Cavum Septum Pellucidum – Overview Of Diagnosis And Treatment Procedure
A cavum septum pellucidum is present in a normal fetus, but over 85% of the fuse by 3-6 months of age, implying that a cavum septum pellucidum remains in 15% of adults.
The cavum septum pellucidum often coexists with and is sometimes mistaken with the cavum vergae, which is located posterior to the fornix's anterior columns.
These gaps erase posteroanteriorly throughout development - the cavum vergae first, followed by the cavum septum pellucidum - and it is not rare for both to arise simultaneously.
Although the word "cavum septum pellucidum" is often used, it is grammatically wrong.
Because it signifies a gap of the septum pellucidum (cavum meaning cave), the second half (septum pellucidum) may be in the genitive noun case, which would be inflected as cavum septi pellucidi.
Both "septum" and "pellucidum" are adjectives of cavum in its recognized misspelling of "cavum septum pellucidum."
The phrase, however, refers to a gap (cavum) between the "septum pellucidum."
Historically, it was also known as the fifth ventricle, but this is no longer recommended since the cavum has no direct interface with the ventricular system.
The septum pellucidum is a structure bordered by the corpus callosum and the fornix body.
It is made up of white matter leaves that run down the medial walls of the lateral ventricles and is bordered with ependyma on the ventricular surfaces.
It is thought to include hypothalamus and hippocampal fibers that diverge from the forniceal columns and is part of the limbic system.
The cavum septi pellucidi et vergae is the total space between the septi pellucidi leaves, with the CSP being the space before either the foramina of Monro or an arbitrary vertical plane produced by the forniceal columns and the cavum vergae being the space posterior.
When the two leaves fail to merge and create the septum pellucidum, many postnatal anatomic variations such as the CSP, cavum vergae, and cavum veli interpositi may occur.
Usually, the CSP and the cavum vergae interact easily with one another. A cavum vergae is generally observed in conjunction with a CSP.
However, it may also be seen on its own. In general, postnatal CSP persistence is regarded as a common form.
Although some studies in the literature relate CSP and cavum vergae to developmental delay and psychiatric illnesses, the clinicopathologic relationship is challenging to establish, considering how frequent this finding is in healthy children.
Cavum septi pellucidum is an essential aspect of the second-trimester central nervous system (CNS) examination; if its normal appearance cannot be established by 20 weeks gestational age, additional investigation is required.
Fetal MRI, performed in the second or third trimester, has become an essential tool in further characterizing the related disorders.
When prenatal MRI is not feasible, postnatal MRI may be utilized to distinguish primary from secondary absence and provide prognostic information and therapy alternatives for patients.
Second-trimester fetal ultrasonography (US) is often conducted between 18 and 22 weeks of gestation.
It may reveal gestational age, the number of fetuses, and placental orientation.
This exam may also identify prenatal anomalies and offer information for birth planning, which can help minimize perinatal death.
The cavum septum pellucidum (CSP) is a well-established feature of the regular screening ultrasonography examination because the absence of an unusual appearance of the CSP may serve as a significant marker for various related brain disorders from holoprosencephaly to isolated septal insufficiency.
It is critical to understand the regular appearance of the CSP to suggest additional workup for early discovery of these related brain abnormalities and to give appropriate prenatal care and counseling.
The cavum septum pellucidum evaluation is necessary for the routine second-trimester fetal anatomy assessment screening.
In an axial picture, the cavum septum pellucidum should be observed as two separate leaves at or slightly above the level of the paired thalami.
The cavum septum pellucidum typically measures 2-10 mm in transverse diameter during the second trimester.
Its breadth usually grows with gestational age, with a minor reduction near term.
The decision to undertake fetal MRI is influenced by many variables, including availability, cost, and pregnancy management.
An absolute absence of the cavum septum pellucidum is caused by either a failure in the formation of the accompanying mid-line structures or destruction due to external factors.
Because fetal MRI has substantially greater sensitivity and specificity for diagnosing central nervous system disorders than ultrasound, several institutions utilize it in addition to ultrasound.
The differential diagnosis might be pervasive when the typical CSP is missed on standard second-trimester ultrasound and seems entirely or partly missing.
Holoprosencephaly spectrum, corpus callosum abnormalities, acquired lack of CSP, hypoplastic optic nerve syndrome, and the isolated septal deficit is among the differential concerns.
Further testing to rule out a CSP cyst is recommended if the CSP is present and enlarged.
- Holoprosencephaly spectrum: Holoprosencephaly is a group of disorders caused by aberrant prosencephalon differentiation and mid-line cleavage during the fifth gestational week. The imaging signature is the exceptional communication of gray matter, white matter, or both across the midline. The spectrum is traditionally divided into alobar, semi lobar, and lobar forms, with no apparent differentiation between subtypes, though all were initially characterized as missing a septum pellucidum. In actuality, the spectrum is broader. We often observe postnatal brain MRI instances that fall into these conventional categories because incomplete cerebral interhemispheric separation may occur in practically all brain parts. These situations are frequently referred to as forme fruste of holoprosencephaly or other midline development defects.
- Spectrum of corpus callosum anomalies: Even in a healthy pregnancy, it may be difficult to distinguish the corpus callosum on the fetal US. Hence the CSP is frequently the greatest signal for screening. In general, there can be no normal CSP without a corpus callosum, and the existence of a typical CSP rules out full corpus agenesis. The lateral ventricles are parallel on axial imaging, with posterior dilatation, colpocephaly, and upturned anterior horns in a "Texas longhorn" or "bull's head" morphology. At 28 weeks and 5 days of gestation, an ultrasound scan of a fetus demonstrates the lack of cavum septi pellucidi and subcortical gray matter heterotopia. On prenatal MRI, hypogenesis of the corpus callosum is simpler to identify and characterize than on the fetal US. On prenatal and neonatal MRI, hypoplasia of the corpus callosum may be challenging to detect. Aicardi syndrome is one of the most well-known disorders, characterized by polymicrogyria, gray matter heterotopia, and interhemispheric cysts in female individuals. MRI is a critical technique for identifying other neuronal migratory aberrations that indicate a poor prognosis.
- Acquired absence of the cavum septum pellucidum: The lack of the CSP has been linked to obstructive hydrocephalus. The lack of CSP is caused by septal necrosis caused by increasing intraventricular pressure. Aqueductal stenosis, Chiari II malformation, and cephaloceles are the most prevalent causes of congenital obstructive hydrocephalus. Although the prenatal US is often used to identify these problems, fetal MRI may help verify the origin of hydrocephalus and prepare for neonatal neurosurgery. In utero, damage like hemorrhage, infarction, infection, or trauma may also result in the lack of the CSP, which can be observed in conjunction with porencephaly, cystic encephalomalacia, or in extreme cases, hydranencephaly. Although the fetal US is commonly used to identify hydranencephaly, fetal MRI may aid confirm the diagnosis. In some circumstances, fetal MRI may be beneficial in detecting whether the lack of the CSP is primary or secondary by revealing concurrent cystic abnormalities or bleeding.
- Hypoplastic optic nerve syndrome: De Morsier coined the phrase "septooptic dysplasia" in 1956. In the absence of the CSP, optic nerve hypoplasia syndrome is the primary differential consideration. Some anomalies, such as schizencephaly and callosal hypogenesis, may be seen on fetal MRI. In prenatal imaging, it is critical to consider the potential of hypoplastic optic nerve syndrome.
- Isolated septal deficiency: In general, it is thought that the lack of the CSP on its own is uncommon and that it is frequently coupled with other abnormalities that are not immediately seen on MRI. On imaging, not all individuals with optic nerve hypoplasia show a missing CSP. Postnatal examination for hypoplastic optic nerve syndrome is still recommended until more is known.
- Isolated enlargement of the cavum septum pellucidum: On fetal US, the transverse diameter of the CSP measures up to 10 mm, and a value greater than 1 cm is considered enlarged. A larger CSP does warrant more investigation. Although a dilated third ventricle and vein of Galen malformation are in the differential diagnosis, both may be ruled out by Doppler US (in the event of a vein of Galen malformation) and fetal MRI. Two potential explanations of an enlarged CSP are isolated enlargement of the CSP or a cyst of the CSP. Even on prenatal MRI, this differentiation may be difficult to discern. Isolated prenatal growth of the CSP has been documented as a normal variation, and isolated interhemispheric cysts may also have usual consequences. Although several studies indicate an expanded CSP post-natally in individuals with developmental delay and psychiatric illnesses (mainly schizophrenia), the sample numbers are modest, and the criteria for CSP enlargement differ. On the other hand, an increased CSP on the fetal US has been linked to trisomy and may justify further genetic testing and counseling.
- Cyst of the cavum septum pellucidum: CSP expansion may potentially be caused by a CSP cyst. A CSP cyst may be challenging to distinguish from an interhemispheric cyst, and fetal MRI may aid further definition. The difference is significant because interhemispheric cysts are often linked with corpus callosum abnormalities, but CSP cysts are not. The histopathologic data of a CSP cyst are limited; some CSP cysts may be choroid or arachnoid in origin, but the ultrastructural study of the cyst walls in two instances revealed that the cyst walls were derived from the septum pellucidum. Although uncommon, a CSP cyst may be linked with ventriculomegaly due to a blockage of cavum septum fluid flow at the foramina of Monro. As a result, the discovery of ventriculomegaly with an enlarged CSP should warrant further counseling since postnatal neurosurgical intervention may be necessary. Similar findings have been made in the context of cavum veli interpositi, and symptomatic cavum veli interpositi cysts may need surgical draining.
Symptomatic cavum septum pellucidum hypertrophy is uncommon and most usually produces intermittent obstructive hydrocephalus with headache and loss of consciousness.
It may be treated surgically by cyst puncture or shunting, ventriculoperitoneal shunting, or radical excision.
The following conditions are treated for cavum septum pellucidum:
- The presence of a CSP cyst on imaging examinations and clinical signs and symptoms due to a blockage of cerebrospinal fluid passage in the foramen of Monro
- The cyst's direct compression of surrounding tissues
- Changes in mental state or localized neurological impairments caused by the CSP cyst
The primary purpose of therapy is to alleviate the cyst's bulk impact, which is solely surgical.
In open surgical procedures, conventional shunting and stereotactic fenestration are the standard treatments in these situations.
Dandy documented the first treated CSP cyst in 1931, when he performed a transcallosal fenestration on a 4.5-year-old kid.
Since the initial endoscopic technique was published, neuroendoscopic fenestration has become a well-established therapeutic alternative and is now the therapy of choice for symptomatic CSP cysts.
There are three endoscopic methods described:
- A frontal approach on the coronal suture 3 cm from the midline, targeting the lateral ventricle's frontal horn (used by the majority of authors)
- The same cortical frontal technique is used, but this time the cyst is directly targeted, and the two walls are fenestrated.
- An occipital burr hole to optimize the trajectory into the atrium of the lateral ventricle, allowing a perpendicular access to both leaflets of the cyst.
Endoscopic fenestration is a less intrusive procedure that provides direct vision and efficacy.
Inadvertent harm is avoided via direct viewing of neuronal and circulatory systems.
It is also critical to examine the Monro foramina for any adhesions that may be causing the hydrocephalus to remain after the cyst has been successfully drained.
Furthermore, this approach eliminates the requirement for a shunt and allows for a biopsy of the cyst walls.
CSP and cavum vergae may influence cerebral endoscopic surgical route selection, with the transcavum interforniceal path favored over the transforaminal approach into the third ventricle.
The cavum septum pellucidum (CSP) is a fluid-filled hollow between septum pellucidum membranes.
It is typically observed by ultrasonography in the second and third trimesters of the pregnancy in most preterm newborns and around 50% of full-term infants.
Cavum septum pellucidum cysts are uncommon, occurring just 0.04 percent of the time.
A cavum septum pellucidum is present in a normal fetus, but over 85 percent of them fuse by 3-6 months of age, implying that a cavum septum pellucidum remains in 15% of adults.
SP is a critical limbic system component connecting to the medial and basolateral limbic circuits.
Diseases affecting the CSP might induce symptoms via a mass impact or disrupt the limbic system's emotional and behavioral activities.
CSP is a vital sign for assessing proper fetal neural axis development.
A thorough assessment and neurological and radiological investigations are required before therapy.
As a result, even if the CSP cysts seem symptomatic, conversations with the radiologist, neurologist, and neuropsychiatrist are required before surgery.