Table 1:

Clinical presentation of acute flaccid myelitis

	Estimated frequency
Age <21 years	80–90%
Prodromal fever or viral illness	85–95%
Neurological onset to nadir <10 days	100%
Headache or neck stiffness at onset	12–60%
Asymmetric onset of weakness	65–95%
Limb weakness	85–95%
Upper limb weakness	60–85%
Flaccidity or hyporeflexia of affected limbs	95–100%
Neck, face, extraocular, or bulbar weakness	20–60%
Trunk weakness	30–70%
Requirement for mechanical ventilation	10–40%
Bladder or bowel dysfunction	5–40%
Non-specific sensory symptoms (eg, paresthesia)	10–20%
Cardiovascular autonomic dysfunction	<10%
CSF pleocytosis (with testing <5 days after	85–95%
Grey-matter predominant spinal cord lesion(s) on MRI	95–100%
Brainstem lesion(s) on MRI	35–45%
Cerebral deep grey matter lesion(s) on MRI	<5%

CSF=cerebrospinal fluid.