Lateralization of cerebral blood flow in juvenile absence seizures

Vascular topology and blood flow are acutely impacted by experimental febrile status epilepticus

Febrile status epilepticus (FSE) is an important risk factor for temporal lobe epilepsy and early identification of those at high risk for epilepsy is vital. In a rat model of FSE, we identified an acute (2 hrs) novel MRI signal where reduced T2 relaxation values in the basolateral amygdala (BLA) predicted epilepsy in adulthood; this T2 signal remains incompletely understood and we hypothesized that it may be influenced by vascular topology. Experimental FSE induced in rat pups reduced blood vessel density of the cortical vasculature in a lateralized manner at 2 hrs post FSE. Middle cerebral artery (MCA) exhibited abnormal topology in FSE pups but not in controls. In the BLA, significant vessel junction reductions and decreased vessel diameter were observed, together with a strong trend for reduced vessel length. Perfusion weighted MRI (PWI) was acutely increased cerebral blood flow (CBF) in cortex, amygdala and hippocampus of FSE pups that correlated to decreased T2 relaxation values compared to controls. This is consistent with increased levels of deoxyhemoglobin associated with increased metabolic demand. In summary, FSE acutely modifies vascular topological and CBF in cortex and BLA that may underlie acute MRI signal changes that predict progression to future epilepsy.

Patterns of postictal cerebral perfusion in idiopathic generalized epilepsy: a multi-delay multi-parametric arterial spin labelling perfusion MRI study

The cerebral haemodynamic status of idiopathic generalized epilepsy (IGE) is a very complicated process. Little attention has been paid to cerebral blood flow (CBF) alterations in IGE detected by arterial spin labelling (ASL) perfusion magnetic resonance imaging (MRI). However, the selection of an optimal delay time is difficult for single-delay ASL. Multi-delay multi-parametric ASL perfusion MRI overcomes the limitations of single-delay ASL. We applied multi-delay multi-parametric ASL perfusion MRI to investigate the patterns of postictal cerebral perfusion in IGE patients with absence seizures. A total of 21 IGE patients with absence seizures and 24 healthy control subjects were enrolled. IGE patients exhibited prolonged arterial transit time (ATT) in the left superior temporal gyrus. The mean CBF of IGE patients was significantly increased in the left middle temporal gyrus, left parahippocampal gyrus and left fusiform gyrus. Prolonged ATT in the left superior temporal gyrus was negatively correlated with the age at onset in IGE patients. This study demonstrated that cortical dysfunction in the temporal lobe and fusiform gyrus may be related to epileptic activity in IGE patients with absence seizures. This information can play an important role in elucidating the pathophysiological mechanism of IGE from a cerebral haemodynamic perspective.

Real-time TCD-vEEG monitoring for neurovascular coupling in epilepsy

PURPOSE

Recently, a novel multi-model monitor has been available, which integrates real-time signals of transcranial Doppler (TCD) and video-EEG (vEEG) into one workstation. We sought to test the feasibility of this device in detecting neurovascular coupling in patients with epilepsy.

METHOD

Cerebral blood flow velocity (CBFV) of bilateral middle cerebral arteries and vEEG during seizure episodes were recorded simultaneously in 12 patients (age 17-58 years) with partial epilepsies. The correlations between vEEG and CBFV findings were analyzed.

RESULTS

Eleven seizure episodes were detected in 5 patients. Of them, bilateral CBFV increase with interhemispheric asymmetry was observed in 4 seizure episodes of 3 patients. EEG abnormalities preceded CBFV increase by 1-3s at the onset of a seizure. In a patient with bilateral middle cerebral artery stenosis, no apparent CBFV changes were detected during 2 of 3 seizure episodes. Another patient with previous frontal hemorrhage displayed CBFV increase without interhemispheric asymmetry during 4 seizure episodes.

CONCLUSION

It is feasible to evaluate neurovascular coupling with good temporal correlation in patients with frequent seizure episodes by real-time TCD-vEEG monitoring.