Transmantle sign in focal cortical dysplasia: a unique radiological entity with excellent prognosis for seizure control

Clinical article

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Object

Focal cortical dysplasia (FCD) represents a spectrum of developmental cortical abnormalities and is one of the most common causes of intractable epilepsy in children and young adults. Outcomes after surgery for FCD are highly variable, and prognosticators of seizure freedom are unclear. In a subset of FCDs, a transmantle sign is observed on imaging that focally spans the entire cerebral mantle from the ventricle to the cortical surface. The aim of this study was to characterize seizure control outcomes and prognostic significance of the transmantle sign in FCD epilepsy.

Methods

Fourteen patients with the transmantle sign underwent epilepsy surgery for medically refractory epilepsy. Thirteen patients underwent resective surgery and 1 underwent multiple subpial transections with vagus nerve stimulator placement. Patient demographics, MRI, electroencephalography, intraoperative electrocorticography (ECoG), and pathology were reviewed. The results of this series were compared with those of 114 previously reported patients with FCD without the transmantle sign.

Results

All patients were found to have childhood seizure onset and concordant MRI and ECoG findings. The primary MRI findings associated with transmantle sign included gray-white junction blurring, appearance of cortical thickening, T2 or FLAIR abnormality, and bottom-of-the-sulcus dysplasia. The transmantle sign was usually a focal finding, typically confined to 1 or several gyri with well-circumscribed epileptic tissue. Correlation of the transmantle sign with FCD histopathological subtypes was highly variable. Patients who underwent complete resection of MRI and ECoG abnormalities (12 of 13 patients) became seizure free. When compared with 114 FCD patients without the transmantle sign, patients with the transmantle sign showed significantly improved seizure-free outcomes after complete resections (p = 0.04).

Conclusions

The presence of the transmantle sign in patients with medically refractory partial epilepsy is associated with highly favorable seizure control outcomes after surgical treatment.

Abbreviations used in this paper:ECoG = electrocorticography; EEG = electroencephalography; FCD = focal cortical dysplasia; GTR = gross-total resection; ILAE = International League Against Epilepsy; STR = subtotal resection.

Article Information

Address correspondence to: Edward F. Chang, M.D., Department of Neurological Surgery, University of California, San Francisco, 505 Parnassus Avenue, M779, San Francisco, California 94143. email: changed@neurosurg.ucsf.edu.

Please include this information when citing this paper: published online December 7, 2012; DOI: 10.3171/2012.10.JNS12119.

© AANS, except where prohibited by US copyright law.

Headings

Figures

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    Axial FLAIR (left) and T2-weighted (right) MR images show examples of the transmantle sign. The FLAIR image shows a deep left superior frontal sulcus with a transmantle sign (arrowhead) extending from the depth of the sulcus to the superolateral margin of the left frontal horn. Histological analysis in this case showed FCD Type IIB. The T2-weighted image shows a similar slice as in the FLAIR image, with a transmantle sign (arrowhead).

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    Coronal FLAIR image (A), T1-weighted image (B), and axial FLAIR image (C) show abnormal hyperintense signal (arrowhead) extending from an enlarged left calcarine gyrus laterally to the inferomedial border of the occipital horn of the left lateral ventricle. The transmantle sign is more difficult to appreciate on the coronal T1-weighted image; FLAIR images are most useful in detecting this sign.

  • View in gallery

    Photomicrographs of specimen obtained in a patient with transmantle cortical dysplasia and FCD Type IIB. A and B: Images showing H & E staining of an area in the subcortical white matter with dysmorphic neurons (asterisk) and balloon cells (arrowhead). Panel B is a magnification of panel A, showing disoriented neurons with large and dysmorphic cytoplasm. C: Bielschowsky staining demonstrating dysmorphic neurons with tangled dendrites and axons in the background. D: Glial fibrillary acidic protein staining demonstrating reactive gliosis in the subcortical white matter in the areas with dysmorphic neurons. Original magnification ×20 (A), ×40 (B–D).

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