Cerebrospinal Fluid Analysis: Pathology and Anatomy

Gross Pathology of Cerebrospinal Fluid

In normal conditions, the cerebrospinal fluid (CSF) is clear and transparent with a pH of 7.4–7.5. Its appearance may change due to various pathological conditions:

• Cloudy or purulent CSF: Indicates an infectious process, such as bacterial meningitis.
• Haematic or yellowish CSF: Suggests hemorrhagic cerebral infarction or trauma. It is important to determine if the presence of blood is due to the procedure or an underlying trauma.

Chemical Composition of CSF

• Glucose Concentration: Normal values range between 50–70 mg/100 mL. Levels decrease in cases of bacterial meningitis or subarachnoid hemorrhage.
• Protein Concentration: Normal values range between 15–40 mg/100 mL. Levels increase in cases of bacterial meningitis or impaired vascular integrity, which may also be observed as CSF turbidity.

Anatomical Structures

Ventricular System

• Lateral Ventricles: Located throughout both hemispheres and connected to the third ventricle through the foramen of Monro.
• Third Ventricle: A thin cavity connected to the fourth ventricle via the cerebral aqueduct (aqueduct of Sylvius).
• Fourth Ventricle: Located between the brainstem and the cerebellum.

From this space, the CSF flows into the subarachnoid space through the foramina of Luschka and Magendie. The ventricles continue into the spinal cord through the ependymal canal, which is lined by a row of cuboidal cells featuring apical cilia.

Choroid Plexus

The choroid plexus is the primary site of CSF formation. These are small projections on the ventricular walls (especially the lateral ventricles) that extend into the ventricular lumen.

Hydrocephalus

Hydrocephalus is the distension of the cerebral ventricles and subarachnoid space caused by an accumulation of CSF due to excessive production, insufficient resorption, or obstruction in its circulation.

Clinical Indicators in CSF

Leukocyte Pleocytosis

A predominant leukocyte pleocytosis in CSF often indicates acute bacterial meningitis (e.g., meningococcus, pneumococcus, etc.).

Cellular Changes

• Reactive CSF: Characterized by increased cell size and prominent nucleoli, often with acquired phagocytic capacity.
• Cerebral Infarction: Red blood cells and polymorphonuclear leukocytes (PMN) may appear.
• Subarachnoid Hemorrhage: Histiocytes containing traces of red blood cells and hemosiderin are often present.
• Lipophages: The presence of lipophages in the CSF is typically caused by trauma, necrosis associated with stroke, or oncological treatments.