Diagnosis of Sciatica

Sciatica is the pain in the lower back or buttocks radiating to the lower leg due to compression or irritation of the Sciatic nerve or the nerve roots (L4 to S3). The pain may be followed by a feeling of numbness and tingling in the legs. There may be symptoms of weakness in the lower extremities and the patients may complain of loss of sensation.

The diagnosis of Sciatica can be made by a physician by mere clinical examination. The majority of patients improve through conservative measures and imaging is not immediately necessary.

Suspicion of Sciatica

Sciatica is suspected when the pain is on one side of the leg and is more than the low back pain. The pain commonly radiates down on the back of the leg. The radiation of the pain is generally below the knee. The presence of numbness and tingling in the involved leg along with neurological findings and positive special tests help the physician to diagnose Sciatica.

History

At the doctors’ office, the physician may extract a thorough history regarding the symptoms and the events preceding the symptoms. Some of the questions the physician may ask are:

• Where do you feel the pain?
• When did the pain start?
• Did the pain start suddenly or insidiously?
• Did any activity precede the onset of pain?
• Is the pain getting worse or better?
• What makes the pain get worse and what makes it better?
• On a scale of 0 to 10 with 10 being the maximum, how would you rate your pain?
• How would you describe the character of your pain?
• Is there any associated tingling sensation in the legs?
• Do you feel any weakness or loss of sensation in the legs?
• Are you able to feel the toilet paper on your bottom?
• Any bowel or bladder incontinence?
• Did any medications help you with the pain?
• Does walking uphill or downhill change the intensity of pain?
• Do you need to stop when walking because of pain?
• Any association of symptoms with coughing, sneezing or bearing down efforts.

Besides these questions, the physician will get a history of the patient’s past medical illness, medications and allergies, and any relevant family history.

The symptoms of Sciatica as a result of a herniated disc usually get worse on sitting, coughing, sneezing, and bearing down efforts.

The nerve root compression secondary to spinal stenosis may get worse with bending backward and walking downhill. Additionally, patients may experience neurological claudication symptoms which are a pain in the legs on walking that is relieved on rest and bending forward.

Physical examination

After the evaluation of the history of the symptoms, the physician conducts a thorough physical examination. The physician looks for motor power in the muscles supplied by the Sciatic nerve to locate the nerve root involved.

To look for L3 nerve involvement, the physician checks the power of the muscles in the inner side of the thigh. The L4 nerve root is checked by the resistance offered on trying to bend the knee. Additionally, a decreased patellar reflex may point towards L4 involvement.

The physician may ask the patients to walk on their heels to look for involvement of the L5 nerve root. Additionally, the physician may test the L5 nerve root by asking the patients to extend the great toe under resistance or to move the leg outward under resistance while laying on the one side.

The physician looks for the strength of muscles supplied by the S1 nerve root by asking the patients to walk on their toes. The Achilles‘ tendon reflex may be diminished with S1 nerve root involvement.

Besides the motor power, the physician looks for sensory input from different dermatomes in the lower extremities and the saddle area. Provocative tests may be done in the form of a straight leg raising test. Various modifications of straight leg tests may make the findings more sensitive and specific.

The walking pattern of the patients is carefully examined to look for weakness in any muscle groups that may change the natural walking pattern.

Imaging

Radiological tests are usually not required for the diagnosis of Sciatica. Radiological tests are done only if there is no improvement of symptoms in 12 weeks or if there are progressive symptoms. Loss of bowel and bladder control is a surgical emergency and the patients are operated on within 48 hours to prevent permanent damage.

An X-ray is usually the first radiological investigation done in a case of Sciatica. The X-ray provides information on the bony structure of the lumbar spine in different views. Bone spurs may be found on an X-ray that may be impinging a nerve root.

A CT scan provides a much clearer image of the bony structures as compared to an X-ray. Additionally, a dye may be injected to differentiate the bony structures and the soft tissue structures.

An MRI is the radiological imaging of choice to diagnose the nerve root compression and the soft tissue structures in the spine. Electromyography (EMG) studies may be done to diagnose the nerve root compression and to localize the site of compression.