Paramedian thalamic and midbrain infarct: clinical and neuropathological study

Artery of Percheron Infarction: Clinical Presentation and Outcomes

Background and Objectives

Occlusion of the artery of Percheron (AOP) produces bilateral thalamic infarction classically leading to deficits of arousal. This nonspecific presentation complicates the diagnosis of acute ischemic stroke. We sought to describe the spectrum of clinical presentation, diagnostic neuroimaging findings, and outcomes in AOP infarction (AOPi).

Methods

We conducted a keyword search of our health system's neuroimaging database from 2014 to 2022 to identify patients with AOPi. We abstracted patient demographics, clinical presentation, neuroimaging findings, acute treatment, and modified Rankin Scale (mRS) scores (at baseline, 3 months, and 12 months). We used descriptive statistics to report our findings.

Results

Our initial keyword search identified 192 potential AOPi cases. Fifteen cases of AOPi were confirmed and included in our study (8 female [53%], median age 65 years [interquartile range (IQR): 59.5-79.5], median presenting NIHSS 6 [IQR: 2-22]). Common clinical findings on presentation were systolic blood pressure (SBP) > 140: 12 patients (80%); decreased level of consciousness (LOC): 11 patients (73%); diplopia: 8 patients (57%); disorientation: 6 patients (42%); dysarthria: 4 patients (28%); and acute memory/cognitive disturbance: 3 patients (21%). Twelve cases (80%) presented to the emergency department (ED). Median time from symptom onset to ED arrival was 774.5 minutes (IQR: 202.25-3789.0), 4 cases (27%) arrived within 4.5 hours, and one patient (7%) received intravenous thrombolysis. The median time from ED arrival to stroke diagnosis was 519.0 minutes (IQR: 227.5-1307). Head CT was only diagnostic when obtained >570 minutes from time last known well; MRI was diagnostic at all time points. Rates of functional independence (mRS ≤2) at baseline, 3 months, and 12 months were 64%, 21%, and 18%, respectively.

Discussion

The diagnosis of stroke was considerably delayed in patients with AOPi, and only one patient received IV thrombolysis. SBP >140, impaired consciousness, and diplopia were the most common findings at presentation. CT was often nondiagnostic, but MRI demonstrated bilateral thalamic infarct in all cases. AOPi caused considerable long-term morbidity. Clinicians should maintain a high degree of suspicion for AOP stroke and consider thrombolysis in appropriately selected patients.

Structural and Functional Neuroanatomy of Core Consciousness: A Primer for Disorders of Consciousness Clinicians

Understanding the structural and functional neuroanatomy of core consciousness (ie, wakefulness and awareness) is an asset to clinicians caring for persons with disorders of consciousness. This article provides a primer on the structural and functional neuroanatomy of wakefulness and awareness. The neuroanatomical structures supporting these elements of core consciousness functions are reviewed first, after which brief description of the clinically evaluable relationships between disruption of these structures and disorders of consciousness (ie, brain-behavior relationships) are outlined. Consideration of neuroanatomy at the mesoscale (ie, the mesocircuit hypothesis) as well as in relation to several large-scale neural networks is offered.

The vascular locked-in and locked-in-plus syndrome: A retrospective case series

The locked-in syndrome (LiS) is defined as the loss of most voluntary muscle movements with preserved cognitive abilities due to a ventral pontine lesion. However, some patients may also have severe impairment of consciousness [locked-in plus syndrome (LiPS)]. Here we aimed to explore structural differences between LiS and LiPS patients of vascular aetiology, focusing on lesion patterns and locations to better delineate the clinical spectrum of LiS and LiPS. In this retrospective case series study, we report nine patients (two women), ages 29-74 years (median 50) with LiS and LiPS who were diagnosed between 2007 and 2021. Clinical parameters, MRI findings including the lesioned structures, and a shape feature calculation are presented for every patient. The lesioned structures were determined by a senior neuroradiologist. Two of nine patients had fully retained consciousness (LiS) and seven showed various degrees of impaired consciousness (LiPS). Lesions of LiS patients are round and confined to the pons, whereas lesions of LiPS patients are more elongated and reach neighbouring areas such as the mesencephalon, thalamus or ascending reticular activating system. Lesions involving the mesencephalon and the thalamus are strong indicators of LiPS, whereas for lesions restricted to the pons, the dorsal extension and the associated damage to the ascending reticular activating system are crucial to differentiate LiS from LiPS. Recognizing LiPS using clinical and radiological findings is important as these patients may need different therapies and care and, most importantly, should not be mistaken as unresponsive wakefulness syndrome.

A common thalamic hub for general and defensive arousal control

The expression of defensive responses to alerting sensory cues requires both general arousal and a specific arousal state associated with defensive emotions. However, it remains unclear whether these two forms of arousal can be regulated by common brain regions. We discovered that the medial sector of the auditory thalamus (ATm) in mice is a thalamic hub controlling both general and defensive arousal. The spontaneous activity of VGluT2-expressing ATm (ATmVGluT2+) neurons was correlated with and causally contributed to wakefulness. In sleeping mice, sustained ATmVGluT2+ population responses were predictive of sensory-induced arousal, the likelihood of which was markedly decreased by inhibiting ATmVGluT2+ neurons or multiple downstream pathways. In awake mice, ATmVGluT2+ activation led to heightened arousal accompanied by excessive anxiety and avoidance behavior. Notably, blocking their neurotransmission abolished alerting stimuli-induced defensive behaviors. These findings may shed light on the comorbidity of sleep disturbances and abnormal sensory sensitivity in specific brain disorders.

Prevalence, clinical features, and radiological pattern of artery of Percheron infarction: a challenging diagnosis

PURPOSE

Occlusion of artery of Percheron (AOP), a rare variant of paramedian branches of posterior cerebral artery, results in a characteristic pattern of ischemic lesions in bilateral paramedian thalami with or without midbrain and anterior thalami involvement.

AIM

To evaluate the prevalence, the clinical, and the imaging features of AOP infarction in a single comprehensive stroke center experience.

METHODS

We retrospectively search in our stroke center database, patients with ischemic lesions in the AOP distribution. We collected clinical features and time between hospital admission and diagnosis. Imaging findings were categorized following a pre-selected classification.

RESULTS

Of 2830 ischemic stroke admitted in our center, we identified 15 patients with AOP infarction (0.53%). Clinical manifestations were variable, but oculomotor disturbances, particularly vertical gaze palsy, were the most observed, followed by consciousness impairment, varying from drowsiness to coma. The most frequent imaging pattern was bilateral paramedian thalamic infarction with midbrain infarction, and the V-sign was recognized in 6 cases from this group. In 8 patients a fetal origin of the PCA was observed. The average time from first hospital admission to diagnosis was 28.09 h.

CONCLUSIONS

The prevalence of AOP infarction in our center was 0.53%. Diagnosis of AOP infarction can be challenging and should be suspected in case of sudden altered consciousness.

Carotid Siphon Calcification Predicts the Symptomatic Progression in Branch Artery Disease With Intracranial Artery Stenosis

Arterial calcification in the aortic arch, carotid bifurcation, or siphon on computed tomography was associated with cardiovascular disease. The association between arterial calcification prevalence and progression of branch atheromatous disease (BAD) in intracranial artery atherosclerosis was little investigated.

Brain plasticity after rehabilitation in a severe case of artery of Percheron stroke assessed with multimodal MR imaging

Artery of Percheron (AOP) stroke is a rare event. We describe an AOP stroke involving both thalami and the midbrain, resulting in a multifunctional clinical impairment. Intensive inpatient multidisciplinary rehabilitation favored the recovery of motor deficits, together with the improvement of cognitive dysfunctions. MRI assessment in the chronic post-stroke phase showed structural and functional reorganization in response to the extended thalamic tissue damage and absence of revascularization. Thalamo-cortical networks involving frontal and prefrontal regions, as well as parietal areas were disrupted, whereas increased functional thalamo-occipital connectivity was found. This report sheds light on brain reorganization following AOP stroke after rehabilitation..

Organizing a Rational Approach to Treatments of Disorders of Consciousness Using the Anterior Forebrain Mesocircuit Model

SUMMARY

Organizing a rational treatment strategy for patients with multifocal structural brain injuries and disorders of consciousness (DOC) is an important and challenging clinical goal. Among potential clinical end points, restoring elements of communication to DOC patients can support improved patient care, caregiver satisfaction, and patients' quality of life. Over the past decade, several studies have considered the use of the anterior forebrain mesocircuit model to approach this problem because this model proposes a supervening circuit-level impairment arising across DOC of varying etiologies. We review both the conceptual foundation of the mesocircuit model and studies of mechanisms underlying DOC that test predictions of this model. We consider how this model can guide therapeutic interventions and discuss a proposed treatment algorithm based on these ideas. Although the approach reviewed originates in the evaluation of patients with chronic DOC, we consider some emerging implications for patients in acute and subacute settings.

Surgical Approach to Thalamic Tumors

Thalamic tumors are deep-seated lesions. Recent improvements in therapeutic approaches and surgical techniques have allowed a more accurate approach to these lesions and a reduction in morbidity and mortality. In this article, the various surgical approaches for the resection of thalamic tumors are described. Each of these approaches has its own indications and risk of complications. Resection of thalamic tumors needs specific anatomical knowledge, especially the vascular anatomy of the region and the thalamic peduncles.

Pure Thalamic Infarct: 8-Year Follow-Up Study in a Hospital in China

Pure thalamic infarct is a rare lacunar stroke type, with little known about long-term outcomes. This 8-year, single-center, retrospective study evaluated the clinical background, etiology, Trial of ORG 10172 in Acute Stroke Treatment (TOAST) classification, and 8-year follow-up results in 27 patients with pure thalamic infarcts identified by MR diffusion-weighted imaging in Dalian, China. All patients presented chief complaints of limb weakness or sensory disturbances. Hypertension (24/27, 88.9%), diabetes (12/27, 44.4%), atrial fibrillation (1/27, 3.7%), hyperlipidemia (10/27, 37%), hyperhomocysteinemia (6/27, 22.2%), smoking history (10/27, 37%; 9/15, 60% for men; 1/12, 8.3% for women), and excessive alcohol consumption history (7/27, 25.9%; 7/15, 46.7% for men; 0 for women) were observed in our patient population. Based on TOAST classification, 1 patient had large artery atherosclerosis (7.14%), 23 had small vessel occlusion (SVO; 85.2%), and 3 patients were unidentified due to lack of cerebral angiography. The thalamic blood supply classification were as follows: 23 (85.2%), inferolateral territory; 1 (3.7%), tuberothalamic territory; 2 (7.4%), combination of tuberothalamic and paramedian arteries; 1 (3.7%), combination of inferolateral and paramedian arteries; 0, posterior choroidal arteries. During the 8-year follow-up, 3 patients died of colon cancer, multi-organ failure, and kidney failure, respectively; 7 presented with a recurrent stroke; while 10 recovered well with their risk factors under control. In conclusion, our cohort of pure thalamic infarcts were mainly due to SVO (TOAST), with hypertension as the main risk factor, and the inferolateral artery as the most implicated arterial territory. Less severe outcome or stroke recurrence are identified in long-term follow-up of pure thalamic infarcts. Other comorbidities would be cause of death in aged patients.

Involvement of Supraoptic Astrocytes in Basilar Artery Occlusion-Evoked Differential Activation of Vasopressin Neurons and Vasopressin Secretion in Rats

Vasopressin (VP) is a key factor in the development of brain injury in ischemic stroke. However, the regulation of VP secretion in basilar artery occlusion (BAO) remains unclear. To clarify the regulation of VP secretion in BAO and the underlying mechanisms, we performed this study in a rat model of BAO with (BC) or without common carotid artery occlusion (CCAO). The results showed that BAO and BC time-dependently increased neurological scores and that BC also increased water contents in the medulla at 2 h and in the pontine at 8 h. Moreover, plasma VP level increased significantly at BAO-8 h, CCAO and BC-2 h but not at BC-8 h; however, VP expressions increased in the supraoptic nucleus (SON) at BC-8 h. The neurological scores were highly correlated with pontine water contents and plasma VP levels. The number of phosphorylated extracellular signal-regulated protein kinase1/2-positive VP neurons increased significantly in the SON at BC-8 h. Similarly, the number of c-Fos-positive VP neurons increased significantly in the SON at BAO-8 h and BC-8 h. In addition, the length of glial fibrillary acidic protein (GFAP) filaments increased significantly in BC compared to BAO only. Aquaporin 4 (AQP4) puncta around VP neurons increased significantly at BC-8 h relative to BC-2 h, which had negative correlation with plasma VP levels. These findings indicate that BAO facilitates VP secretion and increases VP neuronal activity in the SON. The peripheral VP release is possibly under a negative feedback regulation of central VP neuronal activity through increasing GFAP and AQP4 expression in astrocytic processes.

Isolated thalamic stroke - analysis of clinical characteristics and asymmetry of lesion distribution in a retrospective cohort study

Background

More patients with left-hemispheric than right-hemispheric strokes are admitted to hospitals. This is due to the easier recognition of cortical symptoms of the dominant-hemisphere. The thalamus constitutes a “micro-model” of the brain cortex with structure-function relationships known to be asymmetric, especially for language, memory, and visuo-spatial neurocognitive functions. The goal of this study was to characterize clinical symptoms and lesion distribution patterns of patients with acute isolated thalamic stroke (ITS) and to evaluate whether left-sided lesions are overrepresented in the hospital.

Methods

We performed a radiological database search including all brain scans performed in the Center of Neurology and Neurosurgery of the University Hospital Frankfurt between 2010 and 2019. A total of 5733 patients presenting with acute ischemic stroke were screened for ITS. Based on the MRI data, a lesion-overlap map was then generated to visualize the ITS lesion distribution.

Results

Fifty-eight patients with unilateral ITS were identified. A majority of 38 patients (65.5%) showed left-sided ITS, whereas only 20 patients (34.5%) had right-sided ITS (p = 0.012). A particular difference was found for ITS lesions in the anterior thalamus of the anterolateral (n = 10) and anteromedian (n = 3) vascular territory, which were located in the left thalamus in 85% of patients (p = 0.011). No distribution difference was found for ITS lesions in the inferomedial (n = 7), central (n = 8), inferolateral (n = 23) and posterior (n = 7) vascular territories. The neuropsychological symptoms of thalamic aphasia (n = 8), neurocognitive impairment (n = 6), behavioral changes (n = 2), neglect (n = 2) and memory deficits (n = 3) were described predominantly in patients with left-sided ITS (p < 0.01). In contrast, other stroke symptoms (e.g., sensorimotor hemi-syndromes) did not reveal a side preponderance.

Conclusions

The better recognizability of left anterior compared to right anterior thalamic stroke symptoms may have an impact on the frequency in which ITS patients are admitted to the hospital. Clinical characteristics of right anterior thalamic stroke should therefore be further investigated, and diagnostic instruments towards their detection be identified.

The Clinical and Cognitive Spectrum of Artery of Percheron Infarction: 1-Year Follow-Up

OBJECTIVE

Survivors of patients with artery of Percheron infarction (API) often have a prolonged and disabling form of cognitive impairment that remains insufficiently characterized. We aimed to examine the clinical and cognitive features of API in the short and long term after stroke.

METHODS

We reviewed 6400 patients with a first-ever stroke included in the Stroke Registry between 2011 and 2021. The diagnosis of API was based on clinical diagnosis and imaging confirmation. All patients underwent neuropsychological assessment at hospital stay and 1 year after stroke. A z-score of each patients' cognitive test point was calculated, and a z-score inferior to 2 was considered as pathological.

RESULTS

Of the 10 patients enrolled, all had cognitive impairment, consciousness, and behavioral disorders at stroke onset. Six patients had pure bilateral thalamic involvement while four had bilateral thalamic and rostral midbrain involvement. At 12 months, 50% of patients had global mental state scores 2 SD below the population mean (z-score mean ± SD, -2.17 ± 0.4). Most of the prefrontal cortex cognitive processes including executive functions such as planning and cognitive control (z-score mean ± SD, -3.92 ± 0.3), processing speed (-4.42 ± 0.5), working memory (-3.97 ± 0.3) were severely impaired at stroke onset. Especially in patients with thalamic and rostral midbrain involvement, deficiencies in executive function (z-score mean ± SD, -2.60 ± 0.4), processing speed (-2.22 ± 0.5), working (-3.76 ± 0.4), and episodic memory (-2.23 ± 0.3) continued 12 months after stroke.

CONCLUSIONS

The occlusion of the artery of Percheron results in severe behavioral and cognitive disorders in the short and long term after stroke.

Distribution of the Noradrenaline Innervation and Adrenoceptors in the Macaque Monkey Thalamus

Noradrenaline (NA) in the thalamus has important roles in physiological, pharmacological, and pathological neuromodulation. In this work, a complete characterization of NA axons and Alpha adrenoceptors distributions is provided.

NA axons, revealed by immunohistochemistry against the synthesizing enzyme and the NA transporter, are present in all thalamic nuclei. The most densely innervated ones are the midline nuclei, intralaminar nuclei (paracentral and parafascicular), and the medial sector of the mediodorsal nucleus (MDm). The ventral motor nuclei and most somatosensory relay nuclei receive a moderate NA innervation. The pulvinar complex receives a heterogeneous innervation. The lateral geniculate nucleus (GL) has the lowest NA innervation.

Alpha adrenoceptors were analyzed by in vitro quantitative autoradiography. Alpha-1 receptor densities are higher than Alpha-2 densities. Overall, axonal densities and Alpha adrenoceptor densities coincide; although some mismatches were identified. The nuclei with the highest Alpha-1 values are MDm, the parvocellular part of the ventral posterior medial nucleus, medial pulvinar, and midline nuclei. The nucleus with the lowest Alpha-1 receptor density is GL. Alpha-2 receptor densities are highest in the lateral dorsal, centromedian, medial and inferior pulvinar, and midline nuclei.

These results suggest a role for NA in modulating thalamic involvement in consciousness, limbic, cognitive, and executive functions.

Topographic evaluation of bithalamic infarcts: Are these due to occlusion of the artery of Percheron?

Occlusion of the artery of Percheron (AoP) causes bithalamic paramedian infarct (BTPI). Although it can be diagnosed easily in its pure form, it can be underdiagnosed in cases with concomitant extrathalamic acute infarcts (plus-BTPI) as it may be difficult to determine whether BTPI is due to occlusion of AoP or two different paramedian arteries even with conventional angiography. This study was performed to highlight plus-BTPI that could result from occlusion of AoP rather than of two distinct paramedian arteries using topographic evaluation of bithalamic infarcts. We retrospectively reviewed imaging and clinical databases for patients admitted to radiology department between 2013 and 2019. Two radiologists independently evaluated the results of imaging studies, and findings reached by consensus were used in the analysis. This retrospective review yielded 34 patients with bithalamic infarct. Each affected thalamic vascular region was investigated separately. Any patient could have more than 2 different vascular zone infarct. The affected thalamic vascular territories were paramedian (n = 24), inferolateral (n = 13), anterior (n = 10), and posterior (n = 7). When we evaluated bithalamic infarcts in terms of symmetrically affected territories, the distribution of symmetric affected territories was as: paramedian (n = 18), inferolateral (n = 2), anterior (n = 1), and posterior (n = 1). BTPI had a 4.5-fold higher frequency than the sum of symmetric involvement of other territories (p = 0.0552, OR = 4.5,95%CI 0.93-21.5). In addition, mesencephalic involvement was only observed in BTPI, and not in other patterns (p < 0.001). The fact that in bilateral thalamic infarcts the symmetric involvement of paramedic territory is significantly higher and mesencephalic involvement is seen only in BTPI can suggest that plus-BPTI may develop due to AoP occlusion rather than occlusion of two distinct paramedian arteries.

Cognitive Profile of Patients with Thalamic Hemorrhage according to Lesion Localization

BACKGROUND

The thalamus is known as the central sensory and motor relay station of the brain generally. However, cognitive decline due to thalamic lesions has been previously reported in different studies. Also, it has been observed that different cognitive subdomains are affected according to the localization of the lesion in the thalamus.

OBJECTIVES AND METHODS

Detailed neurophysiological tests were performed on 28 patients with thalamic hemorrhage and the control group. Patients were grouped according to lesion localization. The results were compared with both the control group and the hemorrhage groups themselves.

RESULTS

The performance of patients in all neuropsychological tests was significantly worse than that of the control group. Of the 28 patients, 15 had anterolateral, 5 had posterolateral, 5 had dorsal, and 3 had an anteromedial thalamic hemorrhage. The anteromedial group had the worst scores of almost all tests. Also, 2 situations came to notice in these tests. First, the posterolateral group achieved a remarkably low mean in the recall subgroup of the MMSE tests and verbal memory process tests. Second, the anterolateral group was found to have a low mean in both the language subgroup of the MMSE tests and the phonemic subgroup of the verbal fluency tests.

CONCLUSION

It was concluded in this study that thalamic hemorrhages affect cognition entirely regardless of the lesion localization. It was also observed that the lateral part of the thalamus was associated with language, the posterior part with memory, and the anteromedial part with the rest of the cognitive subdomains.

Stroke-Onset Seizures During Midbrain Infarction in a Patient With Top of the Basilar Syndrome

Risk factors for early-onset seizures in acute ischemic stroke include anterior circulation stroke, infarction of the cerebral cortex, large infarct size, and ischemic-to-hemorrhagic transformation. We define stroke-onset seizures as seizures occurring within 2 hours of stroke onset. A 64-year-old woman presented with top of the basilar artery syndrome-thalamic infarction occurred first and midbrain infarction 12 days later. She manifested stroke-onset seizures during midbrain infarction, which was heralded by stupor. Within 2 hours of the onset of stupor, she had a clonic seizure of the lower extremities, electroencephalography (EEG) revealed nonconvulsive status epilepticus, and an episode of convulsive movements of all extremities was recorded on video and on EEG. Continuous EEG recording showed epileptiform discharges that would appear, disappear, and reappear over a 3-week period. It took 3 weeks and 4 antiepileptic drugs to fully suppress cortical hyperexcitability, perhaps because injury to some midbrain structures resulted in global lowering of the seizure threshold. The most important risk factor for stroke-onset seizures appears to be posterior circulation stroke, particularly brainstem infarction. The difference in risk profile between stroke-onset seizures and other forms of early-onset seizures suggest that their pathophysiology is not exactly the same. Focusing some of the research spotlight on stroke-onset seizures can help us better understand their unique clinical, electrographic, radiologic, and pathophysiologic features.

Theoretical Models of Consciousness: A Scoping Review

The amount of knowledge on human consciousness has created a multitude of viewpoints and it is difficult to compare and synthesize all the recent scientific perspectives. Indeed, there are many definitions of consciousness and multiple approaches to study the neural correlates of consciousness (NCC). Therefore, the main aim of this article is to collect data on the various theories of consciousness published between 2007-2017 and to synthesize them to provide a general overview of this topic. To describe each theory, we developed a thematic grid called the dimensional model, which qualitatively and quantitatively analyzes how each article, related to one specific theory, debates/analyzes a specific issue. Among the 1130 articles assessed, 85 full texts were included in the prefinal step. Finally, this scoping review analyzed 68 articles that described 29 theories of consciousness. We found heterogeneous perspectives in the theories analyzed. Those with the highest grade of variability are as follows: subjectivity, NCC, and the consciousness/cognitive function. Among sub-cortical structures, thalamus, basal ganglia, and the hippocampus were the most indicated, whereas the cingulate, prefrontal, and temporal areas were the most reported for cortical ones also including the thalamo-cortical system. Moreover, we found several definitions of consciousness and 21 new sub-classifications.

A case with bilateral thalamic infarction manifesting mutism - Cerebral blood flow and neural fibers evaluation

Background:

Acute bilateral thalamic infarction is rare, and occlusion of the artery of percheron (AOP) may be one of its reasons. AOP occlusion results in an acute disturbance of consciousness, but mutism due to AOP occlusion is rare. We described a mutism patient with bilateral thalamic infarction presumably due to AOP occlusion. We also performed cerebral blood flow (CBF) evaluation by N-isopropyl-p-[¹²³I]-iodoamphetamine single-photon emission computed tomography (¹²³I-IMP-SPECT) as well as neural fiber evaluation by diffusion tensor tractography, discussing the mechanism of mutism.

Case Description:

A 92-year-old woman presented a gradual deterioration of consciousness. Diffusion-weighted images revealed high-intensity areas at the bilateral thalami, and we diagnosed AOP occlusion. We administered a recombinant tissue plasminogen activator. On day 14, her Glasgow Coma Scale score was 11 (E4V1M6), and she did not present any apparent paresis. She was mute but cognitively alert, although she could communicate by nodding or facial expression. ¹²³I-IMP-SPECT showed CBF increase in the bilateral cerebellum and CBF decrease in the infarcted bilateral thalami and frontal lobes. Diffusion tensor tractography revealed the bilateral dentatothalamo-cortical tracts (DTCs). However, the tracts terminated at the parieto-occipital cortex, but not at the frontal cortex. She still had mutism on day 30.

Conclusion:

We reported the bilateral thalamic infarction patient presumably due to AOP occlusion, who presented mutism. The discontinuity of the bilateral DTCs resulted in her mutism, and our results supported the hypothesis that the cerebellum plays a significant role in uttering, associated with the bilateral DTCs.

A Patient with a Delayed Diagnosis of Artery of Percheron Occlusion in Whom Thrombectomy Was Effective

Objective

A case of posterior cerebral artery (P1 segment) occlusion with consciousness disturbance and Weber's syndrome treated by mechanical thrombectomy is reported.

Case Presentation

The patient was a 69-year-old man with consciousness disturbance, left hemiparesis, and anisocoria. MRI revealed acute cerebral infarction in the midbrain and right thalamus. Angiography demonstrated that the right P1 segment was occluded and mechanical thrombectomy was performed. The right P1 segment and its perforator artery, the artery of Percheron (AOP), were both recanalized after the treatment, and the symptoms of perforator occlusion significantly improved.

Conclusion

Mechanical thrombectomy for P1 segment occlusion may be effective for improving the symptoms caused by occlusion of its perforator, the AOP.

Neuro-Ophthalmologic Features and Outcomes of Thalamic Infarction: A Single-Institutional 10-Year Experience

BACKGROUND

Neuro-ophthalmologic deficit after thalamic infarction has been of great concern to ophthalmologists because of its debilitating impacts on patients' daily living. We aimed to describe the visual and oculomotor features of thalamic infarction and to delineate clinical outcomes and prognostic factors of the oculomotor deficits from an ophthalmologic point of view.

METHODS

Clinical and neuroimaging data of all participants were retrospectively reviewed. Among the 12,755 patients with first-ever ischemic stroke, who were registered in our Stroke Data Bank between January 2009 and December 2018, 342 were found to have acute thalamic infarcts on MRI, from whom we identified the patients exhibiting neuro-ophthalmologic manifestations including visual, oculomotor, pupillary, and eyelid anomalies.

RESULTS

Forty (11.7%) of the 342 patients with thalamic infarction demonstrated neuro-ophthalmologic manifestations, consisting of vertical gaze palsy (n = 19), skew deviation with an invariable hypotropia of the contralesional eye (n = 18), third nerve palsy (n = 11), pseudoabducens palsy (n = 9), visual field defects (n = 7), and other anomalies such as isolated ptosis and miosis (n = 7). Paramedian infarct was the most predominant lesion of neuro-ophthalmologic significance, accounting for 84.8% (n = 28) of all patients sharing the oculomotor features. Although most of the patients with oculomotor abnormalities rapidly improved without sequelae, 6 (18.2%) patients showed permanent oculomotor deficits. Common clinical features of patients with permanent oculomotor deficits included the following: no improvement within 3 months, combined upgaze and downgaze palsy, and the involvement of the paramedian tegmentum of the rostral midbrain.

CONCLUSIONS

Thalamic infarction, especially in paramedian territory, can cause a wide variety of neuro-ophthalmologic manifestations, including vertical gaze palsy, skew deviation, and third nerve palsy. Although most oculomotor abnormalities resolve spontaneously within a few months, some may persist for years when the deficits remain unimproved for more than 3 months after stroke.

Brain network motifs are markers of loss and recovery of consciousness

Motifs are patterns of inter-connections between nodes of a network, and have been investigated as building blocks of directed networks. This study explored the re-organization of 3-node motifs during loss and recovery of consciousness. Nine healthy subjects underwent a 3-h anesthetic protocol while 128-channel electroencephalography (EEG) was recorded. In the alpha (8-13 Hz) band, 5-min epochs of EEG were extracted for: Baseline; Induction; Unconscious; 30-, 10- and 5-min pre-recovery of responsiveness; 30- and 180-min post-recovery of responsiveness. We constructed a functional brain network using the weighted and directed phase lag index, on which we calculated the frequency and topology of 3-node motifs. Three motifs (motifs 1, 2 and 5) were significantly present across participants and epochs, when compared to random networks (p < 0.05). The topology of motifs 1 and 5 changed significantly between responsive and unresponsive epochs (p-values < 0.01; Kendall's W = 0.664 (motif 1) and 0.529 (motif 5)). Motif 1 was constituted of long-range chain-like connections, while motif 5 was constituted of short-range, loop-like connections. Our results suggest that anesthetic-induced unconsciousness is associated with a topological re-organization of network motifs. As motif topological re-organization may precede (motif 5) or accompany (motif 1) the return of responsiveness, motifs could contribute to the understanding of the neural correlates of consciousness.

Bilateral, vertical supranuclear gaze palsy following unilateral midbrain infarct

A 60-year-old man recently admitted for bipedal oedema, endocarditis and a persistently positive COVID-19 swab with a history of anticoagulation on rivaroxaban for atrial fibrillation, transitional cell carcinoma, cerebral amyloid angiopathy, diabetes and hypertension presented with sudden onset diplopia and vertical gaze palsy. Vestibulo-ocular reflex was preserved. Simultaneously, he developed a scotoma and sudden visual loss, and was found to have a right branch retinal artery occlusion. MRI head demonstrated a unilateral midbrain infarct. This case demonstrates a rare unilateral cause of bilateral supranuclear palsy which spares the posterior commisure. The case also raises a question about the contribution of COVID-19 to the procoagulant status of the patient which already includes atrial fibrillation and endocarditis, and presents a complex treatment dilemma regarding anticoagulation.

Artery of Percheron Infarct: A Rare Presentation of Acute Ischemic Stroke in a High-Risk Antiphospholipid Syndrome Patient

Artery of Percheron (AOP) is an abnormal variant of the arterial supply of the thalamus. AOP occlusion can lead to bilateral thalamic and rostral midbrain infarct presenting as memory loss, fluctuating levels of consciousness, and altered mental status. A 43-year-old woman with a history of antiphospholipid syndrome (APS), managed on dabigatran, presented with acute confusion and drowsiness. She had slurred and slowed speech, disorientation in time and place, left-sided facial droop, decreased power of the left side (4/5), and was unable to walk due to generalized weakness. Labs showed a prolonged prothrombin time and activated partial thromboplastin time, positive lupus anticoagulant, anti-cardiolipin, beta-2 glycoprotein, anti-nuclear and anti-dsDNA antibodies. Contrast-enhanced CT perfusion showed ischemic changes in the bilateral thalami, suggesting infarct along the AOP territory. AOP infarcts are scarce and the presenting complaints are unusual of cerebrovascular accidents. It requires a high index of suspicion to detect. There are no other reports in the literature of patients with APS presenting with an AOP infarct. Considering the lack of evidence, we recommend against the use of newer oral anticoagulants (NOACs) for secondary prevention of vascular events in patients with triple-positive APS.

Global enhancement of cortical excitability following coactivation of large neuronal populations

Correlated activation of cortical neurons often occurs in the brain and repetitive correlated neuronal firing could cause long-term modifications of synaptic efficacy and intrinsic excitability. We found that repetitive optogenetic activation of neuronal populations in the mouse cortex caused enhancement of optogenetically evoked firing of local coactivated neurons as well as distant cortical neurons in both ipsilateral and contralateral hemispheres. This global enhancement of evoked responses required coactivation of a sufficiently large population of neurons either within one cortical area or distributed in several areas. Enhancement of neuronal firing was saturable after repeated episodes of coactivation, diminished by inhibition of N-methyl-d-aspartic acid receptors, and accompanied by elevated excitatory postsynaptic potentials, all consistent with activity-induced synaptic potentiation. Chemogenetic inhibition of neuronal activity of the thalamus decreased the enhancement effect, suggesting thalamic involvement. Thus, correlated excitation of large neuronal populations leads to global enhancement of neuronal excitability.

Paramedian thalamic infarction caused by cisternal drain placement in open clipping for aneurysmal subarachnoid hemorrhage: Two case reports

Background:

Some complications associated with cisternal drainage have been reported; however, there are few reports on direct vascular injury caused by cisternal drain. We experienced two rare cases of thalamic infarction caused by cisternal drain placement during open clipping for a ruptured anterior communicating artery (AcomA) aneurysm through an anterior interhemispheric approach.

Case Description:

Two cases of ruptured AcomA aneurysm were treated by surgical clipping through an anterior interhemispheric approach, and then a cisternal drain was inserted from opticocarotid space toward prepontine cistern. Postoperatively, the magnetic resonance imaging showed unilateral anterior-medial thalamic infarction in both two cases. By reviewing the postoperative computed tomography and digital subtraction angiography, it was suspected that the cisternal drain, which was inserted slightly deep, obstructed the P1 perforator because of an anatomical variation involving a lowered basilar bifurcation and caused postoperative unilateral paramedian thalamic infarction.

Conclusion:

To avoid these complications, neurosurgeons should consider the potential for P1 perforator injury related to cisternal drain placement.

Network Mapping of Connectivity Alterations in Disorder of Consciousness: Towards Targeted Neuromodulation

Disorder of consciousness (DoC) refers to a group of clinical conditions that may emerge after brain injury, characterized by a varying decrease in the level of consciousness that can last from days to years. An understanding of its neural correlates is crucial for the conceptualization and application of effective therapeutic interventions. Here we propose a quantitative meta-analysis of the neural substrate of DoC emerging from functional magnetic resonance (fMRI) and positron emission tomography (PET) studies. We also map the relevant networks of resulting areas to highlight similarities with Resting State Networks (RSNs) and hypothesize potential therapeutic solutions leveraging network-targeted noninvasive brain stimulation. Available literature was reviewed and analyzed through the activation likelihood estimate (ALE) statistical framework to describe resting-state or task-dependent brain activation patterns in DoC patients. Results show that task-related activity is limited to temporal regions resembling the auditory cortex, whereas resting-state fMRI data reveal a diffuse decreased activation affecting two subgroups of cortical (angular gyrus, middle frontal gyrus) and subcortical (thalamus, cingulate cortex, caudate nucleus) regions. Clustering of their cortical functional connectivity projections identify two main altered functional networks, related to decreased activity of (i) the default mode and frontoparietal networks, as well as (ii) the anterior salience and visual/auditory networks. Based on the strength and topography of their connectivity profile, biophysical modeling of potential brain stimulation solutions suggests the first network as the most feasible target for tES, tDCS neuromodulation in DoC patients.

On the pathophysiology and treatment of akinetic mutism

Akinetic mutism (AM) is a rare neurological disorder characterized by the presence of an intact level of consciousness and sensorimotor capacity, but with a simultaneous decrease in goal-directed behavior and emotions. Patients are in a wakeful state of profound apathy, seemingly indifferent to pain, thirst, or hunger. It represents the far end within the spectrum of disorders of diminished motivation. In recent years, more has become known about the functional roles of neurocircuits and neurotransmitters associated with human motivational behavior. More specific, there is an increasing body of behavioral evidence that links specific damage of functional frontal-subcortical organization to the occurrence of distinct neurological deficits. In this review, we combine evidence from lesion studies and neurophysiological evidence in animals, imaging studies in humans, and clinical investigations in patients with AM to form an integrative theory of its pathophysiology. Moreover, the specific pharmacological interventions that have been used to treat AM and their rationales are reviewed, providing a comprehensive overview for use in clinical practice.

Inferolateral thalamic ischemia secondary to PCA P2 perforator occlusion mimics MCA stroke syndrome

Paramedian thalamic strokes following occlusion of the posterior medial (paramedian) thalamic perforators have been previously described in great detail. However, the stroke syndrome associated with occlusion of posterior lateral (inferolateral) thalamic perforators is less commonly known. We present an illustrative case of an inferolateral thalamic perforator stroke mimicking a middle cerebral artery (MCA) syndrome and provide a review of the literature. A 62-year-old male presented with dysarthria, contralateral hemisensory loss, and contralateral weakness, concerning for possible MCA stroke. However, close examination revealed the hemiparesis to be ataxic in nature. Imaging revealed a left PCA P2 segment occlusion and lacunar infarction of the ventral lateral (VL) and ventral posterior (VP) thalamus, the main thalamic destination of cerebellar and sensory pathways. The case is unique because the P1 segment and posterior communicating artery (Pcom) remained patent, resulting in selective occlusion of only the posterior lateral (inferolateral) thalamic perforators at the P2 level. Acute loss of the posterior lateral (inferolateral) thalamic perforators at the proximal P2 segment results in a ventral lateral and ventral posterior thalamic stroke characterized by contralateral hemisensory loss, contralateral ataxic hemiparesis, and dysarthria. It is important to recognize the inferolateral thalamic stroke syndrome, as it may be mistaken clinically for an MCA occlusion. The benefit of mechanical thrombectomy for this type of stroke is not well established and should be considered carefully.

Reduced Repertoire of Cortical Microstates and Neuronal Ensembles in Medically Induced Loss of Consciousness

Medically induced loss of consciousness (mLOC) during anesthesia is associated with a macroscale breakdown of brain connectivity, yet the neural microcircuit correlates of mLOC remain unknown. To explore this, we applied different analytical approaches (t-SNE/watershed segmentation, affinity propagation clustering, PCA, and LZW complexity) to two-photon calcium imaging of neocortical and hippocampal microcircuit activity and local field potential (LFP) measurements across different anesthetic depths in mice, and to micro-electrode array recordings in human subjects. We find that in both cases, mLOC disrupts population activity patterns by generating (1) fewer discriminable network microstates and (2) fewer neuronal ensembles. Our results indicate that local neuronal ensemble dynamics could causally contribute to the emergence of conscious states.

Neuroradiological and clinical features in ophthalmoplegia

PURPOSE

Especially in acute onset of ophthalmoplegia, efficient neuroradiological evaluation is necessary to assist differential diagnosis, clinical course, and treatment options.

METHODS

Different manifestations of ophthalmoplegia are explained and illustrated by characteristic neuroradiological and clinical findings.

RESULTS

To present those ophthalmoplegic disorders in a clear manner, this review refers to different neuroanatomical structures and compartments. From neuroophthalmological point of view, diseases going ahead with ophthalmoplegia can be divided into (1) efferent infranuclear/peripheral disturbances involving oculomotor cranial nerves, (2) conjugate gaze abnormalities due to internuclear or supranuclear lesions, and (3) diseases of the extraocular eye muscles or their impairment due to intraorbital pathologies.

CONCLUSION

The knowledge of the relationship between neurological findings in ophthalmoplegia and involved neuroanatomical structures is crucial, and neuroradiology can be focused on circumscribed anatomical regions, using optimized investigation protocols.

Initial clinical experience of a prototype ultra-high-resolution CT for assessment of small intracranial arteries

PURPOSE

Diagnostic and neurosurgical procedures require the precise localization of small intracranial arteries, but this may be difficult using conventional computed tomography angiography (CTA). This study was conducted to evaluate the quality of CTA images acquired using a prototype ultra-high-resolution computed tomography (U-HRCT) system compared with those acquired using a conventional computed tomography (C-CT) system.

MATERIALS AND METHODS

From July through September 2015, 10 adult patients (6 women and 4 men) previously scanned by C-CT were examined using U-HRCT to locate and assess cerebral aneurysms. The bilateral ophthalmic artery (Opth A), anterior choroidal artery (Acho A), and thalamoperforating arteries (TPAs) were visually evaluated in randomly presented CTA images. Images were graded on a 5-point scale, and differences in scores between U-HRCT and C-CT were evaluated by the Wilcoxon signed-rank test. A p value < 0.05 was considered statistically significant.

RESULTS

Visual evaluation scores for images of the Opth A, Acho A, and TPAs were significantly higher for U-HRCT than for C-CT. U-HRCT images achieved good visualization (score > 3) for C-CT images with poor visualization (score < 3) in 66.7-100% of all the small arteries.

CONCLUSION

U-HRCT is superior to C-CT for detecting and evaluating clinically significant small intracranial arteries.

Individual spindle detection and analysis in high-density recordings across the night and in thalamic stroke

Sleep spindles are thalamocortical oscillations associated with several behavioural and clinical phenomena. In clinical populations, spindle activity has been shown to be reduced in schizophrenia, as well as after thalamic stroke. Automatic spindle detection algorithms present the only feasible way to systematically examine individual spindle characteristics. We took an established algorithm for spindle detection, and adapted it to high-density EEG sleep recordings. To illustrate the detection and analysis procedure, we examined how spindle characteristics changed across the night and introduced a linear mixed model approach applied to individual spindles in adults (n = 9). Next we examined spindle characteristics between a group of paramedian thalamic stroke patients (n = 9) and matched controls. We found a high spindle incidence rate and that, from early to late in the night, individual spindle power increased with the duration and globality of spindles; despite decreases in spindle incidence and peak-to-peak amplitude. In stroke patients, we found that only left-sided damage reduced individual spindle power. Furthermore, reduction was specific to posterior/fast spindles. Altogether, we demonstrate how state-of-the-art spindle detection techniques, applied to high-density recordings, and analysed using advanced statistical approaches can yield novel insights into how both normal and pathological circumstances affect sleep.

Clinical-radiographic correlates of Artery of Percheron infarcts in a case series of 6 patients

Bilateral thalamic strokes due to Artery of Percheron (AOP) occlusion are rare but have been previously reported in the literature. It is due to a rare anatomic variant where a solitary arterial trunk from the proximal segment of either posterior cerebral artery (PCA) supplies bilateral thalami and midbrain. Despite its description in the literature, these strokes are usually missed and patient's symptoms are not thought to be secondary to a vascular etiology. Through this report we aim to describe the clinical and radiographic features seen in these patients. We describe a series of 6 patients who present with varying levels of somnolence and oculomotor nerve palsies who had an occlusion of the AOP with bilateral thalamic infarcts with midbrain involvement. These clinical presentations, combined with the "V" sign on MRI are important in making the diagnosis.

Artery of Percheron Infarct: An Acute Diagnostic Challenge with a Spectrum of Clinical Presentations

The artery of Percheron (AOP) is a variant of the paramedian thalamic vasculature that supplies blood to the medial aspect of the thalamus and the rostral midbrain. The presentation of an infarct in this territory varies widely and is often characterized by nonspecific neurological deficits, with altered mental status, decreased level of consciousness, and memory impairment being among the most common. AOP infarcts are often missed on initial computed tomography (CT) scan, and additional imaging is usually not done due to low suspicion for stroke in most cases. There have been an increasing number of reports of AOP infarction, illustrating the diversity of clinical presentations and the challenge this presents to clinicians in the acute setting. Lacking the classic signs of stroke, many of these patients experience a delay in recognition and treatment, with the majority of diagnoses occurring outside the tissue plasminogen activator (tPA) window. This case highlights the unusual presentation and diagnostic difficulty of a patient with an AOP infarct, and serves as a reminder to include thalamic pathology in patients presenting with vague neurological symptoms and no obvious signs of stroke.

Local changes in network structure contribute to late communication recovery after severe brain injury

Spontaneous recovery of brain function after severe brain injury may evolve over a long time period and is likely to involve both structural and functional reorganization of brain networks. We longitudinally tracked the recovery of communication in a patient with severe brain injury using multimodal brain imaging techniques and quantitative behavioral assessments measured at the bedside over a period of 2 years and 9 months (21 months after initial injury). Structural diffusion tensor imaging revealed changes in brain structure across interhemispheric connections and in local brain regions that support language and visuomotor function. These findings correlated with functional brain imaging using functional magnetic resonance imaging and positron emission tomography, which demonstrated increased language network recruitment in response to natural speech stimuli, graded increases in interhemispheric interactions of language-related frontal cortices, and increased cerebral metabolic activity in the language-dominant hemisphere. In addition, electrophysiological studies showed recovery of synchronization of sleep spindling activity. The observed changes suggest a specific mechanism for late recovery of communication after severe brain injury and provide support for the potential of activity-dependent structural and functional remodeling over long time periods.

Intraoperative Frontal Alpha-Band Power Correlates with Preoperative Neurocognitive Function in Older Adults

Each year over 16 million older Americans undergo general anesthesia for surgery, and up to 40% develop postoperative delirium and/or cognitive dysfunction (POCD). Delirium and POCD are each associated with decreased quality of life, early retirement, increased 1-year mortality, and long-term cognitive decline. Multiple investigators have thus suggested that anesthesia and surgery place severe stress on the aging brain, and that patients with less ability to withstand this stress will be at increased risk for developing postoperative delirium and POCD. Delirium and POCD risk are increased in patients with lower preoperative cognitive function, yet preoperative cognitive function is not routinely assessed, and no intraoperative physiological predictors have been found that correlate with lower preoperative cognitive function. Since general anesthesia causes alpha-band (8–12 Hz) electroencephalogram (EEG) power to decrease occipitally and increase frontally (known as “anteriorization”), and anesthetic-induced frontal alpha power is reduced in older adults, we hypothesized that lower intraoperative frontal alpha power might correlate with lower preoperative cognitive function. Here, we provide evidence that such a correlation exists, suggesting that lower intraoperative frontal alpha power could be used as a physiological marker to identify older adults with lower preoperative cognitive function. Lower intraoperative frontal alpha power could thus be used to target these at-risk patients for possible therapeutic interventions to help prevent postoperative delirium and POCD, or for increased postoperative monitoring and follow-up. More generally, these results suggest that understanding interindividual differences in how the brain responds to anesthetic drugs can be used as a probe of neurocognitive function (and dysfunction), and might be a useful measure of neurocognitive function in older adults.

A Neurophysiological Perspective on a Preventive Treatment against Schizophrenia Using Transcranial Electric Stimulation of the Corticothalamic Pathway

Schizophrenia patients are waiting for a treatment free of detrimental effects. Psychotic disorders are devastating mental illnesses associated with dysfunctional brain networks. Ongoing brain network gamma frequency (30–80 Hz) oscillations, naturally implicated in integrative function, are excessively amplified during hallucinations, in at-risk mental states for psychosis and first-episode psychosis. So, gamma oscillations represent a bioelectrical marker for cerebral network disorders with prognostic and therapeutic potential. They accompany sensorimotor and cognitive deficits already present in prodromal schizophrenia. Abnormally amplified gamma oscillations are reproduced in the corticothalamic systems of healthy humans and rodents after a single systemic administration, at a psychotomimetic dose, of the glutamate N-methyl-d-aspartate receptor antagonist ketamine. These translational ketamine models of prodromal schizophrenia are thus promising to work out a preventive noninvasive treatment against first-episode psychosis and chronic schizophrenia. In the present essay, transcranial electric stimulation (TES) is considered an appropriate preventive therapeutic modality because it can influence cognitive performance and neural oscillations. Here, I highlight clinical and experimental findings showing that, together, the corticothalamic pathway, the thalamus, and the glutamatergic synaptic transmission form an etiopathophysiological backbone for schizophrenia and represent a potential therapeutic target for preventive TES of dysfunctional brain networks in at-risk mental state patients against psychotic disorders.

Bilateral internuclear and internal ophthalmoplegia due to artery of Percheron infarction

The artery of Percheron (AOP) infarction always manifests as paramedian bilateral thalamic infarcts and might present as paramedian midbrain infarcts. Despite the limited MRA evaluation, due to small size of the artery, careful evaluation of the patient's history, the clinical presentation with imaging findings can facilitate the proper diagnosis.

Clinical Features of Thalamic Stroke

OPINION STATEMENT

The thalamus plays an important role in different brain functions including memory, emotions, sleep-wake cycle, executive functions, mediating general cortical alerting responses, processing of sensory (including taste, somatosensory, visual, and auditory) information and relaying it to the cortex, and sensorimotor control. Thalamic stroke, both in isolation and in combination with infarcts involving other structures, are not rare. The functional complexity of the thalami nuclei and the not uncommon normal variations of arteries supply the thalamus induce wide variations in presentation of thalami infarcts. In patients with an unusual collection of deficits difficult to explain by a single lesion, in particular where there is impaired vigilance, thalamic disease should be considered which may mimic several different neurological conditions. By researching the literature, we found that the characteristic stroke syndrome of paramedian thalamic infarction is probably underdiagnosed. In addition to thalamic infarct, thalamic lesions can be caused by deep cerebral venous thrombosis with neuropsychological and radiological features that should be considered in the differential diagnosis of intracranial artery occlusion or bleeding, especially in young patients.