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Romanian Neurosurgery (2011) XVIII 4: 483 - 490          483 

 
 
 

The role of MR tractography in pre-surgical planning – 
personal series of 25 cases and a review of the literature 

Bogdan Iliescu, Anca Dabija1, Ziyad Faiyad, Sergiu Gavas, Ion Poeată 

Department of Neurosurgery, “Prof. Dr. N. Oblu” Clinical Emergency Hospital, 
“Gr. T. Popa” University of Medicine and Pharmacy, Iasi 
1Department of MR Imaging, Supermeditest, Iasi 

 

Abstract 
Diffusion tensor imaging (DTI) contains 

a wealth of information on molecular 
diffusion in biological tissues [1,2]. 
Visualizing the white-matter tracts using 
diffusion anisotropy maps represents one of 
the applications with a major impact on 
neurosurgical case management [3]. 
Knowledge of the topography, integrity, 
and involvement by the pathological 
process of the white matter tracts is an 
important factor in pre-surgical planning 
for patients with brain lesions. We have 
evaluated the clinical utility of a magnetic 
resonance tractography technique based on 
DTI.  

We studied, in a prospective manner, 25 
cases with lesions involving salient 
intracerebral and medullary tumors (22 and 
3 cases respectively). All cases followed a 
preoperative imaging protocol that included 
DTI on top of the usual MR imaging 
protocol. We analyzed the DTI findings 
preoperatively and looked at the significant 
information that influences the surgical 
plan: position of the significant white 
matter tracts, the degree of their 
involvement in the pathological process and 
anatomical integrity, relationships with 
important anatomical landmarks and with 
the major surgical approach paths. We 
present the postoperative results and some 

of the most illustrative cases in the series 
and compare our results with the similar 
studies in the literature.  

Our experience, based on the results of 
the present study strongly suggests that in 
depth knowledge of the white matter tracts 
involvement in an intracerebral or 
intramedullary pathological process 
improves significantly the surgical planning 
in terms of surgical procedure safety and 
functional outcome. 

Introduction 
Planning the adequate surgical 

procedure for removal of a pathological 
process within the brain or the spinal cord 
requires a thorough knowledge of the 
particular relevant anatomy preoperatively. 
The goal of maximal safe resection is 
difficult to achieve without detailed 
information of functional areas and 
structures and their relationship with the 
pathology. The advent of diffusion tensor 
imaging has revolutionized the study of 
white matter tracts in the living human 
brain. Tractography has made it possible to 
study the detailed anatomy of white matter 
tracts and to depict important information 
for neurosurgical planning. 

Arguably correct pre-operative 
identification of white matter tracts is at 
least as important as the identification of 



 
 
 
484          Bogdan Iliescu et al          MR tractography in pre-surgical planning 

 
 
 

eloquent cortices, such as the motor cortex. 
First, the precentral gyrus (the location of 
the motor cortex) can usually be identified 
by the operating neurosurgeon by visual 
inspection. Second, direct intraoperative 
white matter stimulation is much less 
reliable than cortical stimulation. On the 
other hand, it is essentially impossible to 
identify separate white matter tracts, such as 
the cortico-spinal tract (CST - the main 
motor tract) or the thalomo-cortical tract 
(the main sensory tract) by visual inspection 
as they traverse the corona radiata. 

In the present study we have investigated 
the role of MR tractography in pre-surgical 
planning for pathological processes 
affecting both the brain and the spinal cord. 
All patients underwent neurological 
evaluation, including assessment of motor 
and language functions preoperatively and 
at two points postoperatively. The imaging 
and clinical data was retrospectively 
analyzed to assess the factors that help 
predict the postoperative outcome and the 
contribution of white matter tracts 
involvement in the pathological process as 
an outcome prognostic factor. A special 
emphasis was given to the tailoring of 
surgical approach when tract information 
(direction of displacement, relationship 
with the tumor) is included in the surgical 
algorithm. 

Materials and method 
25 patients with expansive processes of 

functional areas were introduced in the 
study. The age of patients was between 20 
and 66 years (median 48 years). All patients, 
14 men and 11 women underwent a 
magnetic resonance investigation protocol 
which included standard sections (T1, 
enhanced T1, T2, Flair, TOF) 
supplemented with diffusion tensor 

imaging. Magnetic resonance imaging 
studies were performed on a 1.5 T scanner 
standard RM (Siemens Avanto) using a 
standard rectangular cage. DTI studies were 
performed as part of a preoperative imaging 
protocol. Component of an institutional 
protocol, informed consent was obtained 
for each patient to participate in the DTI 
study, prior to investigation. 

The color-coded maps obtained from 
the DTI scan were analyzed. In each case 
the tumors were confined to just one 
hemisphere which favored a direct, within 
subject comparison of the affected white 
matter tracts in the tumor baring 
hemisphere with the contralateral, control 
hemisphere. The white matter tracts were 
characterized as follows: displaced, if they 
maintained normal anisotropy relative to 
corresponding contralateral tract but was 
located in an abnormal location or 
abnormal orientation according to the 
standard color code, edematous, if they 
maintained normal anisotropy and 
orientation but showed obvious increase in 
intensity on T2 images, infiltrated if they 
were characterized by reduced anisotropy 
yet remained visible on the orientation 
maps and degenerated if the anisotropy was 
significantly reduced as such there was no 
identifiable tract on the orientation maps. 
For tracts characterized as infiltrated we did 
not try to determine whether anisotropy 
was reduced as a result of vasogenic edema, 
tumor infiltration or a combination of these 
factors. Such a distinction is extremely 
difficult if not impossible only by DT 
imaging. 

Patients with lesions that involved the 
speech areas underwent awake surgery as a 
method to monitor the specific neurologic 
function intraoperatively. These patients 
received local anesthesia so that the basic 



 
 
 

Romanian Neurosurgery (2011) XVIII 4: 483 - 490          485 

 
 
 

functions of motor speech could be 
evaluated. Patients were not intubated in 
order to be able to respond coherently to 
the tests performed during surgery. In the 
first stage, cortical mapping was performed 
by identifying tumor and sulci and giri 
using macroscopic anatomical landmarks 
and intraoperative ultrasound. The same 
mapping was repeated before resection, to 
avoid any damage to the eloquent area. The 
patient was asked to perform various 
counting exercises (repeat counting several 
times from 1 to 10) and the image naming 
tests. For the naming task, we used the DO 
80, which consists of 80 black and white 
pictures selected according to variables such 
as frequency, familiarity, age of acquisition 
and level of education. [13] 

Results 
For the 25 patients that were included in 

the present study the location of the 
pathological process was temporal lobe in 
two cases, frontal lobe, two cases, insula, 
five cases and parietal region in three cases. 
Dominant neurological symptoms on 
admission, except for headache with or 
without intracranial hypertension 
syndrome (present in 18 cases), were motor 
deficits and motor aphasia (11 and 9 cases 
respectively), and seizures (9 cases), 
accompanied by a severe confusional 
syndrome in 3 cases. Intracranial 
hypertension was manifested in three 
patients enrolled in the study (Figure 1). 

Pathological examination of the 
resection specimens documented 
glioblastoma in twelve cases, grade one 
astrocytomas in five cases and grade two in 
one case, meningioma in five cases, mature 
teratoma and AVM in one case respectively. 
We managed to identify the degree of 
involvement of white matter tracts in all 

cases using DT imaging 2D maps and 3D 
reconstructions. Normal white matter tracts 
were highlighted in the controlateral 
hemisphere in all patients. Changes in tracts 
structure and position were characterized 
for each patient. White matter involvement 
by the expansive replacement space was 
classified according to criteria: 
displacement, infiltration, degeneration and 
edema in relation to contralateral 
correspondents (Figure 2). Upper 
longitudinal beam was deflected in the axial 
direction or lateral median in twelve cases. 
Corticospinal tract was diverted in fifteen 
cases. Locating individual displacement was 
a variation depending on where the tumor 
lesion. Deviation has been emphasized in 
the corona radiate (Figure 3).  

White matter tract edema was 
documented in three cases. Reconstruction 
of DTI showed reduced anisotropy without 
displacement of white matter architecture, 
which is suggestive of tumor invasion. 
Diffusion tensor imaging documented the 
destruction of white matter tracts in seven 
cases (Figure 4). Lower anterior 
longitudinal component of the beam in the 
temporal lobe was engulfed by 
glioblastoma. In the second case, another 
massive temporo-insular glioblastoma 
produced distruction of antero-posterior 
oriented fibers and projections, especially 
cortico-spinal tract and previous thalamic 
radiation, the more evident when compared 
with fibers intact controlateral hemisphere. 
In one case it revealed diffuse swelling 
along the outer edges of the tumor. In one 
case with glioblastoma temporal lobe edema 
on the outskirts of optical radiation 
involved parietal and temporal regions. 
Edema affecting optic radiation white tracts 
was demonstrated on T2 images of 
conventional MRI.   



 
 
 
486          Bogdan Iliescu et al          MR tractography in pre-surgical planning 

 
 
 

 
A 

 
B 

 
C 

 
D 

Figure 1 A Sex distribution of the cases in our 
series. B Major location of cerebral lesions in all 

cases. C Age distribution; D Symptoms at 
presentation 

 

 
Figure 2 The type of white matter tract involvement 

by the pathological process 
 

 
 

 
A 



 
 
 

Romanian Neurosurgery (2011) XVIII 4: 483 - 490          487 

 
 
 

 
 

 
B 

 
C 

Figure 3 Illustrative case for the imagistic work-up 
in our series. A T2-weighted and MRI Angio of the 
primary lesion. B 2D and 3D tractography showing 

displacement of the longitudinal temporal white 
matter tracts and compression on the pyramidal tract. 

C Postoperative control CT with the artefacted 
image of a vascular clip 

 

 
A 

  
B 

Figure 4 Illustrative case for a spinal cord tumor in 
our series. A T1-weighted sagittal (left) and axial 

(right) MR image showing compression at the level 
of D6. B 3D tractography (whole – left and detail – 
right) showing almost complete distruction of the 
descendent white matter tracts in the spinal cord 

 
Using a preoperative planning that takes 

into account important functional mapping 
elements directly or indirectly involved in 
the intracranial expansive process as well as 
an appropriate selection of cases for 
intraoperative monitoring of motor and 



 
 
 
488          Bogdan Iliescu et al          MR tractography in pre-surgical planning 

 
 
 

language functions, postoperative results 
allowed for good postoperative results. 
Thus, all patients included in this study 
showed postoperatively similar or improved 
neurologic status (no iatrogenic 
neurological deficit). Evaluation of pre- and 
postoperative Karnofsky performance scale 
(Karnofsky performance scale - KPS) is 
detailed in Figure 5. 

 
A 

 
B 

 
C 

Figure 5 Karnofsky performance scale values pre- 
and postoperatively (A and B, respectively) and the 

tendency in the KPS in the whole group. Full bars 
indicate a negative tendency while the empty bars 

show positive tendency 

Discussion 
Brain tumors can affect both functional 

cortical gray matter and white matter tracts. 
A good neurological outcome following the 
resection of intracerebral pathological 
processes requires a detailed preoperative 
understanding of their anatomical 
relationships with functional areas and of 
adjacent cortical white matter tracts. This is 
of paramount importance when the tumor 
develops in or near a functional cortical area 
in the dominant hemisphere, be it motor, 
sensory, or cognitive. Understanding the 
location of the lesion in relation to 
surrounding functional tissue is a vital 
element in developing an efficient surgical 
plan. 

The purpose of using various techniques 
of mapping is to delineate functional areas 
so they can be preserved during surgery. 
Maximal tumor resection was shown to be 
an element closely related to patient 
survival and improved clinical status of 
patients on long-term, indicating a main 
predictor of clinical course. The present 
data show that tumors that invade massively 
the functional cortex areas of maintain still 
intact white matter tracts in the mass of the 
pathological tissue. Diffusion tensor 
imaging provides valuable information for 
identifying tracts when they are displaced 
by the tumor. 

Twenty-five cases were analyzed in our 
study to demonstrate how diffusion tensor 
imaging contributes important additional 
information that may help elucidate the 
complex relationship between a tumor and 
surrounding brain tissue. Imaging evidence 
of the existence of intact white matter tracts 

N
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 c

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N

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 c
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 c

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p < 0.0001 (Wilcoxon si Mann-Whitney  test) 



 
 
 

Romanian Neurosurgery (2011) XVIII 4: 483 - 490          489 

 
 
 

in the areas of tumor invasion were 
obtained in four patients. Other patients 
showed tracts displacement from their 
normal anatomy position. In one case with 
glioblastoma located centrally in the left 
hemisphere, corticospinal tract lesion in the 
corona radiata moved medially and 
superiorly. The information on the 
displacement of the tracts helped surgical 
planning by providing information about 
localization and adaptation of new surgical 
corridor so as to avoid intraoperative 
destruction of intact tracts. In this case the 
tumor was approached from a posterior 
temporal direction, allowing for aggressive 
resection of the tumor while avoiding 
motor fibers previously diverted. 

In our study we found that the use of an 
operator plan which aims at maintaining an 
intact neurological function is checked by 
favorable postoperative results. We mention 
that new neurological deficits occurred in 
only 12.5% of patients and have largely 
improved in the first month 
postoperatively. These results indicate that 
although they minimize the risk of injury of 
the functional cortex or tracts adjacent or 
involved in the pathological process, the 
methods used do not guarantee the absence 
of postoperative dysfunction. These deficits 
were caused probably by touching the 
subcortical areas, retraction, edema or 
ischemia. However, based on the results of 
this study, the risk of harming a previously 
intact patient during awake craniotomy 
remains low. This information about the 
risks of surgery is useful and should be 
communicated by the surgeon to the 
patients and their families. 

Conclusions 
In agreement with the existing 

prospective studies, our study suggests that 

preoperative planning based on functional 
criteria and the use of awake craniotomy 
offers clear advantages for the resection of 
intraxial and spinal pathological processes. 
This allows for intraoperative brain 
mapping that helps identify (and by 
consequence, protect) eloquent functional 
cortex, and is an effective surgery for 
lesions of different histological types that 
occur in various locations in the brain. 
Awake craniotomy to avoid complications 
of general anesthesia, based on the data of 
this study and others, is associated with 
reduced complications and mortality rates 
and reduced use of resources. As a general 
principle, we suggest that the awake 
craniotomy provides an excellent alternative 
to traditional surgery for supratentorial 
brain lesions. 

The effect of brain tumors on white 
matter tracts is clearly demonstrated by 
means of standard diagnostic imaging. 
Diffusion tensor imaging allowed 
identification of several viable tracts within 
a cerebral hemisphere invaded by a tumor. 
In our series, information provided by DT 
imaging allowed precise definition of 
relationships between cortical structures 
and subcortical white matter and brain 
tumors. Involvement of white matter tracts 
is important information in planning the 
surgical approach in assessing the extent of 
tumor resection to keep it within safe 
limits. 

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