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NEURORADIOLOGY Table of Contents   
Year : 2002  |  Volume : 12  |  Issue : 3  |  Page : 329-332
Intraventricular cysticerus


Dept of Radiodiagnosis, G.R. Medical College, Gwalior, India

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Keywords: Intraventricular Cyst, Cysticercus

How to cite this article:
Khandelwal S, Sakhi P, Sharma G L, Saxena U D. Intraventricular cysticerus. Indian J Radiol Imaging 2002;12:329-32

How to cite this URL:
Khandelwal S, Sakhi P, Sharma G L, Saxena U D. Intraventricular cysticerus. Indian J Radiol Imaging [serial online] 2002 [cited 2020 Aug 8];12:329-32. Available from: http://www.ijri.org/text.asp?2002/12/3/329/28472

   Introduction Top


Cysticercosis is a Zoonotic parasitic disease caused by infection with the larval stage of pork tapeworm Taenia solium. In humans, the parasite commonly infects the CNS, where it produces a pleomorphic clinical disorder known as Neurocysticercosis (NCC). Cysticercosis is currently considered the most common parasitic disease of the CNS, affecting thousands of individuals living in developing countries [1]. Cysts can be encountered in the parenchyma, ventricles, cisternal spaces or in several locations at one time.

Neuroimaging studies like CT and MRI have drastically improved diagnostic accuracy for NCC by providing objective evidence about the topography of the lesions and the degree of host inflammatory response against the parasite. CT and MR imaging findings in parenchymal NCC depend on the stage of involution of cysticerci. Ventricular cysticerci appear on Neuroimaging studies as cystic lesions that distort the anatomy of the ventricular system and cause asymmetric hydrocephalus [2]. These lesions are usually isodense with CSF and are not well imaged on CT. CT with administration of intraventricular contrast was used to visualize the cysts [3]. Using MR imaging, however, most ventricular cysts are detected, because the scolex is better visualized than on CT and because the signal properties of cystic fluid and CSF are somewhat different on T2 WI [4]. In general, MR imaging is better than CT for the diagnosis of NCC, particularly in patients with lesions in the base of the brain, brain stem cysts, intraventricular cysts and spinal lesions. MR imaging is, however, less sensitive than CT for the detection of small calcifications. Because many patients with NCC have parenchymal calcifications as the sole evidence of disease, this condition may escape detection if only MR imaging is performed [5]. Considering costs, a reasonable approach may be to use CT as the screening neuroimaging procedure for patients with suspected NCC and reserve MR imaging for patients with normal CT scan or for those who have inconclusive CT findings.

The case presented here emphasizes the above mentioned roles of various neuroimaging studies in the diagnosis of intraventricular NCC.


   Case Report Top


The patient is a thirty seven years old, Right handed man with no note worthy medical history. He presented with a chief complaint of Headache for the past 2 months. The patient was a vegetarian and gave a history of loss of consciousness, no history of trauma and no dental work. On physical examination the patient was unremarkable and the neurological examination was intact. He was seen in the Neurology OPD and later imaging was performed.

Plain radiographs of the skull were normal. NECT and subsequent CECT was performed on Toshiba TCT 80A and CTW Hitachi whole body Scanners (3rd Generation). Axial sections showed a dilated 4th ventricle, third and lateral ventricle but no underlying cause could be demonstrated for the hydrocephalus on NE and CECT scans.

MRI was done on AIRIS, MRP 7000, Hitachi, Tokyo, Japan, Both spin echo and TSE sequences with T1 and T2W images in Axial and sagittal planes were done and were compared with post GD-DTP T1 images in axial and sagittal planes. MRI demonstrated a dilated ventricular system including the Lateral, third and fourth ventricles. An intraventricular cystic lesion was seen in the 4th ventricle with an eccentric focus which was iso to intermediate signal intensity on T1 WI and appeared hyperintense on T2WI. A faintly hypointense cyst wall on T1 WI was also seen. Post contrast scans showed patchy enhancement inferior to the cyst.

A Provisional diagnosis of intraventricular cysticercus (in the 4th ventricle) was made which has subsequently confirmed by surgical excision and histopathological evaluation


   Discussion Top


Human beings become infested with the causative agent, the adult pork tapeworm, Taenia solium, by ingesting the ova residing in contaminated food or water or undercooked pork containing its larvae. The ingested ovum matures to its larval stage, which penetrates the human intestinal mucosa and spreads hematogenously to finally encyst in the CNS, eyes, muscles and skin. Although this patient did not ingest pork the transmission was probably through poor sanitation in handling food.

In the CNS, Cysticercosis can affect the brain parenchyma and can seed the subarachnoid space, intraventricular system and spine, usually in subarachnoid location and less commonly, within the cord itself. Symptoms and imaging findings depend on the location of the cyst. Fluid in apparently live cysts has MR signal properties closely paralleling CSF; however cysts presumed to be degenerated, have an increase signal intensity on T1WI

Intraventricular cysticercal cysts constitute 7% - 25% of Neurocysticercosis infections, but the frequency may be as high as 33%. These manifest as symptoms of increased intracranial pressure. However, the lesions are usually clinically silent until obstruction occurs, secondary to either the location of the cystic lesion or associated ependymitis caused by adjacent granulomatous response. They are potentially fatal, with death resulting primarily from acute hydrocephalus. Although the cysts are encountered in the Lateral, third and the fourth ventricles, the fourth ventricle is the most common site of involvement, a location that carries a higher risk for brain herniation and development of basal meningitis [6].

Owing to isoattenuating characteristics of intra cystic fluid, the lesions are occult on CT. They are however more conspicuous on MR imaging and are also associated with obstruction secondary to coexisting ependymitis or adhesions from prior ventricular inflammation.

The differential diagnosis of an intraventricular cyst includes choroid plexus cyst, ependymal cyst, colloid cyst and cysticercal cyst. Choroid plexus cysts are usually asymptomatic and commonly located in the posterolateral ventricles. Ependymal cysts usually occur in the frontal horns of the lateral ventricles and are usually asymptomatic unless they obstruct the foramen of Monro. Colloid cysts are commonly encountered at the roof of the third ventricle, sometimes causing acute hydrocephalus and rarely death.

In the brain parenchyma, the larva undergoes an orderly life cycle, from cysticercus to involution. These pathologic stages can be correlated with progressive radiologic appearance of the lesion [7].

Stage I: Larval tissue invasion phase is not normally imaged owing to the lack of symptoms at this early stage, if imaged, it appears as a localized focus of edema on T2WI and nodular tissue enhancement following administration of Gadopentetate dimeglumine.

Stage II: Vesicular stage: Formation of a cyst that encircles the scolex. These cysts (1-2 cm) are thin walled; contain clear fluid with a scolex 2-4 mm approximately. Being antigenically inert, these do not incite an inflammatory response. MR and CT features are of a cystic thin walled structure that rarely enhances. The fluid within the cyst parallels CSF in signal intensity and the scolex appears as a mural nodule that is isointense with the brain parenchyma. The patient is usually asymptomatic at this stage.

Stage III: Colloidal stage: The parasite dies and the metabolic breakdown results in local inflammatory response, capsule and granulation tissue formation with breakdown of the Blood Brain Barrier, resulting in an avid ring enhancement. The fluid within the cyst transforms into a colloidal suspension containing protein solutes with T1 shortening. The Scolex and Cyst capsule have decreased signal intensity on T2 WI. On CT the cyst contents increase in attenuation. The patient is now symptomatic the most common complaints are seizures, those of headache and signs of raised intracranial tension.

Stage IV: Nodular granular stage: Degeneration of the cysticercus; perilesional edema begins to subside gradually, the cyst involutes and the contents begin to mineralize. The lesion is now isointense with brain parenchyma on T1WI and hypo intense on T2WI. On CT, the lesion is isoattenuating and thick nodular ring enhancement is usually seen.

Stage V: Calcified stage: In this stage there is complete involution of the lesion with continued mineralization. Calcification is obvious on CT and shows susceptibility on MR, particularly on Gradient Echo images.

Subarachnoid (Racemose) Neurocysticercosis usually infiltrates the basal cisterns and sylvian fissures. The cyst may grow several centimeters but they are nonviable and lack scolex. A local meningeal inflammatory reaction may result in fibrosis and hydrocephalus resulting in obstructive symptoms.

Spinal lesions are rare and they are usually subarachnoid, resulting in arachnoiditis. Intra medullary lesions too have been reported and manifest as myelopathic symptoms.

Before the advent of MR imaging, intraventricular cysts were difficult to diagnose noninvasively [8]. Among the invasive procedures used were contrast ventriculography and CT ventriculography. MR imaging with its multiplanar imaging capabilities, excellent depiction of tissue contrast and versatile parameters has made the diagnosis of intraventricular cysticercal cysts easy but still some intraventricular cysticercal cysts are missed on MR studies in which only routine Spin Echo sequences are used. A new MR technique, 3D-CISS i.e. 3 dimensional - constructive interference in steady state, a heavily T2WI high resolution sequence, that is relatively easy and with quicker acquisition time than routine sequences, has been shown useful in this regard.

3D-CISS is routinely used in evaluation of Cerebello Pontine angle lesions, inner and middle ear structures and epidermoids. The millimeter thin sections, short TE (limited signal loss resulting from magnetic susceptibility effect) and low flip angles (limited T1 Weighting) available in this technique allow superb spatial resolution and Signal to Noise Ratio within a clinically feasible acquisition time.

The increased sensitivity of 3D-CISS sequence is a consequence of its higher resolution and may also be related to accentuation of T2 value between the cystic fluid and surrounding CSF

 
   References Top

1.White AC Jr: Neurocysticercosis: A common cause of neurologic disease worldwide. Chin. Infect Dis 24: 101-113, 1997.  Back to cited text no. 1    
2.Madrazo I, Garcia - Renteria JA, Sandoval M, et al: Intra ventricular cysticercosis. Neurosurgery 12: 148 - 152.  Back to cited text no. 2    
3.Madrazo I, Renteria JA, Paredes G, et al: Diagnosis of Intraventricular and cisternal Cysticercosis by computerized Tomography with positive intraventricular contrast medium. J Neurosurgery 55: 947-951, 1981.  Back to cited text no. 3    
4.Ginier BL, Poirier V: MR imaging of intra ventricular Cysticercosis. AJNR Am J Neuroradiol 13: 1247-1248, 1992.  Back to cited text no. 4    
5.Del Brutto OH: Cysticercosis. In Feldmann E (ed): Current Diagnosis in Neurology. St. Louis, Mosby, 1994, pp 125-129.  Back to cited text no. 5    
6.Del Brutto OH: Clues to prevent cerebrovascular hazards of cysticidal drug therapy. Stroke 28: 1088, 1997.  Back to cited text no. 6    
7.Chang KH, Lee JH, Han MH, Han MC: Role of contrast-enhanced MR imaging in diagnosis of Neurocysticercosis. AJNR 12: 509-512, 1991.  Back to cited text no. 7    
8.Govindappa SS, Narayan JP, Krishna Moorthy VM, Shashtry CH. Bela subramanium A, Krishna SS. Improved detection of Intraventricular cysticercal cysts with use of 3D 3D-CISS MR sequence. AJNR Am J Neuroradiol 2000, 21(4): 679-684  Back to cited text no. 8    

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Correspondence Address:
S Khandelwal
Dept of Radiodiagnosis, G.R. Medical College, Gwalior
India
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Source of Support: None, Conflict of Interest: None


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    Figures

[Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4], [Figure - 5]

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    Introduction
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    References
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