Benign Peripheral Nerve Tumors

Diagnosis

If a physical examination indicates signs and symptoms of a peripheral nerve tumor, the doctor may recommend the following diagnostic tests to determine if a tumor is present and identify the type of tumor. In some cases, an enlarged nerve may be due to inflammation caused by other conditions, or peripheral neuropathies.

Because of Mayo's sophisticated diagnostic capabilities, Mayo doctors are often able to identify nerve conditions which either had been misidentified or not identified at all, and many of these conditions can be successfully treated.

Diagnostic Tools

Computed Tomography (CT) Scan

The CT scanner rapidly rotates around the body, taking a series of images that are reconstructed by a computer, into slices of the body. Newly available 64-slice CT scanners can produce incredibly detailed views to identify a peripheral nerve tumor and evaluate how it may be affecting that area of the body.

Magnetic Resonance Imaging (MRI) Scan

This noninvasive test uses a powerful magnet and radio waves to produce a detailed, three-dimensional view of the nerves and surrounding tissue.

Electromyogram (EMG or Electromyography)

By placing small needles in key muscles, one can identify and quantify abnormalities in muscles supplied by specific nerves. An instrument records the electrical activity in the muscle at rest and as the patient tries to move or contract the muscle. Nerve tumors can cause weakened electrical signals.

Nerve Conduction Study

This test measures how quickly nerves are carrying electrical signals to the muscles. A small shock is passed along the course of a nerve to measure the electrical impulses.

Tumor Biopsy

If imaging tests identify a nerve tumor, a small sample of cells may be taken from the tumor (biopsy). The cell samples are then examined and tested to determine the type of tumor and whether the cells are benign (non-cancerous) or malignant (cancerous).

The biopsy may be performed by:

• Image-Guided Biopsy
  In this minimally-invasive procedure, the physician, guided by a CT scan or ultrasound, inserts a needle into the tumor and removes a small, cylindrical-shaped tissue sample. The procedure requires only a topical anesthetic to numb the skin. It leaves little or no scarring. Mayo Clinic uses core needle technology that uses a special vacuum-assisted needle to draw out tissue.
• Surgical Biopsy
  

  In this procedure, the patient may be put to sleep under general anesthesia or receive numbing medication (local anesthesia) in the area of the nerve tumor. A small surgical incision, or cut, is made to remove a sample of cells in the affected area.

Nerve Biopsy

Nerve biopsy may be deemed necessary for some patients with progressive peripheral neuropathies or enlarged nerves that may mimic nerve tumors. Mayo Clinic has significant expertise in obtaining precise samples of tissue from peripheral nerves that allows Mayo to identify and treat unusual nerve diseases.

The technique of biopsying a peripheral nerve for analysis was developed at Mayo Clinic in 1966. In recent years, Mayo has significantly expanded this capability by localizing specific neurologic conditions to an affected area, correlating these to high-resolution MRI abnormalities and biopsying a small piece of a nerve.

The major peripheral nerves (such as the sural nerve in the calf and ankle) are composed of bundles of smaller nerves (fascicles). Mayo specialists are able to analyze portions of nerves one-twentieth the size of major nerves. This technique has helped diagnose many unusual conditions and has been performed safely. This capability is a result of a team effort by neurologists with special interest in focal peripheral nerve problems, radiologists with expertise in obtaining highly detailed nerve images, surgeons willing to remove a tiny piece of nerve for analysis and a nerve laboratory with expertise in staining, preparing, processing and interpreting the nerve specimen.