Understanding the causes of hydrocephalus is essential to diagnosing and managing this complex neurological condition. The term “hydrocephalus” describes the build-up of cerebrospinal fluid (CSF) within the ventricles of the brain.
This extra fluid raises pressure inside the skull. If untreated, it can cause lasting damage to brain tissue. Causes of hydrocephalus vary. They include genetic conditions, developmental problems, infections, injuries, and tumors. Hydrocephalus may start before birth, during infancy, or later in life.
Hydrocephalus happens when the production and absorption of CSF are out of balance or when the flow of CSF is blocked. The brain makes CSF to protect itself and remove waste. Normally, the fluid flows through chambers called ventricles and around the brain and spinal cord, then reabsorbs into the bloodstream. When this balance breaks, hydrocephalus occurs.
1. Congenital Causes (Present at Birth)
One common cause in infants is congenital abnormalities. These problems develop before birth and often get noticed early.
Aqueductal stenosis is a major cause. This means a narrow or blocked channel between the brain’s ventricles stops fluid flow, causing buildup.
Spina bifida, especially myelomeningocele, is a birth defect affecting the spine. It often leads to hydrocephalus by disturbing CSF flow.
Chiari malformations are structural problems at the skull base and cerebellum that block CSF circulation.
Infections in the womb like toxoplasmosis, cytomegalovirus, or rubella may disrupt brain development and lead to hydrocephalus.
Some genetic conditions, such as X-linked hydrocephalus caused by mutations in the L1CAM gene, can block CSF flow and run in families.
Because these causes start early, babies may show an unusually large head (macrocephaly) — often the first sign that leads to testing.
2. Acquired Causes (Develop After Birth)
Hydrocephalus can also develop later in life due to injury, illness, or surgery.
Intraventricular hemorrhage, especially in premature babies, causes bleeding inside brain ventricles. This can block CSF flow and cause hydrocephalus.
Meningitis, an infection of brain and spinal cord membranes, can scar tissues and stop CSF absorption. Tuberculosis meningitis is a common cause in developing countries.
Brain tumors can block fluid flow, especially those near the fourth ventricle.
Traumatic brain injury may cause bleeding or swelling that disrupts CSF circulation. Hydrocephalus can appear soon after or much later.
Cysts like arachnoid cysts can block CSF pathways, raising pressure.
Brain or spinal surgery can sometimes cause scar tissue that stops normal CSF absorption.
3. Normal Pressure Hydrocephalus (NPH)
NPH mainly affects older adults. Even though it’s called “normal pressure,” fluid builds up in brain ventricles without showing high pressure on lumbar puncture.
NPH may happen after:
- Head injuries, even small falls in the elderly
- Bleeding from stroke or aneurysm
- Infections like subarachnoid meningitis
- Age-related changes in CSF flow and absorption
NPH symptoms mimic Alzheimer’s and Parkinson’s disease, making diagnosis tricky. The main symptoms are walking problems, urinary urgency or incontinence, and memory loss. Brain scans help confirm NPH by showing larger ventricles.
4. Idiopathic Hydrocephalus
Sometimes, doctors cannot find the cause of hydrocephalus. This is called idiopathic hydrocephalus. It happens more often in adults. Doctors make this diagnosis by ruling out other causes. Scientists are still researching why it happens.
5. Age-Related Factors
Age affects hydrocephalus causes. Babies mostly have congenital or birth-related hydrocephalus. Older adults, especially over 60, often develop NPH or hydrocephalus after injury or stroke.
Babies’ skulls are soft and can expand, so head size may grow visibly. Adults’ skulls are hard, so fluid build-up causes pressure symptoms without head changes.
Global Differences in Causes
Causes of hydrocephalus differ worldwide. Low-income countries see more infections and birth-related issues causing hydrocephalus. High-income countries detect congenital and tumor-related cases earlier due to better healthcare.
Global health efforts focus on reducing preventable causes. These include improving prenatal care, vaccinations, and infection control.
Conclusion
Causes of hydrocephalus vary widely and depend on age, environment, and healthcare access. Whether congenital, acquired, or idiopathic, finding the root cause helps guide treatment and improve outcomes. Advances in diagnosis and newborn screening are helping catch hydrocephalus earlier, leading to better care worldwide.
Causes of Hydrocephalus
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