Diagnosis?
Figure 182-1 Evaluation of an infant with hypotonia. cDM1, Congenital myotonic dystrophy; CK, creatine kinase; CMS, chromosomal microarray analysis; EMG, electromyelogram; MRI, magnetic resonance imaging; NCV, nerve conduction velocity; PWS, Prader-Willi syndrome; SMA, spinal muscular atrophy. (Courtesy James Dowling, MD.) heads flop, they slip through at the shoulders, do not supportweight on their legs, and form an inverted U in prone suspension (Landau posture). When placed prone as neonates,they may lie flat instead of keeping their arms and legs flexed.Passive tone is decreased, but reflexes are normal. Hypotonia may be associated with significant cerebral disease or maybe a benign phenomenon that is outgrown (Table 182-4). The most common cause of hypotonia is hypoxic-ischemic encephalopathy.
Prader-Willi syndrome (PWS) presents with severe neonatal hypotonia; severe feeding problems leading to failure to thrive; small hands and feet; and, in boys, a small penis, small testicles, and cryptorchidism. Severe hyperphagia and obesity develop in early childhood. Approximately 60% to 70% of affected individuals have an interstitial deletion of paternalchromosome 15q11q13. PWS and trisomy 21 are the most common genetic causes of neonatal hypotonia.
Infants who have a connective tissue disorder, such as Ehlers-Danlos syndrome, Marfan syndrome, or familial laxity of the ligaments, may exhibit marked passive hypotonia, ligamentous laxity, and increased skin elasticity. They have normal strength and cognition and achieve motor and mental milestones normally. They may have peculiar postures of their feet or unusual gaits.
Infants with benign congenital hypotonia typically exhibit the condition at 6 to 12 months old with delayed gross motor skills. They are unable to sit, creep, or crawl, but have good verbal, social, and manipulative skills. Strength appears normal, and the infants can kick arms and legs briskly and bring their toes to their mouths. The children often display head lag, slip-through in ventral suspension, and floppiness of passive tone. The infant seems floppy from birth. The differential diagnosis includes upper and motor neuron disorders and connective tissue diseases. Extensive laboratory investigation is often unrevealing. Most of these children catch up to peers and
Severe brain illness* Structural (hydrocephalus) Infectious Metabolic (e.g., anoxia or hypoglycemia) Intoxication through mother
Connective tissue disorder Ehlers-Danlos syndrome Marfan syndrome Congenital laxity of ligaments *Common.
appear normal by 3 years of age. Often, other family members have exhibited a similar developmental pattern.
The incidence of pediatric stroke is 2.5 to 10 per 100,000 children and is higher among neonates, approaching that of elderly patients. A wide spectrum of conditions can produce stroke in childhood (Table 182-5). Pediatric strokes may be due to ischemia (arterial ischemic stroke, cerebral sinovenous thrombosis) or hemorrhage. Arterial ischemic stroke (AIS)is focal brain infarction that results from occlusion of the arteries in the brain. The most common causes are vasculitis resulting in abnormal cerebral arteries (either autoimmune or infectious, such as vasculitis associated with meningitis) and cardioembolic infarcts due to congenital heart disease, sickle cell anemia, or coagulation disorders. Coagulation disorders also increase the risk of cerebral sinovenous thrombosis (CSVT), the occlusion of venous structures in the brain, which can result in ischemia as the cerebral venous pressure rises.