Case Studies

Case Study 1

PoleStar System Case Study: Right Sided, Deep Temporal Lesion with Discrete Perifocal Edema (PDF, 5.1 MB)
13-year-old boy with right-sided deep temporal lesion with discrete perifocal edema.

Right Sided, Deep Temporal Lesion With Discrete Perifocal Edema

Hospital: University Hospital of Maastricht, Maastricht, Netherlands
Surgeon: E. Cornips, MD
Date: October 15, 2007
Admitting Diagnosis: Right-sided deep temporal lesion with discrete perifocal edema

“Allowing fast setup and repeated scanning without the need to move the patient, the PoleStar provides excellent image quality for navigation as well as resection control.”
–Erwin Cornips, MD

Figure 1: Patient positioned supine, shoulders slightly over the table, head turned to the left, head coil positioned over the vertex. The magnet has been lowered from scanning position, enabling the use of standard instrumentation, microscope, and ultrasonic aspirator.

Presentation

An otherwise healthy, 13-year-old boy presented with two seizures and normal neurological and visual field examinations. Diagnostic MRI showed a right sided, deep temporal lesion with discrete perifocal edema and irregular contrast enhancement.

Procedure

The patient was positioned supine, his upper trunk and shoulders hanging slightly over the table and his head turned to the left (Figure 1). Preoperative nonenhanced PoleStar^® scans nicely showed the tumor, and its relationship to critical structures (Figure 2). During initial approach exact delineation of the tumor was difficult because its color and consistency were almost identical to surrounding healthy tissue. The integrated PoleStar navigation system proved very useful during this stage (Figure 3). The tumor was carefully dissected and resected as much as possible en bloc. It turned out to be a ganglioma grade II.

Figure 2: Precraniotomy nonenhanced iMR images in axial plane nicely show the tumor, its relationship to the trigone, and an isolated temporal horn.

Because of the vicinity of eloquent structures such as the basal ganglia (anteromedial) and optic radiation (posteromedial), safety margins in this neurologically intact boy were quite small. For this reason we were happy to have real-time navigation and resection control available. Comparing postresection PoleStar images without and with gadolinium (Figure 4) confirmed that the tumor has been resected completely. Indeed the young patient has made an uneventful recovery without any visual field deficit.

Interestingly, the resection cavity was much better delineated on iMR images, with open skull and clear irrigation fluid inside, than on high-field strength MR images taken within 24 hours postoperatively (Figure 5). This has consistently been our experience in other cases as well. With more experience we expect these iMR images (though coming from a 0.15 Tesla system) will obviate early postoperative high-field strength MR imaging, certainly in selected cases such as this one.

Figure 3: Reconstructed iMR images with navigational crosshairs on the postero-lateral margin of the tumor confirming visual identification in the surgical field.

Figure 4: Preop and postop axial images with and without gadolinium demonstrate complete tumor resection. The deeper cavity represents the decompressed trigone which is enlarged as the skull is still open.

Figure 5: Diagnostic MR images are compared to postop iMR images. Note that resection cavity, trigone, and temporal horn were much better seen on iMR images.

Case Study 2

Figure 1: Coregistered preoperative diagnostic T1 and T2 and PoleStar T2 images showing the border of the tumor. The PET scan shows a heterogenous hyperfixation in the frontal region (with region of hypermetabolism and deeper region of no hypermetabolism).

 

Figure 2: PoleStar preoperative FLAIR scan showing the tumor border

PoleStar System Case Study: Low Grade Oligodendroglioma (PDF, 3.6 MB)
23-year-old male with low grade oligodendroglioma.

Low Grade Oligodendroglioma

Hospital: Centre Hospitalier Universitaire Sart Tilman, Liege, Belgium
Surgeons: F. Scholtes, MD, D. Martin, MD
Date: April 2008
Admitting Diagnosis: Low grade glioma

“In this case, T2 weighted and FLAIR images proved particularly useful in assessing the degree of tumor resection and, on the basis of the intraoperative images, the surgical strategy was modified in order to obtain macroscopically complete resection.”
—Didier Martin, MD

Presentation

A 23 year-old male patient presented with a first episode of generalized seizure. MRI revealed a frontal lesion with an A-P diameter of 56 mm. The lesion was hypointense on T1-weighted and hyperintense on T2-weighted images, with no contrast enhancement. Spectroscopic imaging showed increased level of choline and reduced NAA. The lesion was partially hypermetabolic on tyrosine PET, especially in its superficial parts. Imaging results were consistent with low grade glioma.

Procedure

The patient underwent a right frontal craniotomy with the PoleStar^® system. The middle frontal gyrus was abnormally large and the tumor was clearly limited by the superior frontal sulcus. The preoperative diagnostic MRI and the precraniotomy PoleStar images (Figure 1, Figure 2) clearly demonstrated the anterior and posterior limits of the tumor. The tumor was resected using neuronavigation based on these images. In the deep parts, the tumor tissue was very similar to normal brain parenchyma. The first intraoperative control iMRI (Figure 3) revealed residual tumor in the deep white matter. Tumor resection continued using intraoperative navigation based on these images (Figure 4). In total four imaging sessions were performed. The last iMRI demonstrated macroscopically complete tumor resection. This was confirmed by the postoperative diagnostic MRI.

Figure 3: First intraoperative PoleStar FLAIR scan demonstrating partial resection

Figure 4: Compare mode display of four FLAIR scans acquired at different stages of the surgery, showing the progress of tumor resection.

Results

In the present case, iMRI was particularly useful to complete the resection of a tumor which was macroscopically almost indistinguishable from normal brain tissue. In this case, T2-weighted and FLAIR images proved particularly useful in assessing the degree of tumor resection and, on the basis of the intraoperative images, the surgical strategy was modified in order to obtain macroscopically complete resection. Postoperative histology confirmed low-grade oligodendroglioma (WHO grade II), mostly GFAP negative, EGFR negative with low proliferative index (5% of cells Ki-67). The postoperative neurological status of the patient was normal and the patient is seizure-free since the tumor resection.