ABNORMAL MOVEMENTS IN AN 8-DAY-OLD BABY
History
Andrew is an 8-day-old infant referred to the paediatric day unit by the midwife. She and the parents report at least six brief (approximately 30 s) episodes of rhythmical shaking of all four limbs associated with abnormal tongue and eye movements. These do not seem to be related to feeds or sleep, nor do they seem to be causing him any distress. Andrew is breast-fed and has regained his birth weight. He was born at term following an uneventful pregnancy to healthy unrelated parents. The delivery was straightforward and Andrew was in good condition at birth. They were discharged home 6 hours after he was born. He is their second baby.
Examination
Andrew looks well. His weight, length and head circumference are all between the 25th and 50th centiles. There are no dysmorphic features. He is afebrile and his pulse is 130 beats/min. Both heart sounds are normal, there are no murmurs and femoral pulses are palpable. Examination of the respiratory and abdominal systems is unremarkable and he has normal male genitalia. His anterior fontanelle is soft. He handles well with normal tone and primitive reflexes. However, during the examination he has two episodes similar to those described by the midwife; both are self-limiting and are accompanied by cyanosis and a change in his cry.
INVESTIGATIONS
Normal
Haemoglobin 16.4 g/dL 14.5–22.5 g/dL
White cell count 8.4 109/L 6.0 17.5 109/L
Platelets 365 109/L 150–400 109/L
Sodium 138 mmol/L 138–146 mmol/L
Potassium 4.5 mmol/L 3.5–5.0 mol/L
Urea 4.2 mmol/L 1.8–6.4 mol/L
Creatinine 46 µmol/L 27–62 µmol/L
C-reactive protein 6 g/L 6 mg/L
Calcium 1.50 mmol/L 2.2–2.7 mmol/L
Phosphate 3.6 mmol/L 1.25–2.10 mmol/L
Alkaline phosphatase (ALP) 305 IU/L 145–420 IU/L
Alanine aminotransferase 28 IU/L 5–45 IU/L
Glucose 4.6 mmol/L 3.3–5.5 mol/L
Questions • Having witnessed the events during the examination, what should be the immediate management prior to the blood test results? • Following the blood test results, what further investigations would you request?
Medicine
Andrew is having seizures. Remember these are a symptom, not a diagnosis, and the causes are numerous. The approach to a fitting child is:
1. Give high-flow oxygen, place on a cardiac monitor.
2. Obtain intravenous access. Send relevant tests, starting with the basic and common.
3. Treat immediately what can be treated. Check blood glucose and treat hypoglycaemia after taking specimens to identify a cause. Start intravenous broad-spectrum antibiotics, e.g. benzylpenicillin and gentamicin – although sepsis is unlikely, it is a possibility that needs to be treated. 4. Control the seizures with appropriate anticonvulsants. In neonates this is usually a loading dose of phenobarbital, followed, if necessary, by maintenance. The results show that Andrew has significant hypocalcaemia, low enough to cause seizures. It is likely to be real because the phosphate is high but, as with all unusual results, it should be repeated. If confirmed, the hypocalcaemia should be treated with intravenous calcium but only after taking samples to investigate the cause. It is crucial not to lose this opportunity to make a diagnosis because endocrine and metabolic pathways correct very rapidly.
Causes of hypocalcaemia in infancy
• Prematurity
• Hypoxic ischaemic encephalopathy (HIE)
• Hypoparathyroidism – transient (associated with prematurity, HIE or maternal diabetes) or permanent
• Hypomagnesaemia – magnesium facilitates release of parathormone (PTH)
• Exchange transfusion – citrate in transfused blood chelates calcium to prevent clotting
• Familial activating mutations of the calcium-sensing receptor – the calcium level at which PTH is released is lower than normal; some cases labelled as ‘familial hypoparathyroidism’ are probably this disorder
• Maternal hypercalcaemia – suppresses fetal PTH
• Maternal vitamin D deficiency
• In older children, vitamin D deficiency is the commonest cause, but the ALP would be high due to the increased bone turnover in rickets (see Case 22, p. 66).
Most of these can be excluded from the history. The next tests to send are magnesium, parathyroid hormone (PTH), vitamin D and maternal bone biochemistry. However, the high phosphate (PTH is phosphaturic) and normal ALP suggest hypoparathyroidism. The causes of permanent hypoparathyroidism that present in the neonatal period include DiGeorge syndrome – a disorder associated with microdeletions of chromosome 22q11.2, congenital heart disease and thymic aplasia. PTH is not available therapeutically so treatment of hypoparathyoidism is with vitamin D, but this does not stop the renal loss of calcium that PTH normally prevents. To minimize the risk of nephrocalcinosis, calcium is maintained at low normal or mildly subnormal levels and the urinary calcium/ creatinine ratio is monitored.
All children with neonatal seizures of any cause are at risk of developmental problems and need surveillance.
KEY POINTS
• In any case of hypocalcaemia or hypoglycaemia, relevant samples should be taken before treatment to maximize the opportunity of making a definitive diagnosis.
• Children with neonatal seizures of any cause are at risk of developmental problems and need surveillance.
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