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Sylviocentral ratio: a novel magnetic resonance imaging marker for differentiating probable idiopathic normal
Ahmet Baytok1, Seyit Erol2, Ayse Ari2
1Department of Radiology, Selçuk University Faculty of Medicine, Konya, Turkey. drahmetbaytok@gmail.com.
Purpose:
Probable idiopathic normal pressure hydrocephalus (pNPH) is a potentially treatable neurological disorder that can be difficult to differentiate from diffuse cerebral atrophy because of overlapping clinical and imaging features. This study evaluated the diagnostic performance of a novel magnetic resonance imaging (MRI)-derived marker, the sylviocentral ratio, for distinguishing pNPH from diffuse cerebral atrophy.
Methods:
In this prospective study, 72 patients (36 with pNPH and 36 with diffuse cerebral atrophy) underwent routine brain MRI, with an additional sagittal 3D T2-weighted SPACE acquisition; axial and coronal reformatted images were generated from the volumetric dataset for standardized measurements. Sylvian fissure and central sulcus diameters were measured on these standardized images using predefined anatomical landmarks, and the sylviocentral ratio was calculated.
Results:
The sylviocentral ratio was significantly higher in patients with pNPH than in those with diffuse cerebral atrophy (10.94 ± 4.67 vs. 2.86 ± 2.00, p < 0.001). Receiver operating characteristic (ROC) analysis demonstrated excellent diagnostic performance, with an area under the curve (AUC) of 0.953 (95% confidence interval [CI]: 0.896-0.994). A cut-off value of ≥ 5.3 yielded a sensitivity of 91.7% and a specificity of 94.4%. Diagnostic performance was comparable to the callosal angle (AUC = 0.951) and superior to the Evans index (AUC = 0.922). The sylviocentral ratio remained independently associated with pNPH after adjustment for age (p < 0.001). Interobserver agreement was excellent (intraclass correlation coefficient [ICC] = 0.94).
Conclusion:
The sylviocentral ratio is a practical, reproducible, and highly accurate MRI marker for differentiating pNPH from diffuse cerebral atrophy and may complement established imaging parameters in clinical assessment. Given the limited size of the age-matched cohort, validation in larger, ideally external cohorts is warranted before widespread clinical implementation.