Dr. Veena Kalra*
Professor and Head of Pediatrics, All India Institute of Medical Sciences, New Delhi.
|A floppy child may represent a very wide and diverse etiological bag, and represents a failure in acquisition of normal tone, which is dependent on an intact spinal reflex pathway - intrafusal fibers, the afferent and efferent nerves and spinal neurons. It is influenced greatly by disorders at the central level, resulting in central hypotonia.
It is influenced greatly by disorders at the central level, resulting in central hypotonia
Acute and systemic illnesses, dysmetabolic states and severe illnesses can also reduce tone in an acute manner. A floppy child was a very poorly understood entity and included conditions like benign congenital hypotonia and essential hypotonia. Recent investigative technology and understanding there of has resulted in categorization of most etiologies into clearly defined groups. The initial step of Embarking on the protocol of approach to a floppy child requires exclusion of a central CNS cause. It is also fundamental to define whether the floppy infant is congenital paralytic or only floppy without significant motor weakness. This distinction is extremely useful for the clinicians to define the algorithm approach used to reach at the final diagnosis. Tone depends on the gestation, age of the child and all these factors may be considered in interpretation of a floppy infant. Central hypotonia may have tone disproportionate to weakness, dysmorphic features, abnormal fisting of hand, history of CNS insult preserved deep tendon reflexes and occasional scissoring on vertical suspension are important clues.
The initial step of Embarking on the protocol of approach to a floppy child requires exclusion of a central CNS cause. It is also fundamental to define whether the floppy infant is congenital paralytic or only floppy without significant motor weakness.
At the spinal level and beyond, the floppiness may have weakness, fasciculations, atrophy, deep tendon jerks are preserved in myopathy vs. neurogenic causes. Peripheral neuropathies may have specific distribution-distal involvement, associated sensory/autonomic features or systemic stigmata. Neuromuscular junction abnormality are often fluctuant with preserved DTRs. Muscle disorders have specific distribution of weakness, age of onset, pattern of progression, muscle atrophy, dystrophy or hypertrophy, an often genetic basis, DTRs preserved till late. The distribution of muscle weakness and the specific involvement of the face, eyes, pharyngeal muscle and respiratory muscles is extremely important to document. Specific syndromes have variable pattern of involvement and will be discussed.
In cohort of floppy infant after exclusion of central systemic causes, the most important causes include spinal muscular atrophy, congenital myopathy, congenital muscular dystrophies and myasthenia and metabolic myopathy. Acute flaccid paralysis and its causes need to be distinguished - parainfectious, autoimmune, toxins, etc.
In cohort of floppy infant after exclusion of central systemic causes, the most important causes include spinal muscular atrophy, congenital myopathy, congenital muscular dystrophies and myasthenia and metabolic myopathy.
Non-paralytic hypotonia may result from hypotonic, cerebral palsy, adverse neonatal events. Early presentation of metabolic disorders, connective tissue disorder, hypothyroidism nonketotic hyperglycinemia, and Down's syndrome are clinically very important causes of hypotonia to ascertain.
Early presentation of metabolic disorders, connective tissue disorder, hypothyroidism nonketotic hyperglycinemia, and Down's syndrome are clinically very important causes of hypotonia to ascertain.
The important laboratory algorithm for floppy baby includes:
- Sr. Creatine Kinase (raised in dysbolism myopathies)
- SMN/NAIP gene deletion
- Muscle Biopsy, etc.
Electrophysiology includes EMG to distinguish neurogenic from myogenic etiology in infants. This is a very difficult test to perform and occasionally erroneous. Nerve conduction velocity helps to confirm a neuropathic cause both inherited and acquired. In myogenic floppiness a properly performed muscle biopsy including H&E staining, immunocytochemistry, immunohistochemistry for muscle protein dystrophin, adhalin, sarcoglycans, merosin etc., and electron microscopy is extremely useful. If this entire gamut is not available, the test will only confirm a myopathy/dystrophy from neurogenic cause.
Spinal muscular atrophy the 2nd most common inherited autosomal recessive inherited disorder is the commonest neurogenic cause of floppy baby. It is easily distinguished by identification of deletion of exon 7, 8 of the SMN gene and NAIP gene. It therefore becomes one of the important first line tests in a patient suspected to have a neurogenic floppiness. Classification of the type of SMA (I-III) is important for management and introduction of therapy. Physiotherapy, occupational therapy, prevention of secondary damage, L-carnitine are some common measures.
Review of data at AIIMS revealed SMA to be the commonest cause of paralytic floppy baby followed by congenital muscle dystrophy and myopathy and peripheral neuropathies after central cause were excluded. Role of neuroimaging is important in identifying central causes and to evaluate the central white matter. It also helps to distinguish neuro degeneration syndromes, basal ganglia and other inherited disorders of metabolism. Plasma endo glycine estimation, lactate, NH3, art pH, urinary ketones, T4 6, TSH are basic screening procedures with karyotyping where necessary.
In conclusion, a proper clinical algorithm followed by investigations helps to identify the cause in almost 90% of floppy children.
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