116 Width of the third ventricle of cerebrum (TVW)

Width of the third ventricle: measurement by ultrasound, conventional range, hydrocephalus and brain atrophy.

The third ventricle is a narrow, fluid-filled cavity in the middle of the brain, between the two halves of the thalamus. It connects with the lateral ventricles above and, through the cerebral aqueduct, with the fourth ventricle below, and it is part of the pathway of cerebrospinal fluid (CSF). Its width is measured by transcranial ultrasound, CT or MRI. It increases when CSF flow is obstructed or reabsorption is impaired (hydrocephalus) and when the surrounding brain tissue shrinks (atrophy). The movement of fluid between the vessels, tissues and CSF depends on osmotic, hydrostatic and oncotic pressure, membrane permeability and active ion transport.

BrainCerebrospinal fluidNeuroimaging

Norm in this application4.5–6 mm

Measured byultrasound, CT, MRI

Increases withage, atrophy, hydrocephalus

Ultrasound cut-offsage- and device-dependent

Figure 1. Conventional third ventricle width ranges used by this application. Imaging studies use age-specific reference values, which differ between methods and devices.

Measurement

In transcranial sonography, the third ventricle is seen through the temporal bone as two bright parallel lines, and its width is measured between them. The method is bedside, radiation-free and repeatable, and correlates well with CT. Its width increases with age, so reference values are age-specific; in neuro-intensive care it is used to detect and follow hydrocephalus.

Clinical significance

Hydrocephalus: obstruction of CSF flow (tumour, bleeding, aqueduct stenosis) or impaired absorption (after meningitis or subarachnoid haemorrhage, normal-pressure hydrocephalus)
Brain atrophy: ageing, Alzheimer disease and other dementias, multiple sclerosis, chronic alcohol use; in Parkinson disease, a wider third ventricle on ultrasound correlated with poorer cognitive performance
Narrow ventricles may occur with brain swelling or after excessive CSF drainage

Seek emergency care

for severe headache with vomiting and drowsiness, or rapidly worsening confusion, gait disturbance or vision problems.

When to see a doctor

Gradually worsening walking, memory problems and urinary urgency in an older person may indicate normal-pressure hydrocephalus, which can be treated.

References

This article is for general information and does not replace a consultation with a doctor. Measurements must be interpreted by a physician together with symptoms and other tests.

Published on 8 May 2024