This is a first study to assess the time caurse of a large series of patients with PAIC diagnosed by MRI-DWI during three consecutive years. Although the PAIC that were from the small case series have frequently been reported[3–11, 15–17], our study used a cohort design. Moreover, our cohort study of PAIC found that acute PAIC accounted for 28.4% of suddenly comas due to acute ischemic strokes and TIA, although previous studies have indicated that acute loss of consciousness accounted for 20% of embolic strokes, and 34% of TIAs. More importently, we found that the only two forms of acute PAIC events were transient and persistent.
In the present study, 30 (32.3%) patients with acute persistent coma events showed new infarcts in the paramedian thalamus/ rostral midbrain bilaterally which were identified by DWI, suggesting that these persistent coma events were caused by acute infarcts of Percheron artery ( i.e., PAICs) as the Percheron artery—a variant single thalamic penetrating artery is supply to the paramedian thalamus/rostral midbrain bilaterally.
Among of 30 persistent PAIC events, 46.7% of lesions was isolated in the paramedian thalamus/rostral midbrain bilaterally. However, 53.3% of persistent PAIC were presented with new lesions in the upper cerebellum, occipital lobe, and/or hippocampus. Though this is met the "top of the basilar" syndrome criteria, we considered that these patients had to have an unique Percheron artery. Thus, our results on DWI revealed that the artery of infarction in persistent PAIC is either at the Percheron artery or at the top of basilar artery with unique Percheron artery.
We also found that the transient PAIC were more likely to occur during three consecutive years. Although only 30.2% of DWI revealed either bilateral small lesions or unilateral lacunar lesion in the paramedian thalamus/rostral midbrain, the remaining patients should be diagnosed the transient comas with naturally recanalization of infarcts or TIA, which is considered that these ischemic events is from the most specific site of impaired consciousness—Percheron artery territory.
In the present study, 63 (67.7%) patients with acute transient PAIC awoke naturally within 24 h after the onset of coma. Moreover, our results showed that rates of awakening in patients with transient PAIC during the first 12-h time window were significantly higher than in those in patients with persistent PAIC. These findings suggest two possible interpretations. First, the natural recanalization may be impacted by the hemodynamic and fibrinolytic systems, or the undissolved emboli may be pushed into the surrounding tissue by the vascular endothelial cell holes. Second, unilateral naturally recanalization or the formation of collateral circulation may also be the mechanism of awakening.
The rates of awakening decreased over time for patients with persistent PAIC, while mortality rates increased. Regarding Percheron artery ischemic infarction with conservative treatment, previous studies have mostly shown a poor prognosis[11–13, 23], although some reports have noted a relatively better prognosis[8, 24]. However, the current study indicated that survival was improved among patients with transient PAIC, while the survival of patients with persistent PAIC showed no improvement. The lesion volumes were larger in the persistent PAIC than in the transient PAIC, which was exactly calculated by the PACS. This involves the following two important issues. First, the transient PAIC usually occurs when the patients has suffered an unilateral ischemic lesion or bilateral small ischemic lesions in the paramedian thalamus/ rostral midbrain. Second, the persistent PAIC can occur when the patients has suffered a larger ischemic lesion in the bilateral paramedian thalamus/rostral midbrain. In the persistent PAIC, blood flow did not undergo natural recanalization, there was a poor outcome, and there was a high risk of death.
In the present study, the different risk factors in patients with transient and persistent PAIC suggests that, among patients with persistent PAIC, risk factors were correlated with atrial fibrillation, increased SBP, lower GCS csores, increased NIHSS scores and ABCD2 scores, and large lesion in bilateral paramedian thalamus/rostral midbrain. However, after controlling for age and sex, the multivariate regression analysis confirmed that only increased NIHSS scores and large lesions in bilateral paramedian thalamus/rostral midbrain were the predictors of higher risk of persistent PAIC (versus transient PAIC),
The main strengths of our cohort study determined that the only two forms of acute PAIC were transient and persistent, but persistent PAIC had a marker of images, i.e., the lesions of Percheron territory infarction plus or minus related involvement of other "top of the basilar" ischemic lesions from the occipital lobe, hippocampal cortex, and cerebellum.
However, the current study is subject to several limitations, including those inherent in retrospective studies. First, the artery of Percheron infarction or emboli has demonstrated by the conventional angiography[11, 25], but in our series, only a few of patients performed MRA. However, we believe that the diagnosis of acute PAIC is mainly identified by MRI-DWI. Furthermore, even some transient PAIC did not show a positive lesion on DWI, the diagnosis of transist PAIC should be still considered, because previous study has showed that the negative DWI may not also be fully excluded an acute infarction[26, 27]. Second, the Percheron artery infarction and top of the basilar syndrome with onset seizure has been reported[28, 29], its mechanism of onset seizure may be related to the acute ischemic lesions. Although 3 transient and 7 persistent PAIC experienced sudden seizure in our series, these patients did not presented with a prior history of epilepsy, so the primary epilepticus should be excluded. In addition, here is a high prevalence zones of cerebrovascular disease, some persistent PAIC may be sent to near tertiary teaching hospital; whereas, the transient PAIC might be a neglected coma events and some patients due to quickly resolved did not be sent to hospital, Therefore, the prevalence of acute PAIC might be underestimated in our study population.