Neurol Med Chir (Tokyo) 48, 318¿321, 2008

Electroencephalography-Guided Resection ofDysembryoplastic Neuroepithelial Tumor—Case Report—
George IMATAKA, Masahiro OGINO*, Eiji NAKAGAWA,
Hideo YAMANOUCHI, and Osamu ARISAKA
Departments of Pediatrics and *Neurosurgery, Dokkyo Medical University, Tochigi

Abstract
A 3-year-old girl presented with a dysembryoplastic neuroepithelial tumor in the right cingulate gyrus
manifesting as epilepsy refractory to anticonvulsant medication. Computed tomography and magnetic
resonance imaging revealed a cystic tumor in the right cingulate gyrus. The tumor was removed underintraoperative electrocorticography guidance. Abnormal spikes recorded adjacent to the tumor disappeared immediately after total removal. Histological examination showed a multinodular, multicysticstructure, satisfying the criteria for the diagnosis of dysembryoplastic neuroepithelial tumor. She hasremained seizure-free for more than 4 years without complications. In this case, intraoperative electrocorticography was very useful to identify the possible focus and prevent unnecessary resection of theadjacent tissue. Total removal of the tumor resulted in a dramatic reduction of seizure activity.
Key words:
surgery

cingulate gyrus,

complex partial seizure,

Introduction

bed, throwing her arms about, and disturbance ofconsciousness at the age of 2 years 8 months. The
seizures continued for several seconds to minutes,
initially twice or three times a day, increasing up to
10 times a day 1 month later.
On admission, physical and neurological examinations found no abnormalities. Interictal electroencephalography showed normal background activity,
but ictal electroencephalography showed 3 Hz
spike-and-wave complexes in the right parietal andcentral areas. Computed tomography (CT) showed alow density area without contrast enhancement in
the right frontal region (Fig. 1A). Magnetic resonance (MR) imaging revealed a cystic tumor (3 cm indiameter) replacing the right cingulate gyrus(Fig. 1B–D). Single photon emission computed
tomography (SPECT) with technetium-99m ethyl
cysteinate dimer showed attenuated blood flow at
the region corresponding to the tumor (Fig. 1E).
Epileptic seizures were not controlled well evenafter administration of full doses of valproic acidand carbamazepine. Surgical resection was performed through a right frontoparietal craniotomy.
The tumor was soft and gelatinous, and was easily
distinguished from the surrounding parenchyma.
Meticulous intraoperative electrocorticography

Dysembryoplastic neuroepithelial tumor (DNT) is
one of the rarest brain tumors and was first described in 1988.3) DNT is classified as a low-grade
tumor, as World Health Organization (WHO) gradeI, but causes intractable seizures as the tumor develops in the temporal or frontal lobe in childhood.
These seizures are difficult to control with conventional anti-epileptic drugs, but surgical resection ismore successful.1,3,4) We describe a successful surgical treatment of intractable epilepsy caused by DNTwith the clinical, neuroradiological, and histologicalfindings.

Case Report
A 3-year-old girl had been born with no complications at the 36th week of pregnancy, weighing 2200
g, as the second child of dizygotic twins. Her development was normal, and her past history was unremarkable. She developed epileptic seizures
characterized by violent tossing and turning in her
Received2008

October 28, 2005;

Accepteddysembryoplastic neuroepithelial tumor,

March 3,318

DNTFig. 1

A–E: Preoperative computed tomographyscans (A), T1-weighted (B), T2-weighted (C),and fluid-attenuated inversion recovery (D)magnetic resonance images, and technetium-99m ethyl cysteinate dimer single
photon emission computed tomography images (E) showing a tumor mass in the rightcingulate gyrus. F: Two years later, postoperative fluid-attenuated inversion recovery
magnetic resonance images revealing evidence of resection of the tumor.

Neurol Med Chir (Tokyo) 48, July, 2008319

Fig. 2

A, B: Intraoperative electrocorticograms
demonstrating frequent spikes (arrowheads)
from the right cingulate gyrus subjacent tothe anterior side of the tumor (A), which immediately disappeared after resection of thetumor (B). C: T1-weighted magnetic resonance image showing the spikes originatedin regions B-1 and B-2. D: Intraoperative
photograph of the electrocorticography procedure during the operation.

Fig. 3

Photomicrograph of a characteristic area ofthe tumor demonstrating abundant mucinous matrix including oligodendrocyte-likecells and prominent neurons. Hematoxylin and eosin stain, original magnification
×400.

G. Imataka et al.

320(ECoG) showed frequent spikes only from the rightcingulate gyrus adjacent to the anterior side of thetumor (Fig. 2A). These abnormal spikes disappeared
immediately after the total removal of the tumor(Fig. 2B), so resection of the adjacent cerebral parenchyma was omitted. The patient's postoperative
course was uneventful and she was discharged
without complication.
Histological examination of the surgical specimen
revealed an alveolar pattern, a mixture of oligodendroglia-like cells as well as neural and glia cells, with
abundant mucinous matrix in the tumor (Fig. 3). The
histological diagnosis was DNT. Follow-up MR imaging in the outpatient department 2 years after theoperation revealed achoresis changes replacing thetumor (Fig. 1F). She has had no seizure for morethan 4 years after the surgery.

Discussion
In the present patient, imaging procedures such as
CT, MR imaging, and SPECT revealed the brain
tumor in the right cingulate gyrus. Fluid-attenuatedinversion recovery MR imaging is essential for thedetection of DNT, as seen in this case, because of theadequate contrast with the adjacent cerebrospinal
fluid.13) Intraoperative ECoG showed spikes in theright cingulate gyrus adjacent to the tumor.
Localization-related epilepsy, with the seizures
originating in the cingulate gyrus and surrounding
regions, is characterized by complex partial seizures
accompanied by specific symptoms of partial dyskinesia such as sudden commencement of walking
or running, violent body movements, and throwing
about of the arms. These typical seizures in thispatient, characterized by violent convulsions in bed
accompanied by throwing about of the arms, andwith disturbance of consciousness, were almost certainly epileptic seizures originating from the region
around the brain tumor in the cingulate gyrus. These
seizures disappeared immediately after tumor removal and focal resection was performed at an areaadjacent to the tumor. Surgical removal of the lesion
is curative in most patients with DNT, and no additional chemotherapy or radiotherapy is needed, so
accurate diagnosis and surgical treatment is encouraged.3,6)
Complete tumor resection is the most important
predictor of seizure-free outcome in patients withDNT.12) However, resection limited to extratemporallesionectomy, as performed in our case, may spare
the residual epileptogenic cortex.2) Intraoperative
ECoG identified the possible focus and prevented
unnecessary resection of the adjacent tissue. This
sparing of tissue is especially important in or near

the eloquent cortex. Intraoperative ECoG can also
replace invasive monitoring, which is not indicatedfor patients who cannot tolerate long-term recording.
The effects of the type and concentration ofanesthetics remain controversial for accurate diagnosis of the focus. Sevoflurane with 1.5% mean alveolar concentration (2.5% end-tidal concentration)
is now believed to be reliable because the intraoperative spikes are most concordant to the ictal onset
zone recorded by invasive monitoring.5,11)
DNTs are generally considered as benign tumors,
but recurrence or rapid increase in tumor size sometimes occur. Therefore, accurate diagnosis and surgical treatment are essential. In our case, the histological findings fulfilled the criteria for the diagnosisof DNT. According to the WHO classification ofbrain tumors revised in 2000, DNT is included in theneuronal and mixed neuronal-glial tumors of thecentral nervous system, and is characterized by amultinodular multicystic structure, containing glial
and neuronal components with minimal atypia andcortical dysplasia in the adjunct area.7) Therefore,
DNT is considered a hamartoma but is generallyclassified as a low-grade glioma. The differential
diagnosis of DNT includes ganglioma, oligodendroglioma, oligoastrocytoma, and benign cerebral
cysts.3,4,6–10,14,15)
Long-term follow up and observation are essential. Our patient has had an uneventful clinicalcourse for more than 4 years after surgery, with noneurological sequelae and no recurrence of seizures.

Acknowledgment
This study was partially supported by the Ministryof Education, Culture, Sports, Science and Technology (MEXT) KAKENHI 18790733 Grant-in-Aid forYoung Scientists (B).

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Address reprint requests to: George Imataka, M.D., Department of Pediatrics, Dokkyo Medical University, 880
Kitakobayashi,
Mibu–machi,
Shimotsuga–gun,Tochigi 321–0293, Japan.
e-mail: geo＠dokkyomed.ac.jp