|Year : 2020 | Volume
| Issue : 1 | Page : 48-52
Caval variations of the septum pellucidum in A North-Central Nigerian population: A retrospective computed tomographic study
Charles Chibunna Ani1, Kuleve Othniel Iyua1, Yetunde Folake Taiwo1, Danaan J Shilong2
1 Department of Radiology, Jos University Teaching Hospital, Jos, Nigeria
2 Department of Surgery, Neurosurgery Unit, Jos University Teaching Hospital, Jos, Nigeria
|Date of Submission||31-May-2020|
|Date of Decision||10-Jun-2020|
|Date of Acceptance||21-Jul-2020|
|Date of Web Publication||25-Sep-2020|
Dr. Charles Chibunna Ani
Department of Radiology, Jos University Teaching Hospital, University of Jos, Jos
Source of Support: None, Conflict of Interest: None
Background: The septum pellucidum (SP) and its cystic variations are occasionally seen as midline structures during computed tomography (CT) brain investigation of individuals. There is no documented evidence of the pattern and frequency of caval variations of the SP in our environment. Aim: The aim of this study is to determine the prevalence of caval variations of the SP in a North-Central Nigerian population using CT scan. Materials and Methods: This retrospective study evaluated the presence of the caval variations on CT brain scans acquired between January 2011 and January 2013 in a tertiary hospital in North Central Nigeria. Data analysis was carried out using SPSS version 16. A value of P < 0.05 was considered as statistically significant. Results: The prevalence of caval variations of the SP in all CTsan of the brainwas 3.5% (n = 49). The male-to-female ratio was 2.3:1 (34:15). The indication for CT brain scan with the highest frequency of caval variations was head injury (21; 42.8%). Higher distribution of caval variation (15; 30.6%) was seen among patients in the 20–39 age group. Forty-six (93.3%) individuals had only cavum septum pellucidum (CSP) and 3 (6.1%) had coexistence of CSP and cavum vergae (CV). CV alone or a cavum veli interpositum were not encountered. The variations observed were each seen more in the male patients: CSP (31; 67.4%) and CSP + CV (3; 100%); P = 0.821. While CSP alone was most distributed among the third and fourth decades age group (14; 30.4%), CSP + CV was found more among the fifth and sixth decades age group (2; 66.7%); P = 0.190. Conclusion: Caval variations of the SP are seen in North Central Nigeria with a prevalence of 3.5%. The distribution of the variations was observed more among males and varied insignificantly with different age groups.
Keywords: Caval variations, cavum septum pellucidum, cavum veli interpositum, cavum vergae
|How to cite this article:|
Ani CC, Iyua KO, Taiwo YF, Shilong DJ. Caval variations of the septum pellucidum in A North-Central Nigerian population: A retrospective computed tomographic study. J Radiat Med Trop 2020;1:48-52
|How to cite this URL:|
Ani CC, Iyua KO, Taiwo YF, Shilong DJ. Caval variations of the septum pellucidum in A North-Central Nigerian population: A retrospective computed tomographic study. J Radiat Med Trop [serial online] 2020 [cited 2023 Mar 26];1:48-52. Available from: http://www.jrmt.org/text.asp?2020/1/1/48/296107
| Introduction|| |
The septum pellucidum (SP) is a thin triangular shaped midline membrane consisting of two adjoined glial layers or laminae, with its base located anteriorly and its apex posteriorly in the vertical plane. It is attached superiorly to the inferior surface of the body of the corpus callosum, posterior-inferiorly to the anterior commissure and anterior limbs of the fornix, and anterior-inferiorly to the upper surface of the rostrum of the corpus callosum. Each lamina forms part of the medial wall of the anterior horn and central part of the respective lateral ventricle. Transient fluid between the laminae is thought to be part of normal brain development. The fluid-filled cleft known as the cavum septum pellucidum (CSP) becomes visible from the second trimester of pregnancy. An extension of the cavity beyond the columns of the fornix, posterior to the foramen of Monro, is known as cavum vergae (CV), bounded posterior-superiorly by the splenium and body of the corpus callosum and inferiorly the body of the fornix, respectively. The developmental cavities start to obliterate between the 36 and 40 weeks of gestation when the two leaflets of laminae fuse together. CSP can be observed in all fetuses and premature infants and is an established ultrasonographic landmark in the fetal period. The fusion, which is effected in the posterior-anterior direction, is usually completed by 3–6 months after birth. Occasionally, however, the fusion of the laminae fails to occur or is incomplete and manifests as persistence of the cavities, alone or in combination and of varying width, into childhood and adult life. If both CSP and CV coexist, a passage between these two cavities is known as Verga's aqueduct. In addition, another cystic variation, cavum veli interpositum (CVI), can be found at the level of the crux of the fornices, above the roof of the third ventricle and anterior-superior to the pineal gland.
Cavum septum pelluicdum and CV have been previously respectively referred to as the fifth and sixth ventricles. These terms are, however, a misnomer as the spaces neither connects with the ventricular system nor do they usually contain cerebrospinal fluid, unlike the ventricular cavities. Their content may originate from either the ependymal secretion of the leaflets or from communication with the third ventricle. Communication with the ventricular system occurs only when the caval leaves are ruptured or fenestrated. The CVI, though is a cerebrospinal fluid-containing space, is in direct contact with the subarachnoid space but not with the ventricular system.
Although most caval variants are asymptomatic, the presence of CSP in relation to neurological and psychopathological states has been a subject of sundry studies., The variants are seldom observed during review and reportage of computed tomographic (CT) brain of individuals of different age, sex, racial, and ethnic background. A study in southwest Nigeria found CV to be the more prevalent variety. The prevalence of the variants in North Central Nigeria has not been documented.
The purpose of this study is to evaluate the prevalence of the caval variations of SP in a population of North Central Nigeria, utilizing archived CT brain images. The research carried out in a tertiary referral institution like ours will hopefully add to the literature on such peculiarities and form baseline information for further studies on the subject in our geographical setting.
| Materials and Methods|| |
A retrospective cross-sectional review of successive CT brain scan images obtained in Jos University Teaching Hospital between 2011 and 2013 was carried out by the authors. Incorporated in the study were all technically adequate axial CT brain images, including those for patients referred from otorhinolaryngology and maxillofacial units. We excluded those with supervening motional blurring and streak artifacts, severe sub-falcine herniation from the mass effect of tumor or trauma, and children with severe hydrocephalus. A total of 1406 brain CT scans were eventually involved in the study.
A General Electric (GE) Bright Speed 4-slice CT scanner (GE Healthcare, Waukesha, WI, USA) manufactured in 2007 was used for the study. All study participants were positioned supine in the scanner gantry and scanned from skull base to the vertex with contiguous axial slices parallel to the inferior orbito-meatal line, at 2.5 mm intervals for the petrous temporal bone and 5 mm intervals for the rest of the cranial axial sections.
Images were retrieved through an examination export command on the CT user interphase and sent to a work station installed with DICOM viewer software (Merge Healthcare Incorporated, Milwaukee, Wisconsin, USA). The CT scan images were reviewed by all the authors. Coronal and sagittal reconstruction images were employed where necessary. The presence or absence of the CSP, CV, or CVI was noted and documented. CSP is identified as an oval strip of fluid hypodensity in-between and of similar hypodensity to the anterior horns of the lateral ventricles on the same axial scan level. CV is a similar strip but may be triangular between the bodies of the lateral ventricles and may be seen as an extension of the CSP on the same axial section when in combination. CVI is seen on axial images as a fluid hypodensity of triangular configuration pointing anteriorly posterior to the foramen of Monro, at the level of the atria of the lateral ventricles. Information regarding demography and indication for cranial CT as well as the CT diagnosis of the patients were also obtained from the CT entries and documented.
Data analysis was performed using SPSS version 16 (SPSS Inc., Chicago, IL, USA). The association between categorical variables was investigated using Chi-square (or Fisher's exact test). A P < 0.05 was considered as statistically significant. The results are presented in Tables and Figures.
Ethical approval for the study was obtained from the Ethical Committee of the Jos University Teaching Hospital.
| Results|| |
A total of 1406 brain CT scans were studied, made up of 916 males and 490 females. CSP and its variations were present in 49 individuals (age range 0–91 years) with a prevalence of 3.5% [Figure 1]. Male patients constituted 34 (69.4%), whereas the females were 15 (30.6%) with a male: female ratio of 2.3:1 [Table 1]. The indication for CT brain scan with the highest frequency of caval variations was head injury (21; 42.8%) [Table 2]. Higher distribution of caval variation (15; 30.6%) was seen among patients in the 20–39 age group [Figure 2]. CSP alone was found in 46 (93.9%) individuals, while CSP in combination with CV was found in 3 (6.1%) patients. CV was not found alone; neither was any CVI encountered in the study [Table 3]. The variations observed were each seen more in the male patients: CSP (31; 67.4%) and CSP + CV (3; 100%); P = 0.821 [Table 1]. While CSP alone was most distributed among the third and fourth decade age group (14; 30.4%), CSP + CV was found more among the fifth and sixth decade age group (2; 66.7%); P = 0.190 [Table 4].
|Table 2: Indication for computed tomography scan by number of caval variation|
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| Discussion|| |
The presence of SP and its variants has been recognized since the 15th century. It is regarded as an important relay between the hypothalamic autonomic system and limbic system and partakes in consciousness, sleep, and in emotional response to the environment. Some authors have submitted that dysgenesis of these neighboring system structures leads to the persistence of caval variations by disrupting the normal closure process of the SP.
There were 916 (65.1%) males and 490 (34.2%) females of the 1406 brain CT scans studied. More males have been associated with CT brain investigations in literature. This may not be unconnected to the males being more involved in smoking and alcoholism that are associated with an intracranial vascular phenomenon or in activities that lead to brain trauma of varying severity and thereby requiring a brain CT scan. It agrees with the finding of Akinola et al. where males made up 121 (55.7%) of the 217 CT brain scan studied. A study in Taiwan had males constituting 52.3% of the CT brain scan studied. However in a novel study in Indonesia, there were more females than males in the cases reviewed. The difference could result from racial genetic peculiarities.
CSP and its variations were present in 49 of the reviewed 1406 CT brain images with a prevalence of 3.5%. Chen et al. found a prevalence of 0.93% for CSP and CV in their CT based study involving a large cohort of the Taiwanese population. A prevalence of 59.9% was found by Akinola et al. in Lagos, Nigeria. But this study involved a cohort of individuals whose streamlined indication for CT brain scan was the neurological disease. A study among 1000 British boxers showed the prevalence of the caval variations on CT brain scan to be 5.5%, 0.5%, and 9.5% for CSP, CV, and CVI, respectively. Furthermore, in a case-control study involving retired American football players, CSP was more prevalent in retired professional football players compared with patients devoid of any history of traumatic brain injury. The present study was, however, conducted in a setting in which both boxing and American football is not the prevailing sports, and there was no such background in the record of the patients.
Oktem et al. evaluated the prevalence of the variations of SP in a retrospective survey of adults in Turkey using magnetic resonance imaging (MRI) and observed a cumulative prevalence of 6.2%. In another MRI study, Born et al. detected a high prevalence of CSP without significant age dependence. Studies using MRI scans reported higher rates that ranged from 5.1% to 58.7%. Further research at the comparison of prevalence of the variants on MRI and CT in our setting will be interesting.
Recent advancements and newer developments in imaging modalities have led to the enhancement of imaging results. The reported a wider range of prevalence of CSP in healthy adults across studies (0.1%–85%) is therefore predictable.,
In a retrospective study by Hsu et al. using cranial ultrasonographic images of neonates, CSP was the most common variation observed in 62.1% of the neonates, and CV was less commonly observed with a prevalence of 1.19%.
Autopsy researchers have found a higher prevalence of caval variations. This may indicate that intracranial potential spaces hitherto imperceptible on axial imaging open up postmortem and are observable on autopsy studies.
CSP alone was found in 46 (93.9%) individuals, while CSP in combination with CV was found in 3 (6.1%) patients. CV was not found occurring alone in any of the images reviewed and we did not encounter any CVI in this present study. CVI as a variant has been reported by various authors to be often present in neonates but very rarely seen after 2 years., In the study in Indonesia by Faried et al., the combination of CSP and CV constituted 84.6%, with CV occurring alone in the remaining 15.4% of individuals. Furthermore, Chen and Chen discovered most subjects they studied (95.5%) had coexistent CSP and CV, CSP existed alone in 2.8% of the patients, while CV was seen in 1.7%. However, Akinola et al. found the most frequent of the caval variations in South West Nigeria was CV having a prevalence of 39.6% with CVI and CSP constituting 24.4% and 23%, respectively, while caval combinations were found in 47% of the patients studied. Differences in recruitment methods and peculiar ethno-genetic factors may account for the frequency dissimilarity in our study in North Central compared with that in southwest Nigerian population. CSP was also the most frequent variation in a Turkish population with a prevalence of 3.7%, while CV and CVI had a prevalence of 3.1% and 1% each.
In this present study, while CSP alone was most distributed among the 20–39 age group, CSP + CV was found more among the 40–59 age group. The caval variations observed were each seen more in the male patients: Our finding shared some similarities to that of Chen et al. where the prevalence of the caval variations was highest in the group aged 20–29 years and lowest in the group aged above 80 years. The prevalence tended to decrease with increasing age and was higher among male patients. This was attributed to the rapid development during adolescence, which may render the shrunken CPS and CV to grow again and become detectable. The clefts however, shrink back again as age progresses. Akinola et al. observed that CSP was more prevalent among males, while CV was the more prevalent variety in females. According to Oktem et al., CSP was found to be more prevalent in the age group of 41–60 years and less prevalent in the age group of 18–25 years.
The presence of caval variations may be obscured in axial CT brain sections in the event of mass effect following trauma, hematoma, or cerebral tumor in which there are sub-falcine herniation and shift of midline. Such scenario formed part of the exclusion criteria for this study, as earlier stated. Notwithstanding, however, the highest number of caval variations in our study was seen in individuals whose indication for a brain CT scan was head injury [Table 2]. The comparable finding was also observed by Akinola et al. This indicates that the degree of head injuries encountered in the studies was milder and suggests that other factors need to considered in cases of head trauma with complete obliteration of the caval spaces. Both studies were indeed conducted in resource-limited environments with a low rate of routine neuroimaging due to associated cost, but where imaging in head trauma is such an inevitable necessity that many authorities have a special plan and protocol for it.
Our limitations include the use of a retrospective design in this study with nonavailability of a few of the desired data such as the age of the patients [Figure 2]. Perhaps, a prospective case-control design will be more encompassing in portraying a more accurate prevalence of the caval variation in this environment, but the challenge of radiation associated with CT imaging in individuals with predetermined exclusion criteria will have to be overcome. It is hoped the present study will form a baseline for further studies on the subject in our geographical setting.
| Conclusion|| |
The prevalence of caval variations of the SP in North Central Nigeria compares to that seen in literature from some other parts of the world. The distribution of the variations was observed more among males and varied insignificantly with different age groups.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3], [Table 4]