腰椎间盘突出症与坐骨神经痛有什么关系？

腰椎间盘突出症引起坐骨神经痛已经为世人普遍接受，患者的症状通常取决于参与的脊神经根。由于95％的腰椎间盘突出症发生在L4或L5椎间盘水平，坐骨神经痛如此普遍不足为奇。 L4和L5椎间盘突出症发生的频率高也是为什么大多数肌电图证实的神经根病变发生在L5或S1根的原因。上海仁济医院疼痛科王祥瑞

It has been known for years and is generally accepted that a compressive lumbar disc herniation is a common cause of sciatica , and the patients symptoms will usually depend upon which spinal nerve root is involved. Since 95% of lumbar disc herniations occurs at either the L4 or L5 disc level , it"s not at all surprising that sciatica is so very commonly. This high frequency of L4 and L5 disc herniation is also the reason why most EMG-confirmed radiculopathy occurs in the L5 or S1 root .

虽然椎间盘突出确实引起的坐骨神经痛，但不是所有的椎间盘突出都会导致坐骨神经痛，有些人有严重的坐骨神经痛，但是没有任何证据提示椎间盘突出症。

Although disc hernation-induced sciatica certainly does occur, it"s common knowledge that not all disc herniations cause sciatica. Some people have severe sciatica without any evidence of compressive disc herniation at all!

Karppinen等研究表明20％有严重急性坐骨神经痛患者MRI上没有压迫性腰椎间盘突出症；，而这些患者都患有严重的背部和腿部疼痛。他们的结论，坐骨神经痛和背痛的严重程度与椎间盘移位的大小（椎间盘突出的大小）与脊髓神经根的压迫量不相关，VAS和Oswestry评分实际上是等效的在评估椎间盘突出症患者（椎间盘突出=突出、脱垂、及游离）和椎间盘膨出或正常椎间盘患者。

In a recent investigation by Karppinen et al. [Karppinen], it was demonstrated that 20% of severely acute sciatica patients had no compressive disc herniation on MRI; all MRI images were negative for protrusion, extrusion, and/or sequestration, yet these patients were suffering from severe back and leg pain!  These researchers concluded that the severity of sciatica and back pain are NOT related to the amount of the disc displacement (size of the herniation) or the amount of spinal nerve root compression! VAS and Oswestry scores were virtually the same for both disc herniations patients (disc herniation = protrusion, extrusion, & sequestration) as they were for disc bulge or normal disc patients! (I would add that patients who were applying for early retirement were removed from this study which enhances its validity). 

如果不是压迫性椎间盘突出造成的痛苦，那是什么原因？

So, if its not a compressive disc herniation that"s causing the suffering, then what it?

Ohnmeiss和Milette等提出一个可能的解释，椎间盘内物质的破裂漏出（纤维环撕裂）不仅造成腰痛，也可造成下肢的“牵涉痛”；我们可以称这个下肢疼痛为椎间盘源性坐骨神经痛

One possible explanation was put forth by both Ohnmeiss et al.  and Milette et al These investigators experimentally demonstrated that disruptions within the substance of the disc (anular tears) not only caused low back pain but also caused ‘referred pain’ into the lower limb; we may call this referred lower limb pain ‘discogenic sciatica’.  

Olmarker等研究表明，压迫神经根髓核，可出现明显的神经根微解剖的形态学改变（轴突损伤）和功能变化（传导速度下降），以及在动物实验中可导致“疼痛相关的行为的发生

Another explanation is based upon the investigations of Olmarker et al.   This group has repeatedly demonstrated that the application of nucleus pulposus upon the spinal nerve root can create marked morphological change (axon damage) and functional change (decreased conduction speed) to the micro-anatomy of that nerve root, as well as cause ‘pain-related behaviors’ to occur within the test animals . 

因此，如果这个髓核在硬膜外腔（犹如5级椎间盘后纤维环的撕裂），它可能导致Olmarker所描述的病理脊髓神经根的变化及无神经根的压迫坐骨神经痛综合征，又称为“化学神经根型”。

Therefore, if this nucleus pulposus get ‘loose’ in the epidural space (most likely from a grade 5 posterior anular disc tear), it may well cause the pathological spinal nerve root changes described by Olmarker and result in a painful sciatica syndrome without nerve root compression.   Researchers have termed this phenomenon “Chemical Radiculopathy” .

不管是什么原因，很显然，非压迫性椎间盘（膨出和容纳型突出）与经典的大型压迫性椎间盘突出产生相同的疼痛和运动受限。因此我们不应该轻视核磁共振检查中无椎间盘突出的坐骨神经痛的患者的症状。

The final theory on non-compression induced sciatica implicates the activation of the patients own immune system against the nucleus pulposus-soaked nerve root. This ‘auto-immune’ type reaction may help perpetuate the syndrome of chronic sciatic pain.

Whatever the cause, it is clear that non-compressive disc defects (bulges and contained herniations) are just as painful and disabling as the classic large compressive disc herniation.   Therefore the symptoms of sciatic patients without disc herniation in MRI should not be dismissed by the doctor.