O papel da membrana de Liliequist na terceiro ventriculostomia endoscópica / The role of the Liliequist membrane in endoscopic third ventriculostomy

A Terceiro Ventriculostomia Endoscópica (TVE) é operação intracerebral que trata a hidrocefalia. Para sua realização é necessário conhecimento da anatomia cirúrgica da membrana aracnoidea de Liliequist, que deve ser aberta durante o procedimento. Porém, a anatomia do ponto de vista neuroendoscópico é pouco conhecida, já que os ângulos de abordagem são diferentes da anatomia descritiva clássica e mesmo da anatomia cirúrgica microscópica. Há discrepância na literatura quanto a eficácia da TVE, sobretudo em crianças, em que pode ocorrer a não abertura completa da membrana de Liliequist (ML). Para compreensão do comportamento da ML, a sua associação com o Tuber Cinereo (TC) e o assoalho do III Ventrículo (IIIVT) e outras peculiaridades, foi realizada, prospectivamente, a observação sistemática destas características durante 57 operações. Os dados foram registrados após o procedimento e posteriormente estudados. Os objetivos eram sistematizar as características anatômicas destas estruturas do ponto de vista neuroendoscópico, avaliar se as alterações seguiam algum padrão e se interferiam no procedimento técnico, correlacionando com a evolução. Pela análise dos dados percebeu-se que as características da ML são variáveis e dificultam, em uma percentagem considerável de vezes, a sua interpretação e seu manejo pelo neurocirurgião. Também, que o TC alterado e separado da ML são fatores associados à maior dificuldade de realização da TVE. Que as TVE realizadas nas hidrocefalias por malformações congênitas, processos inflamatórios e pós sangramento (prevalentes na infância) estão associadas a maior dificuldade de manejar a ML e podem explicar o índice de insucesso maior observado na literatura em crianças abaixo de 2 anos.

Endoscopic Third Endoscopic (ETV) is a neurosurgical procedure to treat hydrocephalus. To be fully performed it is necessary opening an arachnoid structure, the Liliequist Membrane (LM). However the LM surgical anatomy from the neuroendoscopic point of view is not yet completely studied, since approach angles are different from classics descriptive and microsurgical anatomies. There is a literature discrepancy regarding the ETV efficacy, especially in children over 2 years old, which may be due to LM incomplete opening. In order to understand the LM anatomical behavior, the relationship with tuber cinereo (TC), the floor of the III Ventricle and other peculiarities, a systematic prospective observation of these characteristics was performed during the 57 surgeries. Data were recorded after the procedure and studied. Objectives were to systematize LM anatomical characteristics from neuroendoscopic perspective, understand if anatomical changes follows a pattern interfering on the procedure, and if there is correlation with patients evolution. The data analysis shows that LM characteristics are variable, making difficult the neurosurgeon management. Whenever TC anatomy modifies, or when TC and ML are separated, difficulty to perform ETV increases. When hydrocephalies are due to congenital malformations, inflammatory processes and post bleeding (prevalent in childhood), LM management is much harder, witch may explain the higher failure rate in children under 2 years of age observed in literature.

Eficácia da fenestração da lâmina terminal associada à fenestração da membrana de Liliequist na prevenção de hidrocefalia crônica empacientes operados na fase aguda por aneurisma cerebral roto / Efficacy of Lamina Terminalis Fenestration Associated whith Liliequist' Membrane in reducing Shunt- Dependent Hydrocephalus following Aneurysmal Subarachnoid Hemorrhage

Objetivos Hidrocefalia tardia que requer implante de derivação liquórica é frequente após hemorragia subaracnóidea por aneurisma cerebral roto, e contribui para amorbimortalidade tardia. Alguns autores reportam que a fenestração microcirúrgica da Lâmina Terminal, durante a cirurgia do aneurisma diminui a incidência de hidrocefalia tardia. Material e Método No período de Janeiro de 2010 a Janeiro de 2012 realizamos a fenestração da Lâmina Terminal associada à fenestração da Membrana de Liliequist, em 17 pacientes operados na fase aguda por aneurisma roto. Monitoramos por tomografia a presença de hidrocefalia após 6 e 16 meses. Resultados Nenhum paciente apresentou hidrocefalia tardia. Conclusão A fenestração da Lâmina Terminal associada à fenestração da Membrana de Liliequist é eficaz na prevenção da hidrocefalia tardia pós hemorragia subaracnóidea por aneurisma roto.

Objectives Chronic hydrocephalus requiring shunt placement is common following aneurysm subarachnoid hemorrhage, and contributes to the late morbidity and mortality Some authors report that microsurgery fenestration of Lamina Terminalis during aneurysm surgery affords a reduction in the development shunt-dependent hydrocephalus. Methods From January 2010 to January 2012 we performed microsurgery fenestration of Lamina Terminalis and Liliequist's Membrane, in 17 patients operated in the acute phase. CT scans were performed after 6 and 16 months Result There was no development of hydrocephalus in this series. Conclusion Microsurgery fenestration of Lamina Terminalis associated with Liliequist's Membrane fenestration is effective in preventing late hydrocephalus after subarachnoid hemorrhage due to ruptured aneurysm.

Membrana de Liliequist: avaliação radiológica e suas implicações clínicas e terapêuticas / Liliequist membrane: radiological evaluation, clinical and therapeutic implications

A membrana de Liliequist, de maneira simplista e sucinta, pode ser entendida como uma projeção formada pela aracnoide que se estende do dorso da sela turca aos corpos mamilares. Apesar de se tratar de uma estrutura anatômica bem conhecida pelos neurocirurgiões, muitos radiologistas não a conhecem ou não valorizam seu estudo. A avaliação por imagem desta membrana é factível e pode ser interessante para o melhor planejamento pré-operatório, avaliação pós-operatória de terceiro-ventriculostomias e entendimento dos cistos aracnoides suprasselares e hemorragias perimesencefálicas. Ilustramos neste artigo os aspectos anatômicos da membrana, sobretudo do ponto de vista de imagem, além de suas possíveis implicações clinicocirúrgicas.

In a simplistic and succinct way, Liliequist membrane may be understood as a projection formed by an arachnoid membrane extending from the dorsum sellae to the mammillary bodies. In spite of being well known to neurosurgeons, many radiologists neither know this anatomical structure nor give importance to its study. The imaging evaluation of this membrane is feasible and may be interesting for a better preoperative planning; postoperative evaluation of third ventriculostomies; and understanding of suprasellar arachnoid cysts and perimesencephalic hemorrhage. The present article illustrates the anatomy of the membrane, with emphasis on imaging findings, besides describing its possible clinical and surgical implications.

Radioisotope Cisternographic Analysis of Post-operative Subdural Hygroma after Aneurysmal Surgery

Authors analyzed the post-operative subdural hygroma using radioisotope(RI) cisternography in 30 cases following aneurysmal surgery with pterional approach from October, 1995 to March, 1996. Age, CSF flow from basal cisterns, and etent of opening of Liliequist's membrane during operation were significantly related to the development of post-operative subdural hygroma. Computed tomography(CT) scan of brain and RI cisternography were performed in all patients at three weeks following operations. RI diffusion time from the interpeduncular cistern to the cerebral convexity of ipsilateral side with surgically opened Liliequist's membrane was compared with contralateral nonoperated normal side. Diffusion time of ipsilateral side(mean 5.2+/-8.4hr) was faster than that of contralateral one. Age, cerebrospinal fluid(CSF) from basal cistern, and extent of opening of Liliequist's membrane during operation were significantly related to development of post-operative subdural hygroma. Development of subdural hygroma after pterional approach for aneurysmal operations in our series is believed to be caused by stagnation of CSF in the convexity until its absorption into the arachnoid villi. Increased CSF flow from the infratentorial space to the supratentorial space through extensively opened Liliequist's membrane is considered to contribute development of its formation.

Subdural Hygroma Following Pterional Approach for Cerebral Aneurysmal Surgery

The occurrence of subdural hygroma following pterional approach for intracranial aneurysm at Yeungnam University from March 1994 to December 1994 was studied with regard to the patients age, location of aneurysm, preoperative ventricular dilatation, operation time, cortex color, CSF flow, opening degree of Liliequist membrane, dissection degree of sylvian fissure, postoperative intradural air amount and day for mannitol infusion using chi-square test. The following results and conclusions were obtained: 1) Subdural hygroma was observed in 28 of 53 patients(52.8%). 2) The patient's age was significantly related to the occurance of subdural hygroma(p<0.05). 3) CSF flow through the basal cistern was significantly related to the occurrence of subdural hygroma(p<0.05). 4) In cases of good CSF flow, degree of Lilieqist membrane opening was significantly related to the occurrence of subdural hygroma(p<0.05). Preserving of Liliequist membrane will minimize the occurrence of subdural hygroma.