FLOPPY INFANT
The term Floppy infant or child denotes a ‘baby with generalized hypotonia', irrespective of the etiology.
Clinically: These cases characteristically present with bizarre or unusual postures, increased range of passive joint movements, paucity of spontaneous movements and delayed motor milestones.
Newborns who are hypotonic in utero may be born with hip dislocation, arthrogryposis or both. In addition, many of these infants have poor sucking, swallowing and breathing difficulties suggestive of facial or bulbar muscle involvement.Mothers of the newborns with hypotonia may perceive reduced or delayed fetal movements and may have associated polyhydramnios.
Important signs of floppiness include:
• Postural abnormalities, e.g. (i) frog-like posture in vertical suspension, (ii) head lag in pull-to-sit maneuver, and
TABLE 18.42: Causes of floppy infant/child
• Cerebral disorders
- Perinatal hypoxic-ischemic brain injury
- Chromosomal: Down syndrome
- Atonic cerebral palsy
- IEMs: Mucopolysaccharidosis, cerebral lipidosis
• Spinal disorders
- Spinal muscular atrophy (Werdnig-Hoffmann disease)
- Poliomyelitis
• Peripheral neuropathies
- Guillain-Barre syndrome
- HMSN, e.g. Charcot-Marie-Tooth disease
- Familial dysautonomia (Riley-Day syndrome)
- Toxic: diphtheria, lead poisoning, drugs
- Metabolic: Thiamine deficiency, IEMs
• Disorders of myoneural junction
- Myasthenia gravis
- Toxins: Botulism, organophosphorus poisoning
• Disorders of muscles
- Muscular dystrophies, e.g. DMD, others
- Congenital myopathies or benign congenital hypotonia
- Metabolic: GSDs, carnitine deficiency
- Endocrinal: Hypothyroidism
• Miscellaneous
- Prematurity
- Nutritional: Rickets, PEM
- Collagen disorders: Ehlers-Danlos syndrome
IEM: Inborn errors of metabolism, HMSN: Hereditary motor sensory neuropathies, DMD: Duchenne muscular dystrophy, GSD: Glycogen storage disorders
(iii) Rag-doll appearance on ventral suspension, due to head lag, marked curving of back and limp limbs.
• Lack of passive tone, e.g. (i) flabby muscles on palpation, and (ii) excessive range of passive movements, e.g. wide popliteal angle or heel-to-ear maneuver.
• Lack of active tone, e.g. poor arm/leg recoil. d. Paucity of spontaneous movements.
Etiology: Generalized hypotonia usually indicate peripheral neuromuscular disorders, though some cases have cerebral hypotonia or idiopathic origin (Table 18.42).
Diagnostic approach in a floppy child involves:
• Clinical localization, specially differentiation between neuropathies and myopathies (see Table 18.37).
- Cerebral hypotonia is typically static and associated with brisk reflexes. Facial dysmorphism, mental retardation and congenital anomalies are common, suggestive of possible chromosomal defects.
- Spinal or anterior horn cell disorders, e.g. spinal muscular atrophy (SMA) are commonest cause of floppy infant, characterized by: (a) symmetric weakness with hypotonia, sparing extra-ocular muscles and sphincters, (b) muscle fasciculations, specially over tongue, (c) absent tendon jerks, and (d) normal intellect and alert child (Ch 18.18.1).
- Peripheral neuropathies, e.g. GBS are usually acquired and present after infancy with: (a) predominantly distal weakness, (b) marked atrophy, and (c) absent deep reflexes. Sensory involvement is common. (Ch 18.18.2)
- Myopathies, e.g. DMD are generally characterized by—(a) predominantly proximal weakness, (b) pseudohypertrophy with advancing age, and (c) depressed but present deep reflexes. Myotonia, i.e. slow release of grip, may be present in some myopathies. (Ch 18.18.4)
- Neuromuscular junction disorders, e.g. myasthenia presents with—(a) predominant facial weakness with ptosis, ophthalmoplegia and bulbar weakness, (b) diurnal variation in weakness, and (c) increasing weakness on repetitive activity, e.g. gripping/ ungripping of objects. (Ch 18.18.3)
• Specific investigation depends on the probable cause. While CPK estimation, NCS and EMG is indicated in most cases, karyotyping for chromosomal disorders, e.g.
Down syndrome, thyroid function tests for hypothyroidism, edrophonium test for myasthenia gravis, and biochemical enzyme studies for inborn errors of metabolism are necessary in selected cases.Cardiac evaluation with ECG is important in suspected myopathies for early diagnosis of associated cardiomyopathies and conduction defects.
18.20 DISORDERS OF AUTONOMIC SYSTEM
Autonomic nervous system (ANS) is mainly concerned with innervation of unstriated muscles in internal viscera and secretory glands. Although isolated ANS disorders are extremely rare in childhood, ANS disturbances are commonly seen in many neurological and metabolic disorders, poisonings and during drug therapy.
ANS includes two anatomically different and physiologically antagonistic components: (a) sympathetic system, and (b) parasympathetic system. Anatomically, both components include: (a) pre-ganglionic neurons, (b) ganglions, and (c) post-ganglionic neurons, though other characters are markedly different in two systems (Table 18.43).
While ANS involvement is common in many disorders, familial dysautonomia or Riley-Day syndrome is the commonest primary autonomic neuropathy, discussed here.
Riley-Day syndrome (familial dysautonomia) is an autosomal recessive disorder, especially in jews, characterized by sensory and autonomic neuropathy.
Clinical manifestations begin in infancy with feeding difficulties and recurrent aspirations, though more definitive features develop by 2-3 years, including:
• Autonomic crises, i.e. recurrent episodes of cyclic vomiting, hypertension, profuse sweating, skin blotching, temperature fluctuations and irritability, each lasting for few days.
TABLE 18.43: Important differences between sympathetic and parasympathetic ANS
| Sympathetic | Parasympathetic | |
| Anatomical Features | ||
| Pre-ganglionic outflow’ | Thoraco-lumbar | Cranio-sacral |
| Location of ganglions | Paravertebral | Near innervated viscera |
| Post-ganglionic innervation | Visceral | Visceral |
| Neurotransmitter | Adrenergic* | Cholinergic |
| Physiological effects | ||
| Pupil | Dilatation | Constriction |
| Heart rate | Tachycardia | Bradycardia |
| Peripheral vessels | Vasoconstriction | Vasodilatation |
| Blood pressure | Increases | Decreases |
| Bronchi | Relaxation | Constriction |
| Bowels | Constipation | Diarrhea |
| Bladder | Retention | Evacuation |
| Metabolic | Hyperglycemia | Hypoglycemia |
| Skin/mucus membranes | Pili erection, sweating | Lacrimation, salivation |
*except for sweat glands
#Preganglionic outflow from spinal cord is mainly thoracolumbar (from T1-L1) for sympathatic system and craniocaudal (along the cranial nerves III, VII, IX, X and from sacral S2.3) for parasympathatic system.
• Sensory ataxia and insensitivity to pain, with trophic and corneal ulcers.
• Seizures in ~ 40% cases.
Diagnosis is clinical, though positive methacholine challenge test, i.e. miosis after 10-20 minutes of conjunctival instillation of 2.5% methacholine, may be used to support the diagnosis.
Treatment is symptomatic and supportive with topical eye lubricants, anti-emetics, (e.g. chlorpromazine), prevention of injuries to anesthetized parts and vital system support. IV immunoglobulins have shown promising results in severe cases.
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