Diagnostic Accuracy of Epilepsy-dedicated MRI with Post-processing

Abstract

Purpose: To evaluate the diagnostic accuracy of epilepsy-dedicated 3 Tesla MRI including post-processing by correlating MRI, histopathology, and postsurgical seizure outcomes.

Methods: 3 Tesla-MRI including a magnetization-prepared two rapid acquisition gradient echo (MP2RAGE) sequence for post-processing using the morphometric analysis program MAP was acquired in 116 consecutive patients with drug-resistant focal epilepsy undergoing resection surgery. The MRI, histopathology reports and postsurgical seizure outcomes were recorded from the patient's charts.

Results: The MRI and histopathology were concordant in 101 and discordant in 15 patients, 3 no hippocampal sclerosis/gliosis only lesions were missed on MRI and 1 of 28 focal cortical dysplasia (FCD) type II associated with a glial scar was considered a glial scar only on MRI. In another five patients, MRI was suggestive of FCD, the histopathology was uneventful but patients were seizure-free following surgery. The MRI and histopathology were concordant in 20 of 21 glioneuronal tumors, 6 cavernomas, and 7 glial scars. Histopathology was negative in 10 patients with temporal lobe epilepsy, 4 of them had anteroinferior meningoencephaloceles. Engel class IA outcome was reached in 71% of patients.

Conclusion: The proposed MRI protocol is highly accurate. No hippocampal sclerosis/gliosis only lesions are typically MRI negative. Small MRI positive FCD can be histopathologically missed, most likely due to sampling errors resulting from insufficient harvesting of tissue.

Keywords: Epilepsy; Lesion; MP2RAGE; MRI; Post-processing.

Fig. 1

Study flowchart

Fig. 2

A 12-year-old girl presented with daily sensory and bilateral tonic seizures since the age of 6 years. An MRI at the age of 10 years was considered normal (a: arrow). MRI at the age of 11 years revealed a FCD in the depth of the left superior frontal sulcus (b–e) with a thickened cortex and a transmantle sign (d: arrow). Post-processing of the MP2RAGE images using the MAP tool highlights the lesion histopathologically characterized as FCD type IIB (c, e). MRI after 3 months shows the resection of the FCD (f). Outcome after 6 months was Engel 1B

Fig. 3

A 14-year-old girl presented with sleep-related, hyperkinetic, tonic and clonic seizures associated with fear since the age of 5. MRI at the age of 5 did not disclose a lesion (a). MRI at the age of 13 showed a slight FLAIR hyperintensity at the gray-white matter border (b,d,f: arrow) highlighted by post-processing of MP2RAGE images using the MAP tool (e,g)

Fig. 4

A 14-year-old girl presented with hypermotor seizures since the age of 11. MRI showed a hyperintense left-sided cingulate cortex (a,c,e: arrow). The lesion was found by scrolling through the co-registered MP2RAGE images (b: arrow). The junction parameter map displays the gray-white matter blurring (d: arrow). Histopathology revealed gliotic changes, a gray-white matter blurring, some ectopic white matter neurons, no dysplastic neurons, no balloon cells. MRI after 3 months confirmed that the lesion was resected (f). The patient was seizure-free 12 months following surgery

Fig. 5

FCD type IIA in the depth of the right inferior frontal sulcus in a 5-year-old girl with focal motor, tonic and atonic seizures. The FCD shows a funnel-shaped hyperintensity tapering towards the right frontal horn (visible on FLAIR (a) and on T2-weighted (b) images: arrow). The initial histopathological diagnosis of a multinodular vacuolating tumor was revised due to the characteristic MRI pattern also highlighted by post-processing (c). Furthermore, the intracortical black sign is described as a pathognomonic feature of a FCD IIB (d: arrows)

Fig. 6

Left-sided hippocampal sclerosis ILAE type 1 (c: blue arrow) with associated gray-white matter blurring (a,b: hollow arrows) in a 38-year-old patient who had fever-related seizures at the age of 8 months. Right-sided hippocampal sclerosis ILAE type 1 (f: blue arrow) in a 50-year-old patient with temporal lobe seizures since the age of 13 years. Coronal FLAIR (d) and post-processed MP2RAGE images (e) showed no associated gray-white matter blurring