Morphometric aspects of extraforaminal lumbar nerve roots

Usefulness of Oblique Lumbar Magnetic Resonance Imaging for Nerve Root Anomalies and Extraforaminal Entrapment Lesions

Study Design

A retrospective review of prospectively evaluated magnetic resonance (MR) images.

Purpose

Routine lumbar axial and sagittal MR images may not clearly demonstrate nerve root anomalies and entrapments in the extraforaminal region. Thus, lumbar extraforaminal lesions or nerve root anomalies may be underdiagnosed because of unfamiliar radiological anatomy. We aimed to investigate the clinical efficacy of our oblique magnetic resonance imaging (MRI) technique for diagnosing nerve root anomalies and entrapment lesions.

Overview of Literature

Evaluation of clinical usefulness of oblique lumbar MRI for nerve root anomalies and extraforaminal entrapment lesions.

Methods

In total, 162 patients (60 males and 102 females; mean age, 59.8±17.8 years) with suspected nerve root anomalies and entrapments in routine axial and sagittal MR images underwent unilateral or bilateral oblique lumbar T2-weighted MRI. The axial angle of the oblique image was parallel to the foramen. The oblique MRI findings of the symptomatic side were compared with those of the asymptomatic side in cases with unilateral pathologic lesions. Interobserver agreement was analyzed using kappa statistics.

Results

The following abnormal findings were obtained: nerve root entrapment due to foraminal stenosis in 82 cases; extraforaminal disk herniation in 29; conjoined nerve root in six; and foraminal bony cyst in one. Forty-three of the 46 patients experienced unilateral lateralizing symptoms, unilateral nerve root entrapment due to foraminal stenosis, herniated disk, and extraforaminal bony cyst compared with the asymptomatic contralateral side (p <0.05).

Conclusions

Our results suggest that oblique lumbar MRI is a simple and valuable modality for diagnosing anomalous lumbar nerve root lesions and entrapment.

Three-Years Outcome of Microdiscectomy via Paramedian Approach for Lumbar Foraminal or Extraforaminal Disc Herniations in Elderly Patients over 65 Years Old

OBJECTIVE

Lumbar foraminal or extraforaminal disc herniations (FEFDH) have unusual clinical features and higher incidence in elderly patients compared to usual intraspinal canal disc herniations. We evaluated the efficacy of microdiscectomy via paramedian approach for lumbar FEFDH in elderly patients over the age of 65.

METHODS

Retrospective study was performed in 68 patients over the age of 65 (23 male and 45 female patients; 71.46±3.87 years) who underwent microdiscectomy via paramedian approach for unilateral lumbar FEFDH causing sciatica. The radiological factors including degree of slippage, presence of instability, disc height, and degree of disc degeneration; pain and functional status by the means of visual analogue scale score, Oswestry Disability Index score, and Macnab classification were analyzed preoperatively and during the postoperative follow-up period of 3 years to evaluate the efficacy of the surgical treatment.

RESULTS

Pain and functional status improved according to short- and long-term follow-up evaluations after surgery. Radiological changes following surgery, which can be understood as structural deteriorations and deformations, did not represent patient condition. Nine patients underwent additional surgery due to sustained or recurring leg pain of aggravation of back pain, and fusion surgery was required for 3 patients. Degree of preoperative slippage was the only statistically significant factor related to additional surgery (p<0.05).

CONCLUSION

Microdiscectomy via paramedian approach for FEFDH may be a good surgical alternative in elderly patients. Radiological changes after surgery did not show a concordance with patients' actual functional status. The excessive preoperative slippage tended to lead to unfavorable result after surgery and was associated with additional surgery.

The projection of nerve roots on the posterior aspect of spine from T11 to L5: a cadaver and radiological study

STUDY DESIGN

A cadaver and radiological study.

OBJECTIVE

To investigate the projection of nerve roots on the posterior aspect of the spine from T11 to L5.

SUMMARY OF BACKGROUND DATA

Understanding the projection of nerve roots on the posterior lamina will help to determine the decompressing areas of lamina and avoiding unnecessary bony resection. It can prevent segmental instability and postoperative scar formation. No studies regarding this subject are available.

METHODS

Fifteen formalin-preserved spine specimens were used for this study. After exposing the dural sac and bilateral nerve roots, small pieces of stainless steel wires were placed along the root sleeves from their points of origin, and then standard anteroposterior and lateral radiographs were taken. Parameters were measured directly on radiographs using the picture archiving communication system. Measurements included: (1) take-off angles of the nerve roots at the coronal (CA) and sagittal planes (SA); (2) distance from the origin of the root sleeve to the posterior midline (DM); (3) distance from the origin of the root sleeve to the superior (DS) and inferior margin (DI) of its corresponding lamina; and (4) distance between the origins of neighboring nerve roots (DR).

RESULTS

The CA statistically decreased from T11 (52.4° ± 3.13°) to L5 (25.8° ± 3.10°). An opposite variation tendency was observed in SA. The DS increased from 1.8 ± 0.32 mm for T11 to 5.84 ± 1.05 mm for L5. No consistent change was found at DI. The DR was largest at the L1-L2 interval (33.9 ± 1.40 mm) and it decreased progressively to L4-L5 (25.5 ± 2.40 mm). DM statistically increased from T11 (8.9 ± 1.51 mm) to L1 (10.9 ± 1.11 mm) and then progressively decreased until it reached a minimum at L5 (8.1 ± 0.83 mm).

CONCLUSION

The precise projection of nerve roots to the posterior aspect of spine and intraspinal take-off angles at the sagittal plane have been presented. Surgical interventions of the lumbar disc and nerve root may benefit from this quantitative anatomical study.

Lumbar plexus anatomy within the psoas muscle: implications for the transpsoas lateral approach to the L4-L5 disc

BACKGROUND

The transpsoas lateral surgical approach has been advocated as an alternative to direct anterior approaches for less invasive or minimally invasive access to the spine. Postoperative thigh pain, paresthesia, and/or weakness have been described after the use of this surgical approach. The purpose of this cadaveric anatomic study is to provide a description of the lumbar plexus as it relates to the transpsoas lateral surgical approach.

METHODS

Dissection of the lumbar plexus was performed in eighteen cadaveric specimens. Needle markers were placed in the L2-L3, L3-L4, and L4-L5 discs in the midcoronal plane. The anatomic structures were surveyed, and the proximity of the needle to the neural structures was observed.

RESULTS

In thirteen of the eighteen specimens, the femoral nerve received its contributions from the L2 to L4 nerve roots and was formed at the L4-L5 disc space. In all specimens, the femoral nerve passed dorsal to or directly at the midpoint of the disc. In three specimens, the needle displaced or was immediately adjacent to the femoral nerve. The femoral nerve was found between the needle and the posterior aspect of the L4-L5 disc space in thirteen of the eighteen specimens.

CONCLUSIONS

Because of the proximity of the neural elements, in particular the femoral nerve, to the center of the disc space, the transpsoas lateral surgical approach to the L4-L5 disc space will likely cause intraoperative displacement of neural structures from their anatomic course during retractor dilation. Careful attention should be paid to retractor placement and dilation time during transpsoas lateral access surgery, particularly at the L4-L5 disc.

Ultrasound and nerve stimulation-guided L5 nerve root block

STUDY DESIGN

Case series.

OBJECTIVE

Evaluation of ultrasound and nerve stimulation-guided L5 nerve root block technique.

SUMMARY OF BACKGROUND DATA

Ultrasound-guided peripheral nerve block has become clinically applied. However, selective lumbosacral nerve root block is conducted under radiographic guidance, which involves patients and operators being exposed to radiation. In addition, it cannot be carried out easily during outpatient visits or at the bedside. We conducted L5 nerve root block, which is one of the most common lumbosacral nerve root block under ultrasonic guidance, using electrical nerve stimulation.

METHODS

We assessed the effectiveness of ultrasound and nerve stimulation-guided L5 nerve root block on 78 patients with L5 radicular syndrome. To compare ultrasonic guidance using electrical nerve stimulation with radiographic guidance, we used a contrast agent and assessed its distribution.

RESULTS

After nerve block, decreased sensation at L5 neural region and diminished/fully resolved pain was observed in all patients except for 3 in whom nerve block could not be conducted as their articular process protruded laterally. Concerning the response to stimulation, all except for these 3 felt the tapping sensation at their L5 neural regions, but no contraction of muscles was observed. The number of patients who showed an extraneural, paraneural, and intraneural pattern on contrast radiography was 71, 4, and 0, respectively.

CONCLUSION

Ultrasound-guided L5 nerve root block using electrical nerve stimulation is a safe and effective method.

Simple oblique lumbar magnetic resonance imaging technique and its diagnostic value for extraforaminal disc herniation

STUDY DESIGN

Prospective study evaluating the oblique lumbar magnetic resonance imaging (MRI).

OBJECTIVE

To present the technique of oblique lumbar MRI and assess the clinical efficacy of this technique for diagnosis of extraforaminal disc herniation.

SUMMARY OF BACKGROUND DATA

Herniated lumbar discs are traditionally diagnosed using conventional lumbar axial and sagittal MRI. However, conventional lumbar MRI might not reveal nerve root compression in the extraforaminal area. Oblique lumbar MRI can provide clear visualization of the dorsal root ganglion and lumbar nerve root in the foraminal and extraforaminal areas.

METHODS

Ten patients diagnosed with extraforaminal disc herniations underwent bilateral oblique lumbar MRIs before surgery (turbo spin-echo T2-weighted sequence). We compared the side with symptomatic extraforaminal disc herniation to the asymptomatic contralateral side.

RESULTS

Oblique lumbar MRI succeeded in depicting pedicles, dorsal root ganglions, and lumbar nerve roots of the foraminal and extraforaminal areas. In 9 of 10 patients (90.0%), nerve root compression by the herniated disc in the extraforaminal area was clearly demonstrated when compared with the asymptomatic contralateral side (P < 0.05). In 1 patient with scoliosis and spinal stenosis, oblique MRI could not clearly display foraminal or extraforaminal anatomy due to spinal deformity.

CONCLUSION

In light of this data, we suggest that oblique lumbar MRI can precisely demonstrate nerve roots in foraminal and extraforaminal areas. This technique is a simple and useful diagnostic tool for extraforaminal lumbar disc herniations.