, but have led to some uncertainty and confusion as well.
At the2020 CNS-ICNA Conjoint Meeting, held virtually this year, presenters discussed some of the challenges of differential diagnosis and treatment choice in pediatric NMOSD, which is easily confused with multiple sclerosis.
NMOSD used to be considered a monophasic disease restricted to the optic nerve and spinal cord, but is now known to affect other regions of the central nervous system and to relapse in some patients.
Diagnosis
The disease is often mediated by antibodies to the aquaporin-4 (AQP-4) water channel, but about 30% of adult patients lack the antibody, and AQP-4 seronegativity is more common in the pediatric population. Another common antibody found in 40%–50% of children with NMOSD targets myelin oligodendrocyte glycoprotein (MOG).
It is important to be aware that false negatives can occur in serology assays, and false positives are common, particularly in ELISA assays, Silvia N. Tenembaum, MD, said during her presentation. For those reasons, serology is not enough for a diagnosis. “Patients should also have compatible symptoms and MRI findings,” said Dr. Tenembaum, director of the pediatric neuroimmunology program at National Pediatric Hospital in Buenos Aires.
According to international consensus criteria, to be diagnosed with NMOSD, AQP-4 seropositive patients should also have at least one core clinical symptom: optic neuritis, acute myelitis, area postrema syndrome, other acute brainstem syndrome, symptomatic narcolepsy or acute diencephalic clinical syndrome, or symptomatic cerebral syndrome. AQP-4 seronegative patients or with unknown status should have at least two core symptoms, one of which must be optic neuritis, acute myelitis, or area postrema syndrome. Both conventional MRI and advanced new techniques are important for achieving differential diagnosis.
The most common symptom in children is optic neuritis, which occurs in 50%-70% of patients. Cerebral syndromes with or without encephalopathy and large tumefactive white matter lesions are also common, according to Dr. Tenembaum.
There are many conditions that mimic the spinal cord and optic nerve symptoms of NMOSD, which must be ruled out. One example is optic myelopathy and vision loss from late-onset biotinylase deficiency. It is critical to rule that out because it is treatable with supplements. Optic neuropathy, papillitis, and papilledema can also resemble NMOSD.
It is critical to achieve an early diagnosis of NMOSD in children, because some MS drugs can worsen NMOSD, according to Thaís Armangue, MD, PhD, head of neuroimmunology at SJD Barcelona Children’s Hospital, who also presented at the session. She pointed out that the MOG antibody, while common in children, is also associated with many demyelinating diseases. Some 50%-60% of children with acute disseminated encephalomyelitis (ADEM) have high titers of MOG antibodies. Although early studies suggested that persistent anti-MOG antibodies were associated with risk of developing MS, more recent studies show it predicts a non-MS disease course, particularly at titers greater than 1:1280, according to Dr. Tenembaum. Persistent anti-MOG antibodies are also associated with relapsing disease, but it is associated with other syndromes besides NMOSD. “The probability is that [MOG antibodies are] useful, but they cannot guide chronic immunotherapy, because even monophasic patients can last maybe 12 months before they become MOG negative, and we cannot wait so many months” to determine treatment course, said Dr. Tenembaum.
For monophasic ADEM or NMOSD, there is no need for chronic treatment. But children with MS and recurrent NMOSD require early chronic immunotherapy because specific therapies have been shown to improve prognosis.