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Lawrence J. Clein

well as some filaments to the shoulder joint and the scapula 1 ( Fig. 1 ). Fig. 1. Anatomical dissection of the left suprascapular nerve, posterolateral aspect, a. Suprascapular nerve; b. suprascapular artery; c. transverse scapular ligament; d. supraspinatus muscle (divided); e. spine of scapula; f. infraspinatus muscle (divided). The trapezius muscle has been removed. Comparative Anatomy In order to understand the strange course of the suprascapular nerve it is necessary to refer to comparative anatomy. Each vertebrate limb includes not only

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João Luiz Vitorino Araujo, José C. E. Veiga, Hung Tzu Wen, Almir F. de Andrade, Manoel J. Teixeira, José P. Otoch, Albert L. Rhoton Jr., Mark C. Preul, Robert F. Spetzler and Eberval G. Figueiredo

OBJECTIVE

Access to the third ventricle is a veritable challenge to neurosurgeons. In this context, anatomical and morphometric studies are useful for establishing the limitations and advantages of a particular surgical approach. The transchoroidal approach is versatile and provides adequate exposure of the middle and posterior regions of the third ventricle. However, the fornix column limits the exposure of the anterior region of the third ventricle. There is evidence that the unilateral section of the fornix column has little effect on cognitive function. This study compared the anatomical exposure afforded by the transforniceal-transchoroidal approach with that of the transchoroidal approach. In addition, a morphometric evaluation of structures that are relevant to and common in the 2 approaches was performed.

METHODS

The anatomical exposure provided by the transcallosal-transchoroidal and transcallosal-transforniceal-transchoroidal approaches was compared in 8 fresh cadavers, using a neuronavigation system. The working area, microsurgical exposure area, and angular exposure on the longitudinal and transversal planes of 2 anatomical targets (tuber cinereum and cerebral aqueduct) were compared. Additionally, the thickness of the right frontal lobe parenchyma, thickness of the corpus callosum trunk, and longitudinal diameter of the interventricular foramen were measured. The values obtained were submitted to statistical analysis using the Wilcoxon test.

RESULTS

In the quantitative evaluation, compared with the transchoroidal approach, the transforniceal-transchoroidal approach provided a greater mean working area (transforniceal-transchoroidal 150 ± 11 mm2; transchoroidal 121 ± 8 mm2; p < 0.05), larger mean microsurgical exposure area (transforniceal-transchoroidal 101 ± 9 mm2; transchoroidal 80 ± 5 mm2; p < 0.05), larger mean angular exposure area on the longitudinal plane for the tuber cinereum (transforniceal-transchoroidal 71° ± 7°; transchoroidal 64° ± 6°; p < 0.05), and larger mean angular exposure area on the longitudinal plane for the cerebral aqueduct (transforniceal-transchoroidal 62° ± 6°; transchoroidal 55° ± 5°; p < 0.05). No differences were observed in angular exposure along the transverse axis for either anatomical target (tuber cinereum and cerebral aqueduct; p > 0.05). The mean thickness of the right frontal lobe parenchyma was 35 ± 3 mm, the mean thickness of the corpus callosum trunk was 10 ± 1 mm, and the mean longitudinal diameter of the interventricular foramen was 4.6 ± 0.4 mm. In the qualitative assessment, it was noted that the transforniceal-transchoroidal approach led to greater exposure of the third ventricle anterior region structures. There was no difference between approaches in the exposure of the structures of the middle and posterior region.

CONCLUSIONS

The transforniceal-transchoroidal approach provides greater surgical exposure of the third ventricle anterior region than that offered by the transchoroidal approach. In the population studied, morphometric analysis established mean values for anatomical structures common to both approaches.

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João Luiz Vitorino Araujo, José C. E. Veiga, Hung Tzu Wen, Almir F. de Andrade, Manoel J. Teixeira, José P. Otoch, Albert L. Rhoton Jr., Mark C. Preul, Robert F. Spetzler and Eberval G. Figueiredo

OBJECTIVE

Access to the third ventricle is a veritable challenge to neurosurgeons. In this context, anatomical and morphometric studies are useful for establishing the limitations and advantages of a particular surgical approach. The transchoroidal approach is versatile and provides adequate exposure of the middle and posterior regions of the third ventricle. However, the fornix column limits the exposure of the anterior region of the third ventricle. There is evidence that the unilateral section of the fornix column has little effect on cognitive function. This study compared the anatomical exposure afforded by the transforniceal-transchoroidal approach with that of the transchoroidal approach. In addition, a morphometric evaluation of structures that are relevant to and common in the 2 approaches was performed.

METHODS

The anatomical exposure provided by the transcallosal-transchoroidal and transcallosal-transforniceal-transchoroidal approaches was compared in 8 fresh cadavers, using a neuronavigation system. The working area, microsurgical exposure area, and angular exposure on the longitudinal and transversal planes of 2 anatomical targets (tuber cinereum and cerebral aqueduct) were compared. Additionally, the thickness of the right frontal lobe parenchyma, thickness of the corpus callosum trunk, and longitudinal diameter of the interventricular foramen were measured. The values obtained were submitted to statistical analysis using the Wilcoxon test.

RESULTS

In the quantitative evaluation, compared with the transchoroidal approach, the transforniceal-transchoroidal approach provided a greater mean working area (transforniceal-transchoroidal 150 ± 11 mm2; transchoroidal 121 ± 8 mm2; p < 0.05), larger mean microsurgical exposure area (transforniceal-transchoroidal 101 ± 9 mm2; transchoroidal 80 ± 5 mm2; p < 0.05), larger mean angular exposure area on the longitudinal plane for the tuber cinereum (transforniceal-transchoroidal 71° ± 7°; transchoroidal 64° ± 6°; p < 0.05), and larger mean angular exposure area on the longitudinal plane for the cerebral aqueduct (transforniceal-transchoroidal 62° ± 6°; transchoroidal 55° ± 5°; p < 0.05). No differences were observed in angular exposure along the transverse axis for either anatomical target (tuber cinereum and cerebral aqueduct; p > 0.05). The mean thickness of the right frontal lobe parenchyma was 35 ± 3 mm, the mean thickness of the corpus callosum trunk was 10 ± 1 mm, and the mean longitudinal diameter of the interventricular foramen was 4.6 ± 0.4 mm. In the qualitative assessment, it was noted that the transforniceal-transchoroidal approach led to greater exposure of the third ventricle anterior region structures. There was no difference between approaches in the exposure of the structures of the middle and posterior region.

CONCLUSIONS

The transforniceal-transchoroidal approach provides greater surgical exposure of the third ventricle anterior region than that offered by the transchoroidal approach. In the population studied, morphometric analysis established mean values for anatomical structures common to both approaches.

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Setti S. Rengachary, Andrew Xavier, Sunil Manjila, Usha Smerdon, Brandon Parker, Suzan Hadwan and Murali Guthikonda

the father of comparative anatomy and one of the earliest comparative neurologists. Willis was primarily a keen observer who carefully recorded what he observed and then he developed a hypothesis as to the cause of the condition. His interpretations of the diseases he observed in living patients and autopsies were accurate, and many of them unique from what had been reported in the past. Willis' conclusions on the physiology of the nervous system stemmed from his basic supposition that function could be determined by detailed observation of structure: …we have

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R. Shane Tubbs, Andrew J. DeNardo and Aaron A. Cohen-Gadol

A n anastomosis that travels between the left and right cavernous ICAs appears to be an extremely rare phenomenon. First reported by Lie in 1966 (quoted by Midkiff et al. 8 ), this vascular derailment does not have a well-understood embryology. Although the incidence of this arterial variation is not known, Taşar et al. 13 identified such an anomaly in 1 of 5100 angiographic or MR imaging studies. Herein, we report a case of an intercavernous connection between the left and right ICAs and discuss the comparative anatomy, potential embryology, and

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Charles H. Tator, Alex S. Rivlin, Anthony J. Lewis and Beatrice Schmoll

Spitzka 15 first described the unusual location of the pyramidal tract in rats, and this was confirmed later by Barron 1 and Ranson. 10 Ranson also showed its changing shape at various levels of the spinal cord. Linowiecki's study in 1914 9 of the comparative anatomy of the tract showed that, in the rat, the tract is composed primarily of small unmyelinated fibers. To our knowledge, axonal concentrations have not been reported for the spinal segments of the tract, although Lassek and Rasmussen 8 reported area measurements and axonal counts in the medullary portion

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Julian L. Robinson and Carol B. Sedzimir

. , 1961 , 18 : 847 – 848 . Markham , J. W. Arteriovenous fistula of the middle meningeal artery and the greater petrosal sinus. J. Neurosurg. , 1961, 18: 847–848. 7. Padget , D. H. The development of the cranial venous system in man, from the viewpoint of comparative anatomy. Contr. Embryol. , 1957 , 36 : 79 – 140 . Padget , D. H. The development of the cranial venous system in man, from the viewpoint of comparative anatomy. Contr. Embryol. , 1957, 36: 79–140. 8. Pakarinen , S. Arteriovenous fistula

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4. Padget DH : The cranial venous system in man in reference to development, adult configuration, and relation to the arteries. Am J Anat 98 : 307 – 355 , 1956 Padget DH: The cranial venous system in man in reference to development, adult configuration, and relation to the arteries. Am J Anat 98: 307–355, 1956 5. Padget DH : The development of the cranial venous system in man, from the viewpoint of comparative anatomy. Contrib Embryol 36 : 81 – 140 , 1957 Padget DH: The development of the cranial

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James W. Markham

, Including the Central Connections, Development, and Comparative Anatomy of the Visual Apparatus. Philadelphia , Blakiston , 1933 Wolff E: The Anatomy of the Eye and Orbit, Including the Central Connections, Development, and Comparative Anatomy of the Visual Apparatus. Philadelphia, Blakiston, 1933

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Paul P. Huang and Shlomo Constantini

: The development of the cerebellum in man in relation to its comparative anatomy. J Comp Neurol 87 : 85 – 129 , 1947 Larsell O: The development of the cerebellum in man in relation to its comparative anatomy. J Comp Neurol 87: 85–129, 1947 14. Larsell O , Jansen J : The Comparative Anatomy and Histology of the Cerebellum. The Human Cerebellum, Cerebellar Connections, and Cerebellar Cortex. Minneapolis : University of Minnesota , Vol 3 , 1972 Larsell O, Jansen J: The Comparative Anatomy and Histology of the