Baseline Large-Scale Network Dynamics Associated with Disease Progression in Huntington's Disease.

BACKGROUND: Huntington's disease (HD) is a genetically determined disease with motor, cognitive, and neuropsychiatric disorders. However, the links between clinical progression and disruptions to dynamics in motor and cognitive large-scale networks are not well established. OBJECTIVE: To investigate changes in dynamic and static large-scale networks using an established tool of disease progression in Huntington's disease, the composite Unified Huntington's Disease Rating Scale (cUHDRS). METHODS: Sixty-four mutation carriers were included. Static and dynamic baseline functional connectivity as well as topological features were correlated to 2-year follow-up clinical assessments using the cUHDRS. RESULTS: Decline in cUHDRS scores was associated with higher connectivity between frontal default-mode and motor networks, whereas higher connectivity in posterior, mainly visuospatial regions was associated with a smaller decline in cUHDRS scores. CONCLUSIONS: Structural disruptions in HD were evident both in posterior parietal/occipital and frontal motor regions, with reciprocal increases in functional connectivity. However, although higher visuospatial network connectivity was tied to a smaller cUHDRS decline, increased motor and frontal default-mode connections were linked to a larger cUHDRS decreases. Therefore, divergent functional compensation mechanisms might be at play in the clinical evolution of HD.

Clinical characteristics and outcome of amaurosis fugax due to transient retinal ischemia: Results from a contemporary cohort.

BACKGROUND: Whether presenting an episode of amaurosis fugax (AFx) increases the risk of ischemic stroke is controversial and there is a lack of consensus in the following management. We aimed to describe the clinical characteristics and prognosis of patients with AFx due to suspected transient retinal ischemia. METHODS: Observational, retrospective study of patients admitted in a Comprehensive Stroke Center with diagnosis of AFx due to suspected transient retinal ischemia between 2015 and 2020. Clinical characteristics and diagnostic-therapeutic data were collected, as well as recurrences (new episodes of amaurosis and/or ischemic strokes). Multivariable Cox regression analyses were performed to study factors associated with the risk of recurrence. RESULTS: We included 91 patients with a mean age of 67.9±14.8 years, 43(47.3%) were women. After the diagnostic workup 14(15.4%) AFx were attributed to an atherothrombotic etiology, 4(4.4%) cardioembolic source, 10(11%) other determined cause (TOAST-OC) and 63(69,2%) indeterminate etiology. 71(78%) patients started antiplatelet therapy and 2(2.2%) anticoagulant therapy. After a median follow-up of 3.5 years (IQR 1.8-5.2), at least one recurrence was recorded in eight (8.8%) patients (four new AFx and four cerebral infarctions). TOAST-OC (HR=9.66, 95% CI 2.41-38.70; p=0.001) and prior history of ischemic stroke (HR=4.21. 95% CI 1.01-17.66; p=0.049) were both independently associated with the risk of recurrence. CONCLUSIONS: In two out of three patients, AFx due to transient retinal ischemia was of undetermined cause. The risk of stroke recurrence after a first episode of AFx in our cohort was 8.8%. Patients with TOAST-OC etiology identified were at highest risk of recurrence.

Cerebellar Syndrome Induced by Hypomagnesemia: A Treatable Cause of Ataxia Not to be Missed. Report of Three Cases and a Review of the Literature.

Background: Magnesium is an important intracellular cation involved in essential enzymatic reactions. It is necessary for neuronal function and its depletion can produce neurological symptoms such as cramps or seizures. Clinical consequences of its deficit in the cerebellum are less known and the diagnosis can be delayed because of the lack of awareness on this condition. Cases: We present three cases of cerebellar syndrome (CS) due to hypomagnesemia: A midline CS with myoclonus and ocular flutter and two cases of hemispheric CS, one of them entailed a Schmahmann's syndrome and the other suffered a seizure. MRI findings revealed cerebellar vasogenic edema and the symptoms improved after magnesium replacement in all cases. Literature Review: We reviewed 22 cases of CS due to hypomagnesemia, all with subacute onset (days to weeks). Encephalopathy and/or epileptic seizures were common. MRI findings were vasogenic edema involving the cerebellar hemispheres, the vermis, or the nodule. Up to 50% of patients presented hypocalcemia and/or hypokalemia. All the patients showed symptomatic improvement after magnesium replacement, but 50% showed significant sequelae, and 46% relapsed. Conclusions: Hypomagnesaemia should always be considered in the differential diagnosis of CS as it has a potential treatment, and its early recognition can avoid recurrences and permanent cerebellar impairment.

Mechanisms Involved in Epileptogenesis in Alzheimer's Disease and Their Therapeutic Implications.

Epilepsy and Alzheimer's disease (AD) incidence increases with age. There are reciprocal relationships between epilepsy and AD. Epilepsy is a risk factor for AD and, in turn, AD is an independent risk factor for developing epilepsy in old age, and abnormal AD biomarkers in PET and/or CSF are frequently found in late-onset epilepsies of unknown etiology. Accordingly, epilepsy and AD share pathophysiological processes, including neuronal hyperexcitability and an early excitatory-inhibitory dysregulation, leading to dysfunction in the inhibitory GABAergic and excitatory glutamatergic systems. Moreover, both ß-amyloid and tau protein aggregates, the anatomopathological hallmarks of AD, have proepileptic effects. Finally, these aggregates have been found in the resection material of refractory temporal lobe epilepsies, suggesting that epilepsy leads to amyloid and tau aggregates. Some epileptic syndromes, such as medial temporal lobe epilepsy, share structural and functional neuroimaging findings with AD, leading to overlapping symptomatology, such as episodic memory deficits and toxic synergistic effects. In this respect, the existence of epileptiform activity and electroclinical seizures in AD appears to accelerate the progression of cognitive decline, and the presence of cognitive decline is much more prevalent in epileptic patients than in elderly patients without epilepsy. Notwithstanding their clinical significance, the diagnosis of clinical seizures in AD is a challenge. Most are focal and manifest with an altered level of consciousness without motor symptoms, and are often interpreted as cognitive fluctuations. Finally, despite the frequent association of epilepsy and AD dementia, there is a lack of clinical trials to guide the use of antiseizure medications (ASMs). There is also a potential role for ASMs to be used as disease-modifying drugs in AD.