ACUTE DISSEMINATED ENCEPHALOMYELITIS
Acute disseminated encephalomyelitis (ADEM) is a central nervous system (CNS) inflammatory syndrome characterized by rapid-onset encephalopathy along with multifocal neurologic deficits. While ADEM is frequently thought to occur in the context of preceding illness, the specific microbial trigger is rarely identified, and the pathophysiology of the disorder is thought to be immune-mediated.1 Magnetic resonance imaging (MRI) of the brain typically demonstrates large, diffuse, and poorly demarcated T2-hyperintense lesions predominantly affecting white matter. These lesions are apparent during the initial acute to subacute phase (typically 3 months, by definition) and can resolve in the weeks following. Further clinical workup includes lumbar puncture (LP), which is typically remarkable for cerebrospinal fluid (CSF) pleocytosis with lymphocytic predominance and elevated protein. Additional findings may include elevated immunoglobulin (Ig) G index, but oligoclonal bands are rarely positive in ADEM.
Although ADEM is typically monophasic, a smaller subset of children can experience multiphasic ADEM (MDEM) with another attack occurring 3 or more months following the initial attack.2,3 In cases of MDEM, the diagnosis should be considered thoughtfully as ADEM may be the initial presentation of neuromyelitis optica spectrum disorder (NMO-SD), or rarely, ADEM is followed by a non-ADEM event and meeting criteria for a diagnosis of multiple sclerosis (MS). ADEM may also be followed by optic neuritis (ADEM-ON), which more recently has been seen to have high association with myelin oligodendrocyte glycoprotein (MOG) antibodies.
Initial treatment for ADEM is typically intravenous (IV) methylprednisolone. In severe cases, IV immunoglobulin (IVIG) or plasma exchange should be considered, especially in patients requiring intensive care. The majority of patients have good recovery, but there can be long-standing neuropsychological and neurobehavioral symptoms.4
CLINICALLY ISOLATED SYNDROME
Clinically isolated syndrome (CIS) is defined as an isolated occurrence of acute CNS inflammatory demyelination without encephalopathy. Approximately 30% to 70% of patients with CIS can go on to develop MS, with increased risk of progression in female patients, patients over 10 years of age, and patients with multifocal symptoms at onset, presence and appearance of brain lesions on MRI, and presence of oligoclonal bands.5
The clinical presentation of CIS varies depending on location of demyelination in the CNS. Most commonly in CIS, demyelination involves the optic nerves and the spinal cord. If a diagnosis of CIS is being considered, then workup for underlying neuroimmune etiologies such as NMO-SD and MOG antibody-associated disease (MOGAD), in addition to MS, should be considered.
Inflammation of the optic nerves, or optic neuritis (ON), can lead to an acute presentation typically with acute, unilateral or bilateral vision loss and retro-orbital pain that worsens with eye movement. Visual field perimetry, optical coherence tomography, MRI, and serologic and CSF fluid will be helpful to make the correct diagnosis as well as to monitor disease progression and response to ...