João Luiz Vitorino Araujo, MD, PhD,1,2 José C. E. Veiga, MD, PhD,2 Hung Tzu Wen, MD, PhD,1 Almir F. de Andrade, MD, PhD,1 Manoel J. Teixeira, MD, PhD,1 José P. Otoch, MD, PhD,1 Albert L. Rhoton Jr., MD,3 Mark C. Preul, MD,4 Robert F. Spetzler, MD,4 and Eberval G. Figueiredo, MD, PhD1
1 Division(of(Neurosurgery,(University(of(São(Paulo(Medical(School>(2 Discipline(of(Neurosurgery,(Santa(Casa(de(São(Paulo( Medical(School,(São(Paulo,(Brazil>(3 Department(of(Neurological(Surgery,(University(of(Florida,(Gainesville,(Florida>(and(4 Division( of(Neurological(Surgery,(Barrow(Neurological(Institute,(St.(Joseph’s(Hospital(and(Medical(Center,(Phoenix,(Arizona
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 transfornicealYtranschoroidal 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.
The anatomical exposure provided by the transcallosalYtranschoroidal and transcallosalYtransfornicealY
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.
In the quantitative evaluation, compared with the transchoroidal approach, the transfornicealYtranschoroidal
approach provided a greater mean working area transfornicealYtranschoroidal 150 ± 11 mm2
> transchoroidal 121 ± 8 mm2> p < 0.05), larger mean microsurgical exposure area transfornicealYtranschoroidal 101 ± 9 mm2> transchoroidal 80 ± 5 mm2> p < 0.05), larger mean angular exposure area on the longitudinal plane for the tuber cinereum transfornicealYtranschoroidal 71$ ± 7$> transchoroidal 64$ ± 6$> p < 0.05), and larger mean angular exposure area on the longitudinal plane for the cerebral aqueduct transfornicealYtranschoroidal 62$ ± 6$> transchoroidal 55$ ± 5$> p < 0.05). No differencYes were observed in angular exposure along the transverse axis for either anatomical target tuber cinereum and cereYbral 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 transfornicealYtranschoroidal 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.
The transfornicealYtranschoroidal approach provides greater surgical exposure of the third ventricle
anterior region than that offered by the transchoroidal approach. In the population studied, morphometric analysis estabY
lished mean values for anatomical structures common to both approaches.