‘ Migrating ’ intraventricular neurocysticercus cyst

This report describes an intraventricular neurocysticercus cyst of the 4th ventricle with consequent hydrocephalus in an adult man. He was managed with anti-helminthic therapy and a 3rd ventriculostomy. Initial imaging showed the cyst within the 4th ventricle. At follow-up imaging a cyst was present in the 3rd ventricle and the 4th ventricle had returned to normal. It is postulated that the cyst ‘migrated’ from the 4th to the 3rd ventricle.


Introduction
Neurocysticercosis (NCC) is more commonly seen to involve the brain parenchyma and uncommonly involves the ventricular system and subarachnoid spaces. 1 Whereas parenchymal cysticerci can be readily identified on CT and MRI, most authors agree that it is difficult to identify lesions within the cerebrospinal fluid (CSF) spaces. 1 We present a case of NCC of the 4th ventricle which was well demonstrated on conventional MRI sequences.On follow-up imaging the cyst appeared to have 'migrated' to the 3rd ventricle.We are not aware of any reports in the English literature describing 'migrating' intraventricular NCC cysts.

Case description
A 24-year-old male patient presented with progressively worsening occipital headaches and diplopia over a 4-month period.Routine observations were normal and neurological examination was unremarkable.Specifically, there were no cerebellar signs, signs of meningism or papilloedema.A CT scan (Fig. 1) showed hydrocephalus with a disproportionately enlarged 4th ventricle.In addition, multiple calcified punctate lesions were seen scattered throughout the brain parenchyma in keeping with old NCC lesions.There was no abnormal contrast enhancement.The patient was seen by the neurosurgeons who managed the patient as having hydrocephalus of uncertain origin.A 3rd ventriculostomy was performed and the patient responded well.MRI (Fig. 2) showed resolution of the hydrocephalus post 3rd ventriculostomy and a 4th ventricular cyst of CSF signal intensity on T1 and T2-weighted sequences.The cyst wall was best demonstrated on the axial and sagittal FLAIR sequences.Furthermore, an eccentric FLAIR hyperintense mural nodule was easily identified.This nodule represented the scolex and the diagnosis of intraventricular NCC was made.The patient was discharged on albendazole and prednisone.The patient was asymptomatic at follow up 3 months later and repeat MRI (Fig. 3) showed that the 4th ventricle had returned to its normal size and no longer contained the previously seen cyst.
However, a cyst with an eccentric scolex was now present within the 3rd ventricle.It is postulated that the 4th ventricular cyst had 'migrated' to the 3rd ventricle.

Discussion
NCC is an infestation by the larval form of Taenia solium and is the most frequently encountered parasite of the CNS. 2 It is endemic in the developing world 2 and contributes significantly to acquired epilepsy. 1,3The incidence is increasing in the developed world as a result of widespread international travel to endemic regions and immigration of infected individuals. 1,32][3] NCC occurs when cysticercus larvae infect the central nervous system. 1 The larvae normally land in the brain parenchyma and less commonly lodge in the ventricles and the CSF cisterns. 1,4Cysts can also be encountered in several locations at once. 2,4,5CC can be asymptomatic or present with a variety of clinical manifestations including convulsions and signs and symptoms of raised intracranial pressure. 1,2Presentation depends on several factors such as host response, stage of evolution, and number, size and location of cysticerci. 1,2,5Patients with parenchymal cysts normally present with seizures, whereas patients with intraventricular cysts usually present with headaches, vomiting and visual disturbances as a result of hydrocephalus which is potentially fatal. 1,2,5,6The 4th ventricle is the most common intraventricular site 2,5 probably because of gravity or direct entry via the choroid plexus. 6Cysts can degenerate in the ventricular system causing an ependymal reaction identifiable on contrast-enhanced MRI and can lead to permanent neurological complications.

Fig. 1 .
Fig. 1.Uncontrasted CT scan of the brain showing marked hydrocephalus, a disproportionately enlarged 4th ventricle, loss of surface sulcal markings and compression of the basal cisterns.Multiple punctate calcified parenchymal lesions are also present, consistent with old NCC.