Transverse Myelitis and Neuromyelitis Optica
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Direct answer
Transverse myelitis is an inflammatory myelopathy producing motor, sensory and sphincter deficits from one level downward, and neuromyelitis optica spectrum disorder is the aquaporin-4 antibody-driven variant that adds optic neuritis. Lesions in neuromyelitis optica are typically longitudinally extensive, spanning three or more vertebral segments on MRI. Acute attacks are treated with high-dose intravenous methylprednisolone, while relapse prevention uses immunosuppressants rather than the drugs used in multiple sclerosis.
What you must remember
- Transverse myelitis: cord inflammation over a short segment, causing paraparesis or quadriparesis, a sensory level and bladder dysfunction over hours to days.
- Longitudinally extensive lesion: involvement of three or more contiguous segments on MRI, favouring neuromyelitis optica or MOG antibody disease over multiple sclerosis.
- AQP4-IgG: antibody against aquaporin-4 on astrocyte foot processes, found in most patients with classic neuromyelitis optica spectrum disorder.
- MS contrast: cord lesions shorter than two segments, peripheral in position, with periventricular brain plaques and oligoclonal bands in CSF.
- Area postrema syndrome: intractable hiccups, nausea and vomiting, a characteristic brainstem feature of neuromyelitis optica.
- Acute treatment: intravenous methylprednisolone, commonly 1 g daily for three to five days, with plasma exchange when steroid-refractory.
- Relapse prevention: azathioprine, mycophenolate or rituximab are common options; eculizumab, inebilizumab and satralizumab are targeted agents for AQP4-positive disease.
A diagnostic route from sudden paraplegia to a cord diagnosis
A 28-year-old woman develops two days of leg weakness, urinary retention and a sensory level at T6.
- Exclude compression: The first step is an urgent MRI to rule out a compressive myelopathy, because a surgical lesion cannot wait for an antibody result.
- Measure the lesion: The MRI is read for lesion length, and a lesion spanning three or more segments with central (grey matter) involvement points away from multiple sclerosis.
- Examine CSF and antibodies: CSF is checked for pleocytosis, raised protein and oligoclonal bands, while serum AQP4-IgG and MOG-IgG are sent by cell-based assays.
- Search for systemic clues: ANA and anti-Ro for Sjogren syndrome or lupus, HIV and syphilis serology, and HTLV-1 testing are sent, the last mattering in India where it is endemic in parts of the country.
- Consider mimics: Spinal cord infarction and sarcoidosis are also considered before a diagnosis is settled.
- Treat the inflammation: If infection and compression are excluded and the lesion is inflammatory, intravenous methylprednisolone is started, with plasma exchange considered for a poor steroid response.
Bladder care and rehabilitation run in parallel throughout this route.
Where the MS and NMO labels get confused
Optic neuritis plus myelitis pulls many students towards multiple sclerosis, but the examiner expects lesion length and antibody status to decide.
- Trap: giving interferon beta because the picture looks like multiple sclerosis Correct: interferon beta is useful in relapsing multiple sclerosis but may worsen neuromyelitis optica, so AQP4-positive patients should not be started on it.
- Trap: excluding neuromyelitis optica because the brain MRI is normal Correct: the brain can be spared early in the disease, so a normal brain MRI does not exclude it.
- Trap: treating MOG antibody disease as AQP4 disease Correct: MOG disease gives bilateral optic neuritis and papilloedema with a tendency to respond well to steroids, but a different relapse pattern, so testing both antibodies avoids a wrong label and a wrong long-term drug.
Frequently asked questions
Which MRI feature favours neuromyelitis optica over multiple sclerosis?
A longitudinally extensive spinal cord lesion spanning three or more vertebral segments favours neuromyelitis optica spectrum disorder over multiple sclerosis. Multiple sclerosis cord lesions are usually shorter than two segments, while neuromyelitis optica often has a normal brain MRI early on.
Why should interferon beta be avoided in neuromyelitis optica?
Interferon beta is avoided in neuromyelitis optica spectrum disorder because it may worsen the disease course, even though it is an established treatment for relapsing multiple sclerosis. Other multiple sclerosis drugs also need specialist review before use in AQP4-positive patients.
What is the first-line acute treatment for transverse myelitis?
Acute transverse myelitis is treated with high-dose intravenous methylprednisolone, commonly 1 g daily for three to five days, once infection and compressive causes are excluded. Plasma exchange is considered when the response to steroids is poor, and rehabilitation continues alongside.
What does AQP4 antibody testing add in transverse myelitis?
Serum aquaporin-4 IgG testing confirms neuromyelitis optica spectrum disorder in a patient with transverse myelitis. A positive result supports long-term immunosuppression, while a negative result still calls for MOG antibody testing before the illness is labelled multiple sclerosis.