How is the diagnosis made
Like any other condition in neurology the diagnostic process begins with a thorough history and examination. This will give your neurologist a chance to go through the details of the history and formulate a differential diagnosis. Most commonly you will have presented to your GP because of a progressive weakness of an arm or leg or a progressive difficulty with speech and swallow. Sometimes patients develop twitches and cramping of muscles and they are concerned about having motor neuron disease. However, these two symptoms are quite common and are far more likely to be related to a more benign condition than motor neuron disease. There are many different causes for these symptoms so just because you have symptoms that can occur in motor neuron disease does not in any way mean that this is what you have. In general, symptoms of a sensory nature such as numbness or tingling do not tend to occur as a prominent symptom in motor neuron disease. Pain can occur but this tends to be later in the disease course as it is often a result of the other symptoms. For example, muscles that have become stiff or spastic may also become painful. Your neurologist will then perform a neurological examination to look for any signs that may help with making the diagnosis.
The next step will be diagnostic tests. One of the main tests in diagnosing motor neuron disease is nerve conduction studies and EMG. This test involves stimulating nerves and monitoring the responses and then using a needle to record the activity in the muscles (described on the services page).
You may also have an MRI of your brain and spinal cord. This can be abnormal in motor neuron disease but the main reason for doing the MRI of brain is to rule out other abnormalities that may be causing the symptoms. Then there will be various blood tests that your neurologist may decide to do based on the constellation of symptoms that you have presented with. Again these tests are to rule out other conditions. There is no blood test that can make a diagnosis of motor neuron disease.