HEMICONVULSION-HEMIPLEGIA-EPILEPSY SYNDROME (HHE)

	Mandatory	Alerts	Exclusionary
Seizures	Acute stage: febrile, hemiclonic status epilepticus with immediate permanent hemiparesis Chronic stage: focal seizures arising in the same hemisphere		Late development of hemiparesis after focal seizure onset (consider Rasmussen syndrome)
EEG	Background slowing in the affected hemisphere Focal/multifocal epileptiform abnormalities in the affected hemisphere (chronic phase)
Age at onset		>4 years	>6 years
Development at onset		Prior intellectual impairment
Neurological exam		Prior abnormal exam Facial angioma (suggests Sturge-Weber syndrome syndrome)
Imaging	Acute stage: diffuse hemispheric subcortical T2 hyperintensity and restricted diffusion, often with severe edema Chronic stage: hemispheric atrophy		Other structural cause for the epilepsy
Other tests			Other cause for the epilepsy
Long-term outcome	Drug-resistant epilepsy
Are MRI or ictal EEG required for diagnosis? An MRI is required for diagnosis An ictal EEG is not required
Syndrome without laboratory confirmation: in resource-limited regions, this syndrome can be diagnosed without EEG in a person who meets all other mandatory criteria and does not meet alert or exclusionary criteria. However imaging (CT or MRI) is required to exclude other causes

NOTE Alert criteria are absent in the vast majority of patients with the syndrome, but rarely can be seen. Their presence should result in caution in diagnosing the syndrome and consideration of other conditions