海外文献: Failure of Intraoperative Monitoring

Failure of Intraoperative Monitoring to Detect Postoperative Neurologic Deficits: A 25-year Experience in 12,375 Spinal Surgeries.

・25年間、12375脊椎手術における経験 : 術中神経モニタリングで発見できなかった術後神経マヒについて
・これは、1985年から2010年での1施設における12,375脊椎手術の記録....これがどんなにすごいビックデータであるかをぜひともわかって欲しいと思います。 日本でこのような長期間にわたる、しかも膨大な臨床データを調査し、保管し、まとめるということができる医療機関はまず皆無でしょう。 医療技術事態に日米の差があるとは思いませんが、医療機関とその周辺の研究体制には雲泥の差があるのは歴然としていますし、それが残念ながら、新しい医療を切り開くという意味での日本の「遅れ」の原因であろうことは、誰の目にも明らかだと思います。

-SSEP, DNEP, MEP などの複数の方法を用いて術中神経モニタリング12,375例を実施
-このうち45例(0.36%)で false negative (偽陰性)の症状が発生
-およそ82.2%(45例のうちの37例では) あきらかな偽陰性であった。
-45例のうち8例 (0.064%)は、回復不能な神経マヒが残った。

☞ 回復不能な神経マヒが残存した患者さんの疾患名と年齢は、次のとおり。
 ・脊椎下垂症 11歳、17歳、54歳
 ・変性性脊柱管狭窄 61歳、70歳
 ・フラットバック症候 69歳
☞ 回復不能な脊髄マヒが残存した患者さんの疾患名と年齢は、次のとおり。
 ・フラットバック症候 34歳
 ・外傷に多発骨折 18歳

☞ 神経モニタリングを勉強してきた私として、もっとも気になったのは.....あるいは安心したのは、これらの偽陰性であった手術で
 用いられていたモニタリングの方法だったのですが、それは DSEP,spontaneouse EMG, DNEP(descending neurogenic evoked potential) であり、triggered EMGや MEPでの偽陰性ではなかったことです。

☞ この文献で新たに勉強となったのが、DNEP(descending neurogenic evoked potential)なのですが、この方法を国内では見たことがなく

Descending neurogenic evoked potentials (DNEPs)were used during any procedure involving the thoracic
spine. Four different techniques were utilized to elicit a DNEP response:
(1) Percutaneous stimulation: External placement of two 75-mm needle electrodes onto consecutive cervical laminae;
(2) Spinous process stimulation: Placement of two 12-mm, 24-gauge needle electrodes into the spinous
process of two consecutive proximal spinal levels in the wound;
(3) Epidural stimulation: Placement of a flexible stimulating catheter within the epidural space. This was accomplished with a small incision in the ligamentum flavum at the proximal end of the surgical site. The catheter was then threaded cranially to insure stimulating above surgical levels; and
(4) Disc space stimulation: Placement of two 12-mm, 24 gauge needle electrodes into the lateral
disc space of two consecutive spinal levels. This technique was used, as needed, for anterior spinal fusions.
All DNEP responses were recorded bilaterally from the sciatic nerve at the popliteal fossa.
A constant current or voltage was applied until a repeatable response could be obtained with minimum stimulation intensity. Muscle relaxation was required to prevent any stimulation-induced movement of paraspinous musculature and to limit any muscle artifact in the response

Multimodality IOM included somatosensory-evoked potentials (SSEPs), descending neurogenic-evoked potentials (DNEPs), transcranial motor-evoked potentials (MEPs), dermatomal somatosensory-evoked potentials (DSEPs), and spontaneous and triggered electromyography (spEMG, trgEMG). We reviewed 12,375 patients who underwent surgery for spinal pathology from 1985 to 2010. There were 7178 females (59.3%) and 5197 males (40.7%); 9633 (77.8%) primary surgeries and 2742 (22.2%) revisions. Procedures by spinal level were cervical 29.7% (3671), thoracic/thoracolumbar 45.4% (5624), and lumbosacral 24.9% (3080). Age at surgery was > 18 years - 72.7% (8993) and < 18 years - 27.3% (3382).

Forty-five of the 12,375 patients (0.36%) had false negative outcomes. False negative results by modality were as follows: spEMG (n = 22, 48.8%), trgEMG (n = 8, 17.7%), DSEP (n = 4, 8.8%), DNEP (n = 4, 8.8%), SSEP (n = 3, 6.6%), DSEP/spEMG (n = 3, 6.6%), and trgEMG/spEMG (n = 1, 2.2%). Thirty-seven patients had immediate postoperative deficits unidentified by IOM; 30 patients (81%) involved nerve root monitoring, four patients had spinal cord deficits, and three patients had peripheral sensory deficits. Eight patients had permanent neurologic deficits, six (0.048%) were nerve root and two (0.016%) were spinal cord in nature.

Despite correct application and usage, IOM data failed to identify 45 (0.36%) patients with false negative outcomes out of 12,375 surgical patients. Eight patients (0.064%) of these 45 patients had permanent neurologic deficits, six patients had nerve root deficits in nature and two patients had spinal cord deficits. Although admittedly small, this represents the risk of undetected neurologic deficits even when properly using IOM. Deficits are at a higher risk to remain unresolved when not detected by IOM.

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