Acute Disseminated Encephalomyelitis (ADEM) Clinical Features and Diagnosis

Etiology

The Centers for Disease Control and Prevention (CDC) recommends considering vaccination-related ADEM, which has been associated with vaccines against anthrax, Japanese encephalitis, yellow fever, measles, influenza, smallpox, and rabies 1, 2
Common infectious triggers for ADEM include viral infections such as measles, mumps, rubella, varicella zoster, Epstein-Barr virus, cytomegalovirus, herpes simplex, hepatitis A, influenza, and enterovirus infections 2

The American Academy of Neurology (AAN) notes that encephalopathy, ranging from confusion to coma, is a required component for ADEM diagnosis, and is often accompanied by multifocal neurologic deficits affecting various parts of the central nervous system 3
Optic neuritis, which may be bilateral, is a common neurological manifestation of ADEM 4, 5
Myelitis, often longitudinally extensive, is another frequent neurological deficit in ADEM patients 4, 6
Brainstem encephalitis, cerebellar ataxia, motor deficits, and seizures can also occur in ADEM patients 3, 5, 6

The National Institute of Neurological Disorders and Stroke (NINDS) recommends using MRI as the imaging modality of choice for ADEM diagnosis, which can reveal characteristic findings such as large, confluent T2 brain lesions and longitudinally extensive spinal cord lesions 6, 7
Lymphomonocytic pleocytosis and elevated protein levels can be found in the cerebrospinal fluid (CSF) of ADEM patients 5, 8
Perioptic enhancement during acute optic neuritis can be observed on MRI scans 4, 8

The Infectious Diseases Society of America (IDSA) notes that symptoms may flare up after tapering of oral steroids, suggesting steroid-dependence in some ADEM cases 6, 8
High-dose intravenous methylprednisolone is recommended as first-line treatment for ADEM, followed by oral corticosteroid taper over 4-6 weeks 7

Behavioral changes, such as confusion and disorientation, are common features of ADEM, occurring in 41% and 76% of cases, respectively, and speech disturbances are seen in 59% of cases 9, 10
Seizures occur in approximately one-third of patients with ADEM 9, 10
Fever is a common presenting symptom, with up to 80% of patients experiencing febrile illness 11, 12
Focal neurological deficits are present in 36-78% of ADEM cases 11, 12

Children with ADEM may present with non-specific symptoms, including feeding and respiratory difficulties 12
Confusion, irritability, or behavior changes are seen in up to 76% of pediatric ADEM cases 12

A normal Glasgow Coma Score at presentation can be seen in some patients, as it may not detect subtle behavioral changes 9, 10
Subtle presentations of ADEM may include low-grade pyrexia, speech disturbances, and behavioral changes that can be mistaken for psychiatric illness 12
The differential diagnosis for ADEM is broad and includes infectious, metabolic, vascular, neoplastic, and toxic etiologies 10, 11