Artery of Percheron Infarction as an Unusual Cause of Korsakoff's Syndrome

The Fornix May Play a Key Role in Korsakoff's Amnesia Secondary to Subcallosal Artery Infarction

BACKGROUND

Subcallosal artery infarction injures the fornix and anterior corpus callosum and sometimes causes Korsakoff's amnesia. We hypothesized that Korsakoff's amnesia might be caused by fornix dysfunction rather than anterior corpus callosum dysfunction in subcallosal artery infarction.

METHODS

A systematic review approach was applied to search PubMed and Google Scholar for articles to compare patients who had both bilateral fornix and corpus callosum infarction due to subcallosal artery territory ischemia (vascular event group; V group) with patients who had undergone anterior corpus callosotomy (callosotomy group; C group).

RESULTS

The V group comprised 10 patients (mean age, 63 years; median, 69 years; standard deviation (SD), 14.5 years; 5 males, 5 females). The C group comprised 6 patients (mean age, 23.7 years; median, 20 years; SD, 7.3 years; 3 males, 3 females). Six of 10 patients (60%) with subcallosal artery infarction exhibited Korsakoff's amnesia. One patient showed neither confabulation nor amnesia. Conversely, no amnesia episodes were seen in any patients from the C group (p = 0.034).

CONCLUSION

Fornix injury, rather than anterior corpus callosum injury, might be the major cause of Korsakoff's amnesia in patients with subcallosal artery infarction.

Artery of Percheron Stroke as an Unusual Cause of Hypersomnia: A Case Series and a Short Literature Review

The thalamus and the mesencephalon have a complex blood supply. The artery of Percheron (AOP) is a rare anatomical variant. Occlusion of this artery may lead to bithalamic stroke with or without midbrain involvement. Given its broad spectrum of clinical features, AOP stroke is often misdiagnosed. Usually, it manifests with the triad of vertical gaze palsy, memory impairment, and coma. In this article, we report three cases of bilateral thalamic strokes whose clinical presentations were dominated by a sudden onset of hypersomnia. We also reviewed last 5 years’ publications related to the AOP strokes in males presenting sleepiness or equivalent terms as a delayed complication. The AOP stroke may present a diagnostic challenge for clinicians which should be considered in the differential diagnosis of hypersomnia.

Artery of Percheron infarction: A case report and literature review

The artery of Percheron (AOP) represents a rare anatomic variant of the posterior circulation. It is a solitary trunk that provides bilateral arterial supply to the rostral midbrain and paramedian thalamus. AOP infarction presentation varies, most often presents with altered mental status, memory impairment, and supranuclear vertical gaze palsy. Diagnosis of the AOP infarct is most often missed in the initial CT scan. A majority of these diagnoses are made outside the window of thrombolytic treatment for ischemic stroke.

We report a case of a 67-year old male with a history of well-managed diabetes mellitus type 2 and hypertension, presented in the ER sudden onset severe drowsiness. On a physical exam, we found left pupil dilation and left eye deviation. Initial CT scan showed no pathological changes. The diagnosis was made on the third day of hospitalization via an MRI. Our case highlights the unusual presentation and that an absence of evidence of AOP infarction in CT scan does not exclude its diagnosis. The artery of the Percheron infarct requires a comprehensive clinical and radiological examination.

Stroke masquerading as cardiac arrest: the artery of Percheron

The artery of Percheron (AOP) is a rare arterial variant of the thalamic blood supply. Due to the densely packed collection of nuclei it supplies, an infarction of the AOP can be devastating. Here we highlight a patient who had an AOP stroke in the community, which was initially managed as cardiac arrest. AOP strokes most often present with vague symptoms such as reduced conscious level, cognitive changes and confusion without obvious focal neurology, and therefore are often missed at the initial clinical assessment. This case highlights the importance of recognising an AOP stroke as a cause of otherwise unexplained altered consciousness level and the use of MRI early in the diagnostic work-up.

Artery of Percheron infarction with persistent amnesia: a case report of bilateral paramedian thalamic syndrome

Background

The artery of Percheron is an uncommon anatomic variant which supplies the bilateral paramedian thalami and rostral midbrain. While infarction of its vascular territory can result in a wide range of symptoms, paramedian thalamic syndrome is classically described as a triad of symptoms including vertical gaze disturbances, fluctuating level of consciousness, and amnesia. There is minimal evidence to date to characterize the long-term cognitive consequences of infarction of the artery of Percheron utilizing neuropsychological assessment.

Case presentation

We describe a 40-year-old female patient initially presenting with dizziness, confusion and falls with unremarkable head CT scans. Subsequent MRI, more than 24 h after symptom onset, identified evidence of bilateral thalamic and rostral midbrain infarction. Neuropsychological testing was administered at 4 months post-stroke, with follow up testing at 1 year. The patient was found to have profound anterograde and retrograde amnesia, which did not change significantly over the first year of rehabilitation, and which was not easily identifiable in everyday encounters due to her relatively intact working memory and social skills.

Conclusions

As early diagnosis of infarction of the artery of Percheron is challenging, patients have frequently missed the time window for acute management of ischemic stroke. Moreover, this case study highlights the need for further research in deciphering the role of the paramedian thalamus in memory and cognition, as well as the importance of standardized neuropsychological testing for the artery of Percheron stroke patients to identify safety and rehabilitation concerns that may be overlooked.

Disrupted Corollary Discharge in Schizophrenia: Evidence From the Oculomotor System

Corollary discharge (CD) signals are motor-related signals that exert an influence on sensory processing. They allow mobile organisms to predict the sensory consequences of their imminent actions. Among the many functions of CD is to provide a means by which we can distinguish sensory experiences caused by our own actions from those with external causes. In this way, they contribute to a subjective sense of agency. A disruption in the sense of agency is central to many of the clinical symptoms of schizophrenia, and abnormalities in CD signaling have been theorized to underpin particularly those agency-related psychotic symptoms of the illness. Characterizing abnormal CD associated with eye movements in schizophrenia and their resulting influence on visual processing and subsequent action plans may have advantages over other sensory and motor systems. That is because the most robust psychophysiological and neurophysiological data regarding the dynamics and influence of CD as well as the neural circuitry implicated in CD generation and transmission comes from the study of eye movements in humans and nonhuman primates. We review studies of oculomotor CD signaling in the schizophrenia spectrum and possible neurobiological correlates of CD disturbances. We conclude by speculating on the ways in which oculomotor CD dysfunction, specifically, may invoke specific experiences, clinical symptoms, and cognitive impairments. These speculations lay the groundwork for empirical study, and we conclude by outlining potentially fruitful research directions.

Structural Thalamofrontal Hypoconnectivity Is Related to Oculomotor Corollary Discharge Dysfunction in Schizophrenia

By predicting sensory consequences of actions, humans can distinguish self-generated sensory inputs from those that are elicited externally. This is one mechanism by which we achieve a subjective sense of agency over our actions. Corollary discharge (CD) signals-"copies" of motor signals sent to sensory areas-permit such predictions, and CD abnormalities are a hypothesized mechanism for the agency disruptions in schizophrenia that characterize a subset of symptoms. Indeed, behavioral evidence of altered CD, including in the oculomotor system, has been observed in schizophrenia patients. A pathway projecting from the superior colliculus to the frontal eye fields (FEFs) via the mediodorsal thalamus (MD) conveys oculomotor CD associated with saccadic eye movements in nonhuman primates. This animal work provides a promising translational framework in which to investigate CD abnormalities in clinical populations. In the current study, we examined whether structural connectivity of this MD-FEF pathway relates to oculomotor CD functioning in schizophrenia. Twenty-two schizophrenia patients and 24 healthy control participants of both sexes underwent diffusion tensor imaging, and a large subset performed a trans-saccadic perceptual task that yields measures of CD. Using probabilistic tractography, we identified anatomical connections between FEF and MD and extracted indices of microstructural integrity. Patients exhibited compromised microstructural integrity in the MD-FEF pathway, which was correlated with greater oculomotor CD abnormalities and more severe psychotic symptoms. These data reinforce the role of the MD-FEF pathway in transmitting oculomotor CD signals and suggest that disturbances in this pathway may relate to psychotic symptom manifestation in patients.SIGNIFICANCE STATEMENT People with schizophrenia sometimes experience abnormalities in a sense of agency, which may stem from abnormal sensory predictions about their own actions. Consistent with this notion, the current study found reduced structural connectivity in patients with schizophrenia in a specific brain pathway found to transmit such sensorimotor prediction signals in nonhuman primates. Reduced structural connectivity was correlated with behavioral evidence for impaired sensorimotor predictions and psychotic symptoms.

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.