Diagnosis of Sciatica

Sciatica diagnosis involves taking a complete patient history and performing a physical examination (including a neurological exam) and diagnostic tests. The first step often is a patient history, which includes information about past and current medical conditions, medications, and symptoms.

A history of symptoms often includes the following important information:

  • How long ago and under what circumstances did the pain begin?
  • Did the pain develop slowly over time or come on suddenly?
  • Where is the pain located?
  • Does the pain spread (radiate) and, if so, where?
  • Are there additional symptoms, such as numbness, tingling, or weakness?
  • Does anything improve the symptoms? Worsen the symptoms?

During the physical examination, a number of tests may be performed to help locate the area of nerve irritation or compression. The physician may ask the patient to walk on his or her heels or toes, or to squat and then stand up.

In one test, the patient lies on his or her back on the examining table and the physician slowly raises the straight leg to the point of pain. This test can help the physician determine which invertebral disc or nerve root is affected. A neurological exam often is performed to measure muscle strength, reflexes, and nerve impulses.

Imaging tests (e.g., x-ray, CT scan, MRI scan) also may be used to determine the underlying cause for sciatica. X-rays of the spine can show vertebrae alignment and can detect fractures, tumors, and other damage (e.g., degenerative joint disease).

Computerized tomography (CT scan) can be used to produce cross-sectional images of the spine and associated structures. CT scan, which uses special x-rays and a computer, can help detect abnormalities, such as fractures, infections, and tumors. In some cases, a contrast agent (e.g., iodine-based dye) is used to allow structures to be seen more clearly.

Magnetic resonance imaging (MRI scan) also can be used to produce computer images of the spine and determine the cause for sciatica. This procedure, which uses electromagnetic radio waves (i.e., electrical current and magnetism) to produce detailed images, can be used to detect herniated discs, disc deterioration, tumors, and nerve and nerve root abnormalities.

Other tests that may be performed to detect nerve root inflammation, irritation, or compression and determine the cause for sciatica include the following:

  • Bone scan (involves taking x-rays after a radioactive tracer has been injected; used to detect problems in the vertebrae)
  • Electromyogram (EMG; involves inserting tiny electrodes into muscle tissue to detect abnormal electrical signals, which may be caused by a pinched nerve)
  • Myelogram (involves injecting contrast dye into fluid that surrounds the spinal cord [cerebrospinal fluid; CSF] to detect abnormalities)
  • Spinal tap (involves removing and analyzing a sample of cerebrospinal fluid to rule out elevated CSF pressure, infection, bleeding, or tumor)

Publication Review By: Stanley J. Swierzewski, III, M.D.

Published: 05 Nov 2008

Last Modified: 05 Oct 2015