Asymmetries of total arterial supply of cerebral hemispheres do not exist

Human cerebral blood supply via circulus arteriosus cerebri: A scoping review on its variations and clinical implications

Background

Circulus arteriosus cerebri (CAC), responsible for supplying blood to the brain, presents anatomical variations that have been associated with both haemorrhagic and ischemic strokes. Therefore, it is crucial to conduct comprehensive investigations and comparisons of the diverse variant components of the CAC, published in various journals, and analyze them to identify individuals at risk of cerebrovascular pathologies, thereby ensuring enhanced and timely treatment.

Methods

A scoping review according to the five-stage protocol by Arksey and O'Malley was performed between February and June 2023. Seven hundred and seventy-seven records were initially identified, and a total of 51 studies were finally included.

Results

This scoping review focuses on the anatomical variations of the CAC and their clinical implications on cerebrovascular disease and includes more original articles than review s. Consistent with previous findings, most of the records included small populations or samples, while only three records reported larger populations. Surprisingly, the populations enclosed in the included records consisted of autopsied cadaveric specimens more than living subjects. Finally, the qualitative analysis highlighted three main themes concerning the relationship between the normal CAC morphology and the cerebrovascular disease onset as well as the variant CAC morphology and its main features that might be also involved in these diseases. Finally, techniques that can be used to measure CAC have also been assessed.

Conclusion

Variations in the CAC, more common in the posterior part, with genetic and environmental factors influencing these variations impact cerebrovascular disorders. Understanding variants components of CAC can aid in improving brain surgeries and post-stroke care.

Stability of OCT and OCTA in the Intensive Therapy Unit Setting

To assess the stability of retinal structure and blood flow measures over time and in different clinical settings using portable optical coherence tomography angiography (OCTA) as a potential biomarker of central perfusion in critical illness, 18 oesophagectomy patients completed retinal structure and blood flow measurements by portable OCT and OCTA in the eye clinic and intensive therapy unit (ITU) across three timepoints: (1) pre-operation in a clinic setting; (2) 24–48 h post-operation during ITU admission; and (3) seven days post-operation, if the patient was still admitted. Blood flow and macular structural measures were stable between the examination settings, with no consistent variation between pre- and post-operation scans, while retinal nerve fibre layer thickness increased in the post-operative scans (+2.31 µm, p = 0.001). Foveal avascular zone (FAZ) measurements were the most stable, with an intraclass correlation coefficient of up to 0.92 for right eye FAZ area. Blood flow and structural measures were lower in left eyes than right eyes. Retinal blood flow assessed in patients before and during an ITU stay using portable OCTA showed no systematic differences between the clinical settings. The stability of retinal blood flow measures suggests the potential for portable OCTA to provide clinically useful measures in ITU patients.

Unilateral Relapsing Primary Angiitis of the CNS: An Entity Suggesting Differences in the Immune Response Between the Cerebral Hemispheres

OBJECTIVE

To determine whether studying patients with strictly unilateral relapsing primary angiitis of the CNS (UR-PACNS) can support hemispheric differences in immune response mechanisms, we reviewed characteristics of a group of such patients.

METHODS

We surveiled our institution for patients with UR-PACNS, after characterizing one such case. We defined UR-PACNS as PACNS with clinical and radiographic relapses strictly recurring in 1 brain hemisphere, with or without hemiatrophy. PACNS must have been biopsy proven. Three total cases were identified at our institution. A literature search for similar reports yielded 4 additional cases. The combined 7 cases were reviewed for demographic, clinical, imaging, and pathologic trends.

RESULTS

The median age at time of clinical onset among the 7 cases was 26 years (range 10-49 years); 5 were male (71%). All 7 patients presented with seizures. The mean follow-up duration was 7.5 years (4-14.1 years). The annualized relapse rate ranged between 0.2 and 1. UR-PACNS involved the left cerebral hemisphere in 5 of the 7 patients. There was no consistent relationship between the patient's dominant hand and the diseased side. When performed (5 cases), conventional angiogram was nondiagnostic. CSF examination showed nucleated cells and protein levels in normal range in 3 cases and ranged from 6 to 11 cells/μL and 49 to 110 mg/dL in 4 cases, respectively. All cases were diagnosed with lesional biopsy, showing lymphocytic type of vasculitis of the small- and medium-sized vessels. Patients treated with steroids alone showed progression. Induction therapy with cyclophosphamide or rituximab followed by a steroid sparing agent resulted in the most consistent disease remission.

CONCLUSIONS

Combining our 3 cases with others reported in the literature allows better clinical understanding about this rare and extremely puzzling disease entity. We hypothesize that a functional difference in immune responses, caused by such discrepancies as basal levels of cytokines, asymmetric distribution of microglia, and differences in modulation of the systemic immune functions, rather than a structural antigenic difference, between the right and left brain may explain this phenomenon, but this is speculative.