What is Cavum Septum Pellucidum?
The septum pellucidum, also known as the ventricle of Sylvius, is a thin, double-layered structure in the brain that looks like a triangular wall and separates the frontal parts of the right and left brain cavities. It’s situated between the corpus callosum, which is in the front part of your brain, and the fornix body. It’s usually between 1.5 to 3.0 mm wide.
Within the septum pellucidum, there’s a space known as the cavum septum pellucidum. This is a normal variation in brain anatomy and is filled with a filtered fluid transferred from the brain cavities through the septal layers. It doesn’t connect with the fluid-filled space around the brain and spinal cord, but occasionally it can connect to another cavity known as cavum vergae. The cavum septum pellucidum and cavum vergae were previously and incorrectly referred to as the fifth and sixth brain cavities. However, they are not part of the brain cavity system as they originate differently during embryo development and lack typical lining cells.
The walls or boundaries of the septum pellucidum include the corpus callosum on top, the forward bending part of the corpus callosum below and in front, and the corpus and columns of the fornix below and behind. On the sides are the inner walls of the frontal horn of the brain cavities and in the middle is the space that mirrors its other half.
The cavum septum pellucidum has the following borders: the forward bending part of the corpus callosum in front, the corpus callosum body above, the pillars of the fornix behind, the anterior commissure and the rostrum of the corpus callosum below, and the leaves of the septum pellucidum at the sides.
In terms of function, the septum pellucidum belongs to the limbic system, a part of the brain associated with emotions and memory, and has important connections within this system. Illness affecting this area could either cause symptoms due to physical pressure on the surrounding brain tissue or disrupt emotional and behavior-related functions.
What Causes Cavum Septum Pellucidum?
The septum pellucidum is a part of the brain that develops in the womb. It is made up of two closely bound layers that surround a space known as the CSP. These two layers come together from the back to the front when the baby is about six months old in the womb. This CSP area typically closes up by three months after the baby is born. However, if it doesn’t close up properly, CSP can last into adulthood and can still be seen in medical images.
Risk Factors and Frequency for Cavum Septum Pellucidum
Cavum septum pellucidum (CSP) occurs in all premature babies and in 85% of babies born full term. In children between 6 months and 16 years old, it’s seen in 12% of cases. Most often, CSP fuses together around 3 to 6 months after a child is born. In the adult population, its occurrence can range from 4 to 74%, depending on how it’s detected and how it’s defined anatomically. Having a cyst in this area is extremely rare, with an occurrence rate of only 0.04% as cited by Wang and colleagues. Symptomatic cysts in this region are even rarer, with very few cases documented in medical literature.
- All premature babies and 85% of full-term babies have cavum septum pellucidum (CSP).
- In children aged between 6 months to 16 years, CSP is seen in 12% of cases.
- Most CSP cases fuse together within 3 to 6 months of birth.
- In adults, the prevalence of CSP varies from 4 to 74%, based on detection methods and definitions.
- Cysts in the CSP area occur at a very rare rate of 0.04%.
- Very few cases of symptomatic CSP cysts have been described in medical literature.
Signs and Symptoms of Cavum Septum Pellucidum
Cysts of the CSP, or cavum septum pellucidum, have been believed to cause various health issues and symptoms in the past. These include mental problems, unsteady movements, speech problems, epilepsy, and bilateral pyramidal signs, which involve abnormal movements or reflexes. However, there isn’t enough scientific evidence to support these claims.
Some people with CSP cysts might experience other symptoms. These could range from persistent headaches to emotional and behavioral changes. Other possible symptoms include:
- Acute or chronic headaches
- Papilledema, a condition where the optic nerve at the back of the eye swells
- Emesis, or vomiting
- Syncope, also known as fainting
- Cognitive impairment, problems with memory or thinking skills
- Emotional and behavioral disturbances
- Visual and sensorimotor findings, changes in vision and body movement
Testing for Cavum Septum Pellucidum
Assessing the cavum septum pellucidum, a part of the brain, requires a special type of brain scan known as magnetic resonance imaging. This part of the brain is typically visible during the development of a baby in the womb between 18 to 20 weeks. As a result, checking for it is a standard part of the ultrasound conducted in the second trimester of pregnancy. If it’s absent, it could indicate other potential issues with the baby’s development (these are referred to as ‘fetal anomalies’).
Treatment Options for Cavum Septum Pellucidum
There are several reasons why treatment might be needed for a condition called cavum septum pellucidum (CSP):
1. If tests like MRI scans show a CSP cyst and the patient has symptoms due to blockage of the fluid flow in the brain’s foramen of Monro.
2. If the cyst from CSP is pushing on surrounding tissues and causing problems.
3. If someone has changes in their mental state or physical symptoms that can be attributed to a CSP cyst.
The main aim of treatment for CSP is to reduce the pressure caused by the cyst, which can only be achieved through surgery.
Traditionally, open surgery, conventional shunting, and a procedure called stereotactic fenestration have been used to treat this condition. The first treated CSP cyst was reported back in 1931 by a doctor named Dandy, who treated a 4.5-year-old boy using a surgical procedure called transcallosal fenestration.
Since 1995, however, a less invasive surgical technique involving neuroendoscopic fenestration has been increasingly used and is now the preferred treatment for symptomatic CSP cysts. With this method, an instrument known as an endoscope is used to create a hole (or fenestration) in the cyst to relieve pressure. There are three different ways this might be done:
1. A frontal approach targeting the frontal horn of the lateral ventricle in the brain, which most surgeons opt for.
2. The same frontal approach, however, direct targeting of the cyst by puncturing it and then creating a hole in the two walls.
3. A hole in the occipital part of the skull to reach the atrium of the lateral ventricle in the brain, which allows dealing with both leaflets of the cyst perpendicularly.
This less invasive approach allows the surgeon to see directly what they’re doing, which helps avoid damage to nerve and blood vessels. It also makes it easier to inspect and manage potential complications like adhesions in the foramen of Monro, which might otherwise cause continuous fluid buildup in the brain, even after successful drainage of the cyst. Another benefit is that it eliminates the need to place a shunt, and it also makes it possible to take a biopsy of the cyst walls.
The choice of surgical path for intracranial endoscopic surgery might be affected by both the existence of CSP and another condition known as cavum vergae, with a route called the transcavum interforniceal path being preferred.
What else can Cavum Septum Pellucidum be?
The cavum vergae is a space within the brain that starts at the cavum septum pellucidum, which is located behind the forward curves of the fornix and in front of the splenium – the thick back part of the corpus callosum or the area connecting the two brain halves.
The cavum veli interpositi is another space in the brain and it’s located below the splenium, and the column of the fornix, and above the internal cerebral veins. It looks like a triangle, with its point stretched forward towards the foramen of Munro, which is a passage within the brain.
A vein of Galen aneurysm is a kind of bulge in this key vein in the brain, and it can be diagnosed using color Doppler technology, a type of ultrasound that creates a visual map of blood flow.
An arachnoid cyst is a fluid-filled sack that forms in relation to the arachnoid membrane, which is one of the three membranes that covers the brain and spinal cord.
Finally, a dilated third ventricle refers to an enlarged space in the brain, located between the two areas called the thalami.
What to expect with Cavum Septum Pellucidum
The condition known as cavum septum pellucidum is usually found by chance and generally does not cause any symptoms.
Possible Complications When Diagnosed with Cavum Septum Pellucidum
The appearance of an enlarged cavum septum pellucidum can be observed in different conditions. These include:
- People with schizophrenia (First observed by De Greef)
- Individuals showing aggression, especially with alcohol use disorder
- Individuals with neurological development disorders
- Boxers due to repetitive head trauma
- People with post-traumatic stress disorder (PTSD)
- Military personnel actively involved in war conflicts or war veterans
- Individuals with obsessive-compulsive disorders
On the other hand, if the cavum septum pellucidum is missing during fetal development, it may be associated with certain disorders, as such:
- Holoprosencephaly
- Septo-optic dysplasia
- Agenesis of the corpus callosum
- Alexander disease
- Tuberous sclerosis
- Phacomatosis
- Pinealoma
- Trisomy 21
- Schizencephaly
- Lissencephaly
- Chiari malformation
Preventing Cavum Septum Pellucidum
It’s important patients understand that having a cavum septum pellucidum (CSP), a slight difference in brain structure, is completely normal and usually doesn’t need any kind of surgery. It’s also unlikely to get worse over time.
However, if the CSP is larger than 1 cm or causing symptoms, it may require more thorough evaluation and management to make sure it’s not causing any issues.
