Infarction in the pars libera of the column of fornix including pre (cholinergic)- and post (circuit of Papez fiber tracts)-commissural fibers causes "basal forebrain" amnesia

Fornix Integrity Is Differently Associated With Cognition in Healthy Aging and Non-amnestic Mild Cognitive Impairment: A Pilot Diffusion Tensor Imaging Study in Thai Older Adults

Damage to the fornix leads to significant memory impairment and executive dysfunction and is associated with dementia risk. We sought to identify if fornix integrity and fiber length are disrupted in mild cognitive impairment (MCI) and how they associate with cognition. Data from 14 healthy older adult controls (HCs) and 17 subjects with non-amnestic MCI (n-aMCI) were analyzed. Diffusion tensor imaging (DTI) at 1.5 Tesla MRI was performed to enable manual tracing of the fornix and calculation of DTI parameters. Higher fractional anisotropy of body and column of the fornix was associated with better executive functioning and memory, more strongly in the HC than in the n-aMCI group. Fornix fiber tract length (FTL) was associated with better executive function, more strongly in the n-aMCI than in the HC group, and with better memory, more strongly in the HC than in the n-aMCI group. These results highlight a decline in the contributions of the fornix to cognition in n-aMCI and suggest that maintenance of fornix FTL is essential for sustaining executive functioning in people with n-aMCI.

A circuit view of deep brain stimulation in Alzheimer's disease and the possible mechanisms

Alzheimer's disease (AD) is characterized by chronic progressive cognitive deterioration frequently accompanied by psychopathological symptoms, including changes in personality and social isolation, which severely reduce quality of life. Currently, no viable therapies or present-day drugs developed for the treatment of AD symptoms are able to slow or reverse AD progression or prevent the advance of neurodegeneration. As such, non-drug alternatives are currently being tested, including deep brain stimulation (DBS). DBS is an established therapy for several neurological and psychiatric indications, such as movement disorders. Studies assessing DBS for other disorders have also found improvements in cognitive function, providing the impetus for clinical trials on DBS for AD. Targets of DBS in AD clinical trials and animal model studies include the fornix, entorhinal cortex (EC), nucleus basalis of Meynert (NBM), and vertical limb of diagonal band (VDB). However, there is still no comprehensive theory explaining the effects of DBS on AD symptoms or a consensus on which targets provide optimal benefits. This article reviews the anatomy of memory circuits related to AD, as well as studies on DBS rescue of AD in these circuits and the possible therapeutic mechanisms.

Ischemic stroke in the combined territories of the septum pellucidum and the cingulate gyrus: A case report and literature review

INTRODUCTION

Cases of isolated septum pellucidum infarction have not yet been reported. To date, there are only 2 stroke reports involving septum pellucidum infarction. The etiology of septum pellucidum infarction was subcallosal artery (ScA) injury. The abnormalities were strictly confined to the septum pellucidum and the right cingulated gyrus, making this the first case to report such confined abnormalities.

PATIENT CONCERNS

In this report, we present a case of ischemic stroke confined to the septum pellucidum and cingulated gyrus in a 48-year-old male patient who presented with transient ischemic attack-like paroxysmal lower left limb weakness.

DIAGNOSIS

Even no obvious abnormalities were revealed by an emergency computed tomography, the infarction in the combined territories of the septum pellucidum and the cingulate gyrus was detected on magnetic resonance imaging.

INTERVENTIONS

Aspirin with clopidogrel was administered for 3 weeks as a secondary preventive drug. Clopidogrel was selected as a long-term antiplatelet drug based on a thromboelastogram.

OUTCOMES

The patient showed no positive signs related to the nervous system in the hospital, and there was no recurrence during the 3-month follow-up.

CONCLUSIONS

Infarction in the septum pellucidum and cingulate gyrus is rare and has atypical clinical manifestations. Physical examination may not yield obvious positive signs. False-negative computed tomography findings of the head may result in misdiagnosis. Thus, it is necessary to perform whole-brain magnetic resonance imaging in time. Moreover, ScA protection should be paid attention to during surgery for anterior communicating artery aneurysm.

Subcallosal and Heubner artery infarcts following surgical repair of an anterior communicating artery aneurysm: a causal relationship with postoperative amnesia and long-term outcome

Since the 1950s, amnesia or memory impairment has been repeatedly reported in patients following surgical repair of anterior communicating artery (ACoA) aneurysms. Postoperative infarctions following surgical repair of ACoA aneurysms are classified as involvement of the subcallosal artery (the largest unpaired perforator of the ACoA), the recurrent artery of Heubner (RAH), or a combination of both. Postoperative amnesia can seriously affect the patient's quality of life, thus prompting physicians to discuss the symptomatology of the three infarction patterns. We made the following speculations regarding the causal relationship between the infarction pattern and postoperative amnesia. First, postoperative amnesia is most likely caused by an infarction in the territory of the subcallosal artery, particularly in the column of the fornix, a constituent of the Papez neuronal circuit. Second, infarction in the RAH territory alone is unlikely to cause significant amnesia. Third, infarcted foci in the RAH territory, when associated with a subcallosal artery infarction, can cause considerable frontal dysfunction due to impaired frontostriatal circuits in patients with postoperative amnesia, with resultant worsening of the long-term outcome or quality of life.