Cerebellar neurodegenerative ataxias are a group of disorders affecting the cerebellum and its pathways with different neurological structures. Transcranial sonography (TCS) has been used for the evaluation of brain parenchymal structures in various diseases because of its fast and safe utilization, especially in neuropsychiatric and neurodegenerative diseases. The aim of our study was to investigate TCS characteristics of patients with neurodegenerative cerebellar ataxias. In our study, we included 74 patients with cerebellar degenerative ataxia; 36.5% had autosomal dominant onset, while 33.8% had sporadic onset. Standardized ultrasonographic planes were used for the identification of brain structures of interest. The SARA, INAS, neuropsychological and psychiatric scales were used for the further clinical evaluation of our study participants. The brainstem raphe was discontinued in 33.8% of the patients. The substantia nigra (SN) hyperechogenicity was identified in 79.7%. The third and fourth ventricle enlargement had 79.7% and 45.9% of patients, respectively. A positive and statistically significant correlation was found between SN hyperechogenicity with dystonia (p < 0.01), rigidity and dyskinesia (p < 0.05). The higher SARA total score is statistically significantly correlated with the larger diameter of the III (r = 0.373; p = 0.001) and IV ventricles (r = 0.324; p = 0.005). In such patients, the echogenicity of substantia nigra has been linked to extrapyramidal signs, and raphe discontinuity to depression. Furthermore, ataxia and its clinical subtypes have positively correlated with the IV ventricle diameter, indicating brain atrophy and brain mass reduction.

Background/Objectives: “Ring-like” intracranial aneurysms—historically described as “doughnut-like” or “donut sign”—represent a rare configuration in which a central thrombus coexists with a circumferential mural flow ring. Traditionally considered a radiologic curiosity, this morphology likely reflects a shear-driven hemodynamic state rather than a stable organized thrombus. We aimed to summarize all PubMed-documented cases of ring-like aneurysms, define their morphologic and clinical spectrum, and assess their hemodynamic significance, rupture risk, and treatment outcomes. An additional aim is to formalize the use of the term “ring-like aneurysm” as a distinct morphologic subtype and to clearly differentiate it from the neuroradiologic “donut sign,” which represents an imaging appearance rather than a specific anatomic configuration. Methods: A systematic PubMed search (1996–2024) was conducted using the following combinations of keywords and Boolean operators: (“ring-like aneurysm” OR “donut aneurysm” OR “doughnut aneurysm” OR “ring-shaped aneurysm” OR “circumferential lumen” OR “central thrombus”) AND (“intracranial” OR “cerebral” OR “basilar” OR “aneurysm”). Only English-language, PubMed-indexed reports describing true ring-like (donut-shaped) aneurysms were included. Non-indexed, non-English, and serpentine or fusiform aneurysms mimicking ring-like morphology were excluded. Extracted data included aneurysm location, size, presentation (ruptured, symptomatic, or incidental), treatment strategy, and clinical outcome. Statistical proportions were analyzed using descriptive methods, Wilson 95% confidence intervals, and a binomial test to compare the observed subarachnoid hemorrhage (SAH) rate against the expected conservative rupture proportion. Results: The search identified 16 individual patients reported in 10 publications. All aneurysms were large or giant (14–36 mm) displaying characteristic thrombosed pattern. Ruptured presentation occurred in 6 out of 16 cases (37.5%) and symptomatic unruptured in 10 (62.5%). No incidental cases were reported. Posterior circulation involvement was present in 44%, with a female predominance of 69%. Conclusions: Ring-like aneurysms constitute a distinct, shear-maintained hemodynamic entity combining mural jet flow with central thrombosis. Their frequent symptomatic or ruptured presentation supports the concept that this morphology represents a pre-ruptural configuration rather than a chronic thrombotic residue. Early recognition and targeted endovascular exclusion of the inflow zone are essential to prevent delayed rupture.