Abstract
The most common cause of acquired hydrocephalus in infants is hemorrhage, most often as a consequence of prematurity. Other important causes include neoplasm and infection, usually bacterial meningitis. Hypoxic ischemic encephalopathy (HIE) in term infants usually results in secondary microcephaly. We report an infant with severe HIE at birth treated by therapeutic hypothermia who developed progressive acquired hydrocephalus over 2 months, although no cause of the hydrocephalus was identified. Although hydrocephalus, even intraventricular hemorrhage, is uncommon in term infants with HIE, careful follow-up of the head circumference is important, even if no findings indicating possible causes of hydrocephalus, such as hemorrhage, are detected on ultrasound or magnetic resonance imaging.
Introduction
Some term infants with hypoxic ischemic encephalopathy (HIE) develop secondary microcephaly [1]. Causes of pediatric acquired hydrocephalus include intraventricular hemorrhage (IVH) of prematurity, inflammation of the meninges or ventricles from infection, and brain tumors [2, 3]. Hydrocephalus is an uncommon consequence of HIE. Here, we present an infant with severe HIE at birth who developed acquired hydrocephalus beginning at 2 months of age that required a ventriculoperitoneal (V-P) shunt.
Case report
A 3450 g girl was delivered at 40 weeks of gestation by emergency cesarean section because of an abnormal fetal heart rate after five attempts at vacuum delivery. There were no complications during the pregnancy and no family history of neurological disease. Her Apgar score was 1 at 1 minute and 4 at 5 minutes. She was intubated 30 minutes after birth and admitted to our hospital. Hypotonia, abnormal reflexes, and an absent suck reflex were found. She had no major congenital abnormalities. Acidosis was found at admission, with a pH of 7.199 and arterial base excess of –13.9. Amplitude-integrated electroencephalography showed a burst suppression pattern with no clinical or subclinical seizures. Head ultrasound showed no ventricular dilation or hemorrhage. These findings met the criteria for therapeutic hypothermia and selective head cooling was started 3.5 hours after birth. No adverse events were recognized during the 72 hours of hypothermia. The mechanical ventilation was halted 9 days after birth. Brain magnetic resonance imaging (MRI) performed 11 days after birth showed white matter lesions and severe basal ganglia and thalamic lesions without IVH or ventricular dilation although a slight subdural hematoma in posterior fossa was noted (Fig. 1). A gastrostomy was planned to be performed before discharge because she could not take milk orally and aspiration pneumonia occurred repeatedly due to gastroesophageal reflux.
Brain MRI. Eleven days after birth, the T1-weighted axial images (A, B) show slight subdural hematoma in posterior fossa (arrowheads), and severe basal ganglia and thalamic lesions (arrows) with abnormal highlighting of bilateral cortex. T1-weighted sagittal (C) and T2*-weighted axial (D) images show no hemorrhagic lesions. At 138 days after birth, the T1-weighted axial (E, F) and T1-weighted sagittal (G) images show extreme dilation from the lateral ventricle to the fourth ventricle suggesting hydrocephalus with hyper-intense thalami (arrows), while no subdural hematoma is showed in posterior fossa. T2*-weighted axial image (H) shows no hemorrhagic lesions.
Her head circumference increased at 2 months of age and was 32.6, 35, 38, and 41 cm at 1, 2, 3, and 4 months of age, respectively (Fig. 2). Brain MRI performed 138 days after birth showed extreme dilation from the lateral to the fourth ventricle suggesting progressive hydrocephalus (Fig. 1). However, MRI did not suggest any causes of hydrocephalus, such as IVH or tumor. A V-P shunt was performed 158 days after birth because of progressive enlargement of the ventricle and head circumference. At shunt insertion, the cerebrospinal fluid (CSF) examination revealed an intracranial pressure of 9.56 mmHg, a cell count of 1 cell/mm. She was discharged from the hospital 205 days after birth, after a gastrostomy was performed; her head circumference was 44.7 cm at that time. At 1 year of age, severe neurological deficits were found.
Head circumference chart showing macrocephaly. Her head circumference increased at 2 months of age and continued to increase until 4 months of age, when a V–P shunt was performed.
Term infants with HIE generally develop microcephaly, rather than macrocephaly due to hydrocephalus. Secondary microcephaly was present in 48% of the term infants with HIE, but there were no cases of macrocephaly [1]. Hydrocephalus results from obstruction of the CSF flow anywhere from its origin to its most distal point of absorption, impaired absorption of CSF, or excessive production of CSF [4]. Classically, obstruction of the CSF flow within the ventricles is classified as obstructive or non-communicating hydrocephalus, whereas impaired absorption in the subarachnoid spaces is known as communicating hydrocephalus. The most common cause of acquired hydrocephalus in infants is IVH of prematurity. Other important causes include neoplasm and infection, usually bacterial meningitis [3]. In patients with a hemorrhage as a consequence of prematurity or infection, inflammation of the meninges or ventricles often leads to hydrocephalus via impaired CSF circulation and absorption. Mass lesions such as tumors can cause hydrocephalus by obstructing the CSF pathway [2]. In our patient, MRI did not show any lesions that might cause hydrocephalus in any sequence, including T2*-weighted images, which can detect small hemorrhages [5]. There was no sign of central nervous system infection and no obstructive lesions due to tumor.
Hydrocephalus can evolve over weeks in premature infants with a small IVH and is called subacute-chronic hydrocephalus. The mechanism might be related to either obliterative arachnoiditis in the posterior fossa or aqueduct obstruction caused by a blood clot, disruption of the ependyma, and reactive gliosis [6]. Four of 28 fetuses from pregnancies that were terminated because of hydrocephalus had evidence of cryptic microhemorrhages within a structurally normal aqueduct [7]. Intraventricular blood may also cause progressive ventricular dilatation, even in the absence of a clinically obvious hemorrhage. However, IVH is uncommon in term infants with HIE; only 7% of term infants with HIE were diagnosed with IVH [8], and three of 30 cases (10%) with IVH due to HIE were referred to the surgical ward because of hydrocephaly [9]. In all of these cases, the IVH was detected on head ultrasound or MRI.
Although the cause of the hydrocephalus in our patient was unknown and hydrocephalus in term infants with HIE is uncommon, inflammatory processes due to inflammation of the meninges or ventricles from a cryptic hemorrhage might have led to hydrocephalus through impaired CSF circulation and absorption. Follow-up of head circumference is important even if no hemorrhage is detected on ultrasound or MRI.
Conflict of interest
The authors report no conflicts of interest.