Various pathophysiological mechanisms of Todd’s palsy revealed by 1.5-Tesla magnetic resonance imaging including arterial spin labeling perfusion imaging during neurological emergencies

Although Todd’s palsy is a well-known pathological condition, its pathophysiological mechanisms remain unclear. We evaluated two patients using magnetic resonance imaging (MRI), including 1.5-Tesla pseudo-continuous arterial spin labeling (ASL) perfusion imaging, to observe ictal hyperperfusion and associated hemodynamic changes in the peri-rolandic region. In Patient 1, marked ictal ASL hyperperfusion and cytotoxic edema were observed in the interhemispheric cortex of the right peri-rolandic region. Persistence of this edema was associated with left leg palsy lasting 25 days. In Patient 2, prominent ictal ASL hyperperfusion was observed in the right parieto-occipito-temporal lobes without direct involvement of the precentral gyrus. The palsy and MRI findings improved within one day and on Day 4, respectively. We speculate the palsy was caused by transient hypoperfusion of the precentral gyrus, resulting from blood stealing by ictal hyperperfusion. Todd’s palsy may involve various pathophysiological conditions, and combined use of MRI including ASL and electroencephalography is useful in diagnosing this pathophysiology.