Racemose and intraventricular neurocysticercosis are uncommon types of neurocysticercosis, resulting in a multiloculated, grape-like cluster appearance in the cerebrospinal fluid (CSF) spaces. A male patient presented with symptoms of raised intracranial pressure and demonstrated racemose neurocysticercosis at an atypical location involving the region of the crus of the fornix at the level of the body of lateral ventricles on magnetic resonance imaging. Associated intraventricular neurocysticercosis was seen in the atrium of the left lateral ventricle and fourth ventricle.
Neurocysticercosis is the most common parasitic infection of the central nervous system. It is more prevalent in Latin America, Asia and Africa. It can affect the brain parenchyma, subarachnoid spaces and ventricles. In racemose neurocysticercosis, cysticerci are located in basal cisterns, subarachnoid spaces and ventricles producing multiloculated cystic lesions with mass effect and a surrounding inflammatory reaction.
A 34-year male presented with a history of gradually progressive headache, nausea, vomiting and dizziness for 15 days. There was no history of seizures or visual symptoms and neurological examination did not reveal any focal neurological deficits or signs of meningitis.
Initially, a non-contrast CT scan was performed, which revealed moderate dilatation of both lateral ventricles, as well as the third and fourth ventricles with a few cystic lesions in the forniceal region. No calcified lesions were appreciated at CT imaging.
For further evaluation, MRI with contrast was acquired using a 3 tesla (T) magnetic resonance (MR) scanner at our institute. Magnetic resonance imaging revealed multiple small clustered thin-walled cystic lesions in the region of crus of fornix at the level of the body of lateral ventricles. The lesions were hypointense on T1 weighted imaging (WI), hyperintense on T2WI and revealed suppression on fluid attenuated inversion recovery (FLAIR) sequence images. No post-contrast enhancement of the cyst wall was seen. Surrounding parenchymal T2 and FLAIR hyperintensity was observed (
Magnetic resonance imaging of the brain in the axial plane. T2W(a), T1W (b), fluid attenuated inversion recovery (c), 3-D constructive interference in steady-state (d), T1 post-contrast (e) images reveal multiple small T2 hyperintense, T1 hypointense cystic lesions (white arrows) clustered together in the region of the crus of the fornix, anterior to the splenium of the corpus callosum. These lesions were suppressed on fluid attenuated inversion recovery and followed cerebrospinal fluid signal intensity. There was no enhancement of the cyst with no eccentric enhancing dot within the cyst. Axial 3-D constructive interference in steady-state magnetic resonance (d) image better delineates the cystic lesions producing a grape cluster-like appearance.
Magnetic resonance imaging of the brain. Axial T2 weighted (a), T1 weighted (b), fluid attenuated inversion recovery (c), 3-D constructive interference in steady-state (d), T1 post-contrast (e) and (f) sagittal magnetic resonance imaging 3-D T1 weighted post-contrast images demonstrate a T2 hyperintense, T1 hypointense lobulated multi-cystic lesion (white arrow) in the atrium of the left lateral ventricle. The lesion supresses on fluid attenuated inversion recovery and reveals post-contrast enhancement of the cyst wall with no eccentric enhancing foci. Cystic lesions were better delineated on the axial 3-D constructive interference in steady-state magnetic resonance image (d).
Magnetic resonance imaging of the brain. Axial T2 weighted (a) and fluid attenuated inversion recovery (b) images indicate asymmetrically dilated lateral ventricles (yellow arrows) and fourth ventricle (red arrow) with surrounding periventricular signal. Sagittal magnetic resonance imaging 3-D spoiled gradient recalled echo sequence (SGPGR BRAVO) post-contrast sequence image (c) demonstrates the dilated lateral ventricle, third ventricle, aqueduct of Sylvius and fourth ventricle. An abrupt narrowing was observed at the obex of the fourth ventricle (yellow arrow). A thin membrane-like structure (white arrow) was seen in the fourth ventricle, which possibly represented non-enhancing intraventricular cyst or a post-inflammatory membrane in the fourth ventricle, causing obstruction and upstream dilatation.
Based on these MRI findings, a presumptive diagnosis of racemose and intraventricular neurocysticercosis with obstructive hydrocephalus was made. Differentials considered were ependymal cyst, choroid plexus cyst and colloid cyst. The possibility of an intraventricular neurocysticercosis cyst or post-inflammatory membrane was considered for the fourth ventricle lesion causing upstream obstruction. The patient underwent right ventriculoperitoneal shunting. Cerebrospinal fluid (CSF) was evaluated with enzyme-linked immunoassay (ELISA) was positive for neurocysticercosis. The patient was treated with albendazole and steroids and follow-up imaging was advised.
Neurocysticercosis is endemic in many developing countries, especially in Latin America, South-east Asia, the Indian subcontinent and sub-Saharan Africa. With increasing immigration and travel, the incidence of neurocysticercosis is also growing in developed countries. True disease prevalence is not well known because of the scarcity of case notification systems, systematic population studies and the absence of a gold standard test for screening and detection of asymptomatic disease. Data from different studies have shown that the prevalence of human taeniasis varies from 2.5% to 8.0% in India and the disease burden of neurocysticercosis causing active epilepsy is about one per 1000 population.
Neurocysticercosis is a parasitic disease caused by Taenia solium. Humans are the only known definitive host for the organism and neurocysticercosis occurs when the human acts as an intermediate host after ingestion of its egg present in food contaminated with faeces of the tapeworm carrier. No inflammatory response is elicited when the cyst wall is intact, but when the parasite dies, then cyst contents are released, causing oedema and surrounding inflammatory changes.
Cysticerci can reach the ventricles through the choroid plexus, moving freely within the ventricles or attaching to the ependyma. From the ventricles, it can travel to the basal cisterns, cerebral and spinal subarachnoid spaces and become lodged in these regions. The most common site of intraventricular neurocysticercosis is the fourth ventricle, followed by the third ventricle, lateral ventricle and cerebral aqueduct, respectively.
Bickerstaff et al. suggested that in cisterns, there is no limiting host response of encapsulation leading to uncontrolled proliferation.
Neurocysticercosis is one of the most common causes of recurrent seizures in both the parenchymal and subarachnoid forms because of oedema and encephalitis.
The diagnosis is confirmed by neuroimaging and serological tests. Computed tomography (CT) is the initial imaging study that can identify active neurocysticercosis and the calcified stage of the disease. However, identifying racemose and intraventricular neurocysticercosis is difficult on CT because the cysts are iso-dense to CSF and usually non-enhancing. Magnetic resonance imaging with contrast is the imaging modality of choice for neurocysticercosis.
Racemose neurocysticercosis is mainly seen around the rostral brainstem or Sylvian fissure and usually lacks a scolex with mild or no surrounding oedema.
Intraventricular neurocysticercosis is usually appreciated on FLAIR imaging when CSF is suppressed. On post-contrast T1W images, intraventricular neurocysticercosis appears as an enhancing lobulated cystic lesion with or without adjoining ventriculitis. Obstructive membranes and adhesions can also develop in ventricles because of ependymitis. Additionally, complications such as ventricular dilatation and vasculitis can be seen on MRI. In this case, similar intraventricular cysts were illustrated in the atrium of the left lateral ventricle associated with an obstructive membrane in the fourth ventricle. Differential diagnosis includes ependymal cyst, choroid plexus cyst, choroid plexus papilloma, colloid cyst, arachnoid cyst and cystic metastasis. An ependymal cyst is usually unilocular, non-enhancing, behaves like CSF and displaces the choroid plexus. Choroid plexus cysts are generally bilateral and most commonly seen in the atrium of lateral ventricles within the choroid plexus glomus. The colloid cyst contains mucin and is not completely suppressed on FLAIR. Choroid plexus papilloma is usually seen below five years of age and has a solid enhancing component. Arachnoid cysts and cystic metastasis are very rarely seen in the ventricles.
Newer MR sequences are now being utilised for demonstrating intraventricular and subarachnoid space neurocysticercosis. Three-dimensional CISS is a fully refocussed steady-state gradient-echo MRI sequence. This is a heavy T2W sequence that increases lesion visibility in ventricles, cisterns and subarachnoid spaces.
Amongst the serological tests available for neurocysticercosis, enzyme linked electro-immuno transfer blot (EITB) using lentil lectin glycoproteins (LLGPs) has a sensitivity of >90% and a specificity of 100% for detection of NCC. This assay can be performed on both serum and CSF samples and it has outperformed the classic ELISA test.
Medical management of neurocysticercosis includes cysticidal drugs such as albendazole and praziquantel, steroids and antiepileptic drugs. Medical management is highly effective in the parenchymal and subarachnoid forms. Surgical management in the form of a ventriculoperitoneal shunt is required in cases of symptomatic hydrocephalus. As a result of recurrent blockage of a ventriculoperitoneal shunt, the endoscopic approach for removal of an intraventricular cyst is nowadays the preferred method of treatment.
Racemose neurocysticercosis and intraventricular neurocysticercosis are both rare types of neurocysticercosis. The presence of these cysts in the region of the crus of the fornix, anterior to the splenium of the corpus callosum, is very rare. For intraventricular neurocysticercosis, the atrium of the lateral ventricle is also quite an unusual location. Knowledge of the imaging appearance of racemose neurocysticercosis and the different locations where it can develop will prevent overlooking the diagnosis and excluding other differentials. Moreover, newer MR sequences like CISS and 3-D SPGR should also be acquired, in addition to conventional MR sequences, for better delineation of any cyst or membrane obstructing the ventricles and CSF spaces.
The authors declare that they have no personal or financial relationships that may have inappropriately influenced them in writing of this article.
P.S. was the primary author. All other authors supervised and contributed equally to the final version of the manuscript.
This article followed all ethical standards for research.
This research received no specific grant from any funding agency in the public, commercial or not-for-profit sectors.
Data sharing is available from the corresponding author, P.S.
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