Application of Cine Phase Contrast MRI in Spontaneous Intracranial Hypotension Before and After Treatment I-HsIao Yang1 HsIu-LIng CHen1,2 Meng-HsIang CHen1 CHun-CHung LuI1 CHen-san su3 MIn-Yu Lan3 Yu-Feng CHeng1 CHeng-HsIen Lu3 WeI-CHe LIn1

Spontaneous intracranial hypotension (SIH) is characterized by orthostatic headache. Typical abnormal magnetic resonance imaging (MRI) findings have been considered to be the sine qua non of SIH, but a sizeable minority of patients has normal results using conventional MRI. The purpose of this study was to evaluate the difference in cerebrospinal fluid (CSF) flow dynamics between patients and healthy people using cine phase contrast (PC) MRI, and to assess the CSF flow dynamics in patients before and after treatment. From November of 2007 to December of 2012, twenty patients with SIH (10 men and 10 women, mean age = 40.9 ± 7.77 years) and 31 ageand gendermatched healthy subjects (15 men and 16 women, mean age = 46.3 ± 7.53 years) were enrolled in this retrospective study. Cine PC MRI was performed on the patients and on the healthy subjects to measure the CSF flow in cerebral aqueduct. Patients underwent repeated cine PC MRI at 24 hours and at one month after treatment respectively. Five parameters including peak positive and negative velocity, average flow, and average positive and negative flow were recorded to evaluate their differences. Seventeen patients (85%) received epidural blood patching (EBP) owing to the failure of conservative treatment. All patients experienced resolution of symptoms after treatment. Before treatment, the patients had a significantly lower average CSF flow than the healthy subjects (p< 0.001). The average CSF flow was elevated in patients with SIH at 24 hours after treatment and was significantly increased one month after treatment (p= 0.003). By establishment of the receiver operating characteristic (ROC) curve, the best cutoff value for the average CSF flow was determined to be 14.0μl/beat, while the sensitivity and specificity were determined to be 90.3% and 72.2%, respectively. Patients with SIH showed lower CSF flow compared to healthy subjects, but this decreased CSF flow was shown by cine PC MRI to be gradually recovered after treatment. This study provides evidence that cine PC MRI is useful for assessing the dynamic changes of CSF flow in the cerebral aqueduct noninvasively and for demonstrating the effectiveness of treatment in patients with SIH reliably. Correspondence Author to: Wei-Che Lin Department of Diagnostic Radiology, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan No. 123, Ta-Pei Road, Niao-Sung, Kaohsiung 83305, Taiwan J radiol sci 2014; 39: 67-76 Application of cine Pc MrI in sIH before and after treatment 68 J Radiol Sci September 2014 Vol.39 No.3 pachymeningeal enhancement on cranial MRI, evidence of CSF leakage or CSF opening pressure less than 60 mm-H2O, and relies on the resolution of the typical symptoms after epidural blood patching (EBP). However, some studies have reported that up to 20% of patients with clinically apparent SIH lack any abnormal cranial MRI findings [4-7]. Several types of SIH have been reported, including patients with normal CSF pressure, the absence of pachymeningeal enhancement, or non-orthostatic headache [7-10]. Thus, Schievink et al. reported a new set of diagnostic criteria for spontaneous spinal CSF leaks and SIH encompassing varied clinical and radiographic manifestations (Table 1) [1]. There are several imaging modalities available to assist in the diagnosis of SIH, such as cranial and spinal MRI, computed tomography (CT) myelography, and radionuclide cisternography (RC) [3, 11]. Despite the fact that the characteristic MRI findings consist of subdural fluid collections, enhancement of the pachymeninges, engorgement of venous structures, pituitary hyperemia, and sagging of the brain (mnemonic, SEEPS) [12], there is a sizeable minority of patients who lack such typical results on cranial MRI [5, 6, 8]. Spinal MRI is sufficiently sensitive, in comparision to CT myelography, to show CSF leaks, dural enhancement, engorged spidural venous plexus, and spinal abnormalities, and may be of particular value to patients with equivocal clinical or brain imaging findings [13, 14]. RC has also been used extensively in the evaluation of SIH, but detection of the exact site of CSF leakage is limited in one third patients [4, 15-17]. Because SIH varies widely in terms of clinical symptoms and is easily misdiagnosed initially in the absence of typical imaging findings, several different diagnostic criteria are suggested. An objective interpretation of imaging findings was proposed by measuring the mamillopontine distance and the pontomesencephalic angle in qualitative MRI to improve diagnostic accuracy [18]. Another study proposed the quantitative analysis of CSF flow in the cerebral aqueduct by cine phase contrast (PC) MRI to demonstrate its direct relationship with the values of CSF opening pressure [19]. Cine PC MRI has been introduced for many clinical uses because of its ability to assess the flow characteristics quantitatively inside the body without invasive procedures [20, 21]. The detected velocities and flows in the cerebral aqueduct should reflect the pathophysiological changes in SIH. The purpose of this study was to evaluate the differences in CSF flow dynamics between patients and healthy people by cine PC MRI, and to assess the CSF flow dynamics in patients before and after treatment.