Yonsei Med J.  2013 Jan;54(1):21-27. 10.3349/ymj.2013.54.1.21.

Usefulness of Diffusion Tensor Tractography in Pediatric Epilepsy Surgery

• Lee MJ
• Kim HD
• Lee JS
• Kim DS
• Lee SK

• KMID: 1776913
• DOI: http://doi.org/10.3349/ymj.2013.54.1.21

Abstract

PURPOSE
This study was conducted to assess the clinical relevance of diffusion tensor tractography (DTT) in pre- and post-operative evaluations of childhood epilepsy surgery.
MATERIALS AND METHODS
Seventy-two patients who received epilepsy surgery between March 2004 and July 2008 were retrospectively analyzed (M : F=40 : 32, ages of 3 months to 24 years, mean age=8.9 years). DTT was performed using a 3.0 T scanner and single-shot spin-echo echo-planar imaging with 32-different diffusion gradient directions. We reviewed the data focusing on the type of surgery, final pathological diagnosis, and how the DTT data were clinically used.
RESULTS
The most common form of childhood epilepsy surgery was complete resection of an epileptogenic lesion (n=52, 72.2%). The reported etiologies included cortical dysplasia (n=32, 44.4%), hippocampal sclerosis (n=9, 12.5%), brain tumors (n=7, 9.7%), and non-pathologic lesions (n=4, 5.6%) in the final diagnoses. Twenty-one dysplastic cortexes and four brain tumors involved an approximal relationship with the corticospinal tract (n=18), optic radiation (n=2), and arcuate fasciculus (n=5). Additionally, although DTT demonstrated white matter tracts clearly, DTT in the hippocampal sclerosis did not provide any additional information. In cases of callosotomy (n=18, 25%), post-operative DTT was utilized for the evaluation of complete resection in all patients. DTT information was not used in functional hemispherectomy (n=2, 2.8%).
CONCLUSION
Preoperatively, DTT was a useful technique in cases of cortical dysplasia and brain tumors, and in cases with callosotomy, postoperatively. DTT should be included among the routine procedures performed in management of epilepsy.

Keyword

Child; epilepsy; diffusion MRI; tractography

MeSH Terms

Adolescent
Adult
Brain Neoplasms/pathology/surgery
Child
Child, Preschool
Diffusion Tensor Imaging/*methods
Epilepsy/*pathology/*surgery
Female
Hippocampus/pathology
Humans
Infant
Male
Retrospective Studies
Sclerosis/pathology/surgery
Seizures/surgery
Treatment Outcome
Young Adult

Figure

• 

  Fig. 1 Diffusion tensor tractography (DTT) of a 14-year-old male with intractable epilepsy for 8 years. (A, B and C) On pre-operative evaluation of the left parietal brain tumor, tractography revealed a clear relationship between the lesion and corticospinal tract/motor stripe (blue fibers). Note the metal artifacts (arrowheads) due to inserted grids. Lt. hemiparesis developed after surgery in this patient. Post-operative T2WI (D) and DTT (E and F) demonstrated the approximal proximity of the corticospinal tract with the resection margin, suggestive of possible injury or edema. Pathological diagnosis was DNET. This patient was seizure-free after operation. DNET, dysembryoplastic neuroepithelial tumor; T2WI, T2-weighted image.

• 

  Fig. 2 DTT of an 8-year-old male with intractable epilepsy. (A and B) Pre-operative T2WI showed a high signal mass (white arrow) at the left insula and frontotemporal lobe. (C and D) Pre-operative DTT demonstrated the approximal proximity of arcuate fasciculus (blue fibers) to the mass. (E and F) Post-operative T2WI showed partial resection of the tumor, mainly at the inferior aspect of the mass. (G and H) Post-operative DTT clearly visualizes intact arcuate fasciculus after surgery. Pathological diagnosis was DNET. This patient was seizure-free after operation. DTT, diffusion tensor tractography; DNET, dysembryoplastic neuroepithelial tumor; T2WI, T2-weighted image.

• 

  Fig. 3 DTT of a 10-year old male with generalized tonic-clonic seizure. (A and B) Pre-operative T2WI showed a high signal intensity mass at the left occipital lobe. (C, D and E) Pre-operative DTT showed the approximal relationship between the lesion and optic radiation (yellow fibers). Pathological diagnosis was DNET. Post-operative DTT was not performed. There was no complication such as a visual field defect, and no seizure occurred after operation in this patient. DTT, diffusion tensor tractography; DNET, dysembryoplastic neuroepithelial tumor; T2WI, T2-weighted image.

• 

  Fig. 4 Fiber tractography of a 6-year-old female with intractable epilepsy. (A) Pre-operative DTT showed a normal appearing corpus callosum. (B) Post-operative DTT demonstrated complete resection of the corpus callosum. Seizure was improved after operation. DTT, diffusion tensor tractography.

• 

  Fig. 5 DTT of an 8-year-old male with intractable epilepsy. (A) Pre-operative DTT showed a normal appearing corpus callosum. (B) Post-operative DTT demonstrated incomplete resection of the corpus callosum with residual fiber connection at the splenium. No seizures occurred after operation in this patient. DTT, diffusion tensor tractography.

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