第3脳室底正中部破壊の実験的研究—第3脳室経由到達法に関する検討

Experimental Study on Destruction of the Third Ventricle Floor in the Midline:Examination for the trans-third ventricle approach

I．はじめに

　脳底動脈末端部動脈瘤の手術に際しては，通常Drake^4）のsubtemporal approachもしくはYasargil^13）のpterional approachが用いられているが，脳底動脈末端部が高い位置にある場合や，megadolichobasilaranomaly^1）を伴った動脈瘤では，これらのapproachでは到達不可能な場合がある．

　著者らは，megadolichobasilar anomalyを伴った高位脳底動脈末端部動脈瘤の症例において，動脈瘤破裂により第3脳室底が一部破壊されていたことを利用し，第3脳室経由による到達法を試みた．そして，動脈瘤柄部処置の際に充分な視野を得るために，破壊されていない第3脳室底正中部の一部をもさらに切開した．術後は電解質異常，尿崩症，体温異常，消化管出血等の視床下部障害によると思われる症状の出現は認められず良好な結果を得た^6,7）．

Abstract

Surgery of a basilar bifurcation aneurysm is a very difficult operaton in neurosurgery. For the treatment of this lesion, two methods are widely used at pre-sent ; one is the subtemporal approach developed by Drake and the other is the pterional approach byYasargil. With either approach, however, the treatment of a basilar bifurcation aneurysm accompanied by me-gadolichobasilar anomaly is difficult and hazardous due to the necessity for excessive retraction of the brain, nerves and vessels.

Recently we successfully treated two cases of rup-tured basilar bifurcation aneurysm complicated with megadolichobasilar anomaly by the trans-third ventricle approach. The floor of the third ventricle was already partly destroyed by aneurysmal rupture in both cases. It was required to make a small split in the third ven-tricle floor in order to get a wider operative field. Post-operatively, however, no influence from the splitting of the floor was seen.

An experimental study was carried out in dogs to de-termine the influence from the destruction of the floor of the third ventricle.

Using microsurgical techniques, the third ventricle floor was opened along the midline. Dogs were sacri-ficed 30 days after surgery. The following items were evaluated before, during, and after surgery : clinical symptom, blood pressure, pulse, body temperature, serum electrolytes, serum osmotic pressure, pituitary hormones (anterior lobe) , cortisol, ADH (2.5mol NaCl loading test) , electroencephalogram, cerebral blood flow and pathological change.

No significant abnormalities could be detected in en-docrine and metabolic functions, and no histological changes were seen around the hypothalamus.

In conclusion, it is justified to split the third ventricle floor along the midline if it is indicated.