Acute disseminated encephalomyelitis differential diagnosis
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No one test established the diagnosis of ADEM. Supporting features include an appropriate viral or vaccination history, an appropriate acute neurologic illness, and consistent features on CNS imaging.
- Acute infectious encephalitis
- Herpes simplex virus
- Most common and treatable form of infectious encephalitis
- Usually due to Human herpesvirus 1 (HSV-1), though HSV-2 accounts for 5%
- One-third occur during primary infection
- Most commonly involves the temporal and frontal lobes; speech disorders, bizarre behaviors, and gustatory and olfactory hallucinations are common
- Fever present in 90%. Altered state of consciousness present in most.
- Associated with scattered hemorrhages, CSF red cells
- Treated with acyclovir 10 mg/kg IV q8h; reduces mortality and morbidity if started early enough. Untreated mortality is 70%.
- Epstein-Barr virus
- Lyme disease
- Viruses transmitted by arthropods, mosquitos and tick
- Most common in the summer and fall (in contrast to winter and spring presentations of measles, mumps and VZV).
- Present with:
- Gastrointestinal symptoms
- Neurologic disease typically presents day 2 or 3
- CSF typically shows elevated protein, a few hundred white blood cells, normal glucose
- No specific treatment
- Eastern equine encephalitis
- Presents with flu-like symptoms, fever, headache, vomiting, seizures, and progressive neurologic disease
- Seen mostly along the east coast of the U.S.
- Mosquito and bird vectors
- Most common in those <15 or >55 years of age
- Most virulent of arborviruses: 70% mortality
- Western equine encephalitis
- Mosquito vector
- Young children
- Often asymptomatic
- Western U.S.
- California encephalitis
- Most common in school-age children
- Mosquito vector
- Gastrointestinal (GI) symptoms common
- St. Louis encephalitis
- Wild bird reservoir
- Wild bird – mosquito cycle
- Throughout U.S.
- Japanese encephalitis
- Flavivirus endemic in Southeast Asia from India to Japan
- Mosquito transmission
- Vaccine available
- Mycoplasma infection
- Cytomegalovirus infection
- Mumps encephalitis
- CNS features present in ~1% of cases
- Not all patients have parotitis
- Most common in winter and spring
- Most patients recover completely, but some patients left with deafness, seizure, and mental retardation
- Confirmed via culture or serology
- Bacterial meningoencephalitis
- Other infectious encephalitidies
- Herpes simplex virus
- Acute multiple sclerosis (MS)
- MS may not be possible to exclude, and to some extent depends upon the natural history of the patient’s disease; MS is typically a chronic disease with a recurrent or progressive course, and ADEM is usually an acute monophasic disease. Both diseases are characterized by demyelination; it is acute in ADEM, and sustained or progressive in MS. It is sometimes best to refer to the illness as an “acute demyelinating disease”, until the disease course declares itself.
- Simultaneous optic nerve, brain and spinal cord involvement, as well as meningismus, drowsiness, coma and seizures, are features suggestive of ADEM instead of MS.
- Optic nerve involvement is typically bilateral in ADEM, and unilateral in MS. Transverse myelopathy is usually complete in ADEM, and partial in MS.
- CSF protein is usually elevated in ADEM, and is often normal in MS. CSF lymphocyte counts >50, and CSF polys are also uncommon in MS.
- In ADEM in contrast to MS, most MRI lesions enhance with gadolinium, suggestive that all lesions are active, and that the disease is therefore monophasic.
- Hypoxic encephalopathy
- Cerebrovascular disease
- CNS vasculitis
- Lupus cerebritis
- Toxin effect
- Acute toxic hepatoencephalopathy – Reye’s syndrome
- Acute liver and CNS disease in children under 15 years of age, characterized by progressive liver and CNS disease, commonly in association with the use of salicylates.
- Often follows a viral infection, especially chickenpox or influenza.
- Patients often present with vomiting and progressive neurologic disease. Hypoglycemia is common. Jaundice is usually not a prominent feature.
- The liver is enlarged and evidence of liver disease includes elevated transaminases, prothrombin time, and ammonia, hypoglycemia, and metabolic acidosis. Cerebral edema and brain neuronal degeneration occurs.
- Mitochondria dysfunction occurs in the liver, brain and muscle. Liver cells show microvacuolization, as do renal tubules.
- Mortality approaches 50%.