脳室穿刺に伴う局所脳循環代謝の変化について

The changes of regional cerebral blood flow and oxygen metabolism following ventricular puncture

I．はじめに

　脳室穿刺は脳室ドレナージ（CVD），脳室腹腔短絡術（VP shunt）等様々な脳神経外科手術において多用されており，その有用性は明らかではある．また従来より臨床症状の出にくいいわゆるsilent areaを穿刺部位として用いることが多く，穿刺に伴って大きな血腫でも作らない限り臨床的に問題となるような症状が出現することはごく稀であり，その短所に注意が払われることは少ない．しかしながら一方でCVD，shuntの合併症として脳内血腫，硬膜下／外血腫，tension pneumocephalus，痙攣等が存在するのも事実で，その危険性を指摘し，安易な脳室穿刺を疑問視する論文も散見される^1,2,4,5,7）．また，当センターで1983年4月から1990年3月までに脳室ドレナージあるいはシャント手術で脳室穿刺がなされた450例，755回の脳室穿刺例のCT scan所見，臨床症状のreviewを行った結果，直径3cm以上の血腫形成を来した例を中心に低率ながらも臨床的に問題となる合併症を来した症例が存在し，また術後のCT scan所見では穿刺後にこれに伴う高吸収域が12.3％，低吸収域が59.3％，計72.5％と，明らかな臨床症状を来さないまでも画像上はかなり高率に穿刺による脳の器質的変化が観察された^6）．症例によっては脳室穿刺により，従来行われている臨床評価上には現われてこないような脳の局所的機能低下を来していることも推察される．前回のCTscan上の変化の検討に続き，今回脳室穿刺による穿刺部近傍の局所脳循環代謝の変化について検討を行った．

In seven patients who underwent ventricular punc-ture as a procedure for either continuous ventricular drainage or ventriculoperitoneal shunt between April 1983 and December 1988, the changes between pre- and postoperative regional cerebral blood flow (rCBF) and the regional cerebral metabolic rate of oxygen (rCMRO₂) around the regions along the tract of punc-ture were evaluated. In each patient, rCBF and rCMRO₂ were measured using Positron Emission Tomography (PET) by the steady state method. The regions of interest (ROIs) with diameters of 2cm were set as follows: The gray matter (PSG) and white mat-ter (PSW) along the tract of the puncture, the same re-gions on the opposite side (OSG and OSW) and the bi-lateral motor cortex (PSM and OSM) as control. All changes, as well as lateralities at each region were stu-died. In 4 of 7 patients long term follow up PET stu-dies (mean=657 days after the procedure) were per-formed.

After the procedure values of rCBF significantly in-creased in OSG and OSW (p＜0.05) and tended to in-crease in PSG and PSW. But compared with OSG and OSW, the degree of increase in PSG and PSW were suppressed. In the motor cortex evident changes were not recognized. Lateralities between PSG and OSG and those between PSW and OSW tended to increase after procedure. In long term follow up studies the values further increased in all regions including PSG and PSW and lateralities tended to decrease, but suppression of improvement around the puncture site was prolonged. The changes of rCMRO₂ had the same tendency but it was not significant.

The rCBF and rCMRO₂ generally increased follow-ing the procedure accompanying ventricular puncture. Perhaps this was because of adjustment of increased in-tracranial pressure or cerebrospinal fluid circulation. But the degree of improvement around the puncture site was suppressed. Minor brain injury caused by the procedure was considered to be the cause of reduction of improvement of cerebral blood flow and cerebral ox-ygen metabolism.