Diagnosing Herniated Disc

The spine consists of a stack of bones called vertebrae. In between each of these bones is a soft cartilage layer called a disc. These 23 discs act as cushions, absorbing the force put on the spine during movement and allowing the spine to move flexibly. If the outer wall of a disc breaks down, the soft inner core may move into the spinal canal, which is a bony cavity that protects the spinal cord and nerves. If a disc fragment slips into the spinal canal, it may push against the nerves or spinal cord. This displacement is called a herniated or “slipped” disc. 

A herniated disc can occur in anyone, regardless of age or gender. The most common symptom is sharp pain in the back or neck, though many people feel no symptoms. Radiating pain, numbness, tingling, or weakness in the legs or arms may indicate that the disc is pressing on a nearby nerve. Most of the time, pain associated with a herniated disc goes away on its own over a period of weeks or months and does not cause permanent damage to the spine or nerves.

A herniated disc can occur in any part of the spine, but it is most common in the lower back (the lumbar spine) and the neck (the cervical spine). A herniated disc that pinches a nerve in the lumbar spine can result in pain in the lower back that may radiate to the legs and feet. If a disc pinches a nerve in the cervical spine, it can cause pain in the neck that may radiate to the arms and hands.

To determine whether you have a herniated disc—and, if so, its location and severity—specialists at NYU Langone examine your spine and ask you to describe your symptoms in detail. Your doctor may recommend diagnostic tests to get more information on the condition of the nerves, vertebrae, and discs.

Medical History

Doctors ask you about your medical and family history to determine whether a herniated disc is the cause of your symptoms. You may be asked when you first noticed pain, where it is located, whether you felt it suddenly after an incident—such as falling or lifting a heavy object—or noticed it gradually. They may ask about your overall health, including whether you have other medical conditions, are taking medication, or have had previous spinal injuries or surgery. This information helps doctors establish the source of your symptoms. 

Physical Exam

Our doctors perform a thorough physical examination to look for the cause of your symptoms. This includes gently manipulating your legs and arms in different extended positions—such movements may cause pain to radiate from the back to the limbs—and pressing against the spine to test for tenderness. You may also be asked to bend or walk a few steps, so that your doctor can assess whether an injury has affected your balance or ability to move. 

A neurological evaluation may determine whether nerve damage is contributing to your symptoms. Nerves travel through the body, affecting muscles in predictable patterns. These patterns can be used to guide your doctor in matching abnormal physical responses with particular nerves. For example, your doctor may use a small hammer to test for unresponsive nerve reflexes in various parts of your body, which may indicate that a herniated disc is pinching a nerve. A doctor may also expose areas of your skin to stimuli such as warm and cool temperatures to assess whether sensation is affected. 

Signs of physical weakness may also indicate that a herniated disc is compressing a nerve. Your doctor may ask you to use specific muscle groups in moving parts of your body to assess strengths and weaknesses. Visible muscle twitches or spasms may also suggest nerve damage.  

X-ray

Your doctor may recommend an X-ray to look at the vertebrae surrounding a herniated disc. X-rays use high-energy beams of light to create detailed images of the spine. Often, if a disc slips out of place, the space between vertebrae may shrink or the vertebrae may become unstable without the disc to act as a cushion. X-rays can show a change in the height of the disc space or a shift in a vertebra’s position but cannot show a herniation itself.

A flexion–extension X-ray is taken while you bend forward and then backward. When compared with a traditional X-ray, flexion–extension X-rays give your doctor more information about possible instability between vertebrae. 

Your doctor may also choose to take a three-foot standing X-ray. These come in two varieties: anterior–posterior X-rays, which are taken from the front and then the back, and lateral X-rays, taken from the side. These images are called “three-foot” because of the large size of the X-ray film. They provide detail of spinal alignment, which may be affected by a herniated disc.  

MRI Scan

An MRI scan may be used to get a closer view of the vertebrae, discs, and surrounding soft tissues, including the spinal cord and any affected nerves. An MRI machine uses a magnetic field and radio waves to create two- and three-dimensional images of parts of your body.

Electromyogram

If you feel pain radiating into your arms or legs, or weakness, tingling, or numbness, an electromyogram (EMG) can reveal whether nerves are being pinched as a result of a herniated disc. An EMG measures the electrical impulses transmitted along nerves, nerve roots, and muscle tissue. This test helps doctors to determine if pain or weakness originates in the muscles or nerves. If pain originates in the nerves, it may indicate that a herniated disc is compressing a nerve or part of the spinal cord.

During an EMG, a doctor inserts small, thin needles, called electrodes, through the skin and into muscles that correspond to specific nerves. Doctors then ask you to move these muscles one at a time. The signals recorded when each muscle contracts can show the doctor which nerve roots are affected and whether a nerve injury has caused muscle damage.

An EMG is relatively painless, though some people feel uncomfortable with the needles. Usually, this test takes about 15 to 30 minutes to complete.

CT Scan

If you have had a previous spinal injury or surgery, or if your doctor suspects that a herniated disc is caused by another spine condition such as degenerative disc disease, a CT scan may be recommended. A CT scan is a series of X-rays that provide greater detail about the spine than a single X-ray can. NYU Langone uses advanced CT technology with the lowest amount of radiation possible.