Ventricular Size

What is the Ventricular System?

The ventricular system consists of four interconnected cavities, which are filled with circulating cerebral spinal fluid (CSF).

Cerebrospinal fluid (CSF) is a fluid surrounding the brain and spinal cord. It has an important role in protecting the brain from mechanical shocks, as well as maintaining homeostasis within the central nervous system by supplying nutrients to brain cells and getting rid of any waste products.

The ventricles are lined with ependymal cells, which form the choroid plexus, a structure responsible for producing the CSF. The CSF has an important role in protecting the brain from mechanical shocks, as well as maintaining homeostasis within the central nervous system by supplying nutrients to brain cells and getting rid of any waste products.

The brain itself is relatively heavy. Therefore, CSF serves as a cushion to prevent the brain from being crushed by its weight (the average male brain weighs about 1,350 grams, while a female one weighs about 1,200 grams). It also helps keep the brain buoyant, this reduces the brain's effective weight to about 50 grams, which further protects the brain from mechanical damage.

There are four ventricles in total.

• Lateral (first and second) ventricles: these are the largest of the ventricles. The lateral ventricles have a left side and a right side, and have a horn that curves into the different lobes of the brain (temporal, occipital and frontal lobes).
• Third ventricle: the lateral ventricles open into the third ventricle, which lies between the thalamus, via the foramen Monro. It is the thin, slit-like structure seen between the lateral ventricles.
• Fourth ventricle: the third ventricle connects to the fourth ventricle. The CSF flows from the third to the fourth ventricle through the cerebral aqueduct. The fourth ventricle is located in the brainstem (right at the junction of the pons and medulla oblongata), here, the CSF is drained into the central canal and subarachnoid cisterns.

Fig. 2 - Ventricular systems of the brain produce, transport and drain CSF¹

Hydrocephalus Ventricular Size

So, what happens when dysfunctions are present in the ventricular system? Before we look at the ventricular size in schizophrenia, let's consider a condition called hydrocephalus.

Hydrocephalus is relatively rare and usually occurs in infants and older adults. It involves an excessive accumulation of CSF in the ventricular system.

This occurs either to the overproduction of the fluid or if the fluid is not drained properly. When CSF builds up in the ventricles, intracranial pressure is created on the brain and the skull, which can lead to several neurological symptoms and even brain damage. Hydrocephalus is treated by installing a tube that helps drain the excess fluid from the ventricles.

Schizophrenia and Ventricular Size Psychology

Enlargement of ventricular size is considered to be one of the first structural brain changes seen from the onset of schizophrenia.

One of the early studies (Johnstone et al., 1976), which used computerised axial tomography (CAT), compared the size of cerebral ventricles in 17 institutionalised schizophrenic patients to healthy subjects in employment.

• He found that patients with schizophrenia had increased ventricular size.
• Moreover, he found that the increase in the size of the ventricles was associated with the degree of cognitive impairment in patients.

To analyse the findings across the literature, Wright and colleagues (2000) conducted a meta-analysis of structural brain imaging studies investigating the volume of different brain structures in schizophrenia patients. Their analysis included 58 studies and measurements taken from 1,588 patients with schizophrenia.

• The researchers found on average a slightly (2%) lower cortical volume in schizophrenia patients and a greater ventricular volume. The volume of ventricles in patients with schizophrenia was found to be equivalent to 126% of the volume in healthy controls (26% increase).

Fig. 2 - CT scans help identify abnormal areas of the brain.

Since the space within the skull is limited, it's been suggested that an increase in ventricle size could be associated with a loss of volume to other types of brain tissue, possibly leading to lasting cognitive deficits.

Lateral Ventricle Size Schizophrenia

Lateral ventricular volume is increased in patients with schizophrenia. Wright and colleagues (2000) found the volume of the lateral ventricle to be 16% greater in schizophrenia patients, compared to healthy controls.

The lateral ventricle also increases with age, regardless of the presence of schizophrenia. Horga et al. (2011) suggested that ventricular enlargement may result from neurodegeneration, which occurs with age and can affect patients with schizophrenia more than healthy controls.

Enlargement in Ventricular Size in Schizophrenia: Negative Symptoms and Positive Symptoms

Could ventricular size be the cause of schizophrenia symptoms? Andreasen et al. (1982) investigated whether the enlargement of ventricles in schizophrenia would be associated with a difference in symptoms that the patients were experiencing. They divided a sample of schizophrenic patients into a group with the smallest and the largest enlargements.

The researchers found that greater enlargements were associated with a higher prevalence of negative symptoms in patients, while in the group with smaller enlargements, positive symptoms dominated.

Enlarged Ventricles: the Cause or Product of Schizophrenia?

If the enlargement of ventricles precedes the onset of schizophrenia, we could hypothesise about it leading to the development of symptoms. However, if the enlargement develops during the course of the disorder, it would indicate that these changes are a result rather than a cause of the disorder.

The Narr et al. (2006) study supports the latter hypothesis, as it found that patients with schizophrenia showed a small enlargement of the ventricles in the first episode. The study suggested this enlargement occurs with the progression of the disease after its initial onset, rather than being an immediate cause of schizophrenia.

Ventricular Size and the Volume Loss of Brain Tissue

It is often speculated that greater ventricular size could be related to the loss of brain tissue in schizophrenia, leading to severe cognitive impairments in many patients.

However, the evidence linking ventricular enlargement and loss of volume in other brain areas is limited to correlational analyses. Therefore, it's unclear how these two structural changes are linked and whether it's the ventricular enlargement that causes neurodegeneration, or the other way around.