Macrocephaly, Increased Intracranial Pressure, and Hydrocephalus in the Infant and Young Child Alexandra T
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ORIGINAL ARTICLE Macrocephaly, Increased Intracranial Pressure, and Hydrocephalus in the Infant and Young Child Alexandra T. Vertinsky, MD and Patrick D. Barnes, MD megalencephaly is often associated with developmental Abstract: Macrocephaly, increased intracranial pressure, and delay, seizures, a neurocutaneous syndrome (eg, neurofibro- hydrocephalus are common related conditions that lead to cross- matosis), a genetic syndrome (eg, Soto syndrome), hemi- sectional imaging of the infant and young child. Imaging plays a megalencephaly (Fig. 1), or elevated venous pressure (eg, central role in establishing the diagnosis and guiding disposition and achondroplasia) (Fig. 2). Macrocephaly from Brebound[ or treatment of these patients. In this review, a general overview is Bcatch-up[ brain growth occurs in the thriving infant after provided, and the more common causes of hydrocephalus are prematurity or after a period of deprivation or serious illness. presented, including posthemorrhage, postinfection, developmental Familial, dysplastic, and rebound types of MC may manifest malformations, and masses. Imaging guidelines are also outlined for mild to moderate degrees of ventricular or subarachnoid initial evaluation and follow-up, along with a discussion of the space dilatation.3Y5 imaging features of shunt malfunction. MC and accelerated head growth without elevated Key Words: macrocephaly, hydrocephalus, pediatric, MRI pressure and with normal neurological exam may occur as nonprogressive subarachnoid space dilatation with or without Y (Top Magn Reson Imaging 2007;18:31 51) ventricular enlargement. This pattern is most commonly referred to as BECC, but has also been termed as Bbenign acrocephaly (MC), increased intracranial pressure enlargement of the subarachnoid spaces,[Bbenign infantile M(ICP), and hydrocephalus (HC) are common related HC,[ and Bbenign external HC.[1,3Y7 The cause is unknown, conditions that lead to cross-sectional imaging of the infant but it may be related to delayed development of parasagittal and young child. Imaging plays a central role in establishing dural channels responsible for cerebrospinal fluid (CSF) the diagnosis and guiding disposition and treatment of these resorption in young children (who have few arachnoid villi). patients. In this review, a general overview is provided, and Accelerated head growth may continue until 12 to 18 months the more common causes of HC are presented, including of age and then usually stabilizes as a form of megalence- posthemorrhage, postinfection, developmental malforma- phaly. Imaging features of BECC include normal to mildly tions, and masses (Tables 1, 2). Imaging guidelines are also enlarged lateral and third ventricles and symmetric enlarge- outlined for initial evaluation and follow-up, along with a ment of the frontal subarachnoid spaces, interhemispheric discussion of the imaging features of shunt malfunction. fissure, and Sylvian fissures (Fig. 3).4 These extracerebral collections must be differentiated from subdural collections. MACROCEPHALY On magnetic resonance imaging (MRI), the visualization of 2 Macrocephaly is defined as a head circumference more layers of differing signal intensity or of abnormal signal than 2 SD above the mean. Common causes of MC include intensity related to blood products, rather than CSF, is helpful 5 familial megalencephaly (larger-than-normal brain mass), to identify subdural collections (Fig. 4). The presence of benign extracerebral collections of infancy (BECC) and HC. bridging cortical draining veins extending through an extra- Macrocephaly without HC may also be seen in some genetic, axial collection is supportive of, but not specific for, the 7 metabolic, and dysplastic syndromes, or may be caused by subarachnoid space. Infants with BECC may be at increased tumors and cysts, pseudotumor cerebri, or subdural collec- risk of subdural hematoma, spontaneously or from minor 6,8 tions (eg, hematomas, hygromas).1 Evaluation of head growth trauma, resulting from the stretching of cortical veins. rate (ie, serial head circumferences) along with assessment of MC with accelerated head growth due to progressive HC developmental milestones, perinatal history, and signs of ICP is usually associated with signs of ICP and often with declining is important for differential diagnosis, urgency of imaging, milestones. The exception may be an infant or child with and radiological interpretation.2 preexisting brain injury such as the premature infant with HC Macrocephaly with normal growth rate and normal from intraventricular hemorrhage and coexistent periventricular neurological examination is reassuring and is characteristic of leukomalacia (PVL). Other causes of MC with megalencephaly, benign megalencephaly, which is usually familial. Dysplastic hydrocephaly, or craniomegaly (enlarged calvarium) include lipid storage disease, leukodystrophies, cranial dysplasias, and marrow hyperplasia secondary to chronic hemolytic anemia. From the Stanford University Medical Center, Stanford, CA. Reprints: Patrick D. Barnes, MD, Departments of Radiology, Pediatric MRI and CT, Room 0511, Lucille Packard Children_s Hospital, 725 Welch INCREASED ICP Road, Palo Alto, CA 94304 (e-mail: [email protected]). Symptoms and signs of ICP, depending on age, include Copyright * 2007 by Lippincott Williams & Wilkins MC, accelerating head circumference, full or bulging Top Magn Reson Imaging & Volume 18, Number 1, February 2007 31 Copyright @ Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. Vertinsky and Barnes Top Magn Reson Imaging & Volume 18, Number 1, February 2007 TABLE 1. Overview of Clinical Presentations fontanelle, split sutures, poor feeding, vomiting, irritability, vision impairment, headache, lethargy, stupor, encephalo- pathy, Parinaud syndrome, sixth nerve palsy, hypertonia with hyperreflexia, and papilledema.9,10 The causes of ICP include trauma, hemorrhage, acute hypoxic-ischemic insult, infection, parainfectious sequela, metabolic derange- ment, HC, tumors, pseudotumor cerebri, and universal FIGURE 1. Hemimegalencephaly with macrocephaly and craniosynostosis.9Y16 Imaging is indicated to define a mass, epilepsy. Prenatal US showed ventriculomegaly. Axial fluid collection, edema, or HC. The mass may be a cyst, noncontrast CT at 2 days of life shows enlarged right cerebral neoplasm, abscess, or hematoma. The abnormal fluid collec- hemisphere with a large dysplastic right lateral ventricle and tion may be subdural or epidural, whether a hematoma, thickened cortex (A). Axial T2 images (B, C) and coronal short T inversion recovery (D) demonstrate enlargement of the right empyema, effusion, or hygroma. Edema may be traumatic hemisphere and lateral ventricle, prominent trigone (white (Fig. 5), hypoxic-ischemic (Fig. 6), toxic (eg, lead poisoning), arrow) and occipital horn, and thickened gyri. metabolic (eg, ketoacidosis), infectious (meningitis or ence- phalitis), parainfectious (acute disseminated encephalomye- litis, Reye syndrome), or due to pseudotumor. to CSF overproduction is very rare but may occur with choroid plexus papilloma (CPP) or villus hypertrophy. HYDROCEPHALUS Hydrocephalus due to CSF flow block or absorptive block B [ A common cause of MC and ICP in childhood is HC. may be described as communicating when the block occurs Hydrocephalus is the state of excessive CSF volume with outside the ventricular system (eg, basal cisterns or para- B [ progressive enlargement of the ventricles, subarachnoid sagittal arachnoid villi) and noncommunicating when there 17Y20 is intraventricular obstruction (at or proximal to the fourth spaces, or both. Hydrocephalus may be caused by an 9,18 imbalance between CSF production and absorption, by a ventricular outlets). blockage of CSF flow, or from alterations in ventricular Most childhood HC occurs in infancy (Table 3). The compliance and CSF pulse pressure.17,20 Hydrocephalus due most common cause is acquired adhesive ependymitis or arachnoiditis after hemorrhage or infection.9,17,18 Hydroce- phalus is a well-known sequela of neonatal intracranial hemorrhage especially in the preterm (PT).16 Prenatal or TABLE 2. Macrocephaly, ICP, and HC postnatal infection may also lead to HC.11,12 By far the most common developmental cause of HC is the Chiari II malformation associated with myelocele/myelomeningocele (MMC). The HC often develops, or progresses, after repair of the spinal defect.9,21 Other common developmental causes include aqueductal anomalies (forking, stenosis, septation, gliosis) and the Dandy-Walker-Blake spectrum of retro- cerebellar cysts.22 Less common or rare causes of HC include 32 * 2007 Lippincott Williams & Wilkins Copyright @ Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. Top Magn Reson Imaging & Volume 18, Number 1, February 2007 Macrocephaly, ICP, and HC from HC in infants and young children. Periventricular edema due to transependymal CSF flow or hydrostatic stasis from elevated intraventricular pressure may be evident as blurred or ill-defined ventricular margins. This finding favors acute/ subacute or progressive HC (Figs. 10, 11). However, the normally high water content of the immature white matter may obscure edema due to HC in the infant.6,9,24Y26 Hydrocephalus in the fetus and infant is often diagnosed with US or CT initially.9,27 Doppler US using the graded fontanelle compression technique may be used to identify infants with ventriculomegaly and ICP, and help determine the need and timing for shunting.28 Magnetic