Computed tomography (CT) in parenchymatous cerebral cysticercosis

ClinicalRadiology (1980) 31, 521-528

0009-9260/80/01060521502.00

©1980 Royal Collegeof Radiologists

Computed Tomography (CT) in Parenchymatous Cerebral Cysticercosis 13.MI~RVIS and J. W. LOTZ

Department o f Radiology, Groote Schuur Hospital, Observatory, Cape Town, South Africa Cysticercosis is an infection with a larval or a bladder-worm stage of the species of Taenia. Cysticerci have a predeliction for the nervous system where they may be found in the meninges, the ventricles and within the brain itself. Brain involvement or parenchymatous form has an acute and chronic phase. Before the advent of CT scanning radiology was of little value in the acute parenchymatous cysticercosis, but with CT the ctlanges within the brain can be recognised. In reviewing 14 cases of acute parenchymatous cysticercosis three CTpatterns were found. 1. A diffuse low density pattern with no or little change after contrast medium 2. Multiple low densities with small rounded central areas of enhancement. 3. Large cystic lesions which may become ring lesions after contrast medium. We conclude that in an endemic area for cysticercosis, when one of these CT patterns is present, cysticercosis should be considered in the differential diagnosis. In a child where the clinical features are suggestive, the CT pattern may be diagnostic of cysticercosis. In the chronic parenchymatous stage the cysts have calcified and this may occur within one year of the acute onset. In 11 cases of chronic parenchymatous cysticercosis where the calcification was visible on the plain skull radiographs the CT scan added very little additional information. It may however be of value in confirming intracranial calcifications where their presence on the plain skull radiograph is in doubt.

Cysticercosis is an infection with the larval or bladder-worm stage of species of Taenia. Man is an acceptable intermediate host of Taenia solium as well as the only known definitive host of this worm. The encysted larval stage is usually passed in the pig, but if ova are ingested by man, their shells are dissolved in the stomach and they penetrate the wall of the intestine to be carried by the circulation. They fax to any tissue after having crossed the capillary wall. This stage, cysticercus, consists of a scolex like that of an adult, a short neck and a fluid-filled sac. In man, cysticerci can develop in any soft tissue of the body including muscle, subcutaneous layers, the heart and the eye. However, eysticerci have a predeliction for the nervous system where they may be found in the meninges, the ventricles and within the brain itself (Danziger and Bloeh, 1975; Olive and AnguloRivero, 1962). Consequently four separate forms have been described (Cardenas ffaidCardenas, 1962). 1. 2. 3. 4.

Meningeal Ventricular Parenchymatous Mixed

The parenchymatous form of brain involvement may be acute or chronic (Goni, 1962). In the acute form the presence of cysts within the parenchyma of the brain causes a severe irritation similar to an

encephalitis (Danziger and Bloch, 1975; Olive and Angulo-Rivero, 1962; Goni, 1962). This form of presentation is commoner in children and may be associated with considerable cerebral oedema (Balasubramaniam et al., 1971). Up to the time of the development of CT scanning radiology was of little value in the acute parenchymatous form because the lesions tend to be small and diffuse and do not readily produce vascular displacements at angiography or subependymal deformities of the ventricular system at pneumography (Schultz and Ascherl, 1978). Radiology only demonstrated signs of raised intraeranial pressure, i.e. splaying of the sutures or pressure changes on the pituitary fossa (Danziger and Bloch, 1975). With the advent of CT scanning it has become possible to show the parenchymatous changes within the brain itself. The use of CT in eysticereosis has been reported in the two series (Bentson et al., 1977; Carbajal et al., 1977). Only a few of their reported cases were in the acute parenchymatous phase. In the chronic phase the cysts die and calcify and the plain film radiographic appearance may be typical when a circular streak of calcium surrounds an eccentric spot of the same material of major density. More commonly the calcifications are irregular and of varying sizes (Cardenas and Cardenas, 1962; Latovitzki et al., 1978; Santin and Vargas, 1966).

522 Table 1 -

CLINICAL RADIOLOGY

Acute parenchymatous cysticercosis Age

Clinical presen ration

Plain skull radiograph

CT pattern

1 2

2 4

3 4 5

6 17 3

6

12

7 8 9 10

2 8 7 5

11 12

34 3

13 14

10 12

Two convulsions. Drowsiness. Left sided convulsions followed by left hemiplegia. Generalised convulsions. Convulsions. Left sided weakness. Right sided convulsions followed by right hemiplegia. Left sided hemiparesis Right sided hemiplegia Headache and diplopia Left sided convulsions Left sided convulsions followed by left hemiparesis. Right sided convulsions Left sided convulsions followed by left sided hemiplegia. Headaches with personality change Convulsions

Marked sutural splaying Normal

1 III

Normal Normal Normal

II I I

Mild sutural splaying. Early pressure changes on pituitary fossa. Normal Mild sutural splaying Normal Normal

III

Normal Normal

III I1

Normal Small irregular calcification in left parietal region.

I III

II I II I

RESULTS

METHODS

There were 14 cases classified as having acute We have reviewed CT and plain skull radiographs of all patients diagnosed as having parenchymatous parenchymatous involvement. The ages, reason for cerebral cysticercosis over a two and a half year referral, plain skull radiograph findings and CT scan period. Plain skull radiographs were performed on patterns are summarised in Table 1. The plain films all cases prior to CT scanning. Computed tomography were normal in 10 cases. In three cases there was scans were performed using an EMI head unit with evidence of raised intracranial pressure with splaying 160 X 160 matrix. The scans were performed parallel " of the sutures. Only one case had a small rounded to the orbito-meatal line. Scans were generally area of calcification in the left parietal region which performed before and after intravenous contrast on CT scan was adjacent to a cyst. Three different medium administration. CT scan patterns were found.

(a)

(b)

Fig. 1 - Pattern 1 before (a) and after (b) contrast administration.

COMPUTED

(a)

TOMOGRAPHY

IN C E R E B R A L

CYSTICERCOSIS

(b)

Fig. 2 - Pattern 2. (a) Low densities before contrast. ( b ) R o u n d e d central enhancement.

(a)

(b)

Fig. 3 - Pattern 2. (a) Bilateral low densities. ( b ) Rounded contrast enhancement.

(a)

(b)

Fig. 4 - Pattern 3. (a) Rounded cystic lesions with (b) edge enhancement forming a ring lesion.

523

524

CLINICAL RADIOLOGY

Table 2 - Chronic parenchymatous cystieereosis

Age

Clinical presentation

Plain skull radiograph

Convulsions Convulsions

Multiple calcifications Multiple calcifications

1 2

4 5

3 4 5 6 7 8 9

21 3 8 5 15 20 50

Left sided convulsions Convulsions Right sided convulsions Left sided convulsions Convulsions Convulsions Transient ischaemic attacks

Calcifications poorly visible Multiple calcifications Two or three calcifications Multiple calcifications Multiple calcifications Multiple calcifications Calcifications poorly visible

10

50

Convulsions

Multiple calcifications poorly visible

11

5

Convulsions

Multiple calcifications

CT

Multiple calcifications Multiple calcifications. Mild hydrocephalus. Calcifications well shown. Multiple calcifications Multiple calcifications Multiple calcifications Multiple calcifications Multiple calcifications Multiple calcifications well shown. • Multiple calcifications well shown. Multiple calcifications

Pattern 1 - Six Cases

Pattern 2 - Four Cases

Bilateral diffuse low density areas mainly involving the white matter and showing no or irregular patches o f enhancement after contrast medium administration. The ventricles were small but there was no midline shift (Fig. 1).

Multiple small areas o f low density which were rounded and well defined. After contrast medium administration discrete central areas o f enhance. ment were present (Figs 2, 3).

Fig. 5 - Classical calcification. Rounded with an eccentric spot.

COMPUTED

TOMOGRAPHY

IN C E R E B R A L

CYSTICERCOSIS

525

(a)

(b) Fig. 6 - (a) Plain radiograph with small faint intracerebral calcifications. (b) CT scan o f the same patient demonstrating larger and denser intracerebral calcifications.

Pattern 3 - F o u r Cases

Single or multiple rounded cystic lesions which had regular or :irregular edges. The edge enhanced slightly or significantly after contrast medium admini-

stration providing a ring lesion with a low density centre and a high density rim (Fig. 4). There were 11 cases with chronic parenchymal disease. The findings are summarised in Table 2. In all these cases multiple calcifications were present

526

CLINICAL RADIOLOGY

Fig. 7 - (a) 1976. Acute p a x e n c h y m a t o u s phase showing splaying o f sutures. No calcification.

on the plain skull radiographs. These calcifications were generally punctate or comma-shaped. Only one case had the classical appearance of a rounded calcification with an eccentric spot (Fig. 5). The CT scans in these cases confirm the multiple intracranial calcifications which in all cases were above the tentorium cerebelli. The calcifications on the CT were larger and of a different shape to their appearance on the plain films, being generally oval or rounded (Fig. 6). They were also denser than on the plain films demonstrating the greater sensitivity of CT (Fig. 6b). In 10 cases with calcification there were no other abnormal CT findings. The ventricles were normal in size and there was no midline shift. Only one case had ventricular dilatation associated with calcification. Case Discussion

One of our chronic cases aged three years initially presented in 1976 (before we had acquired our

scanner) with fits and a decreased level of conscious. ness. At the initial presentation the plain skull film showed splaying of the sutures but no calcification. A ventriculogram showed small ventricles but was other. wise normal. Since then he has had intermittent convulsions which have been difficult to control. In 1977 the skull radiograph showed normal sutures and very faint calcification. The CT showed normal sized ventricles and confirmed the faint intracranial calcifications. Two years after the initial presentation these intracranial calcifications had increased in density on plain film and CT (Fig. 7). DISCUSSION CT has proved useful in showing the brain changes of the acute parenchymatous cysticercosis. Three CT patterns were found. 1. A diffuse bilateral low density pattern with very little change after contrast mediuna

COMPUTED

TOMOGRAPHY

IN C E R E B R A L

527

CYSTICERCOSIS

Fig. 7 - (b) 1978. Chronic parenchymatous phase with normal sutures and multiple small calcifications. administration. The main differential diagnosis of this pattern is encephalitis or an acute demyelinating condition. 2. Focal low densities with well-defined central rounded areas of enhancement. The differential diagnosis includes cerebral metastases and tuberculomata. 3. Rounded cystic lesions with well-defined or irregular edges which may enhance in a ring fashion. The differential diagnosis is an abscess or a glioblastoma particularly if the lesion is solitary. The first two patterns are probably manifestations of acute cerebral irritation. The third pattern is probably produced by small cysts adhering together forming clusters or a single large vesicle. Although the CT scan patterns are not diagnostic of cysticercosis, it should be considered in the differential diagnosis particularly in a country where cysticercosis is endemic. The CT scan pattern together with the clinical features may be strongly suggestive of cysticercosis.

The clinical manifestations of cosis are varied depending on the their location and host response 1978; Vijayan et al., 1977; Van

cerebral cysticernumber of larvae, (Letovitzki et al., der Heever et al.,

Fig. 7 - (c) CT of same case in 1978 demonstrating chronic calcifications.

528

CLINICAL RADIOLOGY

1970). Epilepsy is reported to have occurred in 94% of cases (Vijayan et al., 1977). Most of our patients presented with localised or generalised convulsions. A few had focal neurological signs or a depressed level of consciousness. It may be difficult to prove that the patient has cysticercosis. The serologic test possibly considered most useful, is the indirect haemagglutination test which can be performed on either the cerebrospinal fluid or the serum. The false negative rate is believed to be about 15% in cases with active disease (Bentson et al., 1977). In our acute cases the diagnosis was confirmed by serology or histology. Twelve of our acute cases (86%) were in children under the age of 12 years confirming the findings of Danziger and Bloch (1975) and Balasubramaniam et al. (1971) who also found that the acute parenchymatous form occurs mainly in children. In the chronic parenchymatous phase the CT did not add much more information than the plain films and our findings correspond with those reported by Bentson et al. (1977). The calcification was noted to be above the tentorium cerebelli in all cases corresponding with the findings of Danziger and Bloch (1975) and Bentson et al. (1977), b.ut this calcification may develop much sooner than the 10 years estimated by Carbajal et al. (1977). We have seen the development of calcification in one patient within one year and the fact that multiple calcifications were noted in five children under the age of five years also refutes this long time interval. Our youngest patient with calcification was three years old. Most of our patients with calcification also had convulsions as the main presenting feature, but in one patient aged 50 with multiple calcifications on plain X-ray, they were discovered as an incidental finding in the investigation of transient ischaemic attacks unrelated to cysticercosis. Most of these cases had no other abnormality on the CT besides the calcification and this confirms the fact that the acute parenchymal involvement is usually self-limiting and that the calcification only occurs when the cysts die. However, reinfestation with the recurrence of symptoms may complicate the recovery (Balasubramaniam et al., 1971). We conclude that CT is useful in the assessment and diagnosis of the acute parenchymal cysticercosis.

In the case of a child presenting with convulsions who has one of three CT patterns described, the possibility of cysticercosis should be strongly COn. sidered in the differential diagnosis particularly in a country where it is endemic. However, in the chronic phase where calcification is present on the plain skull t'rims, the CT scan has not been of much additional value. It may however show evidence of hydro. cephalus or reinfestation. It is also useful to confirm the presence of calcification in those cases where the calcification on the plain f'dms is very faint and is in doubt.

REFERENCES

Balasubramaniam, V., Kanaka, T. S. & Ramamurthi, B. (1971). Cerebral cysticercosis in India. International Surgery, 56, 172-181. Bentson, J. R., Wilson, G. H., Helmer, E. & Winter, J. (1977). Computed tomography in intraeranial eysticercosis. Journal of Computer Assisted Tomography, 1, 464471. Carbajal, J. R., Palacios, E., Azar-Kia, B. & Churchill, R. (1977). Radiology of cysticercosis of the central nervous system including computed tomography. Radiology, 125, 127-131. Cardenas, J. & Cardenas, Y. (1962). Cysticercosis of the nervous system. II. Pathologic and radiologic findings. Journal of Neurosurgery , 19, 635-640. Danziger, J. & Bloch, S. (1975). Tape worm cyst infesta. tions of the brain. Clinical Radiology, 26, 141-148. Goni, P. B. (1962). Cysticercosis of the nervous system. III. Clinical findings and treatment. Journal of Neuro. surgery, 19, 641-643. Latovitzki, N., Abrams, G., Clark, C., Mayeux, R., Ascherl, G. & Sciarra,~D. (1978). Cerebral cysticercosis.Neurology, 28, 838-842. Olive, J. I. & Angulo-Rivero, P. (1962). Cysticercosis of the nervous system. I. Introduction and general aspects. Journal of Neurosurgery, 19,632-634. Santin, G. & Vargas, J. (1966). Roentgen study of cysticercosis of central nervous system. Radiology, 86, 520528. Schultz, T. S. & Ascherl, G. F. (1978). Cerebral cysticercosis: occurrence in the immigrant population. Neurosurgery, 3, 164-168. Van Der Heever, C. M., Plotkin, R. & Ronthal, M. (1970). Tapeworm cyst infestation of the brain. South African Medical Journal, 44, 1290-1293. Vijayan, G. P., Venkataraman, S., Suri, M. L., Seth, H. N. & Hoon, R. S. (1977). Neuroradiological and related manifestations of cysticercosis. Tropical and Geographical Medicine, 29, 271-278.