Yukinari Kakizawa

THREE-DIMENSIONAL MICROSURGICAL AND TRACTOGRAPHIC ANATOMY OF THE WHITE MATTER OF THE HUMAN BRAIN

OBJECTIVE We sought to investigate the three-dimensional structure of the white matter of the brain by means of the fiber-dissection technique and diffusion-tensor magnetic resonance imaging to assess the usefulness of the combination of both techniques, compare their results, and review the potential functional role of fiber tracts. METHODS Fifteen formalin-fixed human hemispheres were dissected according to Klinglers fiber-dissection technique with the aid of 36 to 340 magnification. Three-dimensional anatomic images were created with the use of specific software. Two hundred patients with neurological symptoms and five healthy volunteers were studied with diffusion-tensor magnetic resonance imaging (3 T) and tractographic reconstruction. RESULTS The most important association, projection, and commissural fasciculi were identified anatomically and radiologically. Analysis of their localization, configuration, and trajectory was enhanced by the combination of both techniques. Three-dimensional anatomic reconstructions provided a better perception of the spatial relationships among the white matter tracts. Tractographic reconstructions allowed for inspection of the relationships between the tracts as well as between the tracts and the intracerebral lesions. The combination of topographical anatomic studies of human fiber tracts and neuroanatomic research in experimental animals, with data from the clinicoradiological analysis of human white matter lesions and intraoperative subcortical stimulation, aided in establishing the potential functional role of the tracts. CONCLUSION The fiber-dissection and diffusion-tensor magnetic resonance imaging techniques are reciprocally enriched not only in their application to the study of the complex intrinsic architecture of the brain, but also in their practical use for diagnosis and surgical planning.

NeuRobot: Telecontrolled Micromanipulator System for Minimally Invasive Microneurosurgery—Preliminary Results

OBJECTIVE Microneurosurgery can be performed less invasively with the recent advances in neuronavigation and neuroendoscopy. For even less invasive microneurosurgery, we have developed a telecontrolled micromanipulator system. METHODS The NeuRobot telecontrolled micromanipulator system was developed. With the use of this system, surgical simulations were performed with a human cadaveric head. RESULTS The system consists of four main parts, i.e., a micromanipulator (slave manipulator), a manipulator-supporting device, an operation-input device (master manipulator), and a three-dimensional display monitor. Three 1-mm forceps and a three-dimensional endoscope, which could be remotely controlled with three degrees of freedom (rotation, neck swinging, and forward/backward motion), were installed in the slave manipulator. All surgical procedures were accurately performed with this system. CONCLUSION The use of telecontrolled manipulator systems in neurosurgery is very promising, and we are convinced that this system will facilitate more accurate, less invasive microneurosurgery. The details of the NeuRobot system and preliminary results are presented.

The claustrum and its projection system in the human brain: a microsurgical and tractographic anatomical study

OBJECT The goal in this study was to examine the microsurgical and tractographic anatomy of the claustrum and its projection fibers, and to analyze the functional and surgical implications of the findings. METHODS Fifteen formalin-fixed human brain hemispheres were dissected using the Klingler fiber dissection technique, with the aid of an operating microscope at x 6-40 magnification. Magnetic resonance imaging studies of 5 normal brains were analyzed using diffusion tensor (DT) imaging-based tractography software. RESULTS Both the claustrum and external capsule have 2 parts: dorsal and ventral. The dorsal part of the external capsule is mainly composed of the claustrocortical fibers that converge into the gray matter of the dorsal claustrum. Results of the tractography studies coincided with the fiber dissection findings and showed that the claustrocortical fibers connect the claustrum with the superior frontal, precentral, postcentral, and posterior parietal cortices, and are topographically organized. The ventral part of the external capsule is formed by the uncinate and inferior occipitofrontal fascicles, which traverse the ventral part of the claustrum, connecting the orbitofrontal and prefrontal cortex with the amygdaloid, temporal, and occipital cortices. The relationship between the insular surface and the underlying fiber tracts, and between the medial lower surface of the claustrum and the lateral lenticulostriate arteries is described. CONCLUSIONS The combination of the fiber dissection technique and DT imaging-based tractography supports the presence of the claustrocortical system as an integrative network in humans and offers the potential to aid in understanding the diffusion of gliomas in the insula and other areas of the brain.

Prediction of Functional Outcome in Acute Cerebral Hemorrhage Using Diffusion Tensor Imaging at 3T: A Prospective Study

BACKGROUND AND PURPOSE: Early evaluation of the pyramidal tract is a prerequisite in patients with intracerebral hemorrhage (ICH) in order to decide the optimal treatment or to assess appropriate rehabilitation. The aim of this study was to evaluate and predict the neuromotor and functional outcome of an ICH by using diffusion tensor imaging (DTI) in the acute phase. MATERIALS AND METHODS: Eighteen patients with a hemiparetic supratentorial ICH were prospectively studied with DTI within 2 days after onset. A region-of-interest-based analysis was performed for the fractional anisotropy (FA) of the pyramidal tract in the cerebral peduncles. The degree of paresis was assessed at day 0 and day 28 by paresis grading (PG). The functional outcome was evaluated by the modified Rankin Scale (mRS). RESULTS: The FA in the affected side was significantly lower compared with that of the unaffected side (P = .001) with the mean diffusivity remaining unchanged (P = .50). The ratio of the FA (rFA) in the affected side to the unaffected side was significantly correlated with the PG at day 0 and 28 and the mRS score at day 28 (P = .002, r = −0.674; P < .001, r = −0.767; and P = .002, r = −0.676). The rFA for the good and poor outcomes based on the PG was significantly different (P < .001). The cutoff point of the rFA for the good and poor outcomes was set at 0.85 (sensitivity, 100%, specificity, 100%). CONCLUSIONS: We conclude that DTI can evaluate the motor deficit quantitatively and may predict the functional outcome in patients with an ICH who were scanned within 2 days after the ICH onset.

Anatomical study of the trigeminal and facial cranial nerves with the aid of 3.0-tesla magnetic resonance imaging.

OBJECT Neuroimages often reveal that the trigeminal or facial nerve comes in contact with vessels but does not produce symptoms of trigeminal neuralgia (TN) or hemifacial spasm (HFS). The authors conducted this study to determine how often the trigeminal and facial nerves came in contact with vessels in individuals not suffering from TN or HFS. They also investigated the correlation between aging and the anatomical measurements of the trigeminal and facial nerves. METHODS Between November 2005 and August 2006, 220 nerves in 110 individuals (60 women and 50 men; mean age 55.1 years, range 19-85 years) who had undergone brain magnetic resonance (MR) imaging for other reasons were studied. The lengths, angles, ratio, and contact points were measured in each individual. A correlation between each parameter and age was statistically analyzed. RESULTS The mean (+/- standard deviation) length of the trigeminal nerve was 9.66 +/- 1.71 mm, the mean distance between the bilateral trigeminal nerves was 31.97 +/- 1.82 mm, and the mean angle between the trigeminal nerve and the midline was 9.71 +/- 5.83 degrees . The trigeminal nerve was significantly longer in older patients. Of 220 trigeminal nerves, 108 (49.0%; 51 women and 57 men) came in contact with vasculature. There was 1 contact point in 99 nerves (45%) and 2 contact points in 9 nerves (4.1%). Contact without deviation of the nerve was seen in 91 individuals (43 women and 48 men), and mild deviation was noted in 17 individuals (8 women and 9 men). There was no moderate or severe deviation in any individual in this series. The mean length of the facial nerve was 29.78 +/- 2.31 mm, the mean distance between the bilateral facial nerves was 28.65 +/- 2.22 mm, the angle between the nerve and midline was 69.68 +/- 5.84 degrees , and the vertical ratio at the porus acusticus was 0.467 +/- 0.169. Of all facial nerves, 173 (78.6%; 101 in women and 72 in men) came in contact with some vasculature. Contact without deviation was seen on 64 sides (in 37 women and 27 men), mild deviation on 98 sides (in 57 women and 41 men), and moderate deviation on 11 sides (in 7 women and 4 men). There was no severe deviation of the facial nerve in this series. The proximal length of the facial nerve, interval, angle, and ratio against the age were significantly shorter or smaller in the older individuals. CONCLUSIONS The findings in asymptomatic individuals in this study will help in deciding which findings observed on MR images may cause symptoms. In addition, the authors describe the variations of normal anatomy in older individuals. Knowledge of the normal anatomy helps to hone the diagnostic practices for microvascular decompression, which may increase the feasible results on such surgery.

Distinction between paraclinoid and cavernous sinus aneurysms with computed tomographic angiography.

OBJECTIVETo examine the reliability of using the optic strut as a landmark in computed tomographic (CT) angiography, to differentiate between intradural and extradural (cavernous sinus) aneurysms involving the paraclinoid segment of the internal carotid artery (ICA). METHODSMicroanatomic dissections were performed with five cadaveric heads (10 sides), to establish the relationships of the optic strut to the cavernous sinus and the ICA. Results from these anatomic studies were compared with intraoperative and CT angiographic findings for four patients with nine intracranial aneurysms involving the paraclinoid segment of the ICA. RESULTSThe inferior boundary of the optic strut accurately localized the point at which the ICA pierced the oculomotor membrane (proximal dural ring) and exited the cavernous sinus. The optic strut and its relationship to the ICA could be well observed on CT angiograms. During surgery, six of six aneurysms that arose distal to the optic strut were identified intradurally and were successfully clipped. Conversely, all aneurysms that arose proximal to the optic strut were observed to lie within the cavernous sinus. An aneurysm at the optic strut was within the clinoid segment or interdural, between the proximal and distal rings. CONCLUSIONThe optic strut, as identified with CT angiography, provided a reliable anatomic landmark for accurate discrimination between intradural and extradural (cavernous sinus) aneurysms.

Parameters for contralateral approach to ophthalmic segment aneurysms of the internal carotid artery.

OBJECTIVEThis study was undertaken to define more accurately the feasibility and indications of the contralateral pterional approach to ophthalmic segment aneurysms of the internal carotid artery (ICA). METHODSBetween 1995 and 1999, 46 patients with ophthalmic segment aneurysms of the ICA were surgically treated in our institution. Eleven of the 46 aneurysms were operated using the contralateral pterional approach. All aneurysms were successfully clipped without complications; three patients required bone resection around the aneurysm neck. We studied the 11 patients who were treated with the contralateral approach by defining six parameters to assess the feasibility of the approach and to predict the necessity for bone resection: 1) Parameter A, the distance between the anterior aspect of the optic chiasm and the limbus sphenoidale; 2) Parameter B, the distance between the bilateral optic nerves at the entrance to the optic canal; 3) Parameter C, the interrelation of the optic nerve and the ICA, expressed as a/b in which a is the length from the midline to the optic nerve and b is the length from the midline to the ICA; 4) Parameter D, the size of the aneurysm neck; 5) Parameter E, the direction of the aneurysm from the ICA wall on the anteroposterior angiogram; and 6) Parameter F, the distance from the medial side of the estimated distal dural ring to the proximal aneurysm neck on the lateral angiogram. RESULTSParameters A to F were 8.8 mm (range, 5.4–11.1 mm), 14.5 mm (range, 10.4–22.2 mm), 0.9 mm (range, 0.6–1.3 mm), and 3.0 mm (range, 2.3–4.7 mm), 5 to 160 degrees, and 1.3 mm (range, 0.3–2.4 mm), respectively. All patients had excellent operative outcomes without visual dysfunction. Three patients required drilling of the bone around the optic canal on the craniotomy side; bone drilling was not required when Parameter E was between 30 and 160 degrees and Parameter F was more than 1 mm. CONCLUSIONParameters A to D are important for assessing the feasibility of the contralateral approach to ICA-ophthalmic segment aneurysms, and Parameters E and F are most useful for calculating the difficulty of this approach.

Telecontrolled micromanipulator system (NeuRobot) for minimally invasive neurosurgery

BACKGROUND To perform less invasive neurosurgery, a telecontrolled micromanipulator system has been developed and applied to clinical situations. Basic experiments for telesurgery have also been conducted. METHOD A cadaver head was used to carry out surgical simulation of the opening of the sylvian fissure and third ventriculostomy. After obtaining permission from the Ethical Committee of Shinshu University School of Medicine, part of the recurrent meningioma in a 45-year-old man was removed. As basic experiment for telesurgery, surgical simulation was also conducted in a rat brain with the operating console transported to a hospital 40 km distant from the University. FINDINGS Opening of the sylvian fissure and third ventriculostomy were accurately performed. Tumour removal in a patient with recurrent meningioma was safely achieved. Surgical simulation in the rat brain was accurately and correctly carried out, operated on from a hospital 40 km distant. CONCLUSIONS The NeuRobot, telecontrolled micromanipulator system, can be used as a tool for less invasive neurosurgery.

Low anterior interhemispheric approach--a narrow corridor to aneurysms of the anterior communicating artery.

Summary.Summary.Background: Many approaches for clipping anterior communicating artery (ACoA) aneurysms are reported in the literature. We describe here a new approach called “low anterior interhemispheric approach” for clipping of ACoA aneurysms.Materials and Methods: A low anterior interhemispheric approach utilizing a unilateral frontal craniotomy flap with minimal unilateral frontal lobe retraction was used in treating four patients harboring an unruptured ACoA aneurysm. The approach axis is directed to the ACoA area itself with minimal exposure to the anterior cerebral vessels.Findings: In all patients, complete neck clipping was possible with minimal brain retraction, without vascular damage and preserved olfaction.Interpretation: This approach is preferred on anatomical grounds for cases of unruptured small and medium sized ACoA aneurysms projecting anteriorly or posteriorly because the anterior communicating artery complex area can be fully visualized with minimal manipulation of the frontal lobes and anterior cerebral arteries.

Three-dimensional contrast medium-enhanced computed tomographic cisternography for preoperative evaluation of surgical anatomy of intradural paraclinoid aneurysms of the internal carotid artery: technical note.

OBJECTIVE AND IMPORTANCE Precise preoperative evaluation is especially important when internal carotid artery aneurysms in the paraclinoid region are clipped, because these vascular structures are located in close proximity to various important structures such as the optic nerve and anterior clinoid process. We report a new method for “simultaneously” describing the interrelationships among the aneurysm, internal carotid artery, optic nerve, and bony structures with three-dimensional contrast medium-enhanced computed tomographic (3-D CMECT) cisternography. METHODS Informed consent was obtained from the patient. An 8-ml injection of iotrolan (Isovist; Schering, Berlin, Germany) (240 mg I/ml) was administered into the lumbar intrathecal space. A computed tomographic scan of the head was obtained 2 hours later with a multislice Asteion computed tomographic scanner (Toshiba, Inc., Tokyo, Japan). An Alatoview workstation (Silicon Graphics, Mountain View, CA) was used to reconstruct the three-dimensional images. RESULTS These images, as generated by 3-D CMECT cisternography, were found to accurately demonstrate the interrelationships of the internal carotid artery, aneurysm, and surrounding structures preoperatively. The findings obtained from these images proved to be quite similar to the intraoperative findings. 3-D CMECT cisternography clarified whether the paraclinoid aneurysm was intradural or extradural. CONCLUSION 3-D CMECT cisternography was found to provide a useful means for preoperative evaluation of lesions in the paraclinoid area.