Answer
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Causes of enlarged head in an infant
1- normal variation.
2- familial large head.
3- fluid collection:
a- hydrocephalus.
b- subdural fluid collection.
hematoma- collection of pus.
c- brain edema:
- infections: meningitis/ encephalitis.
- toxins: lead/ tetracycline.
- metabolic: galactosemia/ hypoparathyrodism.
- asphyxia : cardiac arrest/ birth asphyxia.
d- blood :
intracranial hemorrhage.
4- thickened skull:
a- chronic hemolytic anaemia.
b- skeletal disorders: rickets/ osteogenesis
imperfecta.
5- big brain ( megalencephaly):
a- anatomic: neurocutaneous syndromes
e.g. neurofibromatosis.
hemimegalencephaly.
b- metabolic:
mucopolysaccharidosis.
tay sach s disease.
aminoaciduria.
Tests for enlarged head in infant
1- laboratory studies:
a- complete blood picture, hemoglobin, hemoglobin
electrophoresis ( if you suspect hemolytic
anaemia)
b- metabolic studies:
serum calcium, phosphorus etc, according to
the clinical evaluation.
c- lumber puncture & examination:
to exclude acute infections & subarachnoid
hemorrhage ( do CT scan first ).
2- imaging:
a- plain X ray skull:
- will demonstrate abulging anterior fontanel
in infants.
- also, bone changes due to hemolytic anaemia
may be seen.
b- plain X ray both wrist:
for rickets.
c- CT scan:
identifies hydrocephalus & its cause , cysts,
subdural fluid collections & brain edema.
d- MRI scan:
for anatomical or metabolic disorders associated
with megalencephly.
3- fundus examination:
for papilledema, retinal hemorrhages or
pigmentations.
Normal CSF circulation
- CSF is mostly produced by the choroid plexus in the
lateral ventricles of the brain.
- from there it passes through the foramen of Monro
on each side to reach the midline 3rd ventricle.
- the fluid then passes downwards to the aqueduct
of Sylvius ( = cerebral aqueduct) to the 4th ventricle.
- the 4th ventricle has 2 lateral foramina ( of Luschka)
& one medial foramen ( of Magendi), which transmit
CSF to the subarachnoid space around the brain
& spinal cord.
- most of the fluid absorption ocurrs inside the skull
through the arachnoid villi to the blood stream
( systemic circulation)
Constriction of cerebral aqueduct (= aqueduct of Sylvius)
- if constriction occurs in cerebral aqueduct will lead to
enlargement of the 3rd ventricles & lateral ventricles.
- the 4th ventricles & subarachnoid space
enlargement would likely not be visible.
Obstructed arachnoid vilii
there will be enlargement of:
1- subarachnoid space,
2- 4th ventricles.
3- 3rd ventricles.
4- lateral ventricles.
