Lumbar Disc Herniation

The significance of symptom duration for the indication for surgery

Background: Lumbar disc surgery is among the more common spinal procedures. In this paper, we report the current treatment recommendations for patients with symptomatic disc herniation.

Methods: This review is based on pertinent publications retrieved by a selective literature search in PubMed using the terms [timing] AND [lumbar disc herniation], supplemented by other relevant articles and guidelines.

Results: Symptoms resolve in 60% to 80% of patients with herniated discs in 6–12 weeks, and in 80% to 90% over the long term (≥ 1 year). According to the guidelines, 6–12 weeks of conservative treatment are recommended in the absence of significant neurologic deficits. Early surgery is indicated in case of worsening pain or new onset of neurologic deficits. Lumbar disc herniation associated bladder or bowel dysfunction (cauda equina syndrome) is considered an absolute surgical emergency that requires immediate decompression (within 24 to 48 hours). Patients with severe motor deficits (MRC ≤ 3/5) benefit from early intervention and should be offered surgery within three days, if possible, for the best chance of recovery. The degree of weakness and the duration of symptoms have been identified as risk factors for incomplete recovery. Early surgery can be considered in patients with mild paresis (MRC 4/5) in case of functional impairment (e.g., quadriceps paresis).

Conclusion: Longer symptom duration and lower motor scores are associated with worse outcome and a lower chance of neurologic recovery. The recovery rate for motor deficits ranges from 33% to 75%, depending on the timing and modality of treatment as well as the motor score.

Degenerative changes of the spine and the associated symptoms are among the more common reasons for medical consultation in western industrialized countries (1). Disc herniation can cause mechanical and secondary inflammatory irritation of the nerve roots, triggering sciatica (alternative term: lumboischialgia) in the lumbosacral segments (2).

In the general population, the annual incidence of sciatica is 1–5%, and the overall lifetime prevalence is as high as 43% (e1, e2). The pain usually radiates from the low back along the distribution of the sciatic nerve into the leg, but affection of the upper lumbar segments can also cause pain along the distribution of the femoral nerve (ventral thigh).

Pain is generally the leading symptom; it can be accompanied by a sensory and/or motor deficit of the corresponding dermatome or myotome (2). Intervertebral disc surgery is one of the more common spinal operations and has become more common all over the world in the past 20 years (e3, e4).

Low back pain and sciatica due to lumbar disc herniation carry a high socioeconomic cost because of prolonged absences from work, expensive diagnostic evaluations, costly conservative treatments, and, above all, expensive interventional procedures and operations (1).

This disease is, however, generally benign and self-limiting, with symptom resolution in 6–12 weeks in 60–80% of cases and long-term improvement in 80–90% (3, e5, e6).

The important exception to this rule is lumbar disc herniation with manifestations of cauda equina compression, i.e., bladder and/or rectal dysfunction. This situation is an absolute surgical emergency in which immediate surgery (i.e., within 24–48 hours) is needed to enable functional recovery; the earlier the intervention, the higher the chance that bladder and rectal dysfunction will recover (4, 5). In general, surgery is recommended for lumbar disc herniation with persistent radiculopathy, worsening pain, or neurologic deficits that cause functional impairment (6). Despite the commonness of this type of surgery, there is no consensus on the optimal timing of treatment for patients suffering “only” from persistent pain, or for those who have a motor deficit. We address this issue in the present review on the basis of up-to-date evidence retrieved by an an extensive literature search, in order to provide recommendations for treatment based on the particular clinical manifestations in the individual case (7).

We carried out a selective search in PubMed for articles including the search terms (“timing”) AND (“lumbar disc herniation”), supplemented by other suitable or associated articles. The 124 retrieved articles were screened independently by two of the authors of this review independently for clinical relevance with the PRISMA criteria on the basis of the title, abstract, and full text (if available); in case the two screeners arrived at different conclusions, these were harmonized in a further discussion (e7). Randomized controlled trials (RCTs), reviews, meta-analyses, and both prospective and retrospective studies were selected for further analysis. The breadth of types of publication that were selected for analysis here is a result of the nature of the topic itself, the lack of RCTs concerning early treatment for patients with paresis, and the known methodological limitations of meta-analyses. The main publications on the timing of treatment of radiculopathy due to lumbar disc herniation are listed in the Table. Publications on paresis and bladder and/or rectal dysfunction are listed in the eTable. Only limited and low-level evidence for timing of treatment is available, derived mainly from retrospective analyses or small-scale prospective trials. On the other hand, there is high-level evidence from a large number of RCTs, reviews, and meta-analyses on the question of surgical versus conservative treatment for persistent sciatica. The interpretability of the results is impaired by high cross-over rates and intention-to-treat analyses.

Table

eTable

Learning objectives

The purpose of this review is to provide an understanding of the main predictors of outcome in the treatment of lumbar disc herniation so that these can be integrated into routine clinical practice. After reading the article, readers should know:

• which patients with symptomatic disc herniation should be referred immediately for surgery;
• how soon a cauda equina syndrome due to lumbar disc herniation should be treated in order to enable recovery, or at least, improvement of bladder and rectal function;
• and what the risk factors are for incomplete recovery of paresis due to lumbar disc herniation

Symptom duration and outcome of sciatica

Sciatica is usually self-limiting: most patients with acute symptoms report marked improvement within 10 days, and 75% within one month. Nevertheless, around 30% of patients who do not undergo surgery still complain of intermittent pain one year after symptom onset (8). Conservative measures include physical rest including short-term bed rest, physiotherapy, and analgesic drugs according to the WHO scheme. Locally acting medications and periradicular infiltrations are available as well (9, e8). The AWMF guideline currently recommends sustained analgesic therapy in the acute stage through to the chronic phase, as well as short-term rest in the acute phase with the introduction of appropriate exercise therapy in the subacute stage. Back training, manipulation or traction if the affected segment, electrotherapy, ultrasound and massages should be avoided in the acute phase. Orthoses (corsets) should be considered on a case-by-case basis and should not be given to patients at risk of chronification.

Consideration of the potential indication for surgery is recommended at 6–12 weeks (3). Most of the studies that were examined in a systematic review published in 2014 found that longer symptom duration before surgery is associated with poorer outcomes, and that surgery within 6 months of symptom onset yields better results (10). The reported durations of conservative treatment are distributed over a wide range (2–12 months) (10). Accordingly, some studies have shown that surgery yields better outcomes when the symptoms have been present for less than 8 months (11, 12), while others have shown the same with a cutoff of 6 months (13, e9).

The well-known Spine Patient Outcomes Research Trial (SPORT) also identified six months as the critical duration of symptoms. In both the conservative and the surgical arm, patients with a shorter duration of symptoms (< 6 months) had a better long-term outcome, in particular a higher level of activity and less residual pain. Those who were treated surgically had better patient-reported outcome measures (PROMs) at all time points, independently of the timing of treatment (14).

Fisher et al., in their prospective study, stressed the importance of PROMs in modern spinal surgery and documented a significant clinical improvement in the first 6 months after surgery. The beneficial effect of the operation leveled off by 1 year (15). This can be explained by the generally self-limiting and benign course of sciatica due to lumbar disc herniation, but possibly also by late adverse effects of surgery.

A recent meta-analysis by Liu et al. confirmed the beneficial effect of surgery, demonstrating significant short- and medium-term relief of radicular pain in the surgical group compared to the conservatively managed control group. The evidence supporting the conclusion that surgery yields better outcomes than conservative treatment or epidural steroid injection (ESI) is on a low level. The benefit of surgery compared to ESI is over the long term; its benefit compared to conservative treatment is over the short to medium term, with a barely detectable difference at one year. The same holds for the effect of ESI, except for the disability score (9). The interpretability of the findings of this meta-analysis is lessened by the limitations of the included studies, the lack of information on symptom duration, and limited applicability to the heterogeneous population of patients with lumbar disc herniation.

Peul et al., in a landmark study, randomized patients with sciatica of 6–12 weeks’ duration to early surgery or conservative treatment (for at least six months) and found that surgery led to faster recovery. Conservative treatment was also generally followed by recovery, but only after a delay; over the years following randomization, the outcomes converged. The high cross-over rate of 39% within 19 weeks is a critical limitation on the interpretability of the findings and leaves the actual predictive role of symptom duration before surgery unclear (16).

The German and Danish specialty societies recommend a 6– to 12-week trial of conservative treatment, except for patients with functionally impairing neurologic deficits or intractable pain, who should be offered early surgery (6, 17, e10). The NASS (North American Spine Society) points out the poor quality of the data supporting early surgery for patients with motor deficits and accordingly recommends surgery no later than 6–12 months after symptom onset for patients whose deficits are not highly acute (17, 18).

The high cross-over rate (17%–50%) in many RCTs markedly impairs the interpretability of treatment effects determined in an intention-to-treat analysis (8, 14, 19, 20, 21, 22, 23).

Risk factors for worse treatment outcomes

In most of the studies analyzed here, the duration of sciatica before treatment was found to be a negative predictor for the outcomes of both conservative and (usually) surgical treatment outcome. This conclusion is supported by high-level evidence from several RCTs as well as multiple prospective studies from single or multiple centers. The precise figures vary considerably, however, depending on the study design, population and control group: < 12 months (11), < 8 months (12), < 6 months (8, 14, e9, 24), < 3 months (e11, e12), < 2 months (25, e13), < 6 weeks (e14). In the meta-analysis by Sabnis et al., 15 out of 19 studies with low- and medium-level evidence showed a benefit from early surgery, but the two with high-level evidence did not; the latter two studies, however, had high cross-over rates and excluded patients with manifestations requiring acute treatment (e.g. cauda equina syndrome, high-grade paresis) and patients with severe pain (10). In a recent systematic review, Rutzen et al. concluded from 10 selected studies that early treatment is advantageous, but could not supply greater precision regarding timing (beyond simply early vs. late) or any concrete recommendation, because of the heterogeneity of the data (26).

Other risk factors for an unsatisfactory result include:

• older age (27) (> 40 years) (10, e13)
• inability to work for >2 months (10) or > 3 months (13)
• chronic pain (10)
• poor performance scores or neurologic deficits (10)
• a recurrent prolapse (27)
• the type of herniated disc (27, e14)
• social or relationship status and
• psychological factors (10, 14, e13, e15, e16) and
• current receipt of compensation payments (10, e16).

Disc surgery is generally considered safe, with an intraoperative complication rate of 2.7%. The revision rate is approximately 2.1%, and the rate of readmission rate within 90 days is 2.4%. Complications are more common in elderly patients and in patients with comorbidities (28).

The most common intraoperative complication is an incidental durotomy (dural opening or tear), which occurs most commonly in revision surgery in the setting of severe lumbar spinal degenerative changes in an elderly patient (29). The most common postoperative complication is symptomatic recurrent disc herniation, which occurs in 1% to 27% of patients depending on the type of herniation, the size of the annular defect, and the patient’s age and sex.

The 27% figure applies only to the high-risk group in the study of Carragee et al. and is not to be taken as a general reference value (30, e5, e17). The reoperation rate within one year is approximately 6.4% (e18). Impaired wound healing, secondary spinal instability, and postoperative bleeding requiring treatment are rare.

Because outcomes are better with earlier surgery and the complication rate of these operations is low, surgery should be offered if pain persists after 12 weeks of conservative treatment.

The optimal timing of treatment for patients with motor deficits

Pain that lasts for several months because of spinal nerve root compression is not known to cause any long-term physical damage, but neurologists and surgeons who operate on the spine are concerned that motor deficits might persist if surgery is not performed soon enough. The more severe the paresis, the greater the inclination to provide early surgery in order to prevent permanent functional impairment due to persistent weakness, particularly in younger patients (e19). Nevertheless, no recommendation on the timing of surgery has yet been made for this cohort (10, 24).

As 30% to 50% of patients have paresis when they present, this is a very important issue (33, 34). Paresis is more common in patients with acute onset of symptoms, a free or migrated disc herniation, and/or pre-existing spinal canal stenosis (e20). Medium- to high-level of evidence supports the conclusion that the recovery rate is lower for higher degrees of paresis. Studies including the review by Sharma et al. have identified both the degree of paresis (33, 34) and the duration of symptoms (4, 34) as risk factors for incomplete recovery (strength less than 5 on the MRC scale); the operations in question, however, were performed over a broad time span of several weeks after the onset of paralysis (35, 36, e21, e22, e23, e24, e25).

Except for patients with cauda equina syndrome, the evidence on symptom duration as a negative predictor is only moderately strong. The recovery rate varies from 30% to 75% depending on the timing and modality of treatment and the degree of paresis, many patients are left with functional impairment, which may be severe (e25, e26, e27, e28, e29). Because of these poor outcomes, urgent or even emergency treatment of patients with a relevant degree of paresis (MRC ≤ 3/5) is increasingly being advocated, not least because of the short time window (≤ 48 h) for cauda equina syndrome. In a meta-analysis, Ahn et al. calculated an odds ratio (OR) of 9.1 for motor recovery when surgery is performed within 48 hours (4). Although this high value must be viewed critically, one must indeed ask whether acute paresis, analogously to cauda equina syndrome, should optimally decompressed just as rapidly to prevent a disabling residual deficit.

The lack of an existing recommendation on the timing of surgery motivated us to evaluate the utility of early surgery. In a registry study with 390 patients who underwent early surgery at a spinal center for lumbar disc herniation with associated paresis, the relation of the duration and degree of paresis to the long-term outcome was studied (follow-up interval ≥ 1 year; mean, 3.5 years). For this purpose, objectifiable cut-off values for treatment recommendations were determined with the aid of the Unbiased Recursive Partitioning Conditional Inference Tree (URP-CTREE) (7). This statistical method tests the independence of predictors with a predefined outcome; like a tree diagram, it involves partitioning at the lowest p-value (including a Bonferroni correction) (e30).

Strength was measured with manual and functional testing and graded on the MRC scale (37).

Preoperative paresis was mild (MRC 4/5) in 118 patients (30.3%), moderate (MRC 3/5) in 191 (49.0%), and severe (MRC ≤ 2/5) in 81 (20.8%).

According to the URP-CTREE analysis, severe preoperative paresis (p < 0.001) was the main risk factor for incomplete recovery. The calculated time window from the onset of paresis to surgery for a significantly faster and complete recovery (= MRC 5/5) was 3 days (p = 0.022). Surgery within this time window also led to a significantly better outcome in patients with moderate paresis (p < 0.001), with a recovery rate of 97% versus 23% (Figure 1). In the mild paresis cohort, early surgery (≤ 8 days; using URP-CTREE cut-off) also yielded a superior recovery rate (98% versus 75%) (7).

Figure 1

This study lacks a conservatively treated control group, but nevertheless demonstrates the advantage of early treatment with the statistics used and the precise information it contains on symptom duration and degree of paresis. The results are clearly superior to those of other studies in which treatment after multiple weeks or months is advocated (4, 33, 34, 35, e21, e23, e24). The authors advise against generalizing these findings to cases of paresis due to spinal stenosis, in which the pathophysiology is chronic rather than acute (34, e26). Although early surgery may intuitively seem preferable even without supporting evidence, its benefit needs to be properly studied, as the nonzero perioperative risk may be greater than the benefit for some patients. Thus, additional prospective studies to corroborate these findings would be desirable. Only on the basis of the data just cited, early (≤ 3 days) surgery is recommended for patients with acute moderate or severe paresis, as this yields a recovery rate of 97% versus 50%, according to the relevant RCT (33). Only Ahn et al. achieved a similar recovery rate with early required to be within 48 hours of symptom onset (4). Comparisons across studies are generally complicated by inconsistent definitions of the term “foot drop,” varying meanings of the word “recovery” (does a partial recovery count?), and the subjectivity (sometimes) of the determination whether a paresis is mild, moderate, or severe.

To prevent permanent deficits, patients should be referred immediately to a center where spinal surgery is performed. The general practitioners and family physicians who see the patient first should rapidly assess the degree of paresis and refer the patient for surgery if it is moderate or severe. Isolated paresis of the extensor hallucis longus muscle (weakness of great toe dorsiflexion) is not necessarily a clinically relevant indication for surgery, even if severe; this issue should be critically considered by the examiner.

Mild (MRC 4/5) motor deficits are obviously less problematic, and the stated time window of 8 days to surgery should be considered only for patients with weakness causing functional impairment (e.g., quadriceps palsy making it impossible to climb stairs) (recovery rate of 98%). The literature implies a recovery rate of 75% in the later (> 8 days) cohort. Compensatory training of paretic muscle groups should lead to success, particularly the quadriceps; deficits in the muscles innervated by L5 and S1 are more likely to be permanent (e24). Treatment decisions must be made individually on the basis of the symptoms and signs, the affected myotome, the patient’s age and personal requirements, and the degree of functional impairment. Regular follow-up at short intervals is needed at first, so that any neurological worsening can be detected and acted upon quickly. The patient should be informed about the natural course of the problem if untreated and the improved recovery rate in the event of surgical treatment. Marked improvement of weakness can be expected within 2–4 months after surgery (the interval varies depending on the publication) (e23, e24). Our experience is similar, with a strong correlation between strength at 6–12 weeks and final strength (Figure 2). Strength at 3 months is thus a good surrogate marker for the ultimate degree of recovery (7).

Figure 2

Figure 3

The timing of treatment for cauda equina syndrome

The current recommendation for immediate surgery (< 48 hr after symptom onset) for patients with cauda equina syndrome is based on the findings of the meta-analysis by Ahn et al. In a long-term analysis of over 850 patients (20 retrospective and 2 prospective cohort studies), residual bladder, rectal and sexual dysfunction was found in 43%, 31% and 40%, respectively. Acute decompression (< 48 hr) led to the complete resolution of symptoms and signs in 76% of patients so treated (38). Patients who underwent surgery within 24 hours had a higher recovery rate (5). Sangondimath et al. reported improvement in all patients who underwent within 48 hours. Sexual dysfunction was still present after surgery in 70% of men and 60% of women with cauda equina syndrome (39). Other, retrospective studies, including urodynamic studies, confirmed that treatment within 48 hours leads to a favorable recovery, while the adverse consequences of delayed surgery are dramatic (e31-e33).

Take-home messages on the timing of surgery for lumbar disc herniation

• Surgery should be considered 6–12 weeks after the onset of symptoms if radicular pain persists despite conservative treatment.
• Emergency surgery (within 24–48 hr) is indicated for patients with bladder or rectal dysfunction.
• Surgery within 3 days is indicated for patients with moderate or severe paresis (MRC ≤ 3/5).
• Early surgery is indicated for patients who have mild paresis (MRC 4/5) causing functional impairment.

Conflict of interest statement
WL owns Novartis stock.

The other authors state that they have no conflict of interest.

Manuscript received on 12 November 2023, revised version accepted on 10 April 2024.

Translated from the original German by Ethan Taub, M.D.

Corresponding author
Dr. Nikolaus Kögl MSc., BSc.

Universitätsklinik für Neurochirurgie, Medizinische Universität Innsbruck

Anichstrasse 35, A-6020 Innsbruck, Austria

Cite this as:
Kögl N, Petr O, Löscher W, Liljenqvist U, Thomé C: Lumbar disc herniation—the significance of symptom duration for the indication for surgery. Dtsch Arztebl Int 2024; 121: 440–8.
DOI: 10.3238/arztebl.m2024.0074

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