Is this patient's hydrocephalus acute? Why?
This is clearly chronic hydrocephalus. The ventricles are very large for a young patient, and they can only become so large over quite some time. Moreover there is no evidence of transependymal oedema. If this was acute hydrocephalus the patient would be desperately ill and probably dead from raised intracranial pressure.
At what level is the obstruction?
Only the third and lateral ventricles are dilated, suggesting obstruction is at the level of the aqueduct.
What is the likely cause in this case?
The tectum of the midbrain appear bulky suggesting the presence of a mass, most likely a low grade glioma.
The lateral and third ventricles are markedly enlarged down to the level of the aqueduct. The tectum of the midbrain is expanded.