Authors: Flaherty, Alice W.; Rost, Natalia S.
Title: Massachusetts General Hospital Handbook of Neurology, The, 2nd Edition
Copyright 2007 Lippincott Williams & Wilkins
> Table of Contents > Child Neurology > Head Circumference Disorders
Head Circumference Disorders
A. H&P
Maternal history (toxins, infections, hypoxia), family head sizes. Get pt's prior head sizes. Rule of thumb for normal growth rate is premature infants: 1 cm/wk; 1-3 mo: 2 cm/mo; 3-6 mo: 1 cm/mo; 6-12 mo: 0.5 cm/mo.
Ophthalmoscopic exam: Look for papilledema, retinal bleed.
Head shape: Frontal bossing suggests hydrocephalus; lateral bulging suggests SDH.
Fontanelles: Posterior and sphenoid fontanelles closes by 2-3 mo, mastoid fontanelle by 1 yr, anterior fontanelle by 1.5-2.5 years.
Head circumference: Largest measurement around forehead and occiput excluding ears. For a normal baby, it is approximately the crown-rump length. Abnormal = more than 2 SD above mean, circumference out of proportion to height and weight, or upward deviation of growth curve over time (crossing curves).
B. Tests
CT, MRI, or ultrasound. Genetic and metabolic evaluation if microcephaly.
C. Causes of microcephaly
Genetic, intrauterine infections (CMV, toxoplasmosis, rubella), toxins (alcohol, ACDs), asphyxia, metabolic disorders, radiation (especially 4-20 wk gestation).
D. Causes of macrocephaly
Hydrocephalus, SDH, hydranencephaly, megalencephaly.
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Figure 15. Head circumference, girls. (Reproduced with permission from Neilhaus G. Pediatrics. 1968;41:106.) |
Figure 16. Head circumference, boys. (Reproduced with permission from Neilhaus G. Pediatrics. 1968;41:106.) |
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Figure 17. Fetal and infant head circumference, weight, and length. (From Babson SG, Benda GI. J Pediatrics. 1976;89:814.) |
E. Craniosynostosis
H&P: Deformed skull, firm pressure on either side of affected suture fails to cause movement. Look for other facial or body dysmorphisms; developmental delay.
Causes: Premature fusion of sutures, failure of brain growth. Little evidence that it can be caused by shunting for hydrocephalus.
Sagittal synostosis: Most common type, has long, boat-shaped skull with keel-like ridge.
Coronal synostosis: If unilateral, affected forehead is flat or concave, and normal eye falsely appears to bulge. Can cause amblyopia.
Crouzon's syndrome: Coronal synostosis plus midface hypoplasia. Hydrocephalus is rare.
Apert's syndrome: Coronal synostosis plus syndactyly. Hydrocephalus is common.
Metopic synostosis: Pointed forehead with midline ridge. Often with 19p chromosome abnormality and mental retardation.
Lambdoid synostosis: Flattened occiput. If unilateral, causes rhomboid skull with bulging ipsilateral forehead.
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DDx: Lazy lambdoid syndrome (positional flattening from decreased mobility), congenital torticollis (causing baby to always lie on same side).
Rx: Surgery.
F. Hydrocephalus
H&P of active hydrocephalus:
Hydrocephalus before cranial sutures close: Cranium grows faster than face does, bulging fontanelles, irritability, N/V, poor head control, engorged scalp veins, Macewen's sign (cracked pot sound when percussing over dilated ventricles), 6th nerve palsy, upgaze palsy (see Dorsal midbrain lesion, p. 48), hyperactive reflexes, apneic spells.
Hydrocephalus after cranial sutures close: Headache, papilledema, N/V, ataxia, 6th nerve palsy, upgaze palsy.
Entrapped 4th ventricle: Sometimes seen with chronic shunting of lateral ventricles after infections. Headache, lower cranial nerve palsies, decreased alertness, ataxia, N/V.
Differential diagnosis of hydrocephalus: Macrocrania (from rickets, chronic hemolysis, osteopetrosis), megalencephaly, hydranencephaly, benign external hydrocephalus (asymptomatic enlargement of subarachnoid space, with large head size).
Causes of hydrocephalus: Either noncommunicating (obstructive) or communicating (decreased absorption or, rarely, increased production of CSF). Hemorrhage may cause hydrocephalus by either mechanism.
Congenital (70%): Chiari II malformation, aqueductal stenosis, Dandy-Walker malformation, X-linked hydrocephalus.
Hemorrhagic (15%): Postintraventricular, postsubarachnoid. Common in premature infants.
Mass lesion (11%): Often tumors around the aqueduct, e.g., medulloblastoma. Colloid cyst can intermittently block foramen of Monro. Because there is no gray-white differentiation in infants, it is easy to miss small amounts of edema.
Postinfectious (8%): Purulent or basilar meningitis, cysticercosis.