Intraventricular and subarachnoid racemose cysticercosis.

Cysticercosis is endemic in India. Neurocysticercosis most commonly affects the brain parenchyma, which presents as focal lesions with the surrounding edema which later calcify. Rarely, it may affect the ventricular system and subarachnoid spaces and this form is known as racemose cysticercosis. We present magnetic resonance findings in a case of racemose cysticercosis.

INTRODUCTION

Racemose variety of cysticercosis is an uncommon type of neurocysticercosis, characterized by involvement of ventricular system and subarachnoid spaces It is often difficult to diagnose on computed tomography (CT) and may present with only subtle asymmetry of ventricles or enlargement of cisterns. Due to its superior contrast resolution and direct mutiplanar capability, magnetic resonance imaging (MRI) is the investigation of choice for the diagnosis which shows multiple cystic lesions without any scolex and asymmetry of ventricles.

CASE REPORT

A 40-year-old male patient presented with complaint of occipital headache for 2 months. There was no associated history of nausea or vomiting. There was no history of seizures, visual symptoms or altered behavior. There was no history of hypertension or diabetes. Neurological examination did not reveal any focal deficit. Cranial nerves were normal on examination. Cerebrospinal fluid (CSF) examination was normal. Initially, plain CT scan was done. It revealed asymmetrical enlargement of ventricular system. No focal parenchymal lesions were seen. Subsequently, MR imaging of brain with contrast was done on 1.5 T scanner. Axial T1W [Figure 1], post contrast sagittal [Figure 1b] and post contrast coronal [Figure 1c] images revealed multiple cystic lesions of varying sizes in the subarachnoid spaces and in intraventricular location. Cyst walls were not well seen on T2W images [Figure 1d]. No enhancement was seen. No scolex was indentified in the lesions. Largest of them was seen in left temporal horn. There was evidence of hydrocephalus with asymmetrical dilatation of lateral ventricles, which could be attributed to similar cysts in lateral ventricles whose walls may not be discernible on MRI. Third and fourth ventricles were normal in caliber. Based on the characteristic imaging findings, diagnosis of intraventricular and subarachnoid racemose cysticercosis was made. Due to widespread lesions and non-specific symptoms, the patient was managed conservatively.

Figure 1

Axial T1W image (a) shows multiple cysts in the preimesecephalic cisterns (white arrows). Post contrast T1W sagittal (b) and coronal (c) images show multiple cysts in the ventricular system and in the subarachnoid spaces (white arrows). No cyst wall enhancement or meningeal enhancement is seen. No scolex is identified. Also note the asymmetry of lateral ventricles. Cyst wall in not well appreciated on T2W image (d)

DISCUSSION

Cysticercosis is a zoonosis caused by Taenia solium and is endemic in India. Man is the only definite host for T. solium, while pig acts as the intermediate host. Cysticercosis results when man acts as the intermediate host, which could be either due to ingestion of infected food containing eggs or due to reverse persitalsis of eggs into stomach in patients harboring tape worms in the small intestine.[1]

Nervous system in the most commonly infected (in about 60–90% cases) and is known as neurocysticercosis. The condition most commonly affects the brain parenchyma. It undergoes progressive degeneration and depicts four stages of development – vesicular, colloid vesicular, granular nodular and nodular calcified stages. Occasionally, Cysticercus cysts are seen in the ventricular system and in subarachnoid spaces.[2] This is known as racemose variety of cysticercosis. This variety differs from the parenchymal lesions by the absence of usual temporal development of degenerative stages and nonvisualization of scolex in majority of the cases.[3] In our case, the largest of the cysts was seen in left temporal horn which could be related to more space available for growth of the cyst.

Cysts can be identified by their wall or by their mass effect. Cyst walls were seen better on T1 W images in our case. High-resolution constructive interference in steady state (CISS) MR sequence is highly suited for visualizing cyst wall and to look for scolex. Cysts can also be identified by their mass effect when the cyst wall is not identified. In our case, there was asymmetrical dilatation of lateral ventricles which could be due to intraventricular cysts.[4]

Intraventricular cysts can cause noncommunicating hydrocephalus due to obstruction by cysts or scarring due to ependymitis. They can also cause sudden death by causing acute ventricular obstruction. This mandates early surgical intervention to remove the intraventricular cysts.[5]