Diagnosing lumbar nerve root compression at the bedside

Summary: This article finds that the accuracy of the clinical exam (by a very expert clinician) depends on the location of the nerve deficit. For nerve root compression by a disc, the SLUMP and SLR dynamic tests were most sensitive. However, for foraminal compression, which was the most common site, the dynamic tests have less than 50% sensitivity. The presence of any one neurologic deficit (motor, sensory, or reflex) had sensitivities of 90% and 80% for disc and foraminal high-grade compression, respectively. In no analysis was the positive predictive value over 50% – in spite of the high prevalence of compression in this referred population. All patients had at least low-grade nerve compression.

A practical finding is that in the absence of nerve deficits (motor, sensory, or reflect), high-grade nerve compression is unlikely although some high-grade foraminal compression is possible.

Patients: 99 adults who were referred for transforaminal epidural steroid injection from the orthopedic clinic at a single hospital in the south of Sweden. The patients were classified into 3 groups of nerve compression:

  • Low-grade nerve compression (m=61): “neither high-grade subarticular nor high-grade foraminal nerve compression”
  • High-grade subarticular nerve compression (n=14)
  • High-grade foraminal nerve compression (n=25)

One subject was included in both of the latter groups

Examiners: An “experienced physiotherapist … who was blinded to all MRI information.”

Examination method:

Radiculopathy I “was considered when one of the neurologic signs above* was present and corresponded to the nerve root” of the planned injection.

* “patellar reflex, Achilles’ reflex, strength of the large toe in dorsiflexion, or sensibility (sensory deficit) in a specific dermatome area was asymmetrically deranged”

Radiculopathy II “was considered when 2 neurologic signs (sensory deficit + reflex impairment or muscle weakness) were present and corresponded” to the site of the planned injection.

The straight-leg raise test “performed with the patient supine according to the published instructions. The straight leg was slowly raised and the test was classified as positive or negative, using sensitizing maneuvers, beginning with the ankle and continuing with the neck.”

The slump test “was performed with the patient sitting and was assessed through a combination of sitting thoracolumbar flexion, cervical flexion, ankle dorsiflexion, and knee extension. With the use of sensitizing maneuvers, beginning with the ankle and continuing with the neck, the test was considered positive if one of the maneuvers reproduced the symptoms and the symptoms were different from the contralateral side.”

The femoral stretch test was “performed with the patient side-lying on the nonaffected side, assesses the presence/absence of neural mechanosensitivity (L2-4) using a combination of thoracolumbar flexion, cervical flexion, knee flexion, and hip extension. The test was classified as positive or negative, using sensitizing maneuvers, beginning with the knee and continuing with the neck. The test was considered positive if one of the maneuvers reproduced the symptoms and the symptoms were different from the contralateral side”.

Reference standard:

MRI for

  • Disk protrusion or extrusion
  • Subarticular nerve compression by a disc was assessed on axial T2-weighted images (PMID 21539702). High-grade compression required “periradicular cerebrospinal fluid or fat is obliterated”
  • Foraminal nerve compression assess on sagittal T1-weighted images (PMID 20308517). High-grade compression required “distortion or other morphologic change in the nerve root.”

Findings:

All patients had nerve compression:

  • Disc:  low-grade (n=85) and high-grade (n=14)
  • Foraminal : low-grade (n=74) and high-grade (n=25)

High-grade subarticular nerve root compression

L2-S1 (N=99) Sens Spec PPV NPV
Pos slump test 1.00 .38 .21 1.00
Pos SLR test 0.93 .57 .26 0.98
Radiculopathy I 0.93 .34 .19 0.97
Radiculopathy II 0.71 .73 .30 0.94
L2–4 (n=18)
Pos femoral stretch test 1.00 .65 .14 1.00

High-grade foraminal nerve root compression

L2-S1 (N=99) Sens Spec AUC PPV NPV
Pos slump test .48 .26 .37 .18 .59
Pos SLR test .32 .43 .38 .16 .65
Radiculopathy I .80 .34 .57 .29 .83
Radiculopathy II .28 .65 .47 .21 .73
L2-4 (n=18)
Pos femoral stretch test .17 .50 .33 .14 .55

An addition table not shown is the analysis of disk extrusion.

Citation

1. Ekedahl H, Jönsson B, Annertz M, Frobell RB. Accuracy of Clinical Tests in
Detecting Disk Herniation and Nerve Root Compression in Subjects With Lumbar
Radicular Symptoms. Arch Phys Med Rehabil. 2018 Apr;99(4):726-735. doi:
10.1016/j.apmr.2017.11.006. PMID: 29253501.
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