What makes a far lateral disc herniation unique (and PAINFUL)?

We made an important distinction in the last post: that of the far lateral disc herniation.  We’ve just discussed the more common central herniated nucleus pulposus (HNP) in which the disc herniates into the center of the spinal canal (see figure 3 of this post.)  This centrally herniated fragment hits the traversing nerve that is still within the spinal canal (e.g. a central L4/5 disc herniation causes a radiculopathy of the L5 nerve.)  In a far lateral HNP, occurring only in about 10% of cases, the piece of disc herniates on the side of the spine and compresses the nerve along its course within the neural foramen as it exits the spine (e.g. a far lateral L4/5 disc causes a radiculopathy of the L4 nerve.)   See figure 1 for an MRI showing a far lateral HNP. 

Far lateral HNP 2

Figure 1: Axial MRI showing large right far lateral HNP (outlined in pink.)  Note the displaced nerve root (pink arrow) as compared to the normal nerve root free in its neural foramen (green arrow). 

Often I can identify a patient with a far lateral HNP right when I enter the room because they’re MISERABLE.  The pain associated with far lateral HNPs is typically much worse than that seen with central HNPs.  Just as it exits from within the neural foramen, the nerve dilates into an important junction point called the dorsal root ganglion (DRG).  It’s this exquisitely sensitive part of the nerve that is compressed by a far lateral HNP.  Couple that with the fact there’s a very limited amount of space within the bony neural foramen for both the herniated disc fragment and the DRG and one understands why this type of disc herniation is so debilitating (see figure 2).

DRG in foramen 

Figure 2: Image of the right side of the lumbar spine showing the nerve roots exiting via the bony neural foramina.  Note the dilation of the DRG within the confines of the foramen (red arrow.)  

A far lateral HNP requires a different approach than the standard discectomy we discussed in the last post.  In the far lateral discectomy, I’ll typically employ an “outside-in” approach to find the fragment under the nerve as it exits the foramen.  First, the incision for a far lateral discectomy is made a few more centimeters off of midline compared to that of a standard discectomy.  Next, I’ll dock a tubular retractor in between the transverse processes at the level in question (see figure 3).  I’ll then work my way into the foramen and look for exiting nerve within the soft tissue of the intertransverse space.  One benefit of using an outside-in approach is that usually I don’t have to drill away any of the facet joint and avoid potentially destabilizing the spine.  Once I’ve found the nerve (the DRG is usually what I see first) I move it out of the way and the piece of herniated typically found right underneath.  In order to mitigate some of the pain caused by my manipulation of the DRG I will apply some steroids to the nerve when I’m done removing the disc.

Discectomy docking points

Figure 3: Image depicting the docking points for discectomy in relation to bony anatomy at the right L4/5 level. The blue circle illustrates the docking point for the tubular retractor in a standard central discectomy.  The green circle illustrates the docking point for a far lateral discectomy. 

Recovery from far lateral discectomies is typically rougher than after standard discectomies.  The DRG is already inflamed and manipulating it to get to the herniated fragment can often make the patient’s pain and numbness worse before it gets better.  Thus, I always have to get my patients with far lateral HNP mentally prepared for a tough couple of weeks after their discectomy.  In the end, though, patients do very well after a far lateral discectomy. 

Thanks for reading!

J. Alex Thomas, M.D.

12 thoughts on “What makes a far lateral disc herniation unique (and PAINFUL)?

  1. Thx for this info. I was led to believe that I would be fine very soon after this surgery. I was beginning to think something else was wrong. Now I can expect a “rough couple of weeks”.
    I am ar the one week mark!

  2. What a great blog – excellent explanations and illustrations. I’m recovering from a far lateral discectomy, and this explains the condition and surgical process so logically and clearly.

  3. I have mine scheduled for surgery in two weeks. I have DDD but the pain from this disc protrusion is excruciating. The protrusion doesn’t look that big on the MRI, so it is surprising that it causes so much pain. Fortunately I have an excellent neurosurgeon. This helped me understand the procedure much better.

  4. It has been two weeks and three days since my surgery. I can still be in tremendous pain, and I cannot sleep in my bed a full night. I feel like something must have gone wrong, but this article gives me a since of hope. But, at what point do I question the progress of my post op progress?

    • It’s still very early for you. I tell my patients it may take even up to 3-6 months to bounce back from a far lateral disc herniation. If the pain is NO better at the 3 month point it may be worth checking repeat imaging. Good luck.

    • I wanted to follow up with you and share with your patients that I am now two full months out of my surgery. Within the last three weeks or so, I am finally able to return to routine life activities, most of them on a normal basis. I still have some pain, usually localized to my right knee cap, but for the last two weeks, the pain has been such that I have not had to take anything other than acetaminophen 500mg at the recommended doses along with Gabapentin 300mg and Diclofenac 75mg. I still have some quickening of what I think must be nerves awakening, especially when I am in bed at night. In summary, the post op was almost unbearably painful for the first several weeks causing me to have a feeling of hopelessness and doubt of ever getting better, the following several weeks were painful with a feeling that it was going to get better, but not back to normal. Now, as I have stated, I have some pain, have returned to a relatively normal life, and know that I can make it. Dr. Thomas, your article and your email to me were extremely helpful, and I am as thankful to you as I am to my surgeon. You provided me with a very clear and much needed explanation. Many, many thanks to you.

  5. I have a 1.9cm disc protrusion that is displacing the L2 exiting nerve. The pain is excruciating, but I have been able to calm it down a bit. Wondering if steroid in the space is worth a try or if I should just go ahead and meet with neurosurgeon that has operated on L5 in past for me. Also wonder what attributes to these type of herniations vs centrally located ones.

    • If you were my patient I’d definitely suggest a steroid injection. Specifically you want a transforaminal epidural steroid injection (TFESI) at L2. That may buy you time to let that disc fragment get reabsorbed. If that fails then just move towards surgery.

  6. I had a far lateral HNP at L3/L4 about 17 years ago I had already had a360 Fusion with bilateral facet fixation at L5/S1 . I now have another Far Lateral HNP at the same level . Whats the best imaging for diagnosing the full extent of the HNP? My mri shows far lateral HNP super imposed?

    • Strange that you have an HNP at the level where you had your fusion. You may need a CT in addition to your MRI just to be sure the fusion healed properly. If it didn’t fuse then you could get another HNP there because of persistent movement.

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