Infratentorial Superficial Siderosis and Spontaneous Intracranial Hypotension.

OBJECTIVE: Spontaneous spinal cerebrospinal fluid (CSF) leaks cause intracranial hypotension (SIH) and also may cause infratentorial superficial siderosis (iSS) but the rate of development among different CSF leak types and outcome of treatment are not known. We determined the time interval from SIH onset to iSS and the outcome of treatment. METHODS: A total of 1,589 patients with SIH underwent neuroimaging and iSS was detected in 57 (23 men and 34 women, mean age = 41.3 years [3.6%]). We examined the type of underlying CSF leak by various imaging modalities. Percutaneous and surgical procedures were used to treat the CSF leaks. RESULTS: The iSS was detected in 46 (10.3%) of 447 patients with ventral CSF leaks, in 2 (3.9%) of 51 patients with dural ectasia, in 5 (2.6%) of 194 patients with CSF-venous fistulas, in 4 (0.9%) of 457 patients with simple meningeal diverticula, and in none of the 101 patients with lateral CSF leaks or the 339 patients with leaks of indeterminate origin (p < 0.001). The estimated median latency period from SIH onset to iSS was 126 months. Ventral CSF leaks could not be eliminated with percutaneous procedures in any patient and surgical repair was associated with low risk (<5%) and resulted in resolution of the CSF leak in all patients in whom the exact site of the CSF leak could be determined. Other types of CSF leak were treated with percutaneous or surgical procedures. INTERPRETATION: The iSS can develop in most types of spinal CSF leak, including CSF-venous fistulas, but mainly in chronic ventral CSF leaks, which require surgical repair. ANN NEUROL 2023;93:64-75.