Hyperperfusion in the thalamus on arterial spin labelling indicates non-convulsive status epilepticus

Abstract

Non-convulsive status epilepticus describes the syndrome of unexplained impaired consciousness in critically ill patients. Non-convulsive status epilepticus is very likely to lead to delayed diagnosis and poor outcomes because of the absence of convulsive symptoms. EEG is essential for the diagnosis of non-convulsive status epilepticus to establish the association between periodic discharges and rhythmic delta activity in addition to ictal epileptiform discharges according to the Salzburg criteria. Arterial spin labelling, a type of perfusion MRI, has been applied for rapid and non-invasive evaluation of the ictal state. Ictal cerebral cortical hyperperfusion is the most common finding to demonstrate focal onset seizures. Hyperperfusion of the thalamus on single photon emission computed tomography was found in patients with impaired awareness seizures. We hypothesized that thalamocortical hyperperfusion on arterial spin labelling identifies non-convulsive status epilepticus and such thalamic hyperperfusion specifically associates with periodic/rhythmic discharges producing impaired consciousness without convulsion. We identified 27 patients (17 females; age, 39–91 years) who underwent both arterial spin labelling and EEG within 24 h of suspected non-convulsive status epilepticus. We analysed 28 episodes of suspected non-convulsive status epilepticus and compared hyperperfusion on arterial spin labelling with periodic/rhythmic discharges. We evaluated 21 episodes as a positive diagnosis of non-convulsive status epilepticus according to the Salzburg criteria. We identified periodic discharges in 15 (12 lateralized and 3 bilateral independent) episodes and rhythmic delta activity in 13 (10 lateralized, 1 bilateral independent and 2 generalized) episodes. Arterial spin labelling showed thalamic hyperperfusion in 16 (11 unilateral and 5 bilateral) episodes and cerebral cortical hyperperfusion in 24 (20 unilateral and 4 bilateral) episodes. Thalamic hyperperfusion was significantly associated with non-convulsive status epilepticus (P = 0.0007; sensitivity, 76.2%; specificity, 100%), periodic discharges (P < 0.0001; 93.3%; 84.6%), and rhythmic delta activity (P = 0.0006; 92.3%; 73.3%). Cerebral cortical hyperperfusion was significantly associated with non-convulsive status epilepticus (P = 0.0017; 100%; 57.1%) and periodic discharges (P = 0.0349; 100%; 30.8%), but not with rhythmic delta activity. Thalamocortical hyperperfusion could be a new biomarker of non-convulsive status epilepticus according to the Salzburg criteria in critically ill patients. Specific thalamic hyperexcitability might modulate the periodic discharges and rhythmic delta activity associated with non-convulsive status epilepticus. Impaired consciousness without convulsions could be caused by predominant thalamic hyperperfusion together with cortical hyperperfusion but without ictal epileptiform discharges.

Epileptic seizures in the emergency room: clinical and electroencephalographic findings associated with brain perfusion patterns on computed tomography

“…In the first place, no single isolated seizure episode, even accompanied by cortical cerebral hyperperfusion, was associated to increased perfusion in thalamus. Moreover, as reported first on arterial spin labeling sequence on MRI by Ohtomo et al [24] and recently on pCT by Giovannini et al [22], thalamic hyperperfusion, although not sensitive, is highly specific of continuous sustained ictal activity compatible with SE on EEG. Therefore, the present study suggests that early pCT findings, together with other factors, such as clinical presentation [25], could serve as an adjunctive diagnostic tool for NCSE risk stratification; thus, probably avoiding delayed management in acute settings, especially if accompanied by the highly specific feature of thalamic hyperperfusion.…”

Usefulness of arterial spin labeling perfusion as an initial evaluation of status epilepticus

“…In a recent study of 28 NCSE patients, thalamic hyperperfusion were confirmed in 57% of cases and showed particularly high accuracy in diagnosing NCSE 12 . In the same study, cortical hyperperfusion was observed in 86%.…”

“…In comparison with self-limiting seizures, ASL showed a modest degree of specificity (58.7%) for SE. Additionally in some clinical practice such as NCSE or subtle SE, MRI might be taken before EEG, and abnormal findings in MRI can lead to more immediate management taking advantage of high sensitivity of ASL, which can help shorten the time to EEG or administer anti-epileptic drugs 12 . Considering the poor prognosis of refractory SE, appropriate and timely treatment can help improve the prognosis and reduce mortality.…”

“…We measured values of regional cerebral blood flow from ASL according to the Ohtomo S et al 12 . Briefly, regions of interest (ROIs) were drawn on equivalent 10 axial planes of the ASL images.…”

“…Moreover, there was a tight topographical relationship between the localization of ictal ASL findings and the epileptogenic lesion corresponding to EEG abnormalities. In addition, a recent study using ASL images showed that thalamic hyperperfusion in 28 patients with suspected NCSE was particularly correlated with NCSE diagnosis and rhythmic activities of EEG with high accuracy 12 . Thus, ictal hyperperfusion is useful for the diagnosis and localization in SE, and ASL can be a sensitive perfusion MRI technique for detecting ictal changes.…”