Incidentally detected cavum septum pellucidum and cavum vergae

Clinical History

The patient presented with severe lancinating left-sided facial pain which was triggered on chewing. He was clinically diagnosed to have left-sided trigeminal neuralgia and referred for an MRI brain study.

Imaging Findings

MRI Brain showed a loop of the left superior cerebellar artery indenting the superior surface of cisternal segment of left Vth nerve. At the region of indentation the superior surface of the nerve appeared concave suggestive of a possible neuro-vascular conflict.

In addition the septum pellucidum appeared split with CSF filled space between the two laminae. The split was seen extending posterior to the foramen of Monro and columns of fornix. There was no focal expansion of the space or any solid areas.

The rest of the neuroparenchyma was normal.

Discussion

Septum pellucidum is a thin septa made of two laminae extending from anterior surface of corpus callosum to superior surface of the fornix [1]. The Cavum Septum Pellucidum (CSP) is a CSF filled space of several millimetres in diameter present between the two laminae of septum pellucidum [1]. The CSP is bounded anteroinferiorly by anterior commissure, genu and rostrum of corpus callosum (CC); superiorly by the body of corpus callosum and posteriorly by the fornix which also forms the floor of CSP [1]. CSP is an enclosed CSF filled space which is not a part of ventricular system and does not communicate with subarachnoid spaces [2]. Cavum vergae (CV) is an extention of CSP posteriorly above the third ventricle, and beyond the foramen of Monro and anterior columns of fornix [2, 3]. The CV is over third ventricle bounded inferiorly by body of the fornix and the commissure of the fornix, anteriorly by CSP, superiorly by body of CC and posteriorly by splenium of CC [1, 2, 3].

CV is always associated with CSP but never occurs by itself, whereas CSP can exist by itself [1]. This is because CSP and CV developed embryologically from a single cavity lying under the CC called the cavum corpus callosi which starts closing from caudal to cranial end [1]. All fetuses show CSP which grows in size till 27 weeks, plateaus at 28 weeks and then starts gradually closing [4]. Posterior part is completely fused by term and by 6th month postnatally, CSP is completely closed in 85% cases [4].

CSP and CV are usually incidental findings in asymptomatic patients which should be left alone, occasionally they can be symptomatic [3, 4]. Persistence of CSP in the brain has been studied in association with conditions like chronic brain trauma, post-traumatic stress disorder, schizophrenia, dementia and personality changes [1, 3]. Increased incidence of CSP is seen in boxers due to physical forces [1]. Presence of CSP and CV can cause complications during an endoscopic transforaminal approach into the third ventricle [2]. In such cases, endoscopic transcavum interforniceal approach is safer [2].

Differential Diagnosis List

Final Diagnosis

Persistent cavum septum pellucidum and cavum vergae (normal variants)

URL:	https://www.eurorad.org/case/13430
DOI:	10.1594/EURORAD/CASE.13430
ISSN:	1563-4086