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Management of SMA type 1

Management of SMA type 1. History Examination Investigation Treatment Prognosis. History & Examination Prenatal Hx – decreased fetal movement Neonatal Hx – asphyxia, kernicterus, IVH etc Hx of suspected aetiology Muscle bulk Tone Strength Distribution of weakness and muscle wasting

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Management of SMA type 1

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  1. Management of SMA type 1 • History • Examination • Investigation • Treatment • Prognosis

  2. History & Examination • Prenatal Hx – decreased fetal movement • Neonatal Hx – asphyxia, kernicterus, IVH etc • Hx of suspected aetiology • Muscle bulk • Tone • Strength • Distribution of weakness and muscle wasting • Proximal - Myopathy • Distal - Neuropathy • Myotonia is specific for a few myopathies

  3. Tendon stretch reflexes • Lost - in neuropathies and in motor neuron diseases • Diminished but preserved - in myopathy • Fasciculations of muscle – tongue • Present • Absent • Sensory abnormalities - neuropathy • Involvement of the face, tongue, palate, and extra ocular muscles

  4. Muscle pain or myalgias • Present - Acute disease of either myopathic or neurogenic origin. • Acute dermatomyositis • Acute polyneuropathy (Guillain-Barré syndrome) etc • Several metabolic diseases of muscle and in ischemic myopathy • Absent • Muscular dystrophies and spinal muscular atrophies • Contractures of muscles – at birth or developing later • Myopathic and neurogenic diseases.

  5. Descent of testes • Undescended - Gubernaculum is weakened • Spinal muscular atrophy • Myotonic muscular dystrophy • Many congenital myopathies. • Shape of thorax • funnel shape – IUGR • Infantile spinal muscular atrophy • Myotubular myopathy • Neonatal myotonic dystrophy etc

  6. Spinal Muscular Atrophies • Degenerative diseases of motor neurons • 2nd most common neuromuscular disease • Most cases are inherited as an autosomal recessive trait. Incidence of SMA is 10–15 per 100,000 live births • No racial predilection • Genetic locus for all 3 of the common forms of SMA is on chromosome 5

  7. Onset • In fetal life • Continue to be progressive in infancy and childhood • Upper motor neurons remain normal. • Classification based on clinical manifestations • Age at onset • Severity of weakness • Clinical course

  8. SMA type 1 - Werdnig-Hoffmann Dx • Severe infantile form • 25% of cases • SMA type 2 - Dubowitz disease • Late infantile and more slowly progressive form • 50% of cases • SMA type 3 - Kugelberg-Welander disease • More chronic or juvenile form • 25% of cases.

  9. SMA type O • Severe fetal form that is usually lethal in the perinatal period • Rare and accounts for <1%. • A variant of SMA - Fazio-Londe disease • Motor neuron degeneration more in the brainstem than the spinal cord. • Progressive bulbar palsy • Some patients are transitional between types 1 and 2 or between types 2 and 3 in terms of clinical function

  10. SMA type 1 – Werdnig-Hoffmann disease • Johann Hoffmann and Guido Werdnig • A genetic disorder • Inheritance is autosomal recessive • Results from destruction & degeneration of motor neurones in the spinal cord and the brain stem in utero following prolongation of the normal process of programmed cell death • It is the most severe form of SMA • Starts at birth or within 6 mo of age • Incidence is 0.4 per 1000 births.

  11. Clinical Features • Reduced foetal movements in utero • Infant is severely hypotonic at birth with a frog-like posture • Triad of symptoms • Severe hypotonia • Absent reflexes • Fasciculation - tongue & fingers • Severe weakness in a proximal > distal distribution is seen • Thin muscle mass

  12. Absent tendon stretch reflexes • Involvement of the tongue, face, and jaw muscles • Tongue fasciculation – diagnostic • Respiratory muscles are weak, and intercostal muscles are usually affected more than diaphragm, leading to paradoxical abdominal movement and pectus excavatum • Difficulty with swallowing & accumulation of secretions in the mouth because of weak masticatory and pharyngeal muscles • Inability to feed • Aspiration pneumonitis

  13. Congenital contractures • Simple clubfoot • Generalized arthrogryposis • 10% of severely involved neonates • Unable to overcome gravity • Neck control grossly delayed • Weak cry • Unusual delay in achieving developmental milestones • Infants usually not strong enough to sit or sit late

  14. No sphincteric or sensory impairment • Extra-ocular muscles are unaffected • Facial muscles are not weak • The alert state is not affected • Mental development is normal • Normal IQ • Children often appear brighter than their normal peers • Myalgias are not a feature of SMA. • The heart is not involved in SMA. • About 70% die either in early infancy or before the age of 2 yrs

  15. Investigation • Molecular Genetic Studies • Genetic marker in blood for the SMN gene • Simplest, Highly sensitive and specific • By DNA probes in blood samples or in muscle biopsy or chorionic villi tissues • Serum CK level • Isoenzymes • MM for skeletal muscle • MB for cardiac muscle • BB for brain • Normal • Mild elevation

  16. Nerve conduction velocity (NCV) • 80% of the total nerve fibers must be involved before slowing in conduction is detected. • Motor • Normal - usually • Mild slowing in terminal stages of the disease • Sensory may be slowed • Electromyography (EMG) • Shows fasciculations and fibrillations • Muscle Biopsy • Classic finding is grouped atrophy

  17. Treatment • No medical treatment delays the progression • Supportive therapy • Orthopedic care - scoliosis and joint contractures • Mild physiotherapy • Spine fusion • Respiratory care • Non-invasive ventilation • Tracheostomy • Nutritional care • Tube feeding

  18. Mechanical aids for assisting the child to eat and to be as functionally independent as possible • Respiratory depression is the most serious complication and the most common cause of mortality. • Aggressive and early respiratory toilet and treatment is required. • Most Type 1 patients will have severe respiratory compromise and may eventually mechanical ventilation

  19. Prognosis • Poor • Many Type 1 and Type 2 patients do not survive childhood without mechanical ventilation • Do not survive beyond 3yrs • 7months to 7yrs for milder forms

  20. Pull to Sit

  21. Scalf sign

  22. Shoulder suspension

  23. Ventral suspension

  24. Conclusion

  25. References • Asindi AA. Muscular dystrophies and the floppy infant. In: Azubuike JC, Nkanginieme KEO, ed(s). Paediatrics and child health in the tropics. Owerri: African Educational services; 2004. p. 520-4 • Sarnat HB. Neuromuscular Disorders. In: Kleigman RM, Behrman RE, Jenson HB, Stanton BF, ed(s). Nelson textbook of Pediatrics. Philadelphia: WB Saunder Company; 2008. p. • Bodensteiner JB. The evaluation of hypotonic infant. Semin Paediatr Neurol 2008; 15:10-20

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