How is amyotrophic lateral sclerosis diagnosed?
A diagnosis of amyotrophic lateral sclerosis (ALS) is based on a careful medical history, a physical examination of the nervous system, and tests that evaluate nerve and muscle function. The diagnosis of amyotrophic lateral sclerosis begins with a complete medical history and physical exam, plus a neurological exam to determine the distribution and extent of weakness. An electrical test of muscle function, called an electromyogram, or EMG, is an important part of the diagnostic
process. Various other tests, including blood and urine tests, x rays, and CT scans, may be done to rule out other possible causes of the symptoms, such as tumors of the skull base or high cervical spinal cord, thyroid disease, spinal arthritis, lead poisoning, or severe vitamin deficiency. Amyotrophic lateral sclerosis is rarely misdiagnosed following a careful review of all these factors.
If the person has amyotrophic lateral sclerosis, the medical history and physical exam of the nervous system can usually help the doctor begin to establish the diagnosis. Tests needed to confirm the diagnosis include electromyography (EMG) and nerve conduction studies. EMG helps measure how well and how quickly the nerves and muscles are functioning. Nerve conduction studies test nerve function.
Depending on the doctor's findings during the exam of the person's nervous system and the results of EMG or nerve conduction studies, other tests may be needed to rule out other possible causes of the person's symptoms. These tests may include a muscle biopsy, blood tests, or imaging tests, such as computed tomography (CT) or magnetic resonance imaging (MRI) scans.
Amyotrophic lateral sclerosis may be difficult to diagnose, and the diagnosis may not become clear until symptoms have progressed or until additional testing and observation have taken place. If amyotrophic lateral sclerosis is suspected, evaluation by a specialist who has experience treating and diagnosing amyotrophic lateral sclerosis may lead to an earlier diagnosis.