Mayo Clinic doctors who have training in neuromuscular conditions (neurologists) have experience diagnosing Lou Gehrig's disease (ALS) and other brain (neurological) conditions that may cause your symptoms. You often can be evaluated and tested for ALS within two or three days.
Lou Gehrig's disease can be difficult to diagnose in its early stages because the symptoms are similar to many other disorders, including spinal cord diseases, muscle diseases and neurological diseases such as multiple sclerosis, multifocal motor neuropathy, myasthenia gravis, spinal muscular atrophy and stroke. Doctors at Mayo Clinic have experience evaluating people for ALS and other conditions with similar symptoms.
To diagnose your condition, your neurologist will discuss your symptoms and any family history of neuromuscular diseases. Your neurologist will give you a complete physical examination and check for signs of muscle weakness. Your doctor may order various tests, including tests to rule out other conditions.
Diagnostic tests may include:
- Blood tests. Your doctor may use blood tests to check for the enzyme creatine kinase (CK), which leaks out of damaged muscle, or other blood tests for conditions that mimic Lou Gehrig's disease (ALS). Blood tests can also be used for genetic testing to detect familial ALS, which occurs when ALS is present in two or more family members related by blood.
- Cerebrospinal fluid examination. Your doctor may examine the cerebrospinal fluid surrounding your brain and spinal cord. In this test, a specialist will insert a needle into your lower back to withdraw a small amount of spinal fluid in a procedure called a spinal tap or lumbar puncture.
- Electromyogram (EMG). This test measures the tiny electrical signals in muscles. A specialist inserts a thin-needle electrode into the muscle to be tested. An instrument records the electrical activity in the muscle when it's at rest and when it contracts. An EMG may indicate that the motor nerves aren't functioning, yet the sensory nerves are normal, a sign of Lou Gehrig's disease.
- Genetic testing. Sometimes your doctor may perform genetic testing to test for some forms of familial ALS and for other neurological conditions with similar symptoms.
- Magnetic resonance imaging (MRI). This test uses powerful magnets and radio waves to produce a detailed view of your nervous system. Your doctor may order an MRI of your brain or spine to rule out other conditions.
- Muscle biopsy. To determine if you have a muscle disorder (myopathy) such as myositis or muscular dystrophy, rather than ALS, you may have a muscle biopsy. A specialist removes a small amount of tissue from a muscle to test.
- Nerve conduction study (NCS). This test measures electrical nerve impulses and functioning in your muscles and nerves. A specialist places two electrodes on your skin. A small shock is passed through the nerve to measure the electrical impulses in the nerve signals.
- Respiratory testing. Your doctor may order respiratory tests to determine if your condition affects the muscles that control your breathing.
Read more about cerebrospinal fluid examination (spinal tap or lumbar puncture), electromyography, genetic testing and magnetic resonance imaging at MayoClinic.com.