Quantification of Corticospinal Tracts with Diffusion Tensor Imaging in Brainstem Surgery: Prognostic Value in 14 Consecutive Cases at 3T Magnetic Resonance Imaging.
OBJECTIVE
In this study, we investigated the potential prognostic role of morphologic and quantitative diffusion tensor imaging (DTI) in patients with brainstem cavernoma (BSC) in terms of postoperative outcome.


METHODS
In this retrospective study of 14 brainstem cavernoma patients, we analyzed pre- and postoperative DTI data. White matter tractography of corticospinal tracts (CSTs) was performed with the Fiber Assignment by Continuous Tracking algorithm, and morphologic characteristics of CSTs were compared with clinically assessed motor strength. Fractional anisotropy (FA) and apparent diffusion coefficient (ADC) were measured in ipsi- and contralesional regions of interest at the lesion level, as well as levels caudal and rostral to the lesion. Correlation analysis was performed between lateral index (LI) of ipsi-/contralateral FA and ADC values and patients' motor function.


RESULTS
Preoperatively, normal morphologic features of CSTs corresponded to normal motor function in 4 patients. The other 10 morphologically abnormal preoperative CSTs didn't show corresponding motor impairment either in pre- or postoperative follow-up period. The sensitivity, specificity, positive predictive, and negative predictive values of white matter tractographic morphology on preoperative motor function were 100%, 57.1%, 70%, and 100%, respectively. The corresponding values on follow-up motor function were 100%, 33.3%, 20%, and 100%, respectively. The mean FA at lesion level was significantly lower than the corresponding FA at the contralateral hemisphere (P = 0.009). In areas caudal to the lesion the same trend yet without statistic significance was observed (P = 0.23). There was no significant laterality difference of mean FAs rostral to the level of the lesion. No correlation in LI of FA or ADC in the 3 anatomic levels with simultaneous and long-term follow up motor function was observed. Restoration of the morphology of the affected CST postoperatively was associated with a trend for decreasing ADC compared with the preoperative measurements.


CONCLUSIONS
Intact CST morphology in DTI predicts a favorable postoperative outcome in patients with BSC. Interrupted CSTs and decreased FA values correlate well within BSC lesion level; nevertheless, morphologic characteristics and diffusion parameter changes at lesion level cannot predict poor prognosis. Caudal and rostral diffusion parameters can provide more information of the integrity of CSTs compared with morphologic study alone.
Department of Neuroradiology, University Hospital, University of Zurich, Zurich, Switzerland; Department of Neurosurgery, Beijing Jishuitan Hospital, Beijing, China. Electronic address: yuqiangyao@gmail.com.
Yuqiang
Y
Yao
Department of Neuroradiology, University Hospital, University of Zurich, Zurich, Switzerland; Department of Neurosurgery, University Hospital, University of Zurich, Zurich, Switzerland.
Nils H
NH
Ulrich
Department of Neuroradiology, University Hospital, University of Zurich, Zurich, Switzerland.
Roman
R
Guggenberger
Department of Neuroradiology, University Hospital, University of Zurich, Zurich, Switzerland.
Yahea A
YA
Alzarhani
Department of Neurosurgery, International Neuroscience Institute, Hannover, Germany.
Helmut
H
Bertalanffy
Department of Neuroradiology, University Hospital, University of Zurich, Zurich, Switzerland.
Spyros S
SS
Kollias
D000328:Adult; D016880:Anisotropy; D020295:Brain Stem Neoplasms / Q000473:pathology / Q000601:surgery*; D002648:Child; D056324:Diffusion Tensor Imaging; D005260:Female; D006392:Hemangioma, Cavernous / Q000473:pathology / Q000601:surgery*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000295:instrumentation; D008297:Male; D008866:Microsurgery; D008875:Middle Aged; D019635:Neurosurgical Procedures; D011237:Predictive Value of Tests; D011379:Prognosis; D011712:Pyramidal Tracts / Q000473:pathology*; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D016896:Treatment Outcome; D066127:White Matter / Q000473:pathology*
Apparent diffusion coefficient; Brainstem cavernoma; Corticospinal tract; Diffusion tensor imaging; Fractional anisotropy; White matter tractography