Diagnosing CNSV

The process of diagnosing Central Nervous System Vasculitis (CNSV) is a two-fold process of confirmation that an inflamation exists and elimination of all other possible causes. The tests and procedures often do not confirm vasculitis of the central nervous system, but they are necessary to rule out other possible diseases and conditions, many just as dangerous and life-threatening as CNSV.

Doctors usually start with very basic tests and procedures (often in the Emergency Room), attempting to identify the cause of the symptoms. CNSV will not be suspected at all. In fact, because it is rare, it would not be considered initially, even if CNSV were generally known in the medical community. When all other possible diagnoses are eliminated, then CNSV might be considered.

To assist in making a diagnosis of Central Nervous System Vasculitis (CNSV) and to confirm or rule out other conditions -- the following tests and procedures usually are performed:

Lumbar Puncture

Physicians use a procedure called a lumbar puncture to draw samples of cerebrospinal fluid. After a local anesthetic, a small needle is inserted through the lower back, between spinal disks, and into the interior of the spine called the epidural space. The epidural space serves as pipeline for the cerebrospinal fluid, the body's only fluid that carries neurotransmitters throughout the spinal cord and brain. The fluid constantly bathes and protects the brain, and the body can generate between 20 and 24 cc of new fluid an hour.

One traditional theory of why so many patients develop the headaches has been the "leakage theory." That's when the cerebrospinal fluid continues to leak from the needle puncture. The leakage causes the brain to shift down slightly and that leads to the pain.

A common treatment for the headache has been to stop the leak with an epidural blood patch. A small amount of the patient's blood is inserted into the puncture point in the spine, which then clots and, in theory, stops the leakage. Bed rest following the lumbar puncture has been a standard of care designed to prevent the headaches.

Adapted from: "Lumbar Puncture--What Is It?" and "Headaches After Lumbar Punctures -- Why," in Clinical Center News (July 1996), Warren Grant Magnuson Clinical Center, National Institutes of Health.

CT Scan

Computed tomography is a diagnostic procedure in which cross-sectional pictures or "tomographic slices" of the body are made by x-ray. This technique may also be called a CT scan or CAT scan.

CT Scan of Normal Head

During the procedure, the patient lies very still on a table. The table passes through the x-ray machine, which is shaped like a doughnut with a large hole. The machine, which is linked to a computer, rotates around the patient, taking pictures of one thin slice of tissue after another.

To obtain a clearer picture, the patient may be given a solution of contrast material to drink or get an injection into an arm vein before the CT is done. The length of the procedure depends on the size of the area to be x-rayed.

Images from these x-rays are then processed by the computer. The final image, called a "computed tomogram" or "CT slice," is displayed on a cathode-ray tube (CRT), a device similar to a television picture tube and screen. This image can be recorded permanently on film. In addition, a CT scan can be stored on magnetic tape or optical disk.

Computed tomography offers some advantages over other x-ray techniques in diagnosing disease, particularly because it clearly shows the shape and exact location of organs, soft tissues, and bones in any "slice" of the body.

Magnetic resonance imaging, MRI, provides a high resolution image of the brain's internal structure. The scanner contains a large magnet that induces different chemical elements to emit distinctive radio signals. The signal data is translated into 2-D pictures of the brain, slice by slice.

MRI Scan of Normal Head

A person who gets an MRI lies on a table that is then placed inside a device that produces a powerful magnetic field.

When the magnetic field is turned on, certain atoms in the body act like tiny magnets with north and south poles -- they line up in parallel columns that indicate the orientation of the imposed magnetic field. Then a series of radio wave pulses are delivered. These "perturb" (or excite) the atomic "magnets," cause them to move, absorb energy, and, when the pulses are turned off, emit radio signals. The signals are characteristic of the atom that is emitting them. Through changes in the external field and the radio pulses, different atoms in the tissue can be activated.

About two-thirds of all atoms in the human body are hydrogen atoms. These unbalanced hydrogen atoms wobble in the magnetic field and give off detectable radio signals.

MRI detects increases in oxygen in areas of heightened nerve cell activity. Its effectiveness reflects the way in which these cells use oxygen. It has the advantage that it does not depend on the injection of radioactive materials. With MRI, it is possible to detect tumors, chemical reactions, blood clots, and so on.

Cerebral Artiography

Angiogram

Angiography is the name of a procedure that uses X-Rays to produce a picture (the "angiogram"). This is an "invasive" procedure, because it requires the injection into the patient of a substance that is radiopaque (absorbs X-Rays). This substance is commonly called a "contrast agent" or "dye".

Usually a very tiny tube, that has a special shape, is used to place the contrast into a particular artery or vein. While the artery or vein contains this radiopaque material, it will block the X-Rays, and will cast a shadow of the injected vessels onto the X-Ray film or fluoroscope. This image will reveal the shape of the artery, and can help to diagnose an obstruction, blockage, or narrowing ("stenosis").

Adapted from: " Image Source:    

Brain Biopsy

In a brain biopsy, a neurosurgeon removes a small amount of brain tissue that is sent to a pathologist for study and analysis. The pathologist determines or suggests an exact diagnosis. Often a pathologist will be present at the operation to look at the sample immediately, before it is prepared and sent for further analysis. This helps ensure that a useful specimen is available.

Some areas of the brain are considered "inoperable." In those cases the surgeon may perform a biopsy through a small hole drilled into the skull. That hole is called a burr hole.

In a needle biopsy, a narrow, hollow needle is inserted through the burr hole, and tissue is removed from the core of the needle.

Stereotactic biopsy is a computer directed needle biopsy. The computer is programmed to perform a biopsy using information from a CT or MRI scan giving the exact location of the tissue to be taken, particularly the many structures of the brain. For a closed biopsy, stereotactically guided equipment is moved into the burr hole to remove a sample.