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Nusinersen (trade name: Spinraza) is the only approved drug to treat spinal muscular atrophy. It is a 2’-O-methoxyethyl, phosphorothioate modified antisense oligonucleotide targeting intronic splicing silencer N1 which is administered directly to the central nervous system using an intrathecal injection. Developed by Ionis Pharmaceuticals and licensed to Biogen, nusinersen was approved by FDA in December 2016, becoming the first approved pharmacological treatment for SMA. It was approved by the European Commission in centralised procedure in June 2017.
Since the underlying genetic cause of SMA was identified in 1995, several therapeutic approaches have been proposed and investigated that primarily focus on increasing the availability of SMN protein in motor neurons. The main research directions are as follows:
Since December 2016, autosomal recessive proximal spinal muscular atrophy can be treated with nusinersen. No cure is known to any of the remaining disorders of the spinal muscular atrophies group. The main objective there is to improve quality of life which can be measured using specific questionnaires. Supportive therapies are widely employed for patients who often also require comprehensive medical care involving multiple disciplines, including pulmonology, neurology, orthopedic surgery, critical care, and clinical nutrition. Various forms of physiotherapy and occupational therapy are frequently able to slow down the pace of nerve degeneration and muscle wasting. Patients also benefit greatly from the use of assistive technology.
A 2006 study followed 223 patients for a number of years. Of these, 15 died, with a median age of 65 years. The authors tentatively concluded that this is in line with a previously reported estimate of a shortened life expectancy of 10-15 years (12 in their data).
There is no cure for MMA. Treatment consists of muscle strengthening exercises and training in hand coordination. It has been proposed that the changes in this disease are from compression of the spinal cord in flexion due to forward shifting of the posterior dural sac. There have been treatments studies ranging from use of a cervical collar to anterior cervical fusion and posterior decompression.
In terms of the management of spinal and bulbar muscular atrophy, no cure is known and treatment is supportive. Rehabilitation to slow muscle weakness can prove positive, though the prognosis indicates some individuals will require the use of a wheelchair in later stages of life.
Surgery may achieve correction of the spine, and early surgical intervention should be done in cases where prolonged survival is expected. Preferred nonsurgical treatment occurs due to the high rate of repeated dislocation of the hip.
The importance of correctly recognizing progressive muscular atrophy as opposed to ALS is important for several reasons.
- 1) the prognosis is a little better. A recent study found the 5-year survival rate in PMA to be 33% (vs 20% in ALS) and the 10-year survival rate to be 12% (vs 6% in ALS).
- 2) Patients with PMA do not suffer from the cognitive change identified in certain groups of patients with MND.
- 3) Because PMA patients do not have UMN signs, they usually do not meet the "World Federation of Neurology El Escorial Research Criteria" for “Definite” or “Probable” ALS and so are ineligible to participate in the majority of clinical research trials such as drugs trials or brain scans.
- 4) Because of its rarity (even compared to ALS) and confusion about the condition, some insurance policies or local healthcare policies may not recognize PMA as being the life-changing illness that it is. In cases where being classified as being PMA rather than ALS is likely to restrict access to services, it may be preferable to be diagnosed as "slowly progressive ALS" or "lower motor neuron predominant" ALS.
An initial diagnosis of PMA could turn out to be slowly progressive ALS many years later, sometimes even decades after the initial diagnosis. The occurrence of upper motor neurone symptoms such as brisk reflexes, spasticity, or a Babinski sign would indicate a progression to ALS; the correct diagnosis is also occasionally made on autopsy.
In terms of treatment for neuromuscular diseases (NMD), "exercise" might be a way of managing them, as NMD individuals would gain muscle strength. In a study aimed at results of exercise, in muscular dystrophy and Charcot-Marie-Tooth disease, the later benefited while the former did not show benefit; therefore, it depends on the disease Other management routes for NMD should be based on medicinal and surgical procedures, again depending on the underlying cause.
The disease has only been identified as distinct from SMA recently, so research is still experimental, taking place mostly in animal models. Several therapy pathways have been devised which include gene therapy, whereby an "IGHMBP2" transgene is delivered to the cell using a viral vector; small-molecule drugs like growth factors (e.g., IGF-1 and VEGF) or olesoxime; and transplantation of healthy motor neurons grown "in vitro" from the patient's stem cells. Studies in amyotrophic lateral sclerosis are also considered helpful because the condition is relatively similar to SMARD1.
Spinal muscular atrophies (SMAs) are a genetically and clinically heterogeneous group of rare debilitating disorders characterised by the degeneration of lower motor neurons (neuronal cells situated in the anterior horn of the spinal cord) and subsequent atrophy (wasting) of various muscle groups in the body. While some SMAs lead to early infant death, other types permit normal adult life with only mild weakness.
Despite being rarer than ALS, PMA was described earlier, when in 1850 French neurologist François Aran () described 11 cases which he termed "atrophie musculaire progressive". Contemporary neurologist Guillaume-Benjamin-Amand Duchenne de Boulogne also claimed to have described the condition 1 year earlier, although the written report was never found. The condition has been called progressive muscular atrophy (PMA), spinal muscular atrophy (SMA), Aran–Duchenne disease, Duchenne–Aran disease, Aran–Duchenne muscular atrophy, and Duchenne–Aran muscular atrophy. The name "spinal muscular atrophy" is ambiguous as it refers to any of various spinal muscular atrophies, including the autosomal recessive spinal muscular atrophy caused by a genetic defect in the "SMN1" gene.
MMA mostly occurs in males between the ages of 15 and 25. Onset and progression are slow. MMA is seen most frequently in Asia, particularly in Japan and India; it is much less common in North America.
There is no known cure to DSMA1, and care is primarily supportive. Patients require respiratory support which may include non-invasive ventilation or tracheal intubation. The child may also undergo additional immunisations and offered antibiotics to prevent respiratory infections. Maintaining a healthy weight is also important. Patients are at risk of undernutrition and weight loss because of the increased energy spent for breathing. Physical and occupational therapy for the child can be very effective in maintaining muscle strength.
There is no published practice standard for the care in DSMA1, even though the Spinal Muscular Atrophy Standard of Care Committee has been trying to come to a consensus on the care standards for DSMA1 patients. The discrepancies in the practitioners’ knowledge, family resources, and differences in patient’s culture and/or residency have played a part in the outcome of the patient.
Because different types of myopathies are caused by many different pathways, there is no single treatment for myopathy. Treatments range from treatment of the symptoms to very specific cause-targeting treatments. Drug therapy, physical therapy, bracing for support, surgery, and massage are all current treatments for a variety of myopathies.
Muscle atrophy can be opposed by the signaling pathways which induce muscle hypertrophy, or an increase in muscle size. Therefore, one way in which not exercise induces an increase in muscle mass is to down regulate the pathways which have the opposite effect.
β-hydroxy β-methylbutyrate (HMB), a metabolite of leucine which is sold as a dietary supplement, has demonstrated efficacy in preventing the loss of muscle mass in several muscle wasting conditions in humans, particularly sarcopenia. A growing body of evidence supports the efficacy of HMB as a treatment for reducing, or even reversing, the loss of muscle mass, muscle function, and muscle strength in hypercatabolic disease states such as cancer cachexia; consequently, it is recommended that both the prevention and treatment of sarcopenia and muscle wasting in general include supplementation with HMB, regular resistance exercise, and consumption of a high-protein diet. Based upon a meta-analysis of seven randomized controlled trials that was published in 2015, HMB supplementation has efficacy as a treatment for preserving lean muscle mass in older adults. More research is needed to determine the precise effects of HMB on muscle strength and function in this age group.
Since the absence of muscle-building amino acids can contribute to muscle wasting (that which is torn down must be rebuilt with like material), amino acid therapy may be helpful for regenerating damaged or atrophied muscle tissue. The branched-chain amino acids or BCAAs (leucine, isoleucine, and valine) are critical to this process, in addition to lysine and other amino acids.
In severe cases of muscular atrophy, the use of an anabolic steroid such as methandrostenolone may be administered to patients as a potential treatment. A novel class of drugs, called SARM (selective androgen receptor modulators) are being investigated with promising results. They would have fewer side-effects, while still promoting muscle and bone tissue growth and regeneration. These claims are, however, yet to be confirmed in larger clinical trials.
One important rehabilitation tool for muscle atrophy includes the use of functional electrical stimulation to stimulate the muscles. This has seen a large amount of success in the rehabilitation of paraplegic patients.
Currently there is no cure for myotubular or centronuclear myopathies. Treatment often focuses on trying to maximize functional abilities and minimize medical complications, and involvement by physicians specializing in Physical Medicine and Rehabilitation, and by physical therapists and occupational therapists.
Medical management generally involves efforts to prevent pulmonary complications, since lung infections can be fatal in patients lacking the muscle strength necessary to clear secretions via coughing. Medical devices to assist with coughing help patients maintain clear airways, avoiding mucous plugs and avoiding the need for tracheostomy tubes.
Monitoring for scoliosis is also important, since weakness of the trunk muscles can lead to deviations in spinal alignment, with resultant compromise of respiratory function. Many patients with congenital myopathies may eventually require surgical treatment of scoliosis.
Berger, in 1876, first reported a case of 12-year-old child with progressive bulbar paralysis
The Food and Drug Administration is recommending that physicians restrict prescribing high-dose Simvastatin (Zocor, Merck) to patients, given an increased risk of muscle damage. The FDA drug safety communication stated that physicians should limit using the 80-mg dose unless the patient has already been taking the drug for 12 months and there is no evidence of myopathy.
"Simvastatin 80 mg should not be started in new patients, including patients already taking lower doses of the drug," the agency states.
Inactivity and starvation in mammals lead to atrophy of skeletal muscle, accompanied by a smaller number and size of the muscle cells as well as lower protein content. In humans, prolonged periods of immobilization, as in the cases of bed rest or astronauts flying in space, are known to result in muscle weakening and atrophy. Such consequences are also noted in small hibernating mammals like the golden-mantled ground squirrels and brown bats.
Bears are an exception to this rule; species in the family Ursidae are famous for their ability to survive unfavorable environmental conditions of low temperatures and limited nutrition availability during winter by means of hibernation. During that time, bears go through a series of physiological, morphological and behavioral changes. Their ability to maintain skeletal muscle number and size at time of disuse is of significant importance.
During hibernation, bears spend four to seven months of inactivity and anorexia without undergoing muscle atrophy and protein loss. There are a few known factors that contribute to the sustaining of muscle tissue. During the summer period, bears take advantage of the nutrition availability and accumulate muscle protein. The protein balance at time of dormancy is also maintained by lower levels of protein breakdown during the winter time. At times of immobility, muscle wasting in bears is also suppressed by a proteolytic inhibitor that is released in circulation. Another factor that contributes to the sustaining of muscle strength in hibernating bears is the occurrence of periodic voluntary contractions and involuntary contractions from shivering during torpor. The three to four daily episodes of muscle activity are responsible for the maintenance of muscle strength and responsiveness in bears during hibernation.
Fazio–Londe disease (FLD), also called progressive bulbar palsy of childhood, is a very rare inherited motor neuron disease of children and young adults and is characterized by progressive paralysis of muscles innervated by cranial nerves.
The overall incidence of myotubular myopathy is 1 in 50,000 male live births. The incidence of other centronuclear myopathies is extremely rare, with there only being nineteen families identified with CNM throughout the world. The symptoms currently range from the majority who only need to walk with aids, from a stick to a walking frame, to total dependence on physical mobility aids such as wheelchairs and stand aids, but this latter variety is so rare that only two cases are known to the CNM "community".
Approximately 80% of males with a diagnosis of myotubular myopathy by muscle biopsy will have a mutation in MTM1 identifiable by genetic sequence analysis.
Many patients with myotubular myopathy die in infancy prior to receiving a formal diagnosis. When possible, muscle biopsy and genetic testing may still be helpful even after a neonatal death, since the diagnostic information can assist with family planning and genetic counseling as well as aiding in the accurate diagnosis of any relatives who might also have the same genetic abnormality.
Congenital dSMA has a relatively stable disease course, with disability mainly attributed to increased contractures rather than loss of muscle strength. Individuals frequently use crutches, knee, ankle, and/or foot orthoses, or wheelchairs. Orthopaedic surgery can be an option for some patients with severely impaired movement. Physical therapy and occupational therapy can help prevent further contractures from occurring, though they do not reverse the effects of preexisting ones. Some literature suggests the use of electrical stimulation or botulinum toxin to halt the progression of contractures.
The treatment for post-polio syndrome is generally palliative and consists of rest, analgesia (pain relief) and utilisation of mechanisms to make life easier such as powered wheelchairs. There are no reversive therapies. Fatigue is usually the most disabling symptom; energy conservation can significantly reduce fatigue episodes. Such conservation can be achieved with lifestyle changes, reducing workload and daytime sleeping. Weight loss is also recommended if patients are obese. In some cases, the use of lower limb orthotics can reduce energy usage.
Medications for fatigue, such as amantadine and pyridostigmine, have not been found to be effective in the management of PPS. Muscle strength and endurance training are more important in managing the symptoms of PPS than the ability to perform long aerobic activity. Management should focus on treatments such as hydrotherapy and developing other routines that encourage strength but do not affect fatigue levels. The recent trend is towards use of intravenous immunoglobulin (IVIG) which has yielded promising, albeit modest results, but there is insufficient evidence to recommend it as a treatment.
PPS increases the stress on the musculoskeletal system due to increasing muscular atrophy. A recent study showed that in a review of 539 PPS patients, 80 percent reported pain in muscles and joints and 87 percent had fatigue. Joint instability can cause significant pain in individuals with PPS and should be adequately treated with painkillers. Supervised activity programs and decreasing mechanical stress with braces and adaptive equipment are recommended.
Because PPS can fatigue facial muscles, as well as cause dysphagia (difficulty swallowing), dysarthria (difficulty speaking) or aphonia (inability to produce speech), persons with PPS may become malnourished due to difficulty eating. Compensatory routines can help relieve these symptoms such as eating smaller portions at a time and sitting down whilst eating. PPS with respiratory involvement requires special management such as breathing exercises, chest percussion with a stethoscope on regular occasions for observation of the disease and management of secretions. Failure to properly assess PPS with respiratory involvement can increase the risk of missing aspiration pneumonia (an infection of the lower respiratory tract) in an individual. Severe cases may require permanent ventilation or tracheostomy. Sleep apnoea may also occur. Other management strategies that may lead to improvement include smoking cessation, treatment of other respiratory diseases and vaccination against respiratory infections such as influenza.
In terms of the management of congenital muscular dystrophy the American Academy of Neurology recommends that the individuals
need to have monitoring of cardiac function, respiratory, and gastrointestinal. Additionally it is believed that therapy in speech, orthopedic and physical areas, would improve the persons quality of life.
While there is currently no cure available, it is important to preserve muscle activity and any available correction of skeletal abnormalities (as scoliosis).Orthopedic procedures, like spinal fusion, maintains/increases the individuals prospect for more physical movement.
Neuromuscular disease is a very broad term that encompasses many diseases and ailments that impair the functioning of the muscles, either directly, being pathologies of the voluntary muscle, or indirectly, being pathologies of nerves or neuromuscular junctions.
Neuromuscular diseases are those that affect the muscles and/or their direct nervous system control, problems with central nervous control can cause either spasticity or some degree of paralysis (from both lower and upper motor neuron disorders), depending on the location and the nature of the problem. Some examples of central disorders include cerebrovascular accident, Parkinson's disease, multiple sclerosis, Huntington's disease and Creutzfeldt–Jakob disease. Spinal muscular atrophies are disorders of lower motor neuron while amyotrophic lateral sclerosis is a mixed upper and lower motor neuron condition.