How can obstructive hydrocephalus cause a decrease in level of consciousness (LOC)?

From the Guidelines

Obstructive hydrocephalus causes a decrease in sensorium by increasing intracranial pressure, which compresses brain tissue and compromises blood flow, leading to impaired neurotransmission and neural network activity. This condition occurs when cerebrospinal fluid (CSF) flow becomes blocked within the ventricular system, preventing normal CSF circulation and absorption, and resulting in fluid accumulation and ventricular enlargement. The increased pressure affects critical structures such as the cerebral cortex, thalamus, and reticular activating system, which are essential for consciousness and alertness. As cerebral perfusion pressure decreases, blood flow to the brain becomes compromised, causing hypoxia and metabolic disturbances in neurons. Additionally, periventricular edema develops as CSF seeps into surrounding brain tissue, further disrupting neural function. These pathological changes collectively impair neurotransmission and neural network activity, manifesting clinically as confusion, lethargy, decreased responsiveness, and potentially progressing to stupor or coma if left untreated. According to the guidelines for the management of spontaneous intracerebral hemorrhage, ventricular drainage as treatment for hydrocephalus is reasonable, especially in patients with decreased level of consciousness 1. This treatment aims to relieve pressure and prevent permanent neurological damage. The guidelines also recommend considering ICP monitoring and treatment for patients with a GCS score of ≤8, those with clinical evidence of transtentorial herniation, or those with significant IVH or hydrocephalus, and maintaining a CPP of 50 to 70 mm Hg depending on the status of cerebral autoregulation 1. Prompt treatment through CSF diversion procedures like ventriculostomy or shunt placement is essential to alleviate symptoms and improve outcomes. Key points to consider in the management of obstructive hydrocephalus include:

• Increased intracranial pressure due to blocked CSF flow
• Compromised blood flow and impaired neurotransmission
• Critical structures affected, such as the cerebral cortex and reticular activating system
• Clinical manifestations, including confusion, lethargy, and decreased responsiveness
• Treatment options, such as ventricular drainage and CSF diversion procedures 1.

From the Research

Obstructive Hydrocephalus and Decrease in Sensorium

• Obstructive hydrocephalus can cause an increase in intracranial pressure (ICP) due to the accumulation of cerebrospinal fluid (CSF) in the ventricles, which can lead to a decrease in sensorium 2, 3.
• The increased ICP can cause compression of the brainstem and cerebral cortex, leading to impaired consciousness and decreased sensorium 2, 4.
• The relationship between ICP, ventricular size, and resistance to CSF outflow is complex, and a small or normal ventricular size in acute or subacute phases does not preclude defective CSF resorption 4.
• Chronic hydrocephalus can also lead to decreased cerebral blood flow (CBF), which can contribute to a decrease in sensorium, and this decrease in CBF is mediated through cardiac effects, including decreased cardiac output (CO) 5.
• The clinical signs of elevated ICP, including headache, papilledema, nausea, and vomiting, can progress to stupor and coma if left untreated, highlighting the importance of prompt diagnosis and treatment of obstructive hydrocephalus 2.

Pathophysiology

• The pathophysiology of obstructive hydrocephalus involves the accumulation of CSF in the ventricles, leading to increased ICP, which can cause compression of the brainstem and cerebral cortex, leading to impaired consciousness and decreased sensorium 2, 3.
• The increased ICP can also lead to decreased CBF, which can contribute to a decrease in sensorium, and this decrease in CBF is mediated through cardiac effects, including decreased CO 5.
• The relationship between cardiac function and CBF should be considered in the pathophysiology and clinical treatment of chronic hydrocephalus 5.

Clinical Implications

• The clinical implications of obstructive hydrocephalus include the importance of prompt diagnosis and treatment to prevent cerebral hypoperfusion and possible brain death 2.
• The management of elevated ICP is dependent on the underlying cause, and medical options for treating elevated ICP include head of bed elevation, IV mannitol, hypertonic saline, transient hyperventilation, barbiturates, and sedation, endotracheal intubation, mechanical ventilation, and neuromuscular paralysis 2, 3.
• Surgical options include CSF drainage if hydrocephalus is present and decompression of a surgical lesion, such as an intracranial hematoma/large infarct or tumor, if the patient's condition is deemed salvageable 2, 3.