Multiple Sclerosis

Updated 31 October 2016

Diagnosis of multiple sclerosis

Multiple sclerosis (MS) is a chronic (long-term), progressive, degenerative disorder that affects nerve fibers in the brain and spinal cord. Diagnosing MS is often an intricate process.

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Diagnosis of multiple sclerosis (MS) involves taking a family history and a history of symptoms, and performing a physical examination (including neurological examination) and various tests (including blood tests and imaging tests).

Blood tests: Many blood tests may be used to determine if MS is present. They include a complete blood count (CBC), liver function tests, testing for Lyme disease, a creatine kinase test, and a DNA analysis (to determine if the disorder is genetic) among others. In some cases, a cerebrospinal fluid (CSF) analysis also is performed.

Cerebrospinal fluid analysis involves performing a spinal tap or lumbar puncture. In this procedure, about two tablespoons of cerebrospinal fluid is drawn into a needle inserted between two lumbar vertebrae and then examined under a microscope. In cases of MS, the doctor may see an elevation of protein and white blood cells in the cerebrospinal fluid. This procedure is usually performed in a hospital or clinic under local anesthesia, although general anesthesia can be used.

Imaging tests: Imaging tests, including computed tomography (CT scan), magnetic resonance imaging (MRI scan), and positron emission tomography (PET scan), may be used to detect damage (such as shrinkage) in the basal ganglia, structural abnormalities, and stroke (neurological damage due to a lack of oxygen to the brain).

Other imaging tests: An electromyogram (EMG) and an electroencephalogram (EEG) also may be performed. These tests are used to monitor electrical activity within the body and can help detect nerve and muscle disorders. EMG involves placing electrodes on the skin (surface EMG) or needles into the muscle (intramuscular EMG) to record electrical activity of the muscle. In an EEG, electrodes are attached to the scalp and connected to a machine that records electrical impulses in the brain.

Muscle biopsy: A muscle biopsy may also be performed to distinguish between nerve and muscle disorders. This procedure, which is performed under local anesthesia, involves making a small incision and removing a sample of muscle for microscopic evaluation to determine if the muscle tissue is being damaged. Following the procedure, patients may experience minor pain and bruising at the biopsy site for about one week.

Evoked potential tests: Evoked potentials are electrical signals generated by the nervous system in response to stimuli. Evoked potential tests (including somatosensory evoked potentials, visual evoked potentials, and brainstem auditory evoked potentials) are performed to evaluate sensory, visual, and auditory functions and detect slowed nerve impulse conduction caused by demyelination. In these tests, nerves responsible for each type of function are stimulated electronically and responses are recorded using electrodes placed over the CNS (brain and spine) and peripheral nerves (including the median nerve in the wrist and the peroneal nerve in the knee).