Obstructive hydrocephalus, also known as non-communicating hydrocephalus, occurs when there is a blockage or obstruction within the pathways that cerebrospinal fluid (CSF) takes to flow from the brain’s ventricles to other parts of the central nervous system. This obstruction leads to the accumulation of CSF within the ventricles, causing an increase in intracranial pressure. In adults, obstructive hydrocephalus can be caused by various factors, each of which affects the normal flow of CSF. Here are some common causes:

MAIN ARTICLE:- 

Hydrocephalus 

1. Tumors: One of the most prevalent causes of obstructive hydrocephalus in adults is the presence of brain tumors. Tumors can develop within the brain’s ventricles or nearby structures, such as the third ventricle or the cerebral aqueduct. These tumors can physically block the flow of CSF, leading to its accumulation and subsequent hydrocephalus.
2. Colloid Cysts: Colloid cysts are typically benign, gelatinous growths that can occur within the third ventricle of the brain. They can obstruct the foramen of Monro, which is the passage connecting the lateral ventricles to the third ventricle. This obstruction leads to the buildup of CSF in the lateral ventricles and subsequent hydrocephalus.
3. Aqueductal Stenosis: Aqueductal stenosis refers to the narrowing or blockage of the cerebral aqueduct, a narrow passage that connects the third and fourth ventricles. This condition can be congenital or acquired due to inflammation, hemorrhage, or other factors. Aqueductal stenosis obstructs the flow of CSF between these ventricles, causing hydrocephalus.
4. Infections and Inflammation: Infections such as meningitis or encephalitis can lead to inflammation of the meninges or brain tissue, respectively. This inflammation can disrupt the normal flow of CSF through the ventricular system, causing hydrocephalus. In some cases, the inflammation may lead to scarring and fibrosis that obstructs CSF pathways.
5. Hemorrhages: Bleeding within the brain, whether due to trauma, aneurysms, or other vascular abnormalities, can obstruct CSF flow and lead to hydrocephalus. Blood can clot within the ventricles or aqueduct, blocking the normal passage of CSF.
6. Congenital Abnormalities: Some individuals are born with congenital structural abnormalities that can obstruct CSF flow. These abnormalities might include malformations of the aqueduct, narrowings of passageways, or abnormal connections between structures.
7. Post-Traumatic: Severe head injuries can cause bleeding, swelling, or direct damage to brain structures that interfere with CSF flow.
8. Cysts and Lesions: Certain cysts and lesions, both congenital and acquired, can grow within or near the ventricular system. These growths can physically block the flow of CSF, leading to hydrocephalus.

The symptoms of obstructive hydrocephalus in adults can include severe headaches, nausea, vomiting, changes in mental status, vision problems, gait disturbances, and urinary incontinence. The condition is typically diagnosed using imaging techniques like MRI or CT scans. Treatment often involves surgical intervention to remove the obstruction, drain excess CSF, or create alternative pathways for its flow. If left untreated, obstructive hydrocephalus can lead to serious neurological damage, so prompt diagnosis and appropriate management are crucial.