Tractography-guided surgery of brain tumours: what is the best method to outline the corticospinal tract?

BACKGROUND: Diffusion tensor imaging (DTI) is the imaging technique used in vivo to visualise white matter pathways. The cortico-spinal tract (CST) belongs to one of the most often delineated tracts preoperatively, although the optimal DTI method has not been established yet. Considering that various regions of interests (ROIs) could be selected, the reproducibility of CST tracking among different centres is low. We aimed to select the most reliable tractography method for outlining the CST for neurosurgeons. MATERIALS AND METHODS: Our prospective study consisted of 32 patients (11 males, 21 females) with a brain tumour of various locations. DTI and T1-weighed image series were acquired prior to the surgery. To draw the CST, the posterior limb of the internal capsule (PLIC) and the cerebral peduncle (CP) were defined as two main ROIs. Together with these main ROIs, another four cortical endpoints were selected: the frontal lobe (FL), the supplementary motor area (SMA), the precentral gyrus (PCG) and the postcentral gyrus (POCG). Based on these ROIs, we composed ten virtual CSTs in DSI Studio. The fractional anisotropy, the mean diffusivity, the tracts' volume, the length and the number were compared between all the CSTs. The degree of the CST infiltration, tumour size, the patients' sex and age were examined. RESULTS: Significant differences in the number of tracts and their volume were observed when the PLIC or the CP stood as a single ROI comparing with the two- ROI method (all p < 0.05). The mean CST volume was 40054U (SD ± 12874) and the number of fibres was 259.3 (SD ± 87.3) when the PLIC was a single ROI. When the CP was a single ROI, almost a half of fibres (147.6; SD ± 64.0) and half of the CST volume (26664U; SD ± 10059U) was obtained (all p < 0.05). There were no differences between the various CSTs in terms of fractional anisotropy, mean diffusivity, the apparent diffusion coefficient, radial diffusivity and the tract length (p > 0.05). The CST was infiltrated by a growing tumour or oedema in 17 of 32 patients; in these cases, the mean and apparent diffusion of the infiltrated CST was significantly higher than in uncompromised CSTs (p = 0.04). CST infiltration did not alter the other analysed parameters (all p > 0.05). CONCLUSIONS: A universal method of DTI of the CST was not developed. However, we found that the CP or the PLIC (with or without FL as the second ROI) should be used to outline the CST.

Frontal aslant tract projections to the inferior frontal gyrus.

BACKGROUND: Frontal aslant tract (FAT) is a white matter bundle connecting the pre-supplementary motor area (pre-SMA) and the supplementary motor area (SMA) with the inferior frontal gyrus (IFG). The purpose of the present study was to evaluate the anatomical variability of FAT. MATERIALS AND METHODS: Total number of fibres and the lateralisation index (LI) were calculated. We attempted to find factors contributing to the diversity of FAT regarding IFG terminations to the pars opercularis (IFG-Op) and to the pars triangularis (IFG-Tr). Magnetic resonance imaging of adult patients with diffusion tensor imaging (DTI) with total number of 98 hemispheres composed a cohort. V-shaped operculum was the most common (60.5%). RESULTS: Total number of FAT fibres had widespread and unimodal distribution (6 to 1765; median: 160). Left lateralisation was noted in 64.3% of cases and was positively correlated with total number of FAT fibres and the bundle projecting to IFG-Op (p < 0.01). LI correlated with total number of FAT fibres (r = 0.43, p < 0.01). FAT projected predominantly to IFG-Op (88.9%; 88 of 99). Only in 3 (3.1%) cases more fibres terminated in IFG-Tr than in IFG-Op. Total number of FAT fibres and number of fibres terminating at IFG-Op did not correlate with the ratio of fibre numbers: FAT/IFG-Op, FAT/IFG-Tr and IFG-Op/IFG-Tr (p > 0.05). The greater total number of fibres to IFG-Tr was, the higher were the ratios of IFG-Tr/ /FAT (r = 0.57, p < 0.01) and IFG-Tr/IFG-Op (r = 0.32, p = 0.04). CONCLUSIONS: Among the IFG, the major termination of FAT is IFG-Op. Whereas the IFG-Tr projection seems to be related to the expansion of the entire FAT bundle regardless of side, domination and handedness. Nevertheless, FAT features a significant anatomical variability which cannot be explained in terms of DTI findings.

Intracranial region of the vertebral artery: morphometric study in the context of clinical usefulness.

BACKGROUND: The aim of this study was to analyse the morphometry of the intracranial segment of the vertebral artery in the context of clinical usefulness. The results were compared with published data available in full-text archived medical journals. MATERIALS AND METHODS: More than 100 digital subtraction angiography (DSA) and 3-dimensional (3D) angio-computed tomography (CT) examinations were used to measure the following parameters: the whole and partial length of V4 in characteristic anatomical points, the diameter in three places (on the level of foramen magnum, in point of exit to the posterior inferior cerebellar artery, and in the vertebro-basilar junction), the angle of connection to the vertebral arteries, and all anatomical variations including fenestration, duplication, dolichoectasia or absent artery. RESULTS: The left V4 section was predominant over the right artery, which is manifested by length, width, cases of ectasia and fewer cases of hypoplasia. The incidences of V4 ectasia were identified more often than those documented in the accessible literature, and they were found in the natural location of formation of saccular aneurysms. CONCLUSIONS: The presented knowledge of anatomical variation and abnormali-ties of vertebral circulation can improve the accuracy and "safety" of the surgical procedures in this region, help to determine the range of surgical approach and avoid associated complications. The radiological examinations using 3D CT, DSA reveal unlimited observation of anatomical structures in contrast to studies based on cadavers, and can complement the morphometry in anatomical preparations.

Morphometric evaluation of the delayed cerebral arteries response to acetazolamide test in patients with chronic carotid artery stenosis using computed tomography angiography.

BACKGROUND: The evidence accumulates that the response to acetazolamide test is delayed on the ipsilateral side to stenosis. However, the effect of acetazolamide beyond 30 min after acetazolamide administration remains unknown. The aim of this study was to assess the diameters of anterior cerebral arteries (ACAs), middle cerebral arteries (MCAs) and posterior cerebral arteries (PCAs) before and 60 min after the acetazolamide test. MATERIALS AND METHODS: Seventeen patients with carotid artery stenosis ≥ 90% on the ipsilateral side and ≤ 50% on the contralateral side were enrolled into the study. Diagnosis was based on ultrasonography examination and was confirmed using digital subtractive angiography. In all patients, two computed tomography angiography examinations were carried out; the first was performed before the acetazolamide administration, while the second one was carried out 60 min after injections. RESULTS: In response to the acetazolamide test: PCA diameter diminished in both ipsi- and contra-lateral side to stenosis (from 1.31 to 1.24 mm and from 1.23 to 1.15 mm, respectively), ACA and MCA decreased in the contralateral side to the stenosis (from 1.33 to 1.26 mm and from 2.75 to 2.66 mm, respectively), ACA and MCA increased in the ipsilateral side to the stenosis (from 1.29 to 1.46 mm and from 2.77 to 2.96 mm, respectively). All changes were statistically significant. CONCLUSIONS: There were significant differences in reactivity to acetazolamide challenge between the internal carotid artery (ICA) and vertebrobasilar circulation in patients suffering from chronic carotid artery stenosis. Within the ICA territory, ACA and MCA responses vary in the affected and not affected side.

Expression pattern of ISL-1, TTF-1 and PAX5 in olfactory neuroblastoma.

Olfactory neuroblastoma (ONB) is a rare neoplasm of the sinonasal area with neuroendocrine differentiation. ISL-1, TTF-1 and PAX5 are transcription factors that are frequently upregulated in tumors showing neuroendocrine differentiation. The aim of our study was to evaluate these markers in a group of ONBs. We included 11 ONBs from 4 large university hospitals. Immunohistochemical expression of TTF-1, PAX5 and ISL-1 was evaluated. TTF-1, ISL-1 and PAX5 were expressed in 3/11 cases (27.27%, h-score: 3-45), 7/11 cases (63.64%, h-score: 23-200), and in 3/11 cases (27.77%, h-score 3-85), respectively. The patient with the strongest PAX5 reactivity exhibited an aggressive clinical course with rapid dissemination to the spine and death shortly after the diagnosis. No significant correlation in the expression of PAX5 and TTF-1 ( = 0.43; p = 0.18) was observed. ISL-1 is widely expressed in tumors with neuroendocrine differentiation and therefore of limited value in their differential diagnosis. TTF-1 positivity does not exclude the diagnosis of primary ONB, although usually only a small percentage of cells are positive. PAX5 expression is infrequent (27.27%) in ONB; however, if present it can be associated with a very aggressive clinical course.

Future of the nerve fibres imaging: tractography application and development directions.

Tractography is a tool available in a growing number of centres, to enable planning of neurosurgical interventions. This method has some drawbacks and due to its increasing availability is causing a growing controversy over the possibility of an anatomical mapping of the nerve fibres. This article aims at summarising the application of the diffusion magnetic resonance in contemporary neurosurgery method, showing the usefulness and merits of its performance before surgical procedures, limitation of its application and recommendations for its improvement and more effective use for diagnostic purposes.

The posterior communicating artery: morphometric study in 3D angio-computed tomography reconstruction. The proof of the mathematical definition of the hypoplasia.

BACKGROUND: The aim of this study was to investigate the morphometry of the posterior communicating artery (PCoA), on the basis of angio-computed tomography (CT), and to give proof of the mathematical definition of the term "hypopal sia of the PCoA". MATERIALS AND METHODS: One hundred 3-dimensional (3D) angio-CT images, performed in adult patients with bilateral reconstruction of the PCoA (200 results) were used tocalculate the morphometry of the vessel. RESULTS: The average length of the vessel on the right side was 14.48 ± 3.47 mm, andon the left side 14.98 ± 4.77 mm (in women 14.75 mm, in men 14.70 mm). The mean of the diameter at the "proximal" point (the junction with P1) on the right side was 1.49 ± 0.51 mm, and on the left 1.46 ± 0.47 mm (in women 1.44 mm and in men 1.51 mm). The mean of the diameter in the "distal" part (the connection with ICA) on the right side was 1.4 ± 0.49 mm, and on the left 1.37 ± 0.41 mm (in women 1.38 mm, and in men 1.39 mm). No statistical correlation between the length and the diameter of the PCoA in relation to the sex and side was shown. On the basis of our measurements, we defined the hypoplasia of the artery as the estimated value less than the average diameter minus the standard deviation. The percentage distribution was as follows: the left artery 15.5%, the right artery 24%, women 11.5%, and the men 9%. Similarly to the above parameters, we have not found any statistical differences. The presence of the foetal origin was noted in 25% of the radiological examinations. The infundibular widening was visualised in 11.5% of cases of 3D reconstructions. The agenesis of PCoA was found in 9% (never bilaterally), and in 1 case the unilateral duplication of the artery was observed. No statistical differences between those parameters in relation to sex and the examined side were revealed. CONCLUSIONS: Morphological calculation of the PCoA on the basis of angio-CT from adult patients did not show any statistical differences depending on sex or the investigated side. The presented method of the calculations proved to be useful for the mathematical definition of the term "hypoplasia of the PCoA".

Trigeminal neuralgia caused by aneurysm of the posterior cerebral artery: a case description and the analysis of anatomical variety of vascular complex in the root entry zone of trigeminal nerve.

Trigeminal neuralgia is still a riddle, especially in the pathophysiology of the ticdouloureux, although the problem has been described in many medical publications. The major theory of pain based on the compression of the Vth nerve by tumours or vessels in the root entry zone (REZ) does not explain the facial pain in patient without neurovascular conflict, with multiple sclerosis or with conflict in places other than REZ. We report a case of the posterior cerebral artery aneurysm, which caused the isolated trigeminal neuralgia in a 48-year-old woman. She was operated on through microvascular decompression and the aneurysm was wrapped. In the second part of this study we review morphological variations of the neurovascular conflict on the basis of anatomical publications.

Morphometry of the pterional and pterional-orbitozygomatic approaches to the basilar artery bifurcation by the use of neuronavigation systems: a new technical concept.

Much attention has been paid in the neurosurgical literature to optimising the approaches to intracranial pathology. The aims of the innovations reported are to increase the safety of operations by reduction of brain retraction and to improve exposure of the neurovascular structure in the operating area. It was our intention to investigate whether an image-guided frameless stereotactic system is suitable in morphometric studies based on the analysis of the pterional and the cranio-orbitozygomatic approaches to the basilar artery bifurcation (BAB). We analysed 60 virtual models of pterional craniotomy and the same number of those extended by orbitozygomatic osteotomy, created using computer tomography in the neuronavigation system. It was decided to calculate the percentage change of the cranial area of exposure, the depth of the surgical corridor and the angle of view to the bifurcation of the basilar artery. Three positions of the BAB (normal, high and low) were examined for each model of craniotomy. In the material analysed, after the extension of the pterional craniotomy by orbitozygomatic osteotomy, the cranial area of exposure for 60 models of cranio-orbitozygomatic craniotomies increased by a mean of 39.28% (from 30.89% to 48.06%). The decrease in the depth of the surgical corridor for a normal-lying BAB was 19.16%, for a high-lying BAB 19.09% and for a low-lying BAB 19.12%. The mean changes in the individual BAB locations did not differ significantly in statistical terms (F = 0.011; p = 0.99). The mean increase in the cranial angle of attack for a normally located BAB was 10.72 degrees , for a high-lying BAB 11.1 degrees and for a low-lying BAB 10.31 degrees . The post-hoc test showed significant differences in the angle of attack between a normal and a low-lying BAB (p = 0.034) and a high and a low-lying BAB (p = 0.00007). Neuronavigation systems, already well-known for their intraoperative use, can also be useful in morphometric studies, and the advantages of this method are the practically unlimited number of results which can be analysed in detail and the repeatability of the technique. The pterional-orbitozygomatic approach compared to the pterional increases the working area, minimises retraction of the brain, shortens the working distance, enables instruments to be used more easily, widens the angle of view and improves the visibility of the anatomical structures in the working area, especially for a high-lying BAB.

Aneurysm of the meningeal branch of the occipital artery connecting with the distal portion of the posteroinferior cerebellar artery by the dural fistula.

We describe a case involving a ruptured intradural aneurysm of the meningeal branch of the occipital artery arising from the external carotid artery and connecting with the caudal loop of the posteroinferior cerebellar artery (PICA) by the dural fistula. Angiography of the left external carotid artery showed a saccular aneurysm of the occipital artery, but the picture of the left vertebral artery was normal and no vascular pathology such as an aneurysm or a dural fistula was noticeable between the meningeal branch of the occipital artery and the PICA. The diagnosis was confirmed by three-dimensional reconstruction computed tomography (CT) angiography, magnetic resonance imaging and magnetic resonance angiography (MRA). In the knowledge, based on the radiological examinations, that the aneurysm was located intracranially below the tonsil, compressing the lateral surface of the medulla oblongata at the level of the foramen magnum, we decided to operate from the far-lateral suboccipital approach, without removing the arc of the C1. An aneurysm was visualised at the site of the connection of the caudal loop of the PICA and an anastomosis of the meningeal branch of the occipital artery. The aneurysm was successfully clipped and the vascular fistula was coagulated and dissected in the extradural section. To our knowledge, the case presented here is the first report of this kind of vascular pathology. Careful analysis of a cross-sectional CT angiogram, MRA and arteriography is necessary for the proper diagnosis of such atypical vascular pathology. In the study presented we focus our attention on the diversity of the PICA anatomy.