THESES
TECHNICAL DIFFICULTIES IN THE MICROSURGICAL DISSECTION OF THE SYLVIAN FISSURE AND CISTERN: PROSPECTIVE IDENTIFICATION OF THE RESPONSIBLE FACTORS IN 152 ELECTIVE NEUROLOGICAL SURGERIES (ABSTRACT)* * Dificuldades técnicas na dissecção microcirúrgica da fissura e cisterna silvianas: identificação prospectiva dos fatores responsáveis em 152 cirurgias neurológicas eletivas (Resumo). Tese de Doutorado, Faculdade de Medicina da Universidade de São Paulo (Área: Neurologia). Orientador: José Píndaro Pereira Plese. . THESIS. SÃO PAULO, 2000.
MARIO GILBERTO SIQUEIRA** ** Address: Rua Virgílio de Carvalho Pinto 381 / 42, 05415-030 São Paulo SP, Brasil.
The sulci, fissures and subarachnoid cisterns are natural pathways of circulation of the cerebrospinal fluid that may be used by the surgeon to reach deep regions of the brain and the skull base with little risk of damage to the neural vascular structures. Amongst these routes, the sylvian fissure and cistern is the most commonly utilized in the neurosurgical practice. Even though the technique is widely known, the surgical microdissection of these spaces is not always simple and even the most tenacious and experienced surgeon finds it difficult at times.
With the purpose of detecting the factors that might contribute to these technical difficulties during the microsurgical dissection of the sylvian fissure and cistern we have analysed 10 variables observed during 152 surgeries carried through the pterional route for the treatment of aneurysms of the anterior circulation. These variables were confronted with the dissection results. The surgical occurrence of extensive pial lesion and extended microsurgical dissection time (over 60 minutes) were considered as indirect evidence of technical difficulty during dissection and representative of a sylvian fissure and cistern difficult to dissect.
The analysis of the association between the result of the dissection and each of the variables separetely has demonstrated that the percentage of sylvian fissure and cistern difficult to dissect was significantly higher in the patients that harbored a thick arachnoid membrane, in those with severe adherence between the frontal and the temporal operculae, in those where the sylvian cistern was virtual, and in those in which the superficial sylvian vein had a caliber greater than 3 mm. Nevertheless, when the multiple logistic regression technique was employed for the analysis of the effect of all the variables together on the possibility of a difficult dissection, only the first two were significant (p=0.005 and p=0.015 respectively).
The probability of a sylvian fissure and cistern difficult to dissect is approximately 2.76 times higher in those patients with a thick arachnoid membrane and 3.11 times higher when the adherence between the operculae is moderate or severe. Whithout the above two variables considered as risk factors, the probability of a sylvian fissure and cistern difficult to dissect is only 12%. On the other hand, when both factors are present the probability increases to 53%.
The occurrence of an extensive pial lesion or the necessity of a surgical time greater than 60 minutes to perform the microsurgical dissection, considered as representative factors for a sylvian fissure and cistern difficult to dissect, were not directly related to any clinical consequence. When we take into consideration the relevance of this finding and the paramount importance of the surgical microdissection for the opening of the sylvian fissure and cistern through the pterioneal route we may conclude that the technical difficulties that may be found during surgery are not per se a contraindication to the procedure.
KEY WORDS: sylvian fissure and cistern, microsurgical dissection, technical difficulties identification.
Publication Dates
-
Publication in this collection
01 Dec 2000 -
Date of issue
Dec 2000
