Ishaan Mondal is a 5 week old male who presents with an increased head circumference, vomiting, and irritability. His mother, Ziva, reports that while Ishaan appears hungry, he has difficulty suckling when attempting to breastfeed. After an appointment with his pediatrician, Ishaan is directly admitted to the neonatal intensive care unit, or NICU, for monitoring and treatment of hydrocephalus.
Hydrocephalus refers to the excessive buildup of cerebrospinal fluid, or CSF, within the brain. The CSF helps provide cushion and protection, as well as metabolic fuel for the brain. Now, the brain has two lateral ventricles, as well as the third and fourth ventricles, which are all interconnected, and each one contains a structure called a choroid plexus. The choroid plexus is made up of ependymal cells, which produce the CSF that can drain down to the fourth ventricle. From there, the CSF enters the subarachnoid space, and gets reabsorbed by arachnoid granulations into the dural venous sinuses, which are pools of venous blood. Finally, the CSF and venous blood are drained together out of the skull and into the internal jugular vein. Now, since the skull is such a rigid structure, the volume of the brain, CSF, and blood must be constant and in balance. So, with hydrocephalus, the increased CSF volume causes the four ventricles to enlarge and intracranial pressure to rise, which can compress and damage brain structures.
Now, there are two types of hydrocephalus. Noncommunicating, or obstructive hydrocephalus, is caused by an obstruction of the CSF flow anywhere along its path. This can be caused by a brain tumor, cyst, or by congenital causes, like cerebral aqueduct stenosis. On the other hand, communicating, or nonobstructive hydrocephalus is most often caused by decreased CSF reabsorption. This occurs when there’s inflammation or obstruction of the arachnoid granulations, which can be caused by infections, such as meningitis, as well as subarachnoid hemorrhage. Less frequently, communicating hydrocephalus can be caused by increased CSF production, like by a choroid plexus tumor.