Saturday 10 September 2011

Benign Enlargement of Subarachnoid spaces of Infancy

6 month old baby with fever and single episode of convulsion.
Overconscious parents.
Mile stones normal.
Birth history unremarkable.

Non contrast CT Brain
This CT study of brain shows a prominent cortical sulci, wide sub arachnoid spaces in frontal regions iso dense to Csf, wide Sylvain fissures and inter hemispheric fissure. No associated Ventriculomegaly.

After seeing CT, it is important to rule out two things clinically, head circumference which was normal, no abnormal increase in head size and second is any sign of raised ICT, which were absent in this case.

In this scenario, this prominence of sub arachnoid space in frontal regions is a benign finding, considering age, normal mile stones, unremarkable birth history, no Ventriculomegaly, normal head circumference, no signs of raised ICT.
This is a common finding below age of 1 years, most of these infants have normal development , sometimes minor delays resolves if any; they have otherwise normal neurologic examinations and favorable outcomes. Better is to ask for follow up imaging at the age of 2 years.

So one should not be in hurry to label it off as Atrophy.
The preferred terms are “benign enlargement of the subarachnoid spaces of infancy” or at the most “subarachnomegaly,”

Some infants with this finding, may have an associated mild increase in head circumference, signs of mildly increased intracranial pressure like irritability, lethargy, vomiting, wide cranial sutures, bulging anterior fontanel and dilated scalp veins, in that case term external hydrocephalus is used by some. But even other terms for this condition like Hygroma and Effusions should be avoided.

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