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 »  Introduction
 »  Case reports
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Year : 1999  |  Volume : 47  |  Issue : 1  |  Page : 47-50

Reappearing CT lesions : 4 cases.


Department of Medicine, Dayanand Medical College, Ludhiana, Punjab, 141001, India.

Correspondence Address:
Department of Medicine, Dayanand Medical College, Ludhiana, Punjab, 141001, India.

  »  Abstract

An overwhelming majority of disappearing CT lesions in India have been aetiologically linked to cysticercosis. We report 4 patients with disappearing CT lesions in whom the lesion later reappeared at the same (3 patients) or different site (1 patient). One patient was a Taenia carrier. Serial MRI evaluation in one patient revealed a persisting lesion in the interval period. The contribution of these observations towards the understanding of the aetiology of disappearing CT lesions is discussed.

How to cite this article:
Singh G, Bhatia R S, Khurana D, Khurana S. Reappearing CT lesions : 4 cases. Neurol India 1999;47:47-50


How to cite this URL:
Singh G, Bhatia R S, Khurana D, Khurana S. Reappearing CT lesions : 4 cases. Neurol India [serial online] 1999 [cited 2019 Sep 19];47:47-50. Available from: http://www.neurologyindia.com/text.asp?1999/47/1/47/1661




   »   Introduction Top


With the advent of computed tomography in the Indian subcontinent, it was realized that upto 26% of patients with focal seizures, with or without secondary generalization had solitary ring enhancing lesions.[1] These were variously referred to as `disappearing CT lesions', `vanishing CT lesions' or more appropriately, `single, small, enhancing CT (SSECT) lesions'.[2],[3],[4] Chandy et al reported the results of excision biopsy with stereotactic localization in such lesions.[4] Upto 80% of the lesions were due to cysticercosis. Histopathology was inconclusive in the remainder. We have previously reported the results of cysticercus immunoblot assay in patients with SSECT lesions.[5] The assay was positive in 60% cases with SSECT lesions. Current opinion regards the overwhelming majority of the SSECT lesions to be solitary forms of neurocysticercosis.[6]

The majority of the SSECT lesions disappear in the imaging studies, repeated 6 - 12 weeks subsequently. We report 4 cases of `reappearing CT lesions'. These case reports are important because they shed light on the aetiology of the SSECT lesions and the reasons as to why solitary forms of neurocysticercosis are more common than multilesional neurocysticercosis in India.


   »   Case reports Top


Case 1 : A 12 year old male child was seen because of a single right focal motor seizure with secondary generalization. There was no neurological deficit. T1 weighted sequences of MRI revealed a small rounded hypointense lesion with surrounding hypointensity representing oedema in the left middle frontal gyrus [Figure 1a]. T2 weighted sequences revealed a central hyperintense lesion with a hypointense rim and surrounding oedema. Anticonvulsant therapy with phenytoin sodium was started. Four months later, T1 weighted images were nomal. A very small hyperintense spec with no surrounding oedema was noted upon heavy T2 weighted image [Figure 1b]. Phenytoin was gradually tapered off over the next one year. One year after stopping phenytoin therapy, the child again had two serial seizures, similar to the earlier seizure. MRI examination was repeated. A 10 mm x 10 mm lesion with surrounding oedema had reappeared at exactly the same site as in the initial MR scan [Figure 1c]. Therapy with phenytoin was reinstituted. Cysticercus immunoblot assay was positive and repeated stool examinations were negative for the presence of eggs of Taenia solium.

Case 2 : A 10 year old male child had left focal seizures one year ago. Contrast enhanced CT scan at that time revealed a ring enhancing lesion with surrounding oedema in the right frontal region of the brain. Carbamezapine therapy was started. A repeat CT scan 2 months later revealed complete resolution of the lesion. The child presented to us one year after the initial episode because of left focal seizures with secondary generalization. CT scan was repeated and it revealed a new ring enhancing lesion with surrounding oedema in the right frontal region. There was history of pork ingestion in the family. The child had history of passing worms in stools. ELISA for cysticercus antibody was positive and 3 consecutive stool examinations were normal. The dose of carbamazapine was increased. There was no recurrence of seizures.

Case 3 : A 16 year old male presented because of a single generalized tonic seizure. Computed tomography revealed a single enhancing lesion with surrounding oedema in the right posterior parietal region. Imaging was repeated 5 months later and it revealed complete resolution. Anticonvulsants were tapered off. One year later, the patient had another generalized tonic seizure. At this point of time, the CT scan showed a new single enhancing lesion at exactly the previous site. MR examination was also performed ; however, it did not reveal any additional findings. Cysticercus serology was positive and routine stool examinations were negative.

Case 4 : A 7 year old male child presented with history of left focal clonic convulsion, approximately 4 months prior to visit. CT scan done at that time had shown a single contrast enhancing ring lesion with surrounding oedema in the right parietal region [Figure 2a]. Carbamezapine therapy was instituted and there were no subsequent seizures. When the patient presented to us, a CT scan was repeated. The ring lesion in the right parietal region had completely disappeared. Instead, a new lesion of similar morphology had appeared in the left frontal region [Figure 2b]. The patient had never consumed pork. Cysticercus serology was positive and one out of the 3 stool examinations revealed ova of Taenia solium. An MRI done 3 months later, revealed complete resolution of the second lesion without any fresh lesion.


   »   Discussion Top


Reappearance of CT lesions was referred to previously by Ahuja et al, who reported their experience of 5 patients in whom the lesion disappeared and later reappeared at the same or different site after a seizure.[2] The authors felt that these reappearing lesions were different from the usual `disappearing CT lesions', most of which were believed to be due to cysticercosis. They postulated that the breakdown of the blood brain barrier at the epileptogenic focus during a seizure produced the enhancing lesion. Therefore, the enhancing lesion would appear soon after a seizure and disappear during the interictal phase.

In the Indian subcontinent, the SSECT lesions have been aetiologically linked to cysticercosis.[4],[5],[6] It appears to us, that cysticercosis was responsible for both the initial disappearing CT lesions as well as the reappearing lesions. The reappearance of the lesions at the same or different sites is explained by two different hypothesis. As illustrated by case 1, MR examination throws considerable light upon the sequence of events in the case of lesions that reappear at the same site. While the follow up MR examination revealed complete resolution of sur the latter lesion was infact a small additional cyst, adjacent to involuting cyst. Both cysts migrat co-localized to the same region in the brain. At the time of the first seizure, one cyst began to involute and was recognized on the first MR scan [Figure 1a]. The second cyst remained at that site and began to involute at the time of the second seizure [Figure 1c]. Therefore, the location of this cyst was similar to the first cyst. The phenomenon of `reappearing lesions' may, thus be explained by the co-localization of a shower of cysts which involute at different times. This case report illustrates the utility of MR examination in SSECT lesions. It may also be worthwhile to consider albendazole therapy in such cases with the intention of treating the active co-lized cyst.

Case 4 typically exemplifies those lesions that recur at different sites. The putative basis of these lesions may be different. Subjects who suffer brief peods of intestinal taeniasis are likely to develop a single cysticercus cyst in the brain. This cyst later degenerates, manifesting upon the CT scan as a solitary enhancing lesion. However, persons who have either chronic intestinal taeniasis or repeated bouts of intestinal taeniasis may, develop recurrent neurocysticercosis. Such recurrence explains the reappearing CT lesion in case 4. The fact that we could demonstrate carriage of taeniad eggs in the faecal sample of this patient is of significance. Presumably, a taeniid carrier state persisting for a long duration of time, may have led to the recurrent migration of cysticercus larvae to the brain via internal or external autoinfection. Recurrent autoinfection in chronic taeniid carriers can also cause multiple neurocysticercosis. Wadia et al, in a report of multiple - disseminated form of cysticercosis postulated that a shower of a large number of cysticercus larvae into the blood stream at one time was responsible for the multiplicity of lesions.[7]

Nevertheless, the migration of cysticercus larvae to the brain over a period of time explains why the cysts can be found in different stages of development and degeneration at the same time in brain parenchyma of patients with multilesional neurocysticercosis. Most descriptions of neurocysticercosis from the American continents have emphasized upon the multiplicity of lesions in the brain parenchyma.[8],[9] In contrast, the commonest manifestation of neurocysticercosis in India appears to be the SSECT lesion.[5],[10] This geographical variation has been attributed to differences in host immunological status.[6] However, a preliminary evaluation found no immunological differences between patients with solitary and multilesional neurocysticercosis.[11] The majority of the Indian population is vegetarian and most patients with SSECT lesions deny ingestion of pork. Presumably, these persons acquire solitary form of cysticercosis through contamination of food by food handlers and unhygienic culinary practices. On the other hand, multilesional neurocysticercosis develops in persons who have repeated, multiple taeniid exposures arising from frequent consumption of contaminated pork.[12]

 

  »   References Top

1.Wadia RS, Makhale CN, Kelkar AV et al : Focal epilepsy in India with special reference to lesions showing ring or disc like enhance ment on contrast computed tomography. J Neurol Neurosurg Psychiatry 1987; 50 : 1298-1301.   Back to cited text no. 1    
2.Ahuja GK, Behari M, Prasad K et al : Disappearing CT lesions in epilepsy. Is cysticercosis or tuberculosis the cause. J Neurol Neurosurg Psychiatry 1989; 52 : 915-916.   Back to cited text no. 2    
3.Chopra JS, Sawhney IMS, Suresh N et al : Vanishing CT lesions in epilepsy. J Neurol Sci 1992; 107 : 40-49.   Back to cited text no. 3    
4.Chandy MJ, Rajshekhar V, Ghosh S et al : Single, small, enhaning CT lesions in Indian patients with epilepsy. Clinical, radiological and pathological considerations. J Neurol Neurosurg Psychiatry 1991; 54 : 702-705.   Back to cited text no. 4    
5.Gagandeep Singh, Kaushal V, Ram S et al : Cysticercus immunoblot assay in patients with single enhancing CT lesions and multilesional neurocysticercosis. J Assoc Physicians India (In press) 1999.   Back to cited text no. 5    
6.Rajshekhar V : Etiology and management of single small CT lesions in patients with seizures. Understanding a controversy. Acta Neurol Scand 1991; 84 : 465-470.   Back to cited text no. 6    
7.Wadia N, Bhatt M, Desai A : Disseminated cysticercosis. New observations including CT scan findings and experience with treatment by praziquantel. Brain 1988; 111 : 597-614.   Back to cited text no. 7    
8.McCormick GF, Zee CS, Heiden J : Cysticercosis cerebri : review of 127 cases. Arch Neurol 1982; 39 : 534-539.   Back to cited text no. 8    
9.Sotelo J, Guerrero V, Rubio F : Neurocysticercosis : a new classification based on active and inactive forms. A study of 753 cases. Arch Intern Med 1985; 145 : 442-445.   Back to cited text no. 9    
10.Singhal BS, Ladiwala U : Epidemiology of neurocysticercosis in Asia(Abstr.). In : Proceedings 2nd International Congress of Tropical Neurology, Limoges, France 1994; 36.   Back to cited text no. 10    
11.Thussu A, Shah P, Prabhakar S et al : Immunological profile - single small enhancing CT lesions vs neurocysticercosis. Neurol India 1994; 42(suppl.) : 35.   Back to cited text no. 11    
12.Gagandeep Singh. : Cysticercosis in South Central America and the Indian subcontinent. A comparative evaluation. Arq Neuropsiquiatr 1997; 55 : 349-356.   Back to cited text no. 12    

 

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