From the Guidelines
Enlarged brain ventricles on a CT scan can be identified by looking for several key features, including an Evans' index greater than 0.3, which is a strong indicator of ventricular enlargement, as suggested by the study 1. To determine if brain ventricles are enlarged on a CT scan, one should look for the following characteristics:
- The ventricles will appear as darker (hypodense) areas within the brain that are larger than normal size.
- Normal ventricles should be proportional to brain size, with the lateral ventricles typically measuring less than 1.5 cm at the atrium.
- When enlarged, you'll notice widening of these fluid-filled spaces, decreased brain tissue surrounding them, and possibly a rounded appearance rather than their typical shape.
- The frontal horns may appear more prominent, and the temporal horns, which are normally barely visible, become more apparent when dilated.
- Radiologists also look for periventricular hypodensity (decreased density around the ventricles) which may indicate transependymal flow of cerebrospinal fluid due to increased pressure.
- The third and fourth ventricles may also appear enlarged. These findings must be interpreted in clinical context, as some degree of ventricular enlargement can be normal in elderly patients due to age-related brain atrophy, while pathological enlargement may indicate hydrocephalus, brain atrophy from various causes, or other neurological conditions, as noted in the study 1. It's worth noting that the study 1 provides the most recent and relevant guidelines for diagnosing probable INPH, which includes ventricular enlargement not entirely attributable to cerebral atrophy or congenital enlargement, and the Evans' index is a key factor in this diagnosis. In contrast, the studies 1 and 1 provide information on the use of CT scans in stroke diagnosis and treatment, but they do not provide specific guidance on identifying enlarged brain ventricles. Therefore, the recommendation is based on the study 1, which provides the most relevant and up-to-date information on this topic.
From the Research
Enlarged Brain Ventricles on CT Scan
To determine if brain ventricles are enlarged on a CT scan, several methods and indices can be used, as discussed in the studies 2, 3, 4, 5, 6.
- The study 2 proposed a new index, the Cerebro-Ventricular Index (CVI), which can be used to measure ventricular dilatation on CT scans.
- Another study 3 discussed the use of endoscopic fourth ventriculostomy as an alternative treatment for hydrocephalus due to atresia of the Magendie and Luschka foramina, which can cause enlarged ventricles.
- The study 4 highlighted the importance of precise terminology in radiology reports to describe ventricular size, especially in cases of hydrocephalus.
- Ventricular enlargement can also occur after moderate or severe head injury, as discussed in the study 5, which found that ventriculomegaly was present in 39.3% of patients with severe head injury and 27.3% of those with moderate head injury.
- The study 6 created new standards for radiological indices of dilated ventricles and compared these with subjectively assessed ventricular size, finding that subjective evaluation may not be accurate enough.
Indices and Measurements
Several indices and measurements can be used to assess ventricular size, including:
- Evans' index 5
- Cerebro-Ventricular Index (CVI) 2
- Biparietal and occipitofrontal diameters 6
- Width and depth of the frontal and occipital horns 6
- Diameter of the third ventricle 6
- Frontal sub-arachnoid space 6
Clinical Implications
Enlarged brain ventricles can have significant clinical implications, including: