Devic’s disease is an inflammatory disease of the central nervous system, which mainly affects the myelin sheath covering the optic nerve and spinal cord. Devic’s disease resembles multiple sclerosis, but is a distinct clinical entity.
Devic’s disease is characterized by attacks of bilateral acute optic neuritis. This maybe followed by severe transverse myelopathy (acute inflammation of the spinal cord), either at the same time along with the attacks of optic neuritis or after a period of days to months. The course of Devic’s disease maybe monophasic or relapsing.
- Monophasic: the patients experience either unilateral or bilateral optic neuritis or a single episode of myelitis.
- Relapsing: in this course the patients continue to have a discrete exacerbation of optic neuritis and/or myelitis.
Neuromyelitis optica usually affects young adults, but also has been reported in infants. The ratio of men to women may differ according to the course of the disease. Most reports suggest a ratio of approximately 1.4 to 1.8. Neuromyelitis optica (NMO) is more common in African Americans, Japanese and other pacific islanders.
Etiology is unknown but NMO is believed to be an autoimmune disease associated with autoantibodies to aquaporin-4.
Devic’s syndrome consists of one or more episodes of optic neuritis in combination with myelitis.
- A viral prodrome precedes the onset of the disease in 30-50% of the cases. The prodrome consists of headache, fever, fatigue, myalgias and respiratory or gastrointestinal complaints.
- Rapid, bilateral and occasionally, complete visual loss occurs.
- Acute transverse myelitis, defined as, severe bilateral inflammatory spinal cord injury with neurological dysfunction worsening over several hours to days and involving sensory, motor and sphincter function is typical presentation of NMO. The acute tranverse myelitis may present with the following symptoms:
- back and girdle pain
- paresthesia and weakness in lower limbs
- weakness rapidly evolves to paraplegia and or quadriplegia often causing complete sensory loss caudal to the lesion and a flaccid bladder.
- The acute lesion usually traverses at least three contiguous vertebral segments of the spinal cord and may result in a spinal shock with flaccid weakness, absent deep tendon reflexes and mute plantar responses.
- Other symptoms include vertigo, facial numbness, nystagmus, headache and postural tremor.
- MRI of the brain and spinal cord: during acute optic neuritis the MRI may demonstrate a swelling of the affected optic nerve or the chiasm. During acute myelitis the affected region is expanded and swollen. Heterogeneous T2 signal within the lesion may suggest cavitations and necrosis. Typically, the lesions are in the central part of the cord.
- Cerebrospinal fluid (CSF) analysis: occasionally patients may have a pleocytosis around the time of acute myelitis exacerbation. The CSF leukocyte differential may reveal the presence of lymphocytes or neutrophils.
- Serologic Testing: anti-NMO IgG and aquaporin-4 antibodies allow diagnosis of NMO
- Neurophysiologic tests: visual evoked potentials may occasionally detect sub clinical optic nerve lesions.
The mainstay of therapy is the treatment of acute attacks, prevention of medical complications and rehabilitation.
- Intravenous corticosteroids are given during exacerbations of NMO.
- Plasmapheresis is used as the second-line treatment.
- Long-term maintenance treatments are immunosuppressive drugs (azathioprine or mycophenolate mofetil), combined with corticosteroids in some patients, or rituximab therapy.
- Prevention of complications is important. Acute cervical cord attack may cause respiratory failure. Patients at risk of this complication may require intensive care unit observation and evaluation of respiratory and bulbar status.
- Medical measures to prevent thromboembolic complications, aspiration pneumonia, decubiti and urinary tract infections are also required.
The prognosis is variable: patients may recover completely from individual attacks, but residual neurological deficits are common and sometimes severe.
- Unrecognized or untreated, up to 30% of patients may die in the first 5 years of their illness of an attack of severe myelitis leading to respiratory failure.
- A high proportion of patients will become legally blind in one or both eyes and/or have substantial residual paraparesis.