Frontotemporal degeneration is not as rare as once thought; it is considered to be the second most common cause of early onset dementia. However, because of the wide range of symptoms and their gradual onset, FTD is often initially misdiagnosed as a psychiatric problem, Alzheimer’s disease, Parkinson’s disease or vascular dementia.
FTD vs. Alzheimer’s Disease
Both frontotemporal degeneration (FTD) and Alzheimer’s disease (AD) are characterized by atrophy of the brain, and a gradual, progressive loss of brain function. However, several important distinctions can help to differentiate between the two:
- FTD is primarily a disease of behavior and language dysfunction, while the hallmark of Alzheimer’s disease is loss of memory.
- FTD often begins earlier than AD with an average age of onset in the 50s and 60s, a full 10 years before the average Alzheimer’s patient is diagnosed.
- FTD patients exhibit behavioral and personality changes (lack of concern for social norms or other people, lack of insight into their own behaviors), but retain cardinal features of memory (keeping track of day-to-day events, orientation to space and time).
- AD patients display increasing memory deficits, but typically retain socially appropriate behavior.
- Some FTD patients may have only language dysfunction (this is seen in the two types of progressive aphasia: semantic dementia and progressive non-fluent aphasia). And the pattern of language loss may be specific, such as an inability to name a familiar, everyday object.
- The language decline seen in AD patients involves a milder problem with recalling names and words.
- FTD patients are more likely to display early motor abnormalities, such as difficulty walking, rigidity or tremor (similar to Parkinson disease), or muscle atrophy and weakness.
Gathering Information for Diagnosis
A trained and experienced health care professional can look for features that rule out other diagnoses and identify features that pinpoint FTD. The medical specialist best able to evaluate cognitive and behavior changes will be a neurologist, behavioral neurologist or neuropsychologist. If a local physician suspects FTD, you may want to consult a university medical center or a memory and cognitive disorders clinic that has a team of professionals for the comprehensive evaluation needed. Access to brain imaging techniques is an important aspect of diagnosis.
The diagnosis of frontotemporal degeneration generally involves:
- Medical history and detailed neurological examination.
- Neuropsychological examination to assess language, behavior, memory, executive and visual-spatial functions.
- Neuroimaging to determine where and how extensively brain regions have atrophied, or may be experiencing decreased blood flow. Some of these neuroimaging studies are: MRI (magnetic resonance imaging), PET (positron emission tomography), and SPECT (single photon emission computed tomography).
Clinical Diagnosis vs. Pathology
One specific source of confusion for families may be the distinction between clinical diagnosis of FTD and pathological diagnosis. A clinical diagnosis is carried out by the physician meeting with the patient and family, and consists of the elements listed above: detailed examinations of changes in cognition, behavior and personality, and neuroimaging studies.
A pathological diagnosis is determined through autopsy, and requires looking at the brain tissue under a microscope. It is during this examination that physicians can determine the specific type of abnormality present in the brain, and thus the definitive cause of the progressive symptoms experienced during life. A definitive (or an official) diagnosis of FTD can only be made via autopsy.
Tests Used in the Diagnosis of Frontotemporal Degeneration
There are many potential causes that may explain changes in cognition, behavior and motor skills. No single diagnostic test exists to confirm or rule out a diagnosis of FTD. This often results in a long, confusing and frustrating process of testing for other disorders with symptoms similar to FTD to rule them out. It is not uncommon for an individual’s diagnosis to change multiple times. Each time, however, additional information about the patient is incorporated toward a more accurate diagnosis which the physician can use to recommend treatment.
In recent years, advances in diagnostic technology and our understanding of FTD have led to some tools that physicians can use to determine a diagnosis of FTD with more confidence. 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: Tests for specific chemicals, proteins, hormones and antibodies to detect conditions that can have similar clinical features to FTD, such as thyroid disease, B12 deficiency, infections such as syphilis or HIV, dehydration, or cancer. These conditions are treated differently, and some are curable.
Neurological exam: A detailed examination of the entire nervous system including physical and cognitive functioning. 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: Pencil-and-paper tests and interviews that evaluate cognition and try to identify specific areas of strength and weakness. Testing includes measures of memory, concentration, visual-spatial, problem solving, basic math and language skills. These tests take several hours to administer and are interpreted by a neuropsychologist. They can differentiate depression from dementia, and can help in the diagnosis of specific types of dementia or brain disorders. For example, someone with Alzheimer’s 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 test is used to evaluate an individual for seizures, head injury or other brain disorders. It 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. A special needle is inserted through the skin into the muscle and measures the muscles’ response to nerve stimulation. This test can cause discomfort. It is not routinely done for individuals for dementia unless they are also experiencing other problems such as muscle weakness or myoclonus, involuntary contraction or twitching of the muscles. This test is important in the diagnosis of motor neuron diseases such as ALS (Lou Gehrig’s disease).
Lumbar puncture (spinal tap): This test is used to collect and study cerebrospinal fluid, the fluid that surrounds the brain and spinal cord. It can identify conditions to rule out such as rare infections and cancer. 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. 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 arm vein 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 arm vein to enhance the images.
PET (Positron Emission Tomography): A type of nuclear medicine scanning that involves capturing cross-sectional images of the brain, much like CT scanning. The images that are created are functional rather than the structural images of CT and MRI. Functional images capture how various parts of the brain are working, which makes it a diagnostic tool for neurodegenerative conditions such as FTD. Areas of the frontal or temporal lobes that are not as active as they should be may indicate FTD.
The PET scan involves the injection of a radioisotope, or tracer, into a hand or arm vein. The tracer emits positrons, which collide with electrons, or negatively charged particles, producing gamma rays which are 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 brain metabolism. 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.
SPECT (Single Photon Emission Computed Tomography): 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.
Functional MRI (fMRI): A specialized type of MRI scan that shows changes in blood flow in the brain. It can help to identify areas of brain activity which, if decreased in the frontal and temporal lobes, may indicate FTD. Unlike PET and SPECT scans, fMRI is non-invasive and is done in an MRI scanner.