Head Size - Paediatric Neurology

Head Size

Microcephaly

·        Head circumference below the 3^rd centile with abnormally slow head growth

·        Incidence: 1/1000, recurrence in siblings 1/50

·        Causes:

o   Familiar: not associated with developmental delay

o   Autosomal recessive condition, associated with severe learning delay

o   Congenital infection: Rubella, CMV, Toxoplasmosis, Varicella Zoster, Listeria, Syphilis 

o   Brain insult: eg perinatal hypoxia, neonatal meningitis. Likely to be accompanied by cerebral palsy, seizures, visual impairment, etc 

o   Fetal Alcohol Syndrome

Large Head

·        Megalencephaly = oversized brain

·        Hydrocephalus: dilated cerebrum: 

o   ­CSF volume associated with ventricular dilatation and ­intraventricular pressure

o   Due to:

§  Aqueduct obstruction: injury, infection or genes 

§  Arnold Chiari Malformation (downward displacement and elongation of hind brain, with herniation into the cervical canal)

§  Acquired causes: meningeal adhesions, mass lesions, etc

·        Chronic Subdural Haematomas

·        Hydraencephaly: no cerebrum

·        Benign familial anatomic megalencephaly or macrocephaly 

·        Metabolic Megalencephaly: late manifestation of many cerebral degenerative disorders (eg lysosomal storage diseases) 

·        Neurofibromatosis

·        Cerebral Tumour