SSCNS is a rare neurological disorder. We report a case of SSCNS diagnosed as degenerative cerebellar ataxia for ten years, which was responsive to the treatment with iron chelator. The symptoms of SSCNS are particularly numerous. The most common clinical manifestations are ataxia, hearing loss, and pyramidal tract sign. Other clinical symptoms include headache, dizziness, cognitive decline, vision loss, tinnitus, epilepsy, tremor, olfactory dysfunction, back pain, constipation disorder, sexual dysfunction and so on[4–6]. The early symptoms are atypical and confusing. If the clinician has insufficient understanding of SSCNS disease, it’s easy to be misdiagnosed.
In addition to autopsy, the detection of superficial siderosis require imaging support. Brain MR imaging is an important imaging method for the diagnosis of SSCNS. The appearance of SSCNS on MR imaging is derived from hemosiderin-based paramagnetic blood breakdown products, which cause uneven magnetic field distribution and appear as linear low signals along the surface of the cerebral sulci on T2*-GRE and SWI sequences[7]. The detection of superficial siderosis depends on the sequence type and parameters, including spatial resolution, echo time, layer thickness, and magnetic field strength[4]. Several recent studies have shown that SWI is more sensitive to superficial siderosis detection than T2*-GRE, showing low signal around the cerebral, brain stem, cerebellum, spinal cord, and cranial nerves[8, 9]. Most superficial siderosis cannot be detected on T1WI, but can occasionally be displayed on T2WI. In our case, superficial siderosis was not demonstrated obviously on T1WI and T2WI, so the patient was misdiagnosed for several years until he did the SWI sequence. Therefore, SWI should be performed early especially for the patients with unexplained dizziness and cerebellar ataxia.
A biomarker for early diagnosis of SSCNS is urgently needed at a preclinical phase without symptoms or imaging signs. SWI is sensitive to superficial siderosis detection. However, the imaging findings of SSCNS might represent a late stage of disease[10]. The iron-sensitive imaging technology needs to be further developed, thus contributing to the early diagnosis of SSCNS. There is also a lack of body fluid biomarkers. Hani et al reported that CSF ferritin was elevated in patients with spontaneous intracranial hypotension, who were potentially at risk of developing superficial siderosis[11]. The present case showed that serum ferritin was significantly higher than normal level. Serum and CSF ferritin may be a potential biomarker for the early diagnosis and evaluation of therapeutic effect of SSCNS, which need more research to confirm.
Chronic recurrent subarachnoid hemorrhage leads to free iron in the cerebrospinal fluid, resulting in neuronal death, glial cell proliferation and hemosiderosis[12]. The essential treatment of SSCNS is to identify the source of chronic subarachnoid hemorrhage. According to the location of hemosiderin deposition, SSCNS was classified as cortical superficial siderosis and infratentorial superficial siderosis by Wilson et al[3]. Typical SSCNS is thought to be caused by repeated subarachnoid hemorrhage due to trauma, brain tumor, cerebral amyloid angiopathy or vascular malformation[1][1]. Some etiologies may be treated by surgery to remove the cause[13, 14]. The present patient was diagnosed with a spontaneous CSF leak, and the bleeding source was attributed to a ventral dural defect. Two theories have been proposed to explain the pathogenesis: bleeding from intracranial veins caused by brain sagging due to intracranial hypotension or bleeding from fragile vessels associated with dural defect[15, 16].
The main treatment for SSCNS is to remove the etiology of the bleeding. The choices of treatment for cases with CSF leak are epidural blood patch and neurosurgical dural repair[17]. However, currently there is a lack of effective drug treatment for hemosiderosis. Previous studies have shown that SSCNS may be treated by iron chelator[18, 19], which is still controversial[20]. Our patient refused epidural blood patch and neurosurgery. Fortunately, his symptoms were improved with the use of plenty of intravenous fluids and deferoxamine mesylate, which is widely used to reduce iron accumulation and deposition in tissues[21]. It suggests that iron chelator is a worthwhile drug treatment option for SSCNS.
In conclusion, SSCNS with spontaneous intracranial hypotension due to CSF leakage is extremely rare and easily misdiagnosed. SWI is sensitive to detect superficial siderosis. In addition to surgery, the drug iron chelator is a worthwhile treatment for SSCNS. Our results contribute to the diagnosis and treatment of SSCNS.