Low-grade gliomas (LGGs): LLG are diffuse hemispheric infiltrative, WHO classification grades I and II and account for 30% of all gliomas. LGGs characterized by continuous growth and progression to anaplastic transformation. LGG surgery remains a challenge these tumors are hard to differentiate from normal brain at surgery as they can infiltrate into eloquent tissue. Neurosurgical adjuncts have been developed and increasingly being used to achieve maximal resection with a minimal risk of postoperative neurologic morbidity.

1. Presenter: Dr. Shahanur Rahman

2. The Value of Pre- and Intra-
operative Adjuncts on the Extent
of Resection of Hemispheric
Low-Grade Gliomas: A
Retrospective Analysis
Journal of Neurological Surgery
Received: February 22, 2014
Accepted after revision: February 6, 2015

4. Introduction
Low-grade gliomas (LGGs):
• Diffuse hemispheric infiltrative
• WHO classification grades I and II
• account for 30% of all gliomas.
LGGs characterized by
• continuous growth and progression to anaplastic
transformation.

5. LGG surgery remains a challenge
• these tumors are hard to differentiate from
normal brain at surgery
• they can infiltrate into eloquent tissue.
Neurosurgical adjuncts have been
developed and increasingly being used
• to achieve maximal resection
• with a minimal risk of postoperative
neurologic morbidity

6. OBJECTIVES
• To investigate the effect of pre- and
intraoperative adjuncts on the extent of
resection (EOR) of hemispheric LGGs.

7. MATERIALS AND METHODS

8. Inclusion Criteria
Patients of
• 18 years or >18 yrs of age,
• any sex,
• Who underwent craniotomy for resection of
histopathologically confirmed
 astrocytoma,
 mixed oligoastrocytoma, and
 oligodendroglioma
(all WHO grades 1 and/or 2) tumors
• between January 2005 and July 2013 were
included.

9. Exclusion Criteria
• Pilocytic astrocytomas,
• Gemistocytic astrocytomas,
• Gangliogliomas
• Infratentorial gliomas,
• Patients with intractable epilepsy, and
• Patients with insufficient preoperative and/or
postoperative MRI studies.

10. Tumor Volume Measurements
Tumor volumes were assessed by
• manually outlining the tumor areas
• across all axial MRI slices
• on pre- and postoperative studies
• using the brush and/or auto brush function on
the Brainlab software.

11. • LGG segmentation on both pre- and
postoperative MRI studies is indeed a
challenge (even for trained neuroradiologists)
– because these tumers are the ill-defined diffuse
infiltrative in nature, when compared with
circumscribed gliomas.

12. • However, even if the borders are well defined,
– tumor cells can significantly infiltrate normal brain
tissue
– 20 mm beyond the abnormalities visible on
conventional MR images,
– causing an underestimation of tumor volumes.
• Therefore, There is still a lack of consensus on
how tumor volumes can best be measured.

13. • There are several published literature which
supports accurate tumor border identification
can be done on
– T2-weighted images.
• Therefore, they used pre and postoperative T2-
weighted MRI images during segmentation with
the assumption that all of the abnormal T2
hyperintensity should be included within the
tumor borders.
• In 95% of cases, postoperative MRI studies were
obtained within 48 hours of surgery.

14. axial T2 MRI sequence

15. Extent Of Resection (EOR)
• After measuring initial tumor volumes (cm3)
on preoperative MRI and
• residual tumor volumes (cm3) on
postoperative MRI,
• They calculated the extent of resection (%)
with the formula (initial tumor volume-
residual tumor volume)/initial tumor volume
*100.

16. Gross total resection (GTR)
• Gross total resection (GTR) was defined as
100% tumor resection as seen on T2-weighted
MRI images.

17. ELOQUENT TUMORS
They defined eloquent tumors as based on fMRI data
and/or anatomical tumor involvement of one or more
of the following structures:
• precentral gyrus,
• postcentral gyrus,
• Broca and/or Wernicke area,
• visual cortex,
• hypothalamus,
• thalamus,
• Internal capsule,
• and/or basal ganglia.

18. Pre- and Intraoperative
Neurosurgical Adjuncts
• Neuronavigation (NN) alone,
• direct electrical stimulation (DES),
• functional Magnetic resonance & diffusion
tensor imaging (fMRI-DTI) guided
neuronavigation [FD],
• Intraoperative Magnetic resonance imaging (i-
MRI).

19. Direct electrical Stimulation (DES)
• Gliomas involving the eloquent brain area
were targeted to receive an awake craniotomy
with DES that would allow the neurosurgeon
to preserve neurologic function with maximal
possible tumor resection.
• Absolute contraindications for this procedure
were confusion and communication
difficulties (e.g.,
 severe dysphasia or
 language barrier) of the patients.

20. Method of DES
• Bipolar electrical nerve stimulation (interval of 5
mm) is used.
• The stimulation range covered all areas of the
exposed cortex and suspicious subcortical
regions;
• the frequency is 60 Hz,
• the pulse duration is 1 msec, and
• the current is usually 4–6 mA.
• The stimulus duration of every point is
 1 sec for motion and sensation tasks, and
 4 sec for language tasks.

21. Functional MRI & Diffusion Tensor Imaging
(fMRI-DTI) guided neuronavigation [FD]
Functional MRI (fMRI):
• fMRI measures brain activity by detecting changes
associated with blood flow. This technique relies on the
fact that cerebral blood flow and neuronal activation
are coupled. When an area of the brain is in use, blood
flow to that region also increases.
Diffusion Tensor Imaging (DTI):
• DTI is also an MRI-based neuroimaging technique
which makes it possible to estimate the location,
orientation, and anisotropy of the brain's white matter
tracts.

22. fMRI-DTI-g-NN
• An alternative method of DES, used to determine
the anatomical and functional motor and
language areas.
• Contraindication of (reasons why patients could
not receive) fMRI-DTI were their inability to
perform tasks in the MRI scanner due to severe
aphasia, language barrier, motor disability,
claustrophobia, and technical or logistical
hindrances.

23. fMRI

24. DTI

25. DTI

26. NEURONAVIGATION (NN)
• Neuronavigation is the set of computer-
assisted technologies used by neurosurgeons
to guide or "navigate” within the confines of
the skull during surgery.
• Patients with contraindications for DES and/or
patients who had difficulties obtaining
qualitative fMRI-DTI data were alternatively
operated on with NN only or, in more complex
cases, i-MRI only.

28. Intraoperative MRI (iMRI)
• iMRI imaging refers to an operating room
configuration that enables surgeons to image
the patient via an MRI scanner while the
patient is undergoing surgery, particularly
brain surgery.

29. RESULTS
• Of all 128 patients, gross total resection (GTR)
was achieved in 23.4%.
• Overall mean EOR was 81.3% +/- 20.5%.
• Using DES in combination with fMRI-DTI on
eloquent tumors, which improved mean EOR
significantly (mean EOR: 86.7% +/- 12.4%)
when compared with NN alone (mean EOR:
76.4% +/- 25.5%).

30. EOR of tumors located in eloquent brain areas
98%
34%
88%
95%
72%
28%
88%
75%
91%
90%
87% 87%
65%
70%

31. 92%
65%

32. 92%
65%
85%
73%

33. 92%
65% 65%
90%85%
73%

34. 92%
65% 65%
90%85%
73%
39%
82%

35. 100%
97%
83%

36. DISCUSSION

37. • Earlier published literature suggested that DES
should be universally implemented as the
standard of care for glioma surgery.
• The addition of fMRI-DTI to DES is still in its
infancy.
• Neurosurgeons who do not use DES routinely
could use additional fMRI-DTI to understand
functional anatomy and white matter prior to
encountering it.

38. • We know that
– interindividual variability of eloquent areas exist
and
– shifting of eloquent areas can occur due to slow
diffuse growth of LGGs.
• Therefore, an individualized onco-functional
map of both the anatomical and functional
brain could determine more accurately the
relationship between eloquent areas and the
tumor.

39. • Therefore, Instead of a standard anatomical
determination of eloquent areas as we have
done in the past several decades, in the future
we can use this onco-functional mapping.

40. Conclusion
First, Neurosurgical adjuncts (fMRI-DTI, iMRI,
DES)
when used in craniotomies of LGGs that are
located in eloquent areas
• significantly improves EOR
When compared with
• use of NN alone.

41. Conclusion
Second, Tumors involving
• eloquent brain areas
had fewer complete resections
• compared with noneloquent tumors
(in the same pre- and intraoperative group)

42. Conclusion
Third, Small gliomas had
• a significant higher EOR
When compared with
• medium and large gliomas.