A 1-month-old boy is brought to the emergency department by his mother due to fussiness and vomiting. Three days ago, the patient vomited after being laid down for a nap. The vomitus was not bloody or bilious. The mother thought the vomiting was due to gastroesophageal reflux and kept the infant upright after his next feedings. However, he continued to vomit several times a day and today has been difficult to console. Urine output remains normal. The patient was born at home via spontaneous vaginal delivery and is exclusively breastfed. He has received no vaccinations or medications. Temperature is 37.4 C (99.3 F). Vital sign measurement also reveals intermittent bradycardia and hypertension. The anterior fontanelle is bulging. Eye examination shows a persistent downward gaze bilaterally. Cardiac examination reveals no murmurs. Extremities appear normal. Head imaging is as shown: Which of the following is the most likely cause of this patient's presentation?

Question

A 1-month-old boy is brought to the emergency department by his mother due to fussiness and vomiting.  Three days ago, the patient vomited after being laid down for a nap.  The vomitus was not bloody or bilious.  The mother thought the vomiting was due to gastroesophageal reflux and kept the infant upright after his next feedings.  However, he continued to vomit several times a day and today has been difficult to console.  Urine output remains normal.  The patient was born at home via spontaneous vaginal delivery and is exclusively breastfed.  He has received no vaccinations or medications.  Temperature is 37.4 C (99.3 F).  Vital sign measurement also reveals intermittent bradycardia and hypertension.  The anterior fontanelle is bulging.  Eye examination shows a persistent downward gaze bilaterally.  Cardiac examination reveals no murmurs.  Extremities appear normal.  Head imaging is as shown:  Which of the following is the most likely cause of this patient's presentation?

Quizplus · Accepted Answer

11ec25c8_d5dd_74dc_bc81_55f96358c7ed_MD0003_00 This infant with no prior medical care likely has vitamin K deficiency bleeding (VKDB) causing intracranial hemorrhage and obstructive hydrocephalus. Vitamin K is an essential cofactor in the activation of coagulation factors II, VII, IX, and X; deficiency increases the risk of spontaneous bleeding. Newborns are vitamin K deficient due to poor placental transfer, absent gut flora to synthesize vitamin K, and immature liver function (ie, poor vitamin K use). Therefore, intramuscular vitamin K is administered at birth to prevent bleeding. Patients who do not receive vitamin K are at increased risk for VKDB, particularly if exclusively breastfed because breast milk has insufficient vitamin K. Classic VKDB presents in the first week of life with easy bruising and mucosal and gastrointestinal bleeding. Late-onset VKDB occurs between age 2 weeks and 6 months and is more commonly associated with intracranial hemorrhage, as seen in this patient; the layered, hyperdense fluid collection (red area) is located in the posterior ventricles on imaging due to supine positioning. The hemorrhage can block cerebrospinal fluid flow, leading to obstructive hydrocephalus, as seen by enlarged ventricles (blue outline), and signs of increased intracranial pressure (ICP) (eg, irritability, vomiting, bradycardia, hypertension). Infants with hydrocephalus typically have a bulging fontanelle and/or rapidly enlarging head circumference. Pressure on the midbrain may also cause upward gaze impairment (ie, persistent downward gaze). hydrocephalus (Choices A and B) Chiari II malformation and brain tumors (eg, glioblastoma) can cause obstructive hydrocephalus with increased ICP. However, Chiari II malformation is associated with myelomeningocele and inferior displacement of the medulla and cerebellum, neither of which is seen here. In addition, glioblastoma is exceedingly rare in infancy, and no mass is seen on imaging. Chiari II malformation (Choice C) Meningeal inflammation due to meningitis can cause obstructive hydrocephalus, a bulging fontanelle, and signs of increased ICP. This diagnosis is unlikely in an afebrile patient. (Choice D) Trisomy 13 can be associated with hydrocephalus but also with a constellation of other anomalies, including craniofacial abnormalities (eg, ear deformity, microphthalmia) and cardiac defects (eg, ventricular septal defect), none of which is seen here. Trisomy 13 Educational objective: Newborns who do not receive intramuscular vitamin K are at risk of vitamin K deficiency bleeding, which presents with easy bruising or bleeding, including intracranial hemorrhage (ICH). ICH can cause obstructive hydrocephalus, leading to a bulging fontanelle, upward gaze impairment, and signs of increased intracranial pressure (eg, irritability, vomiting, bradycardia, hypertension). References: Prevention of vitamin K deficiency bleeding in newborn infants: a position paper by the ESPGHAN committee on nutrition. (http://www.ncbi.nlm.nih.gov/pubmed/27050049) Vitamin K prophylaxis for prevention of vitamin K deficiency bleeding: a systematic review. (http://www.ncbi.nlm.nih.gov/pubmed/27109090)

A 1-Month-Old Boy Is Brought to the Emergency Department by His