What are the earliest signs of acute disseminated encephalomyelitis (ADEM)?

Olivia

Rockey

@olivia The first signs of ADEM usually include abrupt onset encephalopathy (alteration in consciousness or behavioral change unexplained by fever, systemic illness or postictal symptoms. Rapid-onset encephalopathy is typically associated with multifocal neurologic symptoms.

In most cases, the clinical course is rapidly progressive and typically develops over hours to maximum deficits within days (mean of 4.5 days). [85] A minority of cases show continued deterioration of function for periods as long as 4 weeks.

Strictly speaking, encephalopathy, unexplained by fever, should be present for a diagnosis of ADEM, though it may not be the presenting sign. A single institution follow-up study (at least 5.5 y for each individual) of 52 young individuals (age range 10 mo to 19 y) who presented with their first bout of an acute central nervous system demyelinating disease included 26 children ultimately diagnosed with MS and 24 diagnosed with ADEM. Encephalopathy was the presenting sign in 42% of those with a follow-up diagnosis of ADEM but none of the individuals with a follow-up diagnosis of MS.

Convulsive seizures occur around the onset of ADEM in as many as 35% of cases.

Meningismus may be present and has been reported in up to 30% of cases.

Although almost any portion of the CNS may be clinically involved, certain systems appear to be particularly prone to dysfunction; thus, the descending white matter motor tracts, optic nerves, and spinal cord are particularly commonly involved.

ADEM-associated optic neuritis is typically bilateral, although the onset in a second eye may follow onset in the first by days to months. Bilaterality may provide a degree of reassurance with regard to MS risk as optic neuritis in MS is frequently unilateral. Visual evoked responses may discern abnormalities in a second eye before clinical deterioration in vision is discernible.

A wide variety of cranial nerve abnormalities may occur in addition to optic nerve disease.

Long tract signs (eg, clonus, increased muscle stretch reflexes, upgoing toes) are present early in as many as 85% of cases.

In some instances, reflexes may be lost at the onset. When this is caused by transverse myelitis, the evolution of disease after spinal shock replaces absent reflexes with increased muscle stretch reflexes within a few days or more. A small number of cases manifest loss of reflexes as a sign of associated peripheral nerve disease with ADEM, a condition termed EMRN. Some of these EMRN cases are associated with evidence for acute infection with Epstein-Barr virus.

Weakness may be hemiparetic, double hemiparetic, diparetic, or generalized and symmetric. Fairly symmetric leg weakness is seen in many cases of ADEM-related transverse myelitis with associated abnormalities of bowel and bladder function.