Korean J Radiol.  2017 ;18(4):729-738. 10.3348/kjr.2017.18.4.729.

Value of Repeat Brain MRI in Children with Focal Epilepsy and Negative Findings on Initial MRI

• Jeon TY
• Kim JH
• Lee J
• Yoo SY
• Hwang SM
• Lee M

• KMID: 2427242
• DOI: http://doi.org/10.3348/kjr.2017.18.4.729

Abstract

OBJECTIVE
To evaluate the value of repeat brain magnetic resonance imaging (MRI) in identifying potential epileptogenic lesions in children with initial MRI-negative focal epilepsy.
MATERIALS AND METHODS
Our Institutional Review Board approved this retrospective study and waived the requirement for informed consent. During a 15-year period, 257 children (148 boys and 109 girls) with initial MRI-negative focal epilepsy were included. After re-evaluating both initial and repeat MRIs, positive results at repeat MRI were classified into potential epileptogenic lesions (malformation of cortical development and hippocampal sclerosis) and other abnormalities. Contributing factors for improved lesion conspicuity of the initially overlooked potential epileptogenic lesions were analyzed and classified into lesion factors and imaging factors.
RESULTS
Repeat MRI was positive in 21% (55/257) and negative in 79% cases (202/257). Of the positive results, potential epileptogenic lesions comprised 49% (27/55) and other abnormalities comprised 11% of the cases (28/257). Potential epileptogenic lesions included focal cortical dysplasia (n = 11), hippocampal sclerosis (n = 10), polymicrogyria (n = 2), heterotopic gray matter (n = 2), microlissencephaly (n = 1), and cortical tumor (n = 1). Of these, seven patients underwent surgical resection. Contributing factors for new diagnoses were classified as imaging factors alone (n = 6), lesion factors alone (n = 2), both (n = 18), and neither (n = 1).
CONCLUSION
Repeat MRI revealed positive results in 21% of the children with initial MRI-negative focal epilepsy, with 50% of the positive results considered as potential epileptogenic lesions. Enhanced MRI techniques or considering the chronological changes of lesions on MRI may improve the diagnostic yield for identification of potential epileptogenic lesions on repeat MRI.

Keyword

Focal epilepsy; Brain MRI; Epileptogenic lesion; Child

MeSH Terms

Adolescent
Brain/*diagnostic imaging
Child
Child, Preschool
Epilepsies, Partial/*diagnostic imaging
Female
Humans
Image Processing, Computer-Assisted
Infant
Infant, Newborn
*Magnetic Resonance Imaging
Male
Retrospective Studies

Figure

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  Fig. 1 Flowchart of study population.MRI = magnetic resonance imaging

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  Fig. 2 Results of repeat MRI in children with initial MRI-negative focal epilepsy.MRI = magnetic resonance imaging

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  Fig. 3 Imaging factors alone in case 14 with cerebellar heterotopia.A. Axial proton density T2-weighted initial MR image (0.3T, non-epilepsy protocol) obtained at age of 4 years poorly demonstrates subtle iso-intense lesion (arrow) compared to cerebellar cortex in left cerebellum. B. Axial T2-weighted fast inversion recovery for myelin suppression repeat MR image (3T, dedicated epilepsy protocol) obtained at age of 11 years clearly shows small nodule (arrow), matching with area indicated in (A), with same signal intensity of cerebellar cortex (iso-intense on T1-weighted MR images, image not shown). This lesion is unchanged on second follow-up MRI obtained 15 months later (image not shown).

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  Fig. 4 Lesion factors alone in case 6 with focal cortical dysplasia.A. Axial T2-weighted initial MR image (1.5T, dedicated epilepsy protocol) obtained at age of 3 years reveals focal abnormal gyration in right frontal lobe (arrow). B. Axial T2-weighted repeat MR image (1.5T, dedicated epilepsy protocol) obtained at age of 7 years shows hyperintense cortical thickening and subcortical white matter hyperintensity in right frontal lobe (arrow).

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  Fig. 5 Both imaging and lesion factors in case 3 with focal cortical dysplasia.A. Axial T2-weighted initial MR image (1.5T, non-epilepsy protocol) obtained at age of 8 months shows normal cortical thickness in left temporal lobe (arrows). B. Axial FIRMS repeat MR image (3T, dedicated epilepsy protocol) obtained at age of 9 years demonstrates cortical thickening (arrows), matching with area indicated in (A). Patient underwent temporal lobe resection and pathologic reports revealed focal cortical dysplasia type Ia. FIRMS = fast inversion recovery for myelin suppression

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  Fig. 6 Both imaging and lesion factors in case 7 with focal cortical dysplasia.A. Oblique coronal T2-weighted initial MR image (1.5T, dedicated epilepsy protocol) obtained at age of 4 years after completion of brain myelination shows blurring of gray and white matter junction, thick cortex, and subtle increased underlying white matter signal intensity in left frontal lobe (arrows). B. Oblique coronal T2-weighted repeat MR image (3T, dedicated epilepsy protocol) obtained at age of 15 years demonstrates discernable subcortical white matter hyperintensity in same area (arrows). Patient underwent surgical resection and pathologic reports revealed focal cortical dysplasia type IIb.

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