Herniation, Disc

Article Author:
Ruben Ngnitewe Massa
Article Editor:
Fassil Mesfin
Updated:
10/27/2018 12:31:32 PM
PubMed Link:
Herniation, Disc

Introduction

In the spine, a disc or a nucleus pulposus is localized between vertebral bodies. It supports the spine by acting as a shock-absorbing cushion. A herniated disc in the spine is a condition during which a nucleus pulposus is displaced from intervertebral space. In some instances, a herniated disc can compress the nerve or the spinal cord that causes pain consistent with nerve compression or spinal cord dysfunction also known as myelopathy.

Etiology

An intervertebral disc is composed of annulus fibrous which is a dense collagenous ring encircling the nucleus pulposus. Disc herniation occurs when part or all the nucleus pulposus protrudes through the annulus fibrous. The most common cause of disc herniation is a degenerative process in which as humans age, the nucleus pulposus becomes less hydrated and weakens. This process will lead to progressive disc herniation that can cause symptoms. The second most common cause of disc herniation is trauma. Other causes include connective tissue disorders and congenital disorders such as short pedicles. Disc herniation is most common in the lumbar spine followed by the cervical spine. A high rate of disc herniation in the lumbar and cervical spine can be explained by an understanding of the biomechanical forces in the flexible part of the spine. The thoracic spine has a lower rate of disc herniation.

Epidemiology

The incidence of herniated disc is about 5 to 20 cases per 1000 adults annually and is most common in people in their third to the fifth decade of life, with a male to female ratio of 2:1

Pathophysiology

The pathophysiology of herniated discs is believed to be a combination of the mechanical compression of the nerve by the bulging nucleus pulposus and the local increase in inflammatory chemokines.

Herniation is more likely to occur posterolaterally, where the annulus fibrosus is thinner and lacks the structural support from the anterior or posterior longitudinal ligaments. Because of the proximity to the nerve roots, a posterolateral herniation is more likely to compress the nerve root and to produce radiculopathies in the associated dermatome. On the other hand, spinal cord compression and clinical myelopathy can occur if there is herniation of a large midline disc. The localized back pain is a combination of the herniated disc pressure on the longitudinal ligament, and chemical irritation due to local inflammation.

History and Physical

Cervical Spine

History

In the cervical spine, the C6-7 is the most common herniation disc that causes symptoms, mostly radiculopathy. History in these patients should include the chief complaint, the onset of symptoms, where the pain starts and radiates. History should include if there are any past treatments.

Physical examination

On physical examination, particular attention should be given to weaknesses and sensory disturbances, and their myotome and dermatomal distribution. The examiner should also pay attention at this point to any sign of spinal cord dysfunction.

Table 1: Typical findings of solitary nerve lesion due to compression by herniated disc in cervical spine

  • C5 Nerve - neck, shoulder, and scapula pain, lateral arm numbness, and weakness during shoulder abduction, external rotation, elbow flexion, and forearm supination. The reflexes affected are the biceps and brachioradialis.
  • C6 Nerve - neck, shoulder, scapula, and lateral arm, forearm, and hand pain, along with lateral forearm, thumb, and index finger numbness. Weakness during shoulder abduction, external rotation, elbow flexion, and forearm supination and pronation is common. The reflexes affected are the biceps and brachioradialis.
  • C7 Nerve - neck, shoulder, middle finger pain are common, along with the index, middle finger, and palm numbness. Weakness on the elbow and wrist are common, along with weakness during radial extension, forearm pronation, and wrist flexion may occur. The reflex affected is the triceps.
  • C8 Nerve - neck, shoulder, and medial forearm pain, with numbness on the medial forearm and medial hand. Weakness is common during finger extension, wrist (ulnar) extension, distal finger flexion, extension, abduction, and adduction, along with during distal thumb flexion. No reflexes are affected.
  • T1 Nerve - pain is common in the neck, medial arm, and forearm, whereas numbness is common on the anterior arm and medial forearm. Weakness can occur during thumb abduction, distal thumb flexion, and finger abduction and adduction. No reflexes are affected.

Lumbar Spine

History

In the lumbar spine, herniated disc can present with symptoms including sensory and motor abnormalities limited to specific myotome. History in these patients should include chief complaints, the onset of symptoms, where the pain starts and radiates. History should include if there are any past treatments.  

Physical Examination

A careful neurological examination can help in localizing the level of the compression. The sensory loss, weakness, pain location and reflex loss associated with the different level are described in Table 2.

Table 2. Typical findings of solitary nerve lesion due to compression by herniated disc in lumbar spine

  • L1 Nerve - pain and sensory loss are common in the inguinal region. Hip flexion weakness is rare, and no stretch reflex is affected.
  • L2-L3-L4 Nerves  - back pain radiating into the anterior thigh and medial lower leg; sensory loss to the anterior thigh and sometimes medial lower leg; hip flexion and adduction weakness, knee extension weakness; decreased patellar reflex.
  • L5 Nerve - back, radiating into buttock, lateral thigh, lateral calf and dorsum foot, great toe; sensory loss on the lateral calf, dorsum of the foot, web space between first and second toe; weakness on hip abduction, knee flexion, foot dorsiflexion, toe extension and flexion, foot inversion and eversion; decreased semitendinosus/semimembranosus reflex.
  • S1 Nerve - back, radiating into buttock, lateral or posterior thigh, posterior calf, lateral or plantar foot; sensory loss on posterior calf, lateral or plantar aspect of foot;  weakness on hip extension, knee flexion, plantar flexion of the foot; Achilles tendon; Medial buttock, perineal, and perianal region; weakness may be minimal, with urinary and fecal incontinence as well as sexual dysfunction.
  • S2-S4 Nerves - sacral or buttock pain radiating into the posterior aspect of the leg or the perineum; sensory deficit on the medial buttock, perineal, and perianal region; absent bulbocavernosus, anal wink reflex.

The straight leg raise test: With the patient lying supine, the examiner slowly elevates the patient’s led at increasing angle, while keeping the leg straight at the knee joint. The test is positive if it reproduces the patient’s typical pain and paresthesia.

The contralateral (crossed) straight leg raise test: As in the straight leg raise test, the patient is lying supine, and the examiner elevates the asymptomatic leg. The test is positive if the maneuver reproduces the patient's typical pain and paresthesia. The test has a specificity greater than 90%.

Evaluation

Over 85% patients with symptoms associated with acute herniated disc will resolve within 8 to 12 weeks without any specific treatments. However, patients who have an abnormal neurological examination or refractory to conservative treatments will need further evaluation and treatments.

X-rays: These are very accessible at most clinics and outpatient offices. This imaging technique can be used to assess for any structural instability. If x-rays show an acute fracture, it needs to be further investigated using CT scan or MRI.

CT Scan: It is preferred study to visualize bony structures in the spine. It can also show calcified herniated discs. It is less accessible in the office settings compared to x-rays. But, it is more accessible than MRI. In the patients that have non-MRI comparable implanted devices, CT myelography can be performed to visualize herniated disc.

MRI: It is the preferred and most sensitive study to visualize herniated disc. MRI findings will help surgeons and other providers plan procedural care if it is indicated.

Treatment / Management

Conservative Treatments: Acute cervical and lumbar radiculopathies due to herniated disc are primarily managed with non-surgical treatments. NSAIDs and physical therapy are the first-line treatment modalities. Translaminar epidural injections and selective nerve root blocks are the second line modalities. These are good modalities for managing disabling pain. Patients who fail conservative treatment or patients with neurological deficits need timely surgical consultation.   

Surgical Treatments: As always surgical treatment is the last resort. Surgical treatments for a herniated disc include laminectomies with discectomies depending on the cervical or lumbar area. In addition, a patient with a herniated disc in the cervical spine can be managed via an anterior approach that requires anterior cervical decompression and fusion. This patient can also be managed with artificial disks replacement. Other alternative surgical approaches to the lumbar spine include a lateral or anterior approach that requires complete discectomy and fusion.

Pearls and Other Issues

Thoracic spine herniated disc usually presents with radiculopathy symptoms or myelopathic symptoms depending on the compression of the nerve roots or spinal cord, respectively. As in the cervical and lumbar spine, patients initially are managed conservatively. A patient who has progressive myelopathic symptoms or does not respond to conservative treatment can be managed surgically. The surgical approach for thoracic spine includes the transthoracic or costotransversectomy approach for discectomies and fusion.