Head Circumference

Average at birth 35cmNormal Growth:

1cm/month for 1st 6 months½ cm/month from 6 months to 1 year

Especially important first 3 years of age

Head Circumference

Most concerning: 3 Standard Deviations above or below the mean>97th Percentile: Macrocephaly<3rd Percentile: Microcephaly

Special ChartsDown SyndromeWilliams SyndromeAchondroplasiaVLBW

Head Circumference

Microcephaly: Small HeadMacrocephaly: Large HeadMicrencephaly: Small BrainMegalencephaly: Large BrainBrain growth determines ultimate cranium

size

Head Circumference

2.5% of all childrenSome with no neurologic problems

Asymptomatic familial microcephalyFamily history of small head sizeNormal developmentNormal neuro exam

Microcephaly

Primary (genetic)Usually present at birth

Secondary (environmental)Present at birthDevelop later from postnatal insult

Microcephaly

Autosomal RecessiveBrain is small

Otherwise normal architectureMental retardation

Otherwise unremarkable neuro exam

Primary Microcephaly Vera

Abnormal neuroimagingHoloprosencephaly- failure of forebrain to

divide into hemispheres. Midline facial defectsDisruption of hypothalamic-pituitary axis

Lissencephaly- smooth brainSeizures, spasticity, global dev delay

Microcephaly w Anatomic Abnormalities

Microcephaly: Syndromes

Rett Syndrome

Microcephaly: Syndromes

Rubenstein Taybi SyndromeBroad Thumb-Hallux Syndrome

Microcephaly: Syndromes

Cornelia de Lange

Microcephaly: Syndromes

Miller Dieker

Prenatal CausesDrugs and alcohol, irradiation, intrauterine

infectionsPerinatal asphyxiaSevere malnutrition

Secondary Microcephaly

Macrocephaly

Presenting signs/symptoms vary with age

Communicating vs noncommunicating

Hydrocephalus

Benign hydrocephalusH.C. normal or large at birthIncreases to 98%ile, then

parallels chartNormal neuro exam and

development

Hydrocephalus

Benign or idiopathic (AKA Familial Macrocephaly)Normal neuro examNo increased ICPNo fluid collectionFamily history of large headsMay have some subtle difficulty with

coordination

Megalencephaly

MetabolicInborn errors of metabolismMost autosomal recessiveSignificant dev delay with regressionMucopolysaccharidoses

Megalencephaly

AnatomicIncreased number of cellsSotos syndrome (overgrowth syndrome)Neurocutaneous syndromesMost with developmental delay

Megalencephaly

Macrocephaly

Must entertain the worstSpace-occupying lesions

TumorAVM

Hemorrhage

Macrocephaly

Open fontanelleUltrasound

MRIGives best information on brain parynchymaBest at posterior fossa

CTIntracranial calcificationsHemorrhageSkull

Imaging