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Introduction Middle cranial fossa defects leading to spontaneous cerebrospinal fluid leaks are increasingly recognized as a part of the spectrum of idiopathic intracranial hypertension (IIH). However, not all patients present with the classical diagnostic criteria for IIH. Recent literature demonstrates that such patients without clinical IIH may demonstrate radiological markers of IIH. In patients with spontaneous skull base cerebrospinal fluid leaks, occult idiopathic intracranial hypertension may be an important contributing factor. This study aims to characterize the prevalence of radiological IIH markers in this population and identify clinical factors associated with both radiological features of IIH and clinical IIH.Methods We performed a single-center retrospective analysis of 84 patients with surgically repaired middle cranial fossa CSF leaks from 2019 to 2026. Demographic, clinical, and radiological data were collected. Radiological signs of IIH (Optic nerve tortuosity, empty Sella/partial empty Sella, prominent Meckel’s cave, presence of an encephalocele) were assessed on imaging. Clinical IIH was defined by modified Dandy’s criteria. Logistic regression analyses (univariable and multivariable) were used to identify factors associated with radiological signs of IIH and clinical IIH.Results The cohort was predominantly female (77.4%) with a median age of 56 years and a median BMI of 34.4 kg/m 2. Radiological markers of IIH were present in 78.6% (66/84) [95%CI, 68.7% - 86%] of patients. Only 19.0% with had overt clinical IIH per modified Dandy criteria. Radiological IIH features were significantly associated with patients diagnosed as clinical IIH (p<0.01). Among 84 patients, excluding venous sinus stenosis, 18 (21.4%) had none of the 4 prespecified radiological intracranial hypertension features, 41 (48.8%) had 1 marker, 8 (9.5%) had 2 markers, 15 (17.9%) had 3 markers, and 2 (2.4%) had all 4 signs. Venous sinus stenosis was identified in 61.9% of patients who underwent venographic evaluation, with a median trans-stenotic gradient of 8.0 mmHg. Ten patients (11.9%) underwent venous sinus stenting. On multivariable logistic regression analysis, female sex (OR 5.3, p=0.01) and elevated opening pressure (OR 6.8, p=0.02) were independently associated with radiological signs of IIH. For clinical IIH, venous sinus stenosis was the only independent associated predictor (adjusted OR 9.66, p=0.013).Conclusion Radiological markers of IIH are more prevalent than clinically overt disease in patients with middle cranial fossa defects presenting as CSF leaks. This suggests the presence of a broader intracranial hypertension phenotype. Venous sinus stenosis emerges as the strongest independent factor associated with clinical IIH, suggesting that it may be a key pathophysiologic driver of IIH in patients with middle fossa defects presenting with CSF leak. As a result, preoperative recognition of radiographic signs of idiopathic intracranial hypertension may heighten suspicion for this association, strengthen preoperative counseling, and alert clinicians to the possibility that intracranial hypertension may present a likely therapeutic target in the perioperative care of spontaneous leak patients. Furthermore, in patients with intracranial hypertension diagnosed after repair, treatment of the underlying venous sinus stenosis, including venous sinus stenting, may represent an important adjunctive strategy.Disclosures B. Thorell: None. S. Srinivasan: None. V. Suresh: None. N. Borg: None. D. Surdell: None. W. Thorell: None. M. Sattur: None.