A 6-month-old boy and his parents present to the pediatrician for routine evaluation. The boy’s father notes that the veins on his son’s head have become increasingly prominent over the last two months. The patient has also been more irritable than normal over the same time period. The patient was born at full term, has not had any health complications to date, and is up to date on his vaccines. Physical examination is significant for a bulging anterior fontanelle and paresis of upward gaze of both eyes, making the eyes appear to be driven downward. Review of the boy’s growth charts indicate a head circumference at the 85th percentile, up from 40th percentile two months ago.
Which of the following is the most appropriate next step in evaluation of this patient?
D) Ultrasonography of the head
Rapidly increasing head circumference should raise suspicion for hydrocephalus, which is the accumulation of cerebrospinal fluid (CSF) due to abnormal reabsorption (communicating) or obstruction of flow (noncommunicating). Ultrasound or ultrafast MRI is the preferred initial imaging method, as it avoids unnecessary radiation. In addition to increasing head circumference, hydrocephalus can present with a “setting-sun” phenomenon of the eyes sign due to upward gaze paresis. Cushing’s triad (hypertension, bradycardia, and irregular respirations) may also be present.
Answer choice A: Computed tomography of the head, is incorrect. CT head would be appropriate in the acute settings of hemorrhage or trauma. This child’s presentation is not acute, so unnecessary radiation exposure should be avoided.
Answer choice B: Lumbar puncture, is incorrect. Although meningitis can result in a bulging fontanelle, the child would more likely present acutely with fever, vomiting, and/or seizures. Recall that if bacterial meningitis is suspected, treatment with vancomycin, ceftriaxone, and dexamethasone should be initiated without delay.
Answer choice C: Thyroid stimulating hormone level, is incorrect. Although hypothyroidism can result in large fontanelles, this is most often picked up on newborn screens, with symptoms of lethargy, constipation, hypotonia, and hypothermia developing by 2 weeks.
Answer choice E: Vitamin D level, is incorrect. Vitamin D deficiency can cause delayed fontanelle closure as well as wrist and ankle widening, genu varum/valgum, and frontal bossing. However, this child’s rapid increase in head circumference raises suspicion for other etiologies.
Key Learning Point
Rapidly increasing head circumference should raise suspicion for hydrocephalus and should prompt imaging with minimal radiation exposure (ultrasound or MRI).
