Tests Used in the Diagnosis of Frontotemporal Dementia ...

Tests Used in the Diagnosis of Frontotemporal Dementia

There is no single diagnostic test that can be used by physicians to confirm or rule out a diagnosis of FTD in an individual (just as there is none for Alzheimer's). This is frustrating for healthcare providers, caregivers and families. Therefore, the approach most often taken in the path to a diagnostic work-up is one of excluding all other possibilities . This means that an individual is usually tested for other disorders with symptoms similar to FTD, for which there are diagnostic tests. Once other disorders are ruled out, then a diagnosis of FTD is made. During this process it is not uncommon for an individual to have his or her diagnosis changed multiple times. It can be a long, confusing, and frustrating process for the patient and family. The important thing to keep in mind is that each change in diagnosis incorporates additional information about the individual patient, and is a step forward to the most accurate diagnosis, which will allow the physician to design the best approach to therapy. (In the coming years, as science expands our understanding of the biology of dementia, medicine will have better tools to enable quicker and more accurate diagnosis.)

In recent years, however, advances in diagnostic technology and our understanding of FTD have led to some tools that physicians can use to confirm the FTD diagnosis. Neuropsychological testing and neuroimaging (MRI, SPECT and PET scans) have shown that there are specific features or clinical findings consistent with FTD that can be identified and helpful in the diagnostic work-up.

Research is still looking for a definitive test for FTD. This will be even more important as clinical trials for treatments become available. Areas of research involved in this quest include genetic testing, biochemical testing (studying proteins in the blood, cerebrospinal fluid, and other tissues), and neuroimaging.

Below is a list of some of the tests that may be encountered during a diagnostic work-up, and a brief description of each of these tests.

Routine blood work: Obtaining a blood sample to test specific chemicals, proteins, hormones and antibodies can be useful in distinguishing many conditions that can have similar clinical features to FTD. Thyroid disease, B12 deficiency, infections such as syphilis or HIV, dehydration, or cancer are some of these conditions. These tests are important because these conditions are treated differently, and some are curable.

Neurological exam: A neurologist performs a detailed examination of the entire nervous system that can identify both motor or physical problems and cognitive or behavior changes. An initial evaluation usually takes about an hour and includes:

* Obtaining past medical history
* Physical examination (evaluating motor function such as walking, balance, coordination, reflexes, strength, as well as vision, hearing, and heart function)
* Cognitive examination (evaluating memory, thinking, planning and organizational skills, visual-spatial abilities, behavior and mood)

Even among neurologists there are different specialties; therefore, it is not uncommon for an individual to see more than one neurologist. It is extremely important for an individual to be evaluated by a neurologist experienced with FTD and related neurodegenerative conditions.

Neuropsychological testing: Neuropsychological tests measure memory, concentration, visual-spatial, problem solving, basic math, and language skills. These are pencil and paper tests and interviews that evaluate cognition and try to identify specific areas of deficiency and competency. The testing takes several hours to administer and is interpreted by a neuropsychologist. This testing can differentiate depression from dementia, and can help in the diagnosis of specific types of dementia or brain disorders. For example, someone with Alzheimer disease will show significant deficits in tests of memory while someone with FTD can do fairly well with memory but have more difficulty on language skills.

EEG (Electroencephalogram): This is a test that is used to evaluate an individual for seizures, head injury or other brain disorders. The test is performed by placing special electrodes on the scalp to monitor electrical activity in the brain. Activity is recorded while the patient is awake and asleep. It takes about an hour to perform the study. The electrodes just record information, they do not cause pain or injury. If this test is performed for someone with FTD it can be normal or have non-specific findings, especially early in the course of the disease.

EMG (Electromyography): This test is used to evaluate conditions that affect the muscles and peripheral nerves (the nerves outside of the brain and spinal cord). Specifically, it measures the muscles' response to nerve stimulation. A special needle is inserted through the skin into the muscle and records electrical activity received from the nerves. This test can cause discomfort. This test is not routinely done for individuals for dementia unless they are also experiencing other problems such as muscle weakness or myoclonus (involuntary contraction of the muscles – looks like jumping or twitching of the muscle). This test is important in the diagnosis of motor neuron diseases such as ALS (Lou Gehrig's disease).

Lumbar Puncture (Spinal Tap): This is a procedure used to collect cerebrospinal fluid (fluid that surrounds the brain and spinal cord). The fluid can be studied for rare infections and cancer that can cause symptoms of dementia. These tests are important because the treatments for infections and cancer are very different. The procedure involves inserting a thin needle into the lower area of the back. It takes only a few minutes to collect the fluid. It is uncomfortable but rarely painful, as local anesthesia is used to numb the area.

CT Scan (Computed Tomography Imaging or CAT Scan): A non-invasive procedure using X-rays that creates images of the soft tissue, bone, and blood vessels. Specifically, images can be created of the brain to evaluate for bleeding, tumors or other injury. Sometimes atrophy or shrinkage of the brain can be detected and that might be suggestive of FTD. The procedure involves lying flat and still on a table for several minutes while X-ray beams and computers recreate cross-sectional images of the brain. Sometimes contrast dyes are injected into the vein (arm) to enhance the images.

MRI (Magnetic Resonance Imaging): A non-invasive procedure that uses magnets and radio waves to create images of the brain and other organs. MRI is the procedure of choice for most brain disorders, as it creates images from multiple angles and provides a detailed view of many brain structures not visible by CT scan. Atrophy or shrinkage of the brain that might be suggestive of FTD can be identified by MRI. The procedure involves lying flat and still on a table for several minutes. The scanner makes loud thumping noises, but there is no pain or danger from the magnets. Sometimes contrast dyes are injected into the vein (arm) to enhance the images.

PET (Positron Emission Tomography): PET scanning is a type of nuclear medicine scanning that involves capturing cross-sectional images of the brain, much like Computed Tomography (CT) scanning. The procedure involves the injection of a radioisotope, or tracer, into the vein (hand or arm). The tracer emits positrons, which collide with electrons (negatively charged particles), producing gamma rays (similar to X-rays). These gamma rays are detected by a ring-shaped PET scanner and analyzed by a computer to form an image of the brain metabolism or other functions. The images that are created are functional rather than structural (CT and MRI produce structural images). Functional means that these images capture how various parts of the brain are working, which makes it a diagnostic tool for neurodegenerative conditions, such as FTD. This test can pinpoint which areas of the frontal or temporal lobes are not as active as they should be. These tests are very expensive and not covered by all insurance policies. Check with your insurance provider to see what tests are covered or if pre-approval is needed for such testing.

SPECT (Single Photon Emission Computed Tomography): SPECT scanning is a type of nuclear medicine scanning that is very similar to PET. SPECT measures blood flow and activity levels in the brain, which make it a diagnostic tool for identifying behavioral and cognitive problems in persons with neurodegenerative conditions such as FTD.