Makindo Medical Notes

Related Subjects: |Acute Stroke Assessment (ROSIER&NIHSS) |Atrial Fibrillation |Atrial Myxoma |Causes of Stroke |Ischaemic Stroke |Cancer and Stroke |Cardioembolic stroke |CT Basics for Stroke |Endocarditis and Stroke |Haemorrhagic Stroke |Stroke Thrombolysis |Hyperacute Stroke Care

Introduction

• This section focuses on acquired hydrocephalus due to blockage of cerebrospinal fluid (CSF) flow and absorption as a result of stroke. It does not cover congenital or childhood hydrocephalus.

Cerebrospinal Fluid Physiology

• CSF is primarily produced by the choroid plexuses in the lateral (70%), third (5%), and fourth (5%) ventricles, and by ependymal cells (20%) lining the ventricles.
• The choroid plexus epithelium acts as a barrier between blood and CSF, filtering various substances.
• CSF flows from the lateral ventricles through the foramen of Monro to the third ventricle, then through the aqueduct of Sylvius to the fourth ventricle.
• The aqueduct, only 2 mm in diameter, is a common site for CSF flow obstruction. From the fourth ventricle, CSF drains through the lateral foramina of Luschka or the medial foramen of Magendie into the subarachnoid space.
• CSF is absorbed by the arachnoid villi into the venous sinuses. Obstruction at the aqueduct causes non-communicating hydrocephalus, while obstruction at the arachnoid villi level causes communicating hydrocephalus.
• CSF production is driven by the Na⁺/K⁺ ATPase pump, which moves Na⁺ into the ventricles, followed by water. Approximately 500 ml of CSF is produced daily, with a volume of 100-150 ml at any time, being replaced three times per day.
• CSF cushions the brain, reducing its effective weight from 1400 g to about 50 g, and plays a role in the drainage of the ventricular cavities and subarachnoid space.
• Acute hydrocephalus can be fatal if unrecognized and untreated, as enough CSF is produced in three days to fill the entire brain-free skull volume.

Types of Hydrocephalus

• Hydrocephalus is classified into communicating, where the ventricles communicate with the subarachnoid space, and non-communicating, where this communication is blocked.
• In stroke, obstructive hydrocephalus is more common, resulting from swelling that obstructs the aqueduct or the fourth ventricle.
• This obstruction can lead to elevated intracranial pressure (ICP) and potential brainstem herniation. Up to 20% of patients with subarachnoid hemorrhage (SAH) may develop hydrocephalus within 3-5 days, particularly with large bleeds or intraventricular bleeding.

Clinical Presentation

• Hydrocephalus typically presents with headache, dyspraxia, seizures, nausea, vomiting, eye signs, and can progress to coma and even death if untreated.

Common Sites of CSF Flow Obstruction

Investigations

• CT is the key investigation, showing dilation of the ventricular system. Initial signs include dilation of the temporal horns.
• Axial CT slices can reveal rounded temporal horns, indicating elevated ventricular pressure. MRI may provide further detail and help determine the level and cause of obstruction.
• Signs of mass lesions, posterior fossa edema, blood, or midline shift can be visualized, along with periventricular edema due to increased ventricular pressure.

Management

• Initial management may involve observation, as hydrocephalus can sometimes resolve spontaneously.
• In cases of communicating hydrocephalus, lumbar puncture may be both diagnostic and therapeutic, reducing CSF pressure if no evidence of obstruction exists within the ventricular system.
• Early referral to neurosurgery is essential for rapid intervention if the patient's condition worsens. If necessary, a burr hole can be made to insert an external ventricular drain (EVD) to alleviate pressure by draining CSF.
• With SAH, reducing ICP too rapidly can increase the risk of rebleeding, so maintaining appropriate pressure levels is crucial.
• Hydrocephalus in adults is often associated with intraventricular bleeding, compression of the aqueduct from posterior fossa swelling, or following SAH. Early shunting can be challenging due to the risk of shunt blockage from high-protein or bloody CSF.

References and Further Reading

• Hydrocephalus and Stroke Management: AHA Journal
• NIH: Understanding Hydrocephalus and Its Complications