外傷性髄液瘻のMR所見と手術適応について

MR Findings in Traumatic Cerebrospinal Fluid Leakage with Special Reference to the Indications of the Need for Dural Repair

I．はじめに

　外傷性髄液瘻の治療において最も重要なことは頭蓋内感染症の予防である．外科的修復の適応とその施行時期については議論のあるところである．受傷後数日以内に髄液瘻を認める場合には自然治癒することが多いために2週間程度は保存的に経過をみ，そして髄液の漏出が続いたり再発性の場合には修復術を考慮するのが一般的である^{11,13,15,17）}．しかし外傷後の頭蓋内感染は髄液瘻が自然に停止した例や，経過中に髄液瘻が認められなかった例にも生じており髄液漏の有無のみを指標にして修復術の適応を判断するのは問題がある^{1,2,4,7-9,12）}．

　またこれまで術前に瘻孔の部位，大きさを正確に知ることは困難であったため，再手術を要することも少なくなかった．すなわち外傷性髄液瘻の治療の問題点として①修復術の適応に関するものと②閉鎖すべき瘻孔の部位大きさの決定に関するものがあると思われる．しかし，従来の補助診断法である頭蓋単純写，X線断層撮影，CT scan, RI脳槽撮影などでは痩孔の十分な情報を得ることは困難である^1,17）．

Eleven cases of traumatic cerebrospinal fluid (CSF) leakage (8 cases of rhinorrhea and 3 cases of otorrhea)were reviewed to discuss magnetic resonance (MR) findings and surgical indications of the need for dural repair. Five patients had delayed onset of CSF rhinor-rhea, 12 to 66 days (mean 28 clays) after the trauma, and in the remaining 6 patients (3 rhinorrhea and 3 otorrhea) CSF leakage was noted on admission. MR study was carried out within 7 clays after the onset of CSF leakage using a 0.5 tesla imager. In 7 cases of rhi-norrhea, MR images demonstrated brain herniation into the ethmoid or frontal sinuses and the dural defects were repaired with the vascularized periosteum flap taken from the frontal bone or the fascia lata. In the operations, brain parenchyma was found to be plugged into the fracture line as MR images showed, and also to adhere to the margin of dural fistula. In the remaining 4 patients (without the MR findings of brain herniation into the paranasal sinuses) spontaneous cessation of CSF leakage occurred and their clinical course was good. Spontaneous cessation of CSF leakage in these cases may suggest the complete healing of the lacer-ated dura. However, in cases with the brain herniated into the paranasal sinuses CSF leakage may not be observed, and natural healing of the dural defect cannot be expected. Therefore, such brain herniation indicates the absolute need for dural repair even if CSF leakage is not observed. MR imaging is the diagnostic modality of choice to present direct visualization of brain hernia-tion into the paranasal sinuses, so it must be utilized in cases in which traumatic dural fistula is suspected.