except for those patients whose age of onset is before 6 months and who achieve only "sit with support" as their maximum function (Werdnig-Hoffmann disease or SMA I). This study shows that there is another group of SMA patients whose age of onset and maximum function achieved can be used as prognostic guides. Fifty percent of SMA patients who could walk without assistance and whose onset was prior to age 2 years lost the ability to walk independently by age 12. Fifty percent of SMA patients who walked and whose onset was between 2 and 6 years of age lost walking ability by age 44 years. Fifty percent of SMA patients who could walk with assistance as their best function ever achieved lost this ability by age 7 years, unrelated to age of onset; none could walk with assistance after age 14 years. Seventy-five percent of SMA patients who developed the ability to sit independently as their best function were still sitting after age 7 years independent of age of onset; 50% of this group could sit independently after age 14 years. Eighty-five percent of SMA patients who could walk could not negotiate stairs without holding onto a rail. They could raise their hands above the head; however, as they lost walking ability, they lost this function as well. Only one SMA patient whose maximum function was sitting independently could get to the sitting position on his own. Only two of these patients could hold their hands above their heads. All patients with SMA lose function over time. This function loss occurs slowly and is related primarily to maximum function achieved; knowledge of age of onset provides helpful information, especially for predicting the loss of independent walking.

Dystrophinopathies: clarification and complication.

The purpose of this review is to analyze the clinical applications of a remarkable series of advances made in molecular genetics, primarily with regard to Becker muscular dystrophy. A new classification is required to clarify such syndromes as Duchenne and Becker muscular dystrophy. Dystrophinopathies can be seen in patients with early onset and a severe course (Duchenne muscular dystrophy), patients with later onset and milder weakness (Becker muscular dystrophy), patients with myalgia and cramp syndrome, and patients with dilated cardiomyopathies. Dystrophin testing in muscle is the most sensitive test for identification of dystrophinopathy patients, although gene deletion studies can make the diagnosis in most cases.

Myalgia and cramps: dystrophinopathy with wide-ranging laboratory findings.

We present 12 cases of males with myalgia and cramps and a normal muscle strength examination. All the patients had muscle dystrophin values consistent with Becker muscular dystrophy. Five of the patients had a normal electromyogram, and five had normal light microscopic muscle biopsy results. Of particular note, four of the 12 patients had normal serum creatine kinase levels, and four others had only mild elevations (less than twice the upper limit of normal). These patients establish an identifiable dystrophinopathy of adolescent boys and young men that can present with muscle pain and, in some cases, normal routine laboratory evaluations.

Pulmonary function in spinal muscular atrophy.

We present the first prospective study on pulmonary function in spinal muscular atrophy patients. Seventy-seven spinal muscular atrophy patients, ages 5 to 18 years, from three centers, were studied with regard to forced vital capacity, using height as a predictor. Patients were categorized into four motor function categories. The highest-functioning group had normal or near-normal values, and those who sat with support had the lowest values. Those with intermediate function had intermediate values. Forced vital capacity was studied longitudinally in 40 spinal muscular atrophy patients for 1.1 to 4.4 years. Eighty-eight percent of patients grew in height, but only 35% showed an increase in height-adjusted forced vital capacity percent. In those patients with the least function, 100% lost height-adjusted forced vital capacity over time. In those patients with the highest function, 57% lost height-adjusted forced vital capacity. In addition, the basic forced vital capacity, not correlated to height, decreased in 43% of cases. These pulmonary function alterations appear to be important determinants for function and survival in spinal muscular atrophy patients.

Salvage of wounds following failed tissue transplantation.

During the past 20 years, 972 microvascular transplantations have been performed for 783 patients, with an overall failure rate of 6.2 percent. Fifty-four of the 60 failed transplantations were available for long-term follow-up and were retrospectively reviewed with respect to the original indications for transplantation, the number, and the type of salvage procedures performed following transplant failure. This study illustrates that the choice of salvage procedures performed following transplant failure depends on the original indications, the location, and the severity of the resultant wound. Failure following transplantation for coverage of contour defects or unstable wounds can often be managed by non-microsurgical methods. In contrast, when the indications for transplantation included the transfer of specialized tissues for thumb or digit reconstruction, the restoration of motor or sensory function, or the coverage of a limb-threatening wound, requirements for reconstruction could be satisfied only by a second successful tissue transplant. Eighteen of the 54 cases underwent an additional transplantation, with an 89 percent success rate.

Prospective study of spinal muscular atrophy before age 6 years. DCN/SMA Group.

Spinal muscular atrophy (SMA) is a common neuromuscular disorder of childhood, associated with a high mortality rate during the first 2 years of life. Most practitioners expect patients with SMA to follow a progressive course with loss of muscle strength and function over 2-10 years. Counselling sessions with parents frequently emphasize the high mortality rate and risk for respiratory failure. The progressive nature of SMA has been attributed to the loss of motor neurons. Fifty-eight children, ages 6 years and younger, were examined between January, 1987, and April, 1992, as part of a large, multicenter collaborative study of SMA. Muscle function was evaluated at regular intervals using a standardized protocol that was demonstrated to be reliable. We determined a prevalence of 56% for tongue fasciculations, a prevalence of 22% for facial weakness, and persistent deep tendon reflexes in one patient. Improved motor function and acquired milestones during the study were documented. This work should contribute toward a better understanding of the natural history of SMA.

Spinal muscular atrophy: new thoughts on the pathogenesis and classification schema.

We have established the first prospective, collaborative study of spinal muscular atrophy, the second most common neuromuscular disease of childhood. One hundred and forty-one patients have been evaluated on at least four occasions over a 3-year period. The patients have been grouped by age of onset, as well as by function at the time of initial evaluation. The muscle strength of 96 patients aged 5 years or older was evaluated at 6-month intervals using a fixed myometry system. The new observations made are: (1) The present classification schema is not valid; for example, 49 patients with onset of weakness before 6 months of age (type I or Werdnig-Hoffmann disease), whose life span is said to be only 2 to 4 years, participated in the study and are 4 months to 31 years of age. (2) Thirty-seven patients were evaluated over an 18-month period. None lost strength during this time but four lost function. Although the period of observation was short, the results suggest that the loss of function in patients with spinal muscular atrophy might be explained by a process other than cell death that allows patient strength to be maintained and simultaneously prevents the motor unit from achieving its normal adult potential.

Management of myasthenia gravis by extended thymectomy with anterior mediastinal dissection.

BACKGROUND: Thymectomy has continued to gain acceptance as definitive treatment for myasthenia gravis. Because of the nature of thymic embryology with scattered rests throughout the anterior mediastinum, we advocate a transsternal thymectomy with extended anterior mediastinal dissection. METHODS: A series of 48 patients with myasthenia gravis treated by thymectomy between 1979 and 1991 were reviewed. RESULTS: The mean length of duration of disease from onset to operation was 48.7 +/- 11.3 months, and the mean length of follow-up was 51.6 +/- 6.5 months. The operation was associated with a 21% morbidity rate (4% major morbidity) with no deaths. Forty-five patients (94%) have improved, requiring decreased medication. The overall drug-free remission rate was 42%. Of the 20 patients in remission, three had thymomas and four had hyperplastic glands. All of the patients who achieved drug-free remission were classified as Osserman's I or II. CONCLUSIONS: An aggressive surgical approach to myasthenia gravis can result in a high percentage of overall improvements and drug-free remissions. The best results are achieved in patients with lower-stage disease. Therefore transsternal extended thymectomy for myasthenia gravis appears to be the procedure of choice and should be advocated as soon as the diagnosis is made and the patient stabilized.

Oligodendroglial gliomatosis cerebri.

A 34-year-old man presented with progressive neurologic deterioration though clinically to be multiple sclerosis. At autopsy, the cerebral white matter, deep gray matter, and brain stem were diffusely infiltrated with cells characteristic of oligodendrocytes. Gliomatosis cerebri consisting predominantly of oligodendroglia is rare.

Aggressive surgical approach for drug-free remission from myasthenia gravis.

A series of 27 patients with generalized myasthenia gravis is presented. All patients were treated by a sternal split and extended thymectomy and radical mediastinal dissection. The overall drug-free remission rate was 63%, although three additional patients are likely to achieve drug-free remission in the near future, with the total drug-free remission rate then being 74%. Of the remaining patients, all but three improved and require decreased medication, for an improvement rate of approximately 90%. One patient who has not improved had an invasive malignant thymoma. Drug-free remission was achieved in 46% of the male patients and in 82% of the female patients despite that the mean duration of disease was greater than 3.5 years. There was one serious complication, that of sterile sternal dehiscence. There was no mortality. The results suggest that an aggressive, radical surgical approach to myasthenia gravis, even in a group of patients considered somewhat less favorable because of a relatively long duration of disease, can result in a high percentage of drug-free remissions. Radical surgery for myasthenia gravis appears to be the treatment of choice, with medical therapy being reserved for those patients who are not likely to survive operation.

Decreased creatine kinase activity in cultured Duchenne dystrophic muscle cells.

Muscle cells were cultured from six patients with Duchenne muscular dystrophy and nine normal subjects. Protein and myosin content and pyruvate kinase (PK) activity were similar in normal and Duchenne muscular dystrophy cultures. Creatine kinase (CK) activity was lower in Duchenne muscular dystrophy cultures and the isoenzyme distribution indicated MB-CK was significantly lower, while BB-CK was significantly higher in later Duchenne muscular dystrophy cultures. This abnormal isoenzyme pattern suggested aberrant or impaired maturation of Duchenne muscular dystrophy myotubes in vitro.

Membrane defects in Duchenne dystrophy: protease affecting sarcoplasmic reticulum.

Human muscle sarcoplasmic reticulum (SR) yields three major protein bands. The percent distribution of the mean values of the bands from 15 normal human muscles was 55.4, 14.6, and 30.0 for the 100, 55, and 45-kDa mass proteins, respectively. A mean distribution similar to that in normal muscle SR was found in preparations from 7 patients with polymyositis and from 7 patients with myotonic dystrophy. In 12 preparations from patients with Duchenne dystrophy, the protein distribution differed from that of preparations from normal muscle. The 100-kDa mass protein band was decreased, whereas the 55- and 45-kDa mass bands were increased. Protease inhibitors pepstatin A, antipain, and leupeptin, as well as ethyleneglycol-bis(aminoethyl ether)-N,N,N',N'-tetraacetic acid or ethylenediaminetetraacetic acid, significantly reduced this change. However, some of the changes cannot be prevented by the addition of inhibitors and must be expressed in vivo. Neither protease inhibitors nor chelators affected SR preparations from normal muscle. We found a five- to ten-fold increase in calcium-activated neutral protease activity in Duchenne dystrophic muscles that degraded the calcium-adenosinetriphosphatase of SR. The active protease was identified as the cytoplasmic calpain II. The increased activity in Duchenne muscles may explain many reported abnormalities.

Regulation of cardiac sarcoplasmic reticulum calcium transport by calcium-calmodulin-dependent phosphorylation.

Cardiac sarcoplasmic reticulum contains an endogenous calcium-calmodulin-dependent protein kinase and a 22,000-Da substrate, phospholamban. This kinase is half-maximally activated (EC50) by 3.8 +/- 0.3 microM calcium and is absolutely dependent on exogenous calmodulin (EC50 = 49 nM). To determine the effect of this phosphorylation on calcium transport, sarcoplasmic reticulum vesicles (0.5 mg/ml) were preincubated under conditions for optimal phosphorylation (50 mM potassium phosphate, pH 7.0, 10 mM MgCl2, 0.5 mM EGTA, 0.478 mM CACl2, 0.1 microM calmodulin, 0.5 mM ATP). Control sarcoplasmic reticulum was preincubated under identical conditions but in the absence of ATP to avoid phosphorylation. Both control and phosphorylated vesicles were centrifuged and resuspended in 0.3 M sucrose, 20 mM Tris-HCl, 100 mM KCl, pH 7.0, to remove calmodulin and subsequently assayed for calcium (45Ca) transport in the presence of 2.5 mM Tris-oxalate. Phosphorylation of sarcoplasmic reticulum vesicles by calcium-calmodulin-dependent protein kinase resulted in a significant increase (2- to 4-fold) in the rate of calcium transport at low calcium concentrations (less than 3 microM), while calcium transport was minimally affected at higher calcium. Hill coefficients (n) derived from Hill plots of transport data showed no difference between control and phosphorylated sarcoplasmic reticulum (n = 2.0), indicating that phosphorylation does not alter the cooperativity between calcium sites on the calcium pump. The EC50 for calcium activation of calcium transport by control vesicles was 0.86 +/- 0.1 microM calcium, and phosphorylation of phospholamban decreased this value to 0.61 +/- 0.07 microM calcium (n = 7, p less than 0.028), indicating an increase in the apparent affinity for calcium upon phosphorylation. These results were found to be specific for calcium-calmodulin-dependent phosphorylation of phospholamban. Control experiments on the effects of the reactants used in the phosphorylation assay and subsequent centrifugation of sarcoplasmic reticulum showed no alteration of the rate of calcium transport. Therefore, the calcium pump in cardiac sarcoplasmic reticulum appears to be regulated by an endogenous calcium-calmodulin-dependent protein kinase, and this may provide an important regulatory mechanism for the myocardium.

Mechanism of the stimulation of Ca2+-dependent ATPase of skeletal muscle sarcoplasmic reticulum by protein kinase.

Sarcoplasmic reticulum isolated from moderately fast rabbit skeletal muscle contains intrinsic adenosine 3',5'-monophosphate (cAMP)-independent protein kinase activity and a substrate of 100 000 Mr. Phosphorylation of skeletal sarcoplasmic reticulum by either endogenous membrane bound or exogenous cAMP-dependent protein kinase results in stimulation of the initial rates of Ca2+ transport and Ca2+-ATPase activity. To determine the molecular mechanism by which protein kinase-dependent phosphorylation regulates the calcium pump in skeletal sarcoplasmic reticulum, we examined the effects of protein kinase on the individual steps of the Ca2+-ATPase reaction sequence. Skeletal sarcoplasmic reticulum vesicles were preincubated with cAMP and cAMP-dependent protein kinase in the presence (phosphorylated sarcoplasmic reticulum) and absence (control sarcoplasmic reticulum) of adenosine 5'-triphosphate (ATP). Control and phosphorylated sarcoplasmic reticulum were subsequently assayed for formation (5-100 ms) and decomposition (0-73 ms) of the acid-stable phosphorylated enzyme (E approximately P) of Ca2+-ATPase. Protein kinase mediated phosphorylation of skeletal sarcoplasmic reticulum resulted in pronounced stimulation of initial rates and levels of E approximately P in sarcoplasmic reticulum preincubated with either ethylene glycol bis(beta-aminoethyl ether)-N,N'-tetraacetic acid (EGTA) prior to assay (Ca2+-free sarcoplasmic reticulum), or with calcium/EGTA buffer (Ca2+-bound sarcoplasmic reticulum). These effects were evident within a wide range of ionized Ca2+. Phosphorylation of skeletal sarcoplasmic reticulum by protein kinase also increased the initial rate of E approximately P decomposition. These findings suggest that protein kinase-dependent phosphorylation of skeletal sarcoplasmic reticulum regulates several steps in the Ca2+-ATPase reaction sequence which result in an overall stimulation of the active calcium transport observed at steady state.