Pediatric Neurology 124 (2021) 3e5 Contents lists available at ScienceDirect Pediatric Neurology journal homepage: www.elsevier.com/locate/pnu Clinical Letter Left-Right Brain Mystery in a Child With a Focal Cortical Lesion Mayur Chalia, MBBS a, Eric Payne, MD b, Gesina Keating, MD a, c, Lily Wong-Kisiel, MD a, c, * a Department of Neurology, Mayo Clinic, Rochester, Minnesota Department of Pediatrics, Division of Neurology, Alberta Children's Hospital, Calgary, Alberta, Canada c Department of Pediatrics, Mayo Clinic, Rochester, Minnesota b a r t i c l e i n f o Article history: Received 16 June 2021 Accepted 31 July 2021 Available online 8 August 2021 Keywords: Tumor Secondary epileptogenesis Seizure Cortex Focal cortical brain lesions cause perilesional EEG abnormalities and ipsilateral epileptiform discharges. The seizure semiology due to a brain structural abnormality depends on the epileptogenic network involved. Concordant ictal semiology, EEG ictal onset, and ipsilateral interictal epileptiform discharges are favorable prognostic factors for surgical candidacy in patients with focal MRI lesions.1 Conversely, patients with discordant imaging and neurophysiologic evaluations pose management challenges in determining surgical candidacy. We present a pediatric patient with a malignant brain tumor and focal seizures arising from the contralateral homologous cortex that completely resolved after tumor resection. This three-year-old right-handed girl presented with several months of recurrent stereotyped episodes concerning for focal with impaired awareness seizures, characterized by right-sided facial twitching, behavioral arrest, and drooling. The episodes occurred two to three times a day and lasted 15-30 seconds. Neurological examination was normal. The patient was born at term and reached normal developmental milestones. There was no family history of epilepsy. The paternal grandmother had a pituitary adenoma. MRI Conflicts of interest: The authors declare no conflict of interest or financial disclosures concerning the materials or methods used in this study or the findings specified in this article. * Communications should be addressed to: Dr. Wong-Kisiel; Department of Pediatrics; Mayo Clinic; 200 1st St SW; Rochester, MN 55902. E-mail address: wongkisiel.lily@mayo.edu (L. Wong-Kisiel). https://doi.org/10.1016/j.pediatrneurol.2021.07.018 0887-8994/© 2021 Elsevier Inc. All rights reserved. brain showed a well-circumscribed 19 mm by 18 mm, nonenhancing T2-hyperintense lesion involving the right perirolandic FIGURE 1. Axial brain MRI showing a well-circumscribed 19 mm by 18 mm, nonenhancing T2-hyperintense lesion in the right perirolandic region. M. Chalia, E. Payne, G. Keating et al. Pediatric Neurology 124 (2021) 3e5 FIGURE 2. (A) Preresection EEG demonstrating independent left central spike wave (arrow) and independent right central sharp waves (*). (B) Preresection EEG left central onset seizure (arrow). The color version of this figure is available in the online edition. 4 M. Chalia, E. Payne, G. Keating et al. Pediatric Neurology 124 (2021) 3e5 seizure-free outcomes after resection of a primary epileptogenic lesion despite the presence of mirror focus in six of seven pediatric patients with a pathology confirmed temporal lobe neoplasm.5 Resolution of epileptiform discharges and seizures from the mirror focus was a gradual running-down process rather than immediate. When the independent stage was established, there were increased seizures from the mirror focus, and removal of the primary epileptogenic lesion no longer influenced the secondary epileptogenic focus.4 The autonomous mirror focus could then initiate a tertiary epileptogenic lesion or progressive epileptogenesis. When a homotopic mirror focus arises contralateral to the tumor, a timely surgical resection can be considered.1 Our patient illustrates that surgical resection of the primary epileptogenic lesion can lead to an excellent seizure outcome despite conflicting scalp EEG findings. region (Fig 1), suggesting a low-grade astrocytoma, oligodendroglioma, or a nonenhancing ganglion cell tumor. Initiation of levetiracetam led to significant seizure reduction. The initial routine EEG was normal. Continuous video-EEG monitoring showed frequent interictal epileptiform discharges over the left central region and rarely over the right central region, with habitual symptoms confirmed as left central onset focal seizures (Fig 2). Resective surgery of the right perirolandic lesion was discussed with the family for tissue diagnosis. They were counseled that seizures may or may not improve following the lesion resection. The patient underwent gross total resection of the lesion with pathology showing an anaplastic astrocytoma (isocitrate dehydrogenase wild type, World Health Organization grade 3). Repeat brain MRI after proton radiation treatment showed no tumor recurrence at six months. Levetiracetam was tapered off, and she remained seizure free for 18 months after resection. A repeat routine EEG was normal without focal slowing or epileptiform abnormality. Focal slowing and interictal epileptiform abnormalities on EEG may be seen with focal MRI lesions. When ictal or interictal epileptiform discharges are seen bilaterally or appear highest in the hemisphere opposite the side of lesion, they are contralateral maximum.2 A secondary epileptogenic “mirror focus” may occur in the homotopic area via callosal or commissural pathways contralateral to the primary epileptogenic lesion. Morrell found 61% of children with cerebral tumor had contralateral mirror focus.3 Secondary epileptogenesis appeared reversible when the primary epileptogenic lesion was removed before clinical seizures arise from the mirror focus (dependent stage) or when clinical seizures are still infrequent (intermediate stage).4 Gilmore et al. observed References 1. Sampaio L, Yacubian E, Manreza M. The role of mirror focus in the surgical outcome of patients with indolent temporal lobe tumors. Arq Neuropsiquiatr. 2004;62:9e14. 2. Wyllie E, Lachhwani D, Gupta A, et al. Successful surgery for epilepsy due to early brain lesions despite generalized EEG findings. Neurology. 2007;69: 389e397. 3. Morrell F. Secondary epileptogenic lesions. Epilepsia. 1960;1:538e560. 4. Morrell F. Varieties of human secondary epileptogenesis. J Clin Neurophysiol. 1989;6:227e275. 5. Gilmore R, Morris II H, Van Ness C, Gilmore-Pollak W, Estes M. Mirror focus: function of seizure frequency and influence on outcome after surgery. Epilepsia. 1994;35:258e263. 5