In 1916, Dr. James Walker Dawson noticed a pattern of plaques in the brains of people with multiple sclerosis. Now known as Dawson's finger, these lesions are located around ventricles - fluid-filled spaces - in the brain.
When accompanied by other symptoms, such as difficulties with movement or thinking, Dawson's finger can help to diagnose multiple sclerosis.
Multiple sclerosis (MS) is a chronic disease that targets the central nervous system, which consists of the brain and spinal cord. It is an immune-mediated disease. This means that symptoms occur when the immune system becomes excessively sensitive and begins attacking the body.
The immune cells affected by MS attack myelin, a fatty insulation that coats part of the nerve cells. This process is called demyelination. Without myelin, nerves cannot send and receive information properly. The destruction of neurons' ability to communicate wreaks havoc throughout the body, though symptoms vary from person to person.
Dawson's finger and the diagnosis of MS
Demyelination leaves behind plaques in the brain. These plaques are often visible on brain scans. Dawson's fingers are a type of plaque distributed around a band of nerve fibers that joins the left and right hemispheres. The plaques are arranged at right angles around veins in the brain's ventricles.
MRI brain scans are used to check for changes in the central nervous system, such as Dawson's finger.
Dawson's finger is a classic sign of MS. In one 2014 study, researchers saw Dawson's finger in the majority of people with MS. Two researchers looked at the same patients. One reported Dawson's fingers in 92.5 percent of patients, with the other reporting their presence in 77.5 percent.
- Evidence of damage to at least two regions of the central nervous system
- At least one MS attack
- No evidence that another condition such as an infection or brain injury caused the symptoms
People who have experienced at least two MS attacks may be diagnosed with MS even with evidence of damage to only one area of the central nervous system.
Dawson's fingers are just one sign of damage that can point toward MS. If a brain scan shows Dawson's fingers and a person has no other symptoms, or if they have only had one MS attack, their doctor might continue to monitor them. The person will probably not be diagnosed unless and until they show more symptoms.
Other MS tests
MRI brain and spinal cord scans check for a number of changes in your central nervous system, not just Dawson's fingers. Doctors will look for signs of demyelination in the brain and spinal cord. Brain scans can also help to track the progression over time.
Sometimes, scans show lesions in an area of the brain that does not produce symptoms, offering an early warning that someone may eventually develop symptoms.
Some other tests that help toward diagnosing MS include:
- A lumbar puncture to collect cerebrospinal fluid (CSF)
- An evoked potentials test, which measures electrical activity in the brain
- Optical coherence tomography imaging to look at the nerves at the back of the eye
The doctor will also explore whether someone has symptoms of any other illness. A history of their symptoms can help the doctor determine which tests - for both MS and other illnesses - are most appropriate.
Dawson's fingers and other brain disorders
Although Dawson's fingers are not typically associated with other brain disorders, not everyone with Dawson's fingers has symptoms of MS. Further, because brain scans are not always clear, other brain changes could be mistaken for Dawson's fingers.
A 2014 study explored the ability of evaluators to differentiate symptoms of MS from symptoms of neuromyelitis optica spectrum disorders (NMOsd). NMOsd are immune-mediate disorders that, like MS, trigger demyelination. However, NMOsd typically target optic nerves, therefore affecting vision.
One evaluator saw Dawson's fingers in one patient with NMOsd, suggesting that evaluators may either misinterpret MRI findings, or that Dawson's fingers may be present in some other disorders.
Symptoms of MS
Symptoms of MS may be subtle at first. Some early warning signs of MS include:
Blurred vision, alongside other symptoms, may be an early warning sign of multiple sclerosis.
- Changes in vision, including blurred vision and pain when moving the eye
- Unusual body sensations, including tingling, numbness, or an electrical shock sensation in the limbs
- Unexplained itchiness
- Extreme fatigue, particularly in response to heat
- Unexplained muscle pain and weakness
- Difficulty walking and problems with balance or coordination
- Ringing in the ears
- Changes in bladder or bowel function
- Changes in thinking, including feelings of "brain fog" or unclear thinking
As the disease destroys more myelin, symptoms progress. Most people with MS experience periodic attacks, then brief improvements. As the disease progresses, the attacks may become more frequent.
Common symptoms as the disease progresses include:
- Long-term fatigue that interferes with daily functioning
- Stiffness and uncontrollable muscle spasms
- Muscle weakness that can limit mobility
- Sexual dysfunction
- Emotional difficulties such as depression, mood swings, and involuntary laughing or crying
- Loss of bladder or bowel control
Less frequently, other symptoms can occur. Those include:
Treatment for MS may include medication such as antidepressants.
MS is a chronic illness and there is no known cure. Because symptoms tend to appear in the form of attacks and then later disappear, however, it is possible to go extended periods of time without an MS attack. Rarely, people with MS stop experiencing attacks.
Most treatment focuses on increasing the time between attacks and reducing their severity.
- Lifestyle changes: Exercise, yoga, dietary changes, and stress management may improve symptoms in some people with MS.
- Medications to treat symptoms. The doctor might prescribe stimulants to reduce fatigue, or antidepressants and anti-anxiety medications.
- Muscle relaxants to reduce muscle spasms.
- Pain medication to manage headaches, muscle pain, and other painful symptoms.
- Physical therapy to slow the loss of functioning, improve muscle strength, and increase mobility.
- Steroid drugs to reduce inflammation.
- Immunosuppressant drugs to inhibit the immune response that causes demyelination.
- Beta interferon drugs to reduce the frequency of MS attacks. These are among the most commonly prescribed MS drugs, and require a doctor to monitor the liver's health.
- Other drugs to reduce the frequency of attacks, including those that target immune proteins and inhibit the movement of immune cells.
- Alternative and complementary medicine. Some people with MS use massage, acupuncture, or other forms of alternative medicine to manage symptoms. There is no clear evidence that these strategies work, though some people report impressive improvements.
- Plasma exchange therapy.
Although MS can reduce quality of life, it is rarely fatal. Many people with MS live full and active lives. However, the course of the disease is unpredictable, with symptoms ranging from relatively minor to debilitating. Symptoms tend to worsen over time as more neurons become demyelinated. This is not always the case, though, and some people with MS experience remission for years.
MS attacks tend to develop suddenly, with the worst symptoms lasting for a few days. Symptoms typically persist for around 8 weeks, and may recur every 12-18 months.
Tracking symptoms over time may help people to predict the next attack. Logging symptoms may also make it easier to get a diagnosis, and can help people assess whether medications and lifestyle management strategies are working.