Rationale and Objectives
Magnetic resonance imaging (MRI) is an important tool for the diagnosis and management of various central nervous system infections. In the present study, we investigated the role of T2*-weighted angiography (SWAN) imaging in the diagnosis of neurocysticercosis (NCC) viz-a-viz conventional MRI.
Methods
Symptomatic ( n = 46) and asymptomatic ( n = 88) cases from a pig-farming community were imaged using both conventional and SWAN MRI between July 2009 and May 2011. Two experienced neuroradiologists independently reviewed all the images to characterize the lesions as well as detection of the scolex.
Results
A total of 250 lesions were detected in 70 individuals. On conventional MRI, the lesion and scolex visibility was 82.4% (206/250) and 60% (150/250), respectively, which increased to 96.8% and 81%, respectively, using SWAN imaging. On combining SWAN with conventional MRI, the scolex visibility increased to 85% (213/250) of the total 250 lesions detected. Overall, adding SWAN to conventional MRI increased the lesion detection and scolex visibility up to 18% (206 vs. 250) and 30% (150 vs. 213), respectively.
Conclusion
SWAN imaging when added to the conventional MRI protocol for population screening for NCC in endemic regions improves both lesion detection and definitive diagnosis of neurocysticercosis.
Introduction
Neurocysticercosis (NCC) is a parasitic infection of the central nervous system (CNS) caused by the larvae of Taenia solium , commonly known as tapeworm. It is the most common cause of acquired epilepsy in the developing world including India . The diagnosis of NCC is masked by its polymorphic clinical presentation. A wide range of serological assays has been developed for the diagnosis of NCC such as detection of anticysticercal antibodies in serum or cerebrospinal fluid (CSF) by enzyme linked immunosorbent assay (ELISA) or immunoblot with varying sensitivity and specificity . However these assays have been less than satisfactory giving high false positive and false negative reactions. An enzyme linked immunoelectrotransfer blot (EITB) assay using specific glycoprotein (GP) antigens was developed by the Centers for Disease Control and Prevention, Atlanta, GA, with reported sensitivity of 98% and specificity of 100% . A study showed only 28% sensitivity in serum samples of patients with single cyst infection . Subsequent studies from other countries have shown variable results. In Ecuador, 86% of patients with active lesions, 67% with transitional lesions, and only 41% of patients with inactive lesions were positive by the EITB, thus having an overall sensitivity of only 53.6% . In a recently published report from South India, only 12 of 46 (26.1%) patients with computed tomography (CT) diagnosis of NCC were positive by EITB .
Neuroimaging modalities such as CT and magnetic resonance imaging (MRI) have greatly improved the accuracy of diagnosis of NCC. Although CT is considered a more sensitive tool for the detection of calcifications , MRI is better to resolve the differential diagnosis of NCC as it provides objective evidence on the number and topography of lesions, its stage of involution, and the degree of inflammatory reaction. It provides both morphological and functional information and is considered the best neuroimaging tool for the detection of degenerating and innocuous (viable) cysticercosis .
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Materials and methods
Study Subjects
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Neuroimaging
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Imaging Analysis and Quantification
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Serology
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Sample Size Estimation and Statistical Methods
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Results
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Table 1
Distribution of NCC Patients According to Number of Lesions Detected by Both Techniques
Cyst Distribution No. of Patients No. of Lesions No. of Lesions Detected by Statistical Significance Conventional SWAN Single cysts 38 38 32 34 2–10 cysts 30 168 132 166 >10 cysts 2 44 42 42 Total 70 250 206 242 Mean (±SD) ∗ 2.94 (±3.89) 3.46 (±4.25) <0.001
NCC, neurocysticercosis; SWAN, T2*-weighted angiography.
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Table 2
Stagewise Distribution of a Total of 250 Lesions and Scolex as Detected on MRI
Imaging Vesicular Degenerating Calcified_n_ /Scolex_n_ Scolex_n_ Scolex_n_ Scolex CI 51 38 22 15 133 97 206/150 SWAN 45 30 20 13 177 160 242/203 CIS 51 38 22 15 177 160 250/213
CI, conventional MRI; CIS, conventional imaging including SWAN imaging; MRI, magnetic resonance imaging; SWAN, T2*-weighted angiography.
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Table 3
A Total of 113 Lesions Were Seen in Asymptomatic Neurocysticercosis Patients
Imaging Vesicular Degenerating Calcified_n_ /Scolex_n_ Scolex_n_ Scolex_n_ Scolex CI 28 21 8 6 58 37 94/64 SWAN 24 16 8 5 77 69 109/90 CIS 28 21 8 6 77 69 113/96
CI, conventional MRI; CIS, conventional imaging including SWAN imaging; MRI, magnetic resonance imaging; SWAN, T2*-weighted angiography.
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Table 4
A Total of 137 Lesions Were Seen in Symptomatic Neurocysticercosis Patients
Imaging Vesicular Degenerating Calcified_n_ /Scolex_n_ Scolex_n_ Scolex_n_ Scolex CI 23 17 14 9 75 60 112/86 SWAN 21 14 12 8 100 91 133/113 CIS 23 17 14 9 100 91 137/117
CI, conventional MRI; CIS, conventional imaging including SWAN imaging; MRI, magnetic resonance imaging; SWAN, T2*-weighted angiography.
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Serology
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Discussion
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