Risk factors for hydrocephalus may include birth defects in the brain and spinal cord, developmental issues resulting from premature birth or genetic factors, or infection and injury. Certain conditions, such as spina bifida or meningitis, can increase the risk of developing hydrocephalus, especially in infants and children.
Congenital hydrocephalus is present at birth and may be caused by infections during pregnancy, hereditary factors, or developmental issues in the brain and spinal cord. In cases of congenital hydrocephalus, the ventricles (cavities) in the brain are often blocked and unable to effectively drain CSF.
Acquired hydrocephalus develops after birth and can result from various factors, including infections like meningitis or encephalitis, brain tumors, head injury, and bleeding in the brain or skull. In these cases, swelling or pressure inside the skull can block the pathways that allow CSF to flow through the brain and spinal cord.
There are several different types of hydrocephalus, which can be acquired or congenital:
Non-Communicating (Obstructive) Hydrocephalus
This type of hydrocephalus occurs when CSF can no longer flow through the ventricles in the brain because one or more of the passages between ventricles are blocked. Brain tumors are a common cause of obstructive hydrocephalus.
This type of hydrocephalus occurs when the brain’s ventricles remain open and CSF can still flow through them like normal, but the ability of smaller blood vessels to absorb CSF after it leaves the ventricles is impaired. Brain trauma and bleeding inside the skull are significant risk factors for communicating hydrocephalus.
Normal Pressure Hydrocephalus (NPH)
This is a common type of communicating hydrocephalus that occurs when CSF is blocked from flowing normally through the brain and spinal cord and the ventricles in the brain are enlarged, but with no significant increase in pressure inside the skull. The exact cause of NPH is often unclear, but risk factors include age, a history of traumatic brain injury, and some underlying medical conditions. Because it typically occurs in older adults and symptoms include difficulty with thinking and memory, NPH is often confused with Alzheimer’s disease.
This is not a true form of hydrocephalus, but rather occurs when a brain injury, stroke, or neurodegenerative disease like Alzheimer’s causes tissues around the ventricles to shrink and the ventricles to enlarge. For this reason, the ventricles appear enlarged and there may be an excess of CSF, but pressure in the brain remains normal.