This 7 mths old boy was noted to have a large head at 3 mths of age; however he was not investigated further at that time since the he was normal with normal mile stones. There was no significant family or perinatal history.
A month ago he was involved in a bad road traffic accident where his mother sustained serious injuries. Following the accident he was irritable and CT suggested extracerebral collection bilaterally with specs of blood.
He had bifrontal burrholes and drainage elsewhere. He gradually improved. About 2 weeks later a repeat CT suggested increase in extracerebral collection with normal ventricles, prominent sulci and no suggestion of pressure effects.
On examination the head circumference was 47cms which is within the normal range for this age group. The left burrole site was bulging, but not tense and the bulge collapsed on making the child sit up. Anterior fontanelle was open and not full. The child was normal otherwise, cheerful and feeding well.
A diagnosis of ‘Benign communicating hydrocephalus’ was made;the residual extracerebral hematoma, if any, is expected to clear up in few weeks. It was decided to review the child after a month with delayed diffusion MRImages.
Benign communicating hydrocephalus’ is also known as Idiopathic External hydrocephalus and subdural effusion. It is characterized by rapid head growth, enlarged subarchnoid spaces with little or no ventriculomegaly. The pathogenesis is not clear; it may be the result from a delayed maturity of the cerebrospinal fluid resorption sites. Arachnoid villi are not mature at birth. There is often a family history of large heads. At roughly 18 months of age, the enlarging head circumference will plateau, allowing the child's body growth to catch up
CT and MRI reveal bilateral extracerebral fluid collections, prominent sulci, normal ventricles, and no evidence of compression of the brain. Chronic subdural hygromas must be ruled out. Intracranial pressure monitoring and delayed diffusion MRI with gadolinium may help. The natural history is one of gradual resolution of the fluid collection. These families need reassurance that the problem will resolve without a shunt