Diagnosing NMOSD
The most common symptoms of neuromyelitis optica spectrum disorder (NMOSD) are changes in vision, including blindness, weakness or paralysis in arms and legs, nausea, uncontrollable vomiting, and hiccups.1–3
These symptoms often appear in the form of an attack, evolving over a period of days.3 Patients may also often experience nerve and eye pain.2,3 Some of these symptoms may also occur in other diseases, in particular multiple sclerosisAn autoimmune disease that affects the brain and spinal cord causing a wide range of symptoms, including problems with vision, arm or leg movement, sensation and balance (MS).1,3 This is why healthcare professionals consider the combination of all symptoms – including previous symptoms and illnesses – and numerous test results when making a diagnosis. They need to rule out other disorders with similar symptoms and ensure a correct diagnosis of NMOSD.4,5
Most individuals with NMOSD have autoantibodies Antibodies produced by the immune system that mistakenly target and attack the body’s own tissues or cells in their blood against a common protein called aquaporin-4 (AQP4)A protein that acts as channels for water and is most abundant in the brain, spinal cord and the optic nerve .3,5,6 These autoantibodies – specific proteins that the body’s immune systemThe body’s defence system that protects against disease and infection (e.g. bacteria and viruses) produces – do not appear in healthy individuals or in individuals with other diseases.3,6 Therefore, if a patient experiences an attack with one of the symptoms of the disease and also tests positive for AQP4 autoantibodies, the diagnosis of NMOSD is certain.3,7
Another key test for diagnosing NMOSD is magnetic resonance imaging (MRI).5 The MRI is particularly important to help diagnose the disease in patients who test negative for AQP4 antibodies, or when the antibody status is unknown.7
When healthcare professionals suspect NMOSD, they review the patient’s symptoms and medical history and perform physical and neurological examinations.5 They also conduct blood tests – in particular to test for AQP4 antibodies in the blood – and MRI scans of the brain and spinal cord.5 Occasionally a spinal tap (read more below) may be performed to confirm NMOSD in patients with negative or unknown AQP4 antibody test results.5,7
A healthcare professional conducts a physical examination to collect basic information about the patient. This may include measurements of weight, blood pressure, heart rate and temperature, examination of the eyes and ears, and listening to the heart and lungs.8 The patients may also be examined for potential bladder, bowel and sexual dysfunction.5
Some possibilities of what to expect during a physical examination:
- Measurements of weight, blood pressure, heart rate and temperature8
- Examination of the eyes, tapping the body using a reflex hammer and listening to the sounds of the heart and lungs8
During a neurological examination, specialists will evaluate how well the nervous system functions by measuring muscle strength and coordination, checking for sensation and numbness, and assessing memory, vision, speech and thinking capabilities.4,5 Pain may also be assessed.5
Some possibilities of what to expect during neurological examinations:
- Performing certain mental and memory tasks such as remembering items4
- Various tests to examine muscle strength, coordination and sensation4
- To test how the brain responds to stimuli of different kinds – like sound, sight or touch – a stimuli response test may be done. For this test, harmless wires are attached to the scalp and different areas of the body to record the brain’s response to the stimuli4
- An eye exam may be performed by an eye doctor4
To ensure a correct diagnosis for NMOSD, a blood test is required to detect autoantibodies against AQP4.7 A positive result helps differentiate NMOSD from other diseases with similar symptoms because most patients with NMOSD (more than 70%) have AQP4 autoantibodies.3,9
What to expect during blood tests:
- Insertion of a needle into a vein to draw blood
Did you know?
MRI is a painless medical imaging test that uses a large magnet to produce detailed images of the insides of the human body. During the procedure, patients lie on a motorised bed that moves inside a large tube – the MRI scanner. Although MRI is not intrusive, it's worth noting that the scanner makes loud noises when in use.10
MRI scans of the central nervous system (the brain and the spinal cord) play an important role in distinguishing NMOSD from other diseases with similar symptoms.5,7 When healthcare professionals review these scans, they can see specific patterns or lesions in the brain, the optic (or eye) nerve and the spinal cord that are specific to NMOSD and lead to correct diagnosis.7,11
Some possibilities of what to expect during an MRI:
- Possible injection of a dye (so called contrast agent) into the blood10
- Laying on a flat motorised bed as it moves inside an MRI scanner10
Did you know?
A spinal tap, also called lumbar puncture, involves inserting a thin needle into the lower back (i.e. the lumbar region) to remove a small amount of the cerebrospinal fluid (CSF), which is the fluid that surrounds the brain and spinal cord.4 The procedure usually involves a local anaesthetic before the needle is inserted.12What to expect during a spinal tap:
- Insertion of a needle into the lower back to remove fluid4,12
After undergoing testing, patients will need to discuss the results of their diagnostic tests as well as next steps with their healthcare professionals.