Transseptumpellucidumrostrostomy: anatomical considerations and neuroendoscopic approach

25 - ORIGINAL ARTICLE NEW METHODOLOGY Transseptumpellucidumrostrostomy. Anatomical considerations and neuroendoscopic approach1 Transseptopelucidorostrostomia. Considerações anatômicas e abordagem neuroendoscópica Eduardo José Takashi FuzikiI, Roberto Alexandre DezenaII, Benedicto Oscar ColliIII PhD, Neurosurgeon, Division of Neurosurgery, Department of Surgery and Anatomy, FMRP-USP, Ribeirao Preto-SP, Brazil. Responsible for acquisition and interpretation of data, statistical analysis, designed the protocol, involved with technical procedures. II PhD, Neurosurgeon, Division of Neurosurgery of Department of Surgery and Anatomy, FMRP-USP, Ribeirao Preto-SP, Brazil. Responsible for manuscript writing, responsible for English language. III PhD, Chairman and Head of Division of Neurosurgery of Department of Surgery and Anatomy, FMRP-USP, Ribeirao Preto-SP, Brazil. Responsible for intellectual and scientific content of the study, supervised all phases of study, critical revision. I ABSTRACT PURPOSE: Verify the presence of the rostral lamina of the corpus callosum, and set parameters for neuroendoscopy. METHODS: Relationship of the floor of the frontal horn of lateral ventricle and the hypothalamic-septal region were studied after sagittal and axial sections of the brains. Measurements were compared using F and Student t tests. The correlations between anterior-posterior diameter of the interventricular foramen / anterior-posterior diameter of the fornix column, and between anterior-posterior diameter of the interventricular foramen / length of the rostral lamina were performed by Pearson index test. RESULTS: There was no statistically significant difference in measurements performed in both hemispheres (p<0.05). Positive correlations were observed between the anterior-posterior diameter of the interventricular foramen / anterior-posterior diameter of the fornix column (R = 0.35), and between the anterior-posterior diameter of the interventricular foramen / length of the rostral lamina (R = 0.23). CONCLUSION: Rostral lamina was observed in all brains. It was possible to perform an endoscopic fenestration in the rostral lamina, communicating safely the lateral ventricle with a polygonal subcallosal cistern. Key words: Hydrocephalus. Neuroendoscopy. Septum Pellucidum. Anatomy. RESUMO OBJETIVO: Verificar a presença da lâmina rostral do corpo caloso e padronizar parâmetros para a realização de neuroendoscopia. MÉTODOS: A relação do assoalho do corno frontal do ventrículo lateral e a região hipotálamo-septal lateral foi estudada através de secções sagitais e axiais dos cérebros. As medidas foram comparadas utilizando os testes F e t-Student. As correlações entre diâmetro ântero-posterior do forame interventricular / diâmetro ântero-posterior da coluna do fornix, e entre o diâmetro ântero-posterior do forame interventricular / comprimento da lâmina rostral foram estudadas pelo teste de Pearson. RESULTADOS: Não houve diferença estatisticamente significante nas medidas realizadas em ambos hemisférios (p <0.05). Correlações positivas foram observadas entre diâmetros ântero-posteriores do forame interventricular / coluna do fornix (R = 0.35), os diâmetros ântero-posteriores do forame interventricular / comprimento da lâmina rostral (R = 0.23). CONCLUSÃO: A lâmina rostral foi observada em todos espécimes. Foi possível realizar uma fenestração endoscópica na lâmina rostral, comunicando com segurança o ventrículo lateral a uma cisterna poligonal subcalosa. Descritores: Hidrocefalia. Neuroendoscopia. Septo Pelúcido. Anatomia. Acta Cirúrgica Brasileira - Vol. 26 (Suppl. 2) 2011 - 133 Fuziki EJT et al. Introduction Surgical techniques for treating obstructive hydrocephalus have been described even before the identification of communication between the CSF and other compartments of the brain. Dandy, in 1922, for the first time opened the lamina terminalis through a craniotomy, communicating the third ventricle with the basal cysterns1. Mixter, in 1923, performed the first endoscopic third ventriculostomy toward interpeduncular cistern1. Contemporary authors have observed reduction in the incidence of hydrocephalus in subarachnoid hemorrhage, opening the lamina terminalis during surgical clipping of cerebral aneurysms1,2,3. Nakao and Itakura described the opening of the lamina terminalis with flexible endoscope to treat hydrocephalus secondary to tuberculous meningitis1 and since then the procedure became routine to treat obstructive hydrocephalus. Another brain internal shunt described, performed with endoscope, is the communication of the third ventricle with the quadrigeminal cistern, through the suprapineal recess4. In some situations, third ventriculostomy may became technically difficult, mainly when there is thickening of the floor of the third ventricle (for instance due to inflammatory reaction), hindering the identification of anatomical parameters, or when the interpeduncular cistern is reduced by an ecstatic basilar artery. In these situations, the knowledge of internal ventricular system alternative shunts may have its value. Remarks of functioning catheters from ventricular shunts placed accidentally in the longitudinal fissure of the brain are evidence that this place can act as an alternative shunt pathway. The objective of this paper was to study the feasibility to perform anatomical communication between the ventricular system and the longitudinal fissure of the brain through a fenestration of the rostral lamina of the corpus callosum and establish the anatomical parameters for its completion as a neuroendoscopic procedure. FIGURE 1 - Midline sagittal section of the brain showing the rostral lamina, hypothalamic-septal triangle, and neighbor structures. The central sulcus, the pre-central gyrus and pre-central sulcus were identified in the hemispheres surfaces and a point, 4 cm anterior to pre-central sulcus and 3 cm from the midline (Kocher point) was marked, and used as an entry point to the ventricle (Figure 2). Methods Identification and measurement of anatomical references to the floor of the frontal horn of lateral ventricle and cerebral longitudinal fissure Sixteen 10% formalin fixed brains provided by Department of Pathology, Faculty of Medicine – Alfenas University (UNIFENAS), obtained from autopsies, which showed normal appearance in the initial macroscopic inspection, were used. Nine were female and seven males, aged ranged from 13-69 years (43.5 ± 13.14) and weights varied from 940-1533 grams (1162.7 ± 148.75). After a midline sagittal cut, the following anatomical structures were identified in each hemisphere: the corpus callosum and its divisions, the interventricular foramen, the fornix column, the lamina terminalis, the supra-optic recess, the mammillary bodies, the tuber cinereum, the paraterminal gyrus and anterior cerebral artery (Figure 1). 134 - Acta Cirúrgica Brasileira - Vol. 26 (Suppl. 2) 2011 FIGURE 2 - Superior view of a left brain hemis (...truncated)