The coexistence of brain parenchymal cysts at various stages of evolution, both intraventricular and subarachnoid racemose, is reported in a patient with neurocysticercosis. The condition has a variety of presentations, depending on the location of the cyst. This case is of particular interest because of the rarity of this condition in India.
- brain parenchymal cyst
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Cysticercosis is caused by cysticercus larvae ofTenia solium. The most common manifestation of neurocysticercosis is seizure due to brain parenchymal cysts at various stages of evolution.1 Subarachnoid and intraventricular cysts are rarely seen in India. In Mexicans, however, they are more common (up to 10% of all cases).2Subarachnoid cysts are of the racemose type, as are the majority of intraventricular ones. A combination of cysticercus cysts in these locations is rather uncommon, especially in the Asian subcontinent. Considering the varied presentations of neurocysticercosis, depending on the location of the cysts, it was felt to be worthwhile reporting this case. Some of the varied presentations and their pathogenesis are also discussed.
A 50-year-old man presented to the neurology out-patient department with history of left-sided sensorimotor seizures for the last 3 years with a frequency of once every one or two months. There was secondary generalisation at times. There was also a history of complex partial seizures for the last 6 months. These were characterised by episodic altered behaviour, aimless running around, and complete amnesia for the events. He had suffered from recurrent, nonthrobbing left parieto-occipital headaches, each lasting for a few hours, for the last 18 months. Accompanying the headache, he experienced tinnitus in both ears and vertigo, but there was no vomiting or visual symptoms. He gave a history of pork ingestion. He was on a maintenance of dose of phenytoin. He had received albendazole for a month in November 1994.
His general examination was normal. Systemic examination was unremarkable. The fundus did not show any papilloedema. There was no neurodeficit or meningeal signs. The haemogram was normal and biochemical parameters were within normal limits. Cerebrospinal fluid (CSF) analysis showed 55 cells (all lymphocytes) with protein 2 g/l, sugar 0.2 g/l (corresponding blood sugar 1.1 g/l), Gram stain was negative and culture sterile. Cysticercus serology (IHA) in blood and CSF was 1:8 (not suggestive). Contrast-enhanced computed tomography (CT) scan of the head showed multiple active parenchymal cysts and an enlarged left sylvian fissure (figure 1). Magnetic resonance imaging (MRI) of the brain showed multiple hypointense lesions on T1- becoming hyperintense on T2- weighted image, with multiple cysts in the left sylvian fissure with septations (figure 2A and B). No scolex was seen within the racemose cyst. There was an intraventricular cyst in the right posterior horn, seen more clearly on proton density imaging (figure 2C).
In summary, this patient had multiple cysts (cysticercus) in the brain parenchyma, intraventricular region, and a racemose cyst in the left sylvian fissure. In the absence of any acute neurological signs, it was decided to try medical therapy for one month and then re-evaluate the situation.
The clinical manifestations of neurocysticercosis are determined by the load of organisms, location of cysts, whether the cyst is dead or alive, and the response of the host.1 Parenchymal neurocysticercosis occurs most commonly at grey–white matter junctions. Neurocysticercosis is a common cause of late-onset seizure in countries where it is prevalent. Focal seizures are most common, but generalised tonic–clonic seizures are also observed. While parenchymal neurocysticercosis presents with seizures, subarachnoid neurocysticercosis usually presents with meningitis and raised intracranial pressure. Cysticercosis of the basal cistern is severe and frequently fatal. This variant is caused by a racemose form of cysticercosis which may cause obstruction to 4th ventricular outflow.3Subarachnoid cysticercosis can cause specific neurologic syndromes when large lesions are located in the cerebellopontine angle, sylvian fissure,4 or the convexity. Intraventricular cysts are frequently found in association with subarachnoid cysts. The fourth ventricle is the most common site.5 They usually present as a syndrome of hydrocephalus and increased intracranial pressure. Free floating cysts in ventricles can cause Brun's syndrome, characterised by intermittent foramen obstruction causing episodic recurrent headaches, vertigo, ataxia and drop attacks.5
The racemose form of neurocysticercosis is a collection of transient membranes forming a cluster like a bunch of grapes,6thought to be a forme fruste of cysticercus cellulosae.7Supratentorial racemose cysts are usually found in the sulci. When vesicles break down, an intense inflammatory reaction may occur in the subarachnoid space, causing arachnoiditis and hydrocephalus.
Cysticercus racemose was first described by Virchow in 1860. It is found in serious cases of cerebral cysticercosis and is characterised by larger size (4–12 cm), absence of scolex and a variable appearance. The coexistence of racemose and cellulosae is rare in Asian countries but not uncommon in Mexico (found in 10% of cases).2 The racemose type is more common in the suprasellar area, the cerebellopontine angle and sylvian fissure. The proliferating connective tissue encircles the characteristic bladder wall of the parasite.
Subarachnoid and intraventricular racemose cysts are more easily diagnosed by gross inspection than by microscopy, as they show typical budding of the vesicular wall. In intraventricular cysts there is more intense granulomatous inflammation. The ependymal lining is lost, with subependymal gliosis, ependymitis, and perivascular cuffing.8 As the cyst degenerates, granulomatous ependymitis and gliosis are the only residual histological findings.
According to some authors, cysticercus racemose may actually be due to a different variety of cestode, including Tenia solium, Tenia multiceps, and Tenia serialis.9 In few specimens degenerated scolices have been found, suggesting T solium as the aetiological agent.1 11
CT scan in subarachnoid cysticercosis most commonly shows hydrocephalus, which may be communicating or non-communicating.12 There may be contrast enhancement of tentorium and basilar cistern secondary to arachnoiditis and fibrosis. The vessel involvement can lead to infarction. Intraventricular cysticercus is difficult to diagnose by CT scan alone. Obstructive hydrocephalus in the presence of a low-density intraventricular lesion may give a clue. The cysts enhance with contrast.
CT criteria to differentiate between cellulose and racemose cysts
cellulose cysts are usually located intra-axially, ie, in brain tissue, while racemose cysts are frequently seen in basal cisterns, particularly the suprasellar area and cerebellopontine angle
racemose cysts are usually bigger, appear as multiloculated cysts resembling ‘bunches of grapes’, elicit a more intense inflammatory reaction and frequently act as a space-occupying lesion
in racemose varieties, no scolex is found
MRI is currently the most useful imaging tool for neurocysticercosis. Subarachnoid neurocysticercosis is better seen on MRI than on CT. Similarly, MRI is better for detection of cisternal cysts.13 T1-Weighted images are better for delineating cisternal wall while T2-weighted images are better in detecting oedema and arachnoiditis. Gadolinium-DTPA contrast in T1 images enhances leptomeninges, suggesting inflammation. Racemose cysts have a similar signal intensity to that of CSF.14 Intraventricular neurocysticercosis must be suspected when hydrocephalus is present. MRI is superior to CT scan in detection of intraventricular cyst.14 Proton density images may better delineate the cyst from the CSF around the cyst,13 as shown in the present case.
Ventricular shunting is indicated for hydrocephalus.12 Cyst extirpation and drainage is indicated for racemose cysticercosis. Intraventricular neurocysticercosis also needs extirpation and/or surgical drainage. A few cases have been treated successfully by albendazole alone.15
Subarachnoid, intraventricular, spinal and mixed types of neurocysticercosis may behave in a malignant way with worse outcome.12