Intraspinal intradural variations of nerve roots

Broad and Asymmetric Lower Extremity Myotomes: Results From Intraoperative Direct Electrical Stimulation of the Lumbosacral Spinal Roots

STUDY DESIGN

Retrospective review of prospectively collected data.

OBJECTIVE

This study aimed to accurately map the lower extremity muscles innervated by the lumbar spinal roots by directly stimulating the spinal roots during surgery.

SUMMARY OF BACKGROUND DATA

Innervation of the spinal roots in the lower extremities has been estimated by clinical studies, anatomic studies, and animal experiments. However, there have been discrepancies between studies. Moreover, there are no studies that have studied the laterality of lower limb innervation.

MATERIALS AND METHODS

In 73 patients with lumbar degenerative disease, a total of 147 spinal roots were electrically stimulated and the electromyographic response was recorded at the vastus medialis (VM), gluteus medius (GM), tibialis anterior (TA), biceps femoris (BF), and gastrocnemius (GC). The asymmetry index (AI) was obtained using the following equation to represent the left-right asymmetry in the compound muscle action potential (CMAP) amplitude. Paired t tests were used to compare CMAP amplitudes on the right and left sides. Differences in the AI among the same spinal root groups were determined using one-way analysis of variance.

RESULTS

The frequency of CMAP elicitation in VM, GM, TA, BF, and GC were 100%, 75.0%, 50.0%, 83.3%, and 33.3% in L3 spinal root stimulation, 90.4%, 78.8%, 59.6%, 73.1%, and 59.6% in L4 spinal root stimulation, 32.2%, 78.0%, 93.2%, 69.5%, and 83.1% in L5 spinal root stimulation, and 40.0%, 100%, 80.0%, 70.0%, and 80.0% in S1 spinal root stimulation, respectively. The most frequent muscle with maximum amplitude of the CMAP in L3, L4, L5, and S1 spinal root stimulation was the VM, GM, TA, and GM, respectively. Unilateral innervation occurred at high rates in the TA in L4 root stimulation and the VM in L5 root stimulation in 37.5% and 42.3% of patients, respectively. Even in patients with bilateral innervation, a 20% to 38% AI of CMAP amplitude was observed.

CONCLUSIONS

The spinal roots innervated a much larger range of muscles than what is indicated in general textbooks. Furthermore, a non-negligible number of patients showed asymmetric innervation of lower limb by the lumbar spinal roots.

A broad and variable lumbosacral myotome map uncovered by foraminal nerve root stimulation

OBJECTIVE

The human myotome is fundamental to the diagnosis and treatment of neurological disorders. However, this map was largely constructed decades ago, and its breadth, variability, and reliability remain poorly described, limiting its practical use.

METHODS

The authors used a novel method to reconstruct the myotome map in patients (n = 42) undergoing placement of dorsal root ganglion electrodes for the treatment of chronic pain. They electrically stimulated nerve roots (n = 79) in the intervertebral foramina at T12-S1 and measured triggered electromyography responses.

RESULTS

L4 and L5 stimulation resulted in quadriceps muscle (62% and 33% of stimulations, respectively) and tibialis anterior (TA) muscle (25% and 67%, respectively) activation, while S1 stimulation resulted in gastrocnemius muscle activation (46%). However, L5 and S1 both resulted in abductor hallucis (AH) muscle activation (17% and 31%), L5 stimulation resulted in gastrocnemius muscle stimulation (42%), and S1 stimulation in TA muscle activation (38%). The authors also mapped the breadth of the myotome in individual patients, finding coactivation of adductor and quadriceps, quadriceps and TA, and TA and gastrocnemius muscles under L3, L4, and both L5 and S1 stimulation, respectively. While the AH muscle was commonly activated by S1 stimulation, this rarely occurred together with TA or gastrocnemius muscle activation. Other less common coactivations were also observed throughout T12-S1 stimulation.

CONCLUSIONS

The muscular innervation of the lumbosacral nerve roots varies significantly from the classic myotome map and between patients. Furthermore, in individual patients, each nerve root may innervate a broader range of muscles than is commonly assumed. This finding is important to prevent misdiagnosis of radicular pathologies.

Nerve root anomaly as a cause of unexpected outcomes of epidural steroid injections in lumbar radiculopathy: A case report

BACKGROUND

Spinal nerve root anomaly is a rare feature that can result in unexpected outcomes in epidural steroid injections or surgical procedures. Preoperative diagnostic tools for root anomalies are limited, as they are usually found intraoperatively.

OBJECTIVE

This case report aims to propose an effective diagnostic process for nerve root anomalies by introducing clinical manifestations, electrodiagnostic findings, and sophisticated imaging techniques such as coronal view magnetic resonance imaging (MRI) of the lumbosacral spine.

CASE DESCRIPTION

A 43-year-old female complained of low back pain with radicular pain to the lower extremities. Based on physical examination, electrodiagnosis, and imaging studies, right L5 radiculopathy was diagnosed. Repetitive image-guided epidural steroid injections presented unsuccessful outcomes. She was then referred to a neurosurgeon for surgical decompression, which resulted in significant improvement in her radicular pain. A nerve root anomaly was found intraoperatively, and the coronal images of postoperative MRI depicted the conjoined nerve root of the lumbar spine.

CONCLUSION

When proper image-guided spinal interventions for discogenic radicular pain are not effective, a clinician should be advised to consider the possibility of anatomical variation, including nerve root anomalies. Early diagnosis of nerve root anomalies by utilizing multiple diagnostic tools, especially coronal MRI, can aid in preoperative diagnosis and proper clinical decisions for symptom management.

Cervical nerve root variant: report of two cases under the cervical endoscopy and review of clinical literature

Background: We know of five cases of cervical nerve root variants that have been reported, all of which were found during posterior cervical surgery. We reported two cases of cervical nerve root variants. One had two anomalous branches of the C7 root, is the other had a C5, C6 nerve root communication branch. Case description: A 62-year-old female presented with neck and right upper extremity pain, accompanied by hypaesthesia in her right forearm for 4 months. Preoperative X-ray film, magnetic resonance imaging (MRI) and computed tomography (CT) scan demonstrated C6-7 uncovertebral joint hyperplasia and foraminal stenosis. She underwent posterior cervical endoscopic foraminoplasty. The right C7 nerve root was observed to have two anomalous branches originated from a proximal trunk. After the surgery, the symptoms resolved. A 54-year-old female presented with radiating pain and numbness in her right arm and hand for 4 months. Preoperative MRI showed a C5/6 intervertebral disc herniation. She had hypaesthesia in radial side of her right arm and 1st-3rd fingers. Posterior cervical endoscopic foraminalplasty was performed for the patient. After decompression of the bony wall of the posterior nerve root canal, a 2-mm thick communicating nerve was observed emerging from the dura with the C6 nerve root and exiting to the caudal level. After the surgery, the symptoms resolved immediately. Conclusions: Cervical nerve root variant may be more apparent on edoscopic approaches to the cervical foraminae than at open surgery.

Perineal pain: Think beyond gynaecological reasons

Introduction:

Perineal pain is multifactorial in nature. Gynaecological consultation is the first point of contact in females with perineal pain for diagnosis and treatment.

Case description:

Three females above 60 years presented with non-radiating perineal pain and bladder disturbance. Magnetic resonance imaging revealed severe L5 S1 dural compression, which was released by posterior laminectomy. Patients felt relief in perineal pain, though bladder symptoms persisted for several months.

Conclusion:

Sacral roots compression leading to pain along pudendal nerve distribution may present with cauda equina symptoms with pain radiating to legs. Awareness of this condition can prevent the delay and lead to better prognosis after the surgery.