CSF Flow and Spinal Cord Motion in Patients With Spontaneous Intracranial Hypotension: A Phase Contrast MRI Study

Skull Base CSF Leaks: Potential Underlying Pathophysiology and Evaluation of Brain MR Imaging Findings Associated with Spontaneous Intracranial Hypotension

BACKGROUND AND PURPOSE

CSF leaks of the skull base and spine share a common process of CSF volume loss, and yet only the latter has been associated with spontaneous intracranial hypotension (SIH). Despite published claims that only spinal leaks cause SIH, no prior studies have evaluated brain MR imaging in patients with skull base leaks for findings associated with SIH, such as dural enhancement. The purpose of our study was to use a validated brain MR imaging scoring system to evaluate patients with skull base CSF leaks for findings associated with SIH.

MATERIALS AND METHODS

We included patients with confirmed skull base CSF leaks and contrast-enhanced preoperative brain MRI. The preoperative MR images were reviewed for findings associated with SIH by using the Bern score. Patient age, presenting symptoms and their duration, and leak site were also recorded.

RESULTS

Thirty-one patients with skull base CSF leaks were included. Mean Bern score was 0.9 (range 0-4, standard deviation 1.1), and only 1 patient (3%) had dural enhancement. Mean age was 53 years (range 18-76). Mean symptom duration was 1.3 years, with 22 patients presenting within 1 year of symptom onset. Twenty-three patients (74.2%) had intraoperative confirmation of leak from the middle cranial fossa, involving the temporal bone, while 7 (22.6%) had leaks from the anterior skull base. One patient, who had dural enhancement, had an infratentorial CSF leak along the petrous segment of the internal carotid artery.

CONCLUSIONS

Our study provides further evidence that skull base and spinal CSF leaks represent distinct pathophysiologies and present with different brain MRI findings.

Four-dimensional flow MRI for quantitative assessment of cerebrospinal fluid dynamics: Status and opportunities

Neurological disorders can manifest with altered neurofluid dynamics in different compartments of the central nervous system. These include alterations in cerebral blood flow, cerebrospinal fluid (CSF) flow, and tissue biomechanics. Noninvasive quantitative assessment of neurofluid flow and tissue motion is feasible with phase contrast magnetic resonance imaging (PC MRI). While two-dimensional (2D) PC MRI is routinely utilized in research and clinical settings to assess flow dynamics through a single imaging slice, comprehensive neurofluid dynamic assessment can be limited or impractical. Recently, four-dimensional (4D) flow MRI (or time-resolved three-dimensional PC with three-directional velocity encoding) has emerged as a powerful extension of 2D PC, allowing for large volumetric coverage of fluid velocities at high spatiotemporal resolution within clinically reasonable scan times. Yet, most 4D flow studies have focused on blood flow imaging. Characterizing CSF flow dynamics with 4D flow (i.e., 4D CSF flow) is of high interest to understand normal brain and spine physiology, but also to study neurological disorders such as dysfunctional brain metabolite waste clearance, where CSF dynamics appear to play an important role. However, 4D CSF flow imaging is challenged by the long T1 time of CSF and slower velocities compared with blood flow, which can result in longer scan times from low flip angles and extended motion-sensitive gradients, hindering clinical adoption. In this work, we review the state of 4D CSF flow MRI including challenges, novel solutions from current research and ongoing needs, examples of clinical and research applications, and discuss an outlook on the future of 4D CSF flow.

Non-invasive biomarkers for spontaneous intracranial hypotension (SIH) through phase-contrast MRI

BACKGROUND AND OBJECTIVE

Spontaneous intracranial hypotension (SIH) is an underdiagnosed disease. To depict the accurate diagnosis can be demanding; especially the detection of CSF-venous fistulas poses many challenges. Potential dynamic biomarkers have been identified through non-invasive phase-contrast MRI in a limited subset of SIH patients with evidence of spinal longitudinal extradural collection. This study aimed to explore these biomarkers related to spinal cord motion and CSF velocities in a broader SIH cohort.

METHODS

A retrospective, monocentric pooled-data analysis was conducted of patients suspected to suffer from SIH who underwent phase-contrast MRI for spinal cord and CSF velocity measurements at segment C2/C3 referred to a tertiary center between February 2022 and June 2023. Velocity ranges (mm/s), total displacement (mm), and further derivatives were assessed and compared to data from the database of 70 healthy controls.

RESULTS

In 117 patients, a leak was located (54% ventral leak, 20% lateral leak, 20% CSF-venous fistulas, 6% sacral leaks). SIH patients showed larger spinal cord and CSF velocities than healthy controls: e.g., velocity range 7.6 ± 3 mm/s vs. 5.6 ± 1.4 mm/s, 56 ± 21 mm/s vs. 42 ± 10 mm/s, p < 0.001, respectively. Patients with lateral leaks and CSF-venous fistulas exhibited an exceptionally heightened level of spinal cord motion (e.g., velocity range 8.4 ± 3.3 mm/s; 8.2 ± 3.1 mm/s vs. 5.6 ± 1.4 mm/s, p < 0.001, respectively).

CONCLUSION

Phase-contrast MRI might become a valuable tool for SIH diagnosis, especially in patients with CSF-venous fistulas without evidence of spinal extradural fluid collection.

Spinal cord motion and CSF flow in the cervical spine of 70 healthy participants

Pulsatile spinal cord and CSF velocities related to the cardiac cycle can be depicted by phase-contrast MRI. Among patients with spontaneous intracranial hypotension, we have recently described relevant differences compared with healthy controls in segment C2/C3. The method might be a promising tool to solve clinical and diagnostic ambiguities. Therefore, it is important to understand the physiological range and the effects of clinical and anatomical parameters in healthy volunteers. Within a prospective study, 3D T2-weighted MRI for spinal canal anatomy and cardiac-gated phase-contrast MRI adapted to CSF flow and spinal cord motion for time-resolved velocity data and derivatives were performed in 70 participants (age 20-79 years) in segments C2/C3 and C5/C6. Correlations were analyzed by multiple linear regression models; p < 0.01 was required to assume a significant impact of clinical or anatomical data quantified by the regression coefficient B. Data showed that in C2/C3, the CSF and spinal cord craniocaudal velocity ranges were 4.5 ± 0.9 and 0.55 ± 0.15 cm/s; the total displacements were 1.1 ± 0.3 and 0.07 ± 0.02 cm, respectively. The craniocaudal range of the CSF flow rate was 8.6 ± 2.4 mL/s; the CSF stroke volume was 2.1 ± 0.7 mL. In C5/C5, physiological narrowing of the spinal canal caused higher CSF velocity ranges and lower stroke volume (C5/C6 B = +1.64 cm/s, p < 0.001; B = -0.4 mL, p = 0.002, respectively). Aging correlated to lower spinal cord motion (e.g., B = -0.01 cm per 10 years of aging, p < 0.001). Increased diastolic blood pressure was associated with lower spinal cord motion and CSF flow parameters (e.g., C2/C3 CSF stroke volume B = -0.3 mL per 10 mmHg, p < 0.001). Males showed higher CSF flow and spinal cord motion (e.g., CSF stroke volume B = +0.5 mL, p < 0.001; total displacement spinal cord B = +0.016 cm, p = 0.002). We therefore propose to stratify data for age and sex and to adjust for diastolic blood pressure and segmental narrowing in future clinical studies.

The Pressure of Headache at the United Kingdom CSF Disorders Day 2023

Headache in intracranial disorders drives significant disability in our patients. Management principles for secondary headaches require a multidisciplinary approach with expertise from the neurological, neuro-ophthalmological, neuroradiological, and neurosurgical specialities. The Pressure of Headache was the theme of the annual United Kingdom CSF Disorders Day and saw speakers and panellists from Australia, Europe, and the United States. Among the topics presented were the newest concepts underpinning idiopathic intracranial hypertension management and spontaneous intracranial hypotension. Advances in our knowledge of cerebrospinal fluid secretion and the visual snow syndrome debate were particular highlights. This review provides a summary of the research on headache disorders that overlap the neuro-ophthalmological axis of care for patients.

Increased cranio-caudal spinal cord oscillations are the cardinal pathophysiological change in degenerative cervical myelopathy

Introduction

Degenerative cervical myelopathy (DCM) is the most common cause of non-traumatic incomplete spinal cord injury, but its pathophysiology is poorly understood. As spinal cord compression observed in standard MRI often fails to explain a patient's status, new diagnostic techniques to assess DCM are one of the research priorities. Minor cardiac-related cranio-caudal oscillations of the cervical spinal cord are observed by phase-contrast MRI (PC-MRI) in healthy controls (HCs), while they become pathologically increased in patients suffering from degenerative cervical myelopathy. Whether transversal oscillations (i.e., anterior-posterior and right-left) also change in DCM patients is not known.

Methods

We assessed spinal cord motion simultaneously in all three spatial directions (i.e., cranio-caudal, anterior-posterior, and right-left) using sagittal PC-MRI and compared physiological oscillations in 18 HCs to pathological changes in 72 DCM patients with spinal canal stenosis. The parameter of interest was the amplitude of the velocity signal (i.e., maximum positive to maximum negative peak) during the cardiac cycle.

Results

Most patients suffered from mild DCM (mJOA score 16 (14-18) points), and the majority (68.1%) presented with multisegmental stenosis. The spinal canal was considerably constricted in DCM patients in all segments compared to HCs. Under physiological conditions in HCs, the cervical spinal cord oscillates in the cranio-caudal and anterior-posterior directions, while right-left motion was marginal [e.g., segment C5 amplitudes: cranio-caudal: 0.40 (0.27-0.48) cm/s; anterior-posterior: 0.18 (0.16-0.29) cm/s; right-left: 0.10 (0.08-0.13) cm/s]. Compared to HCs, DCM patients presented with considerably increased cranio-caudal oscillations due to the cardinal pathophysiologic change in non-stenotic [e.g., segment C5 amplitudes: 0.79 (0.49-1.32) cm/s] and stenotic segments [.g., segment C5 amplitudes: 0.99 (0.69-1.42) cm/s]). In contrast, right-left [e.g., segment C5 amplitudes: non-stenotic segment: 0.20 (0.13-0.32) cm/s; stenotic segment: 0.11 (0.09-0.18) cm/s] and anterior-posterior oscillations [e.g., segment C5 amplitudes: non-stenotic segment: 0.26 (0.15-0.45) cm/s; stenotic segment: 0.11 (0.09-0.18) cm/s] remained on low magnitudes comparable to HCs.

Conclusion

Increased cranio-caudal oscillations of the cervical cord are the cardinal pathophysiologic change and can be quantified using PC-MRI in DCM patients. This study addresses spinal cord oscillations as a relevant biomarker reflecting dynamic mechanical cord stress in DCM patients, potentially contributing to a loss of function.

Cerebral venous thrombosis caused by spontaneous intracranial hypotension due to spontaneous spinal cerebrospinal fluid leakage in the high cervical region: a case report

Spontaneous intracranial hypotension (SIH) may lead to cerebral venous thrombosis (CVT). This case report describes the diagnostic and treatment processes used for a patient with CVT caused by SIH due to spontaneous spinal cerebrospinal fluid (CSF) leakage in the high cervical region. Clinical data were collected from a 37-year-old man with an initial symptom of spontaneous posterior cervical pain. The diagnostic and treatment processes of SIH-induced CVT were described. A magnetic resonance imaging (MRI) study showed superior sagittal sinus thrombosis, and a lumbar puncture revealed a low initial CSF pressure of less than 60 mmH2O. The patient underwent anticoagulation and fluid rehydration therapies. No abnormalities were observed in the thoracic MRI scan, but a cervical MRI scan revealed a spontaneous CSF leak. An epidural blood patch with autologous blood was performed, and symptoms completely resolved 3 days after the procedure. This report proposes a diagnostic procedure for detecting rare cases of SIH-induced CVT, thereby preventing future misdiagnoses and delayed treatment. When a patient presenting with CVT in conjunction with intracranial hypotension has no history of trauma or piercing, SIH caused by spontaneous spinal CSF leakage should be considered as a potential cause of secondary low intracranial pressure. For detection of CSF leaks at rare sites, an MRI of the whole spine rather than a localized MRI of the spine needs to be performed to avoid misdiagnosis. An epidural blood patch should be performed as soon as possible as it may shorten the length of hospitalization and improve prognosis.

Unusual neuroimaging findings in spontaneous intracranial hypotension

PURPOSE

The most common neuroimaging manifestations of patients suffering from spontaneous intracranial hypotension (SIH) include subdural fluid collections, enhancement of the pachymeninges, engorgement of venous structures, pituitary hyperemia, sagging of the brainstem, and cerebellar hemosiderosis. However, infrequently patients may present with separate neuroradiological findings which could be easily mistaken for other pathology.

METHODS

We describe patients who presented with unique neuroimaging findings who were eventually found to have a spinal CSF leak or venous fistula. Relevant clinical history and neuroradiology findings are presented, and a relevant review of the literature is provided.

RESULTS

We present six patients with a proven CSF leak or fistula who presented with dural venous sinus thrombosis, compressive ischemic injury, spinal hemosiderosis, subarachnoid hemorrhage, pial vascular engorgement, calvarial hyperostosis, and spinal dural calcifications.

CONCLUSION

Radiologists should be familiar with atypical neuroimaging manifestations of SIH in order to avoid misdiagnosis and guide the clinical trajectory of the patient towards accurate diagnosis and eventual cure.

Spinal cord motion assessed by phase-contrast MRI - An inter-center pooled data analysis

BACKGROUND

Phase-contrast MRI of CSF and spinal cord dynamics has evolved among diseases caused by altered CSF volume (spontaneous intracranial hypotension, normal pressure hydrocephalus) and by altered CSF space (degenerative cervical myelopathy (DCM), Chiari malformation). While CSF seems to be an obvious target for possible diagnostic use, craniocaudal spinal cord motion analysis offers the benefit of fast and reliable assessments. It is driven by volume shifts between the intracranial and the intraspinal compartments (Monro-Kellie hypothesis). Despite promising initial reports, comparison of spinal cord motion data across different centers is challenged by reports of varying value, raising questions about the validity of the findings.

OBJECTIVE

To systematically investigate inter-center differences between phase-contrast MRI data.

METHODS

Age- and gender matched, retrospective, pooled-data analysis across two centers: cardiac-gated, sagittal phase-contrast MRI of the cervical spinal cord (segments C2/C3 to C7/T1) including healthy participants and DCM patients; comparison and analysis of different MRI sequences and processing techniques (manual versus fully automated).

RESULTS

A genuine craniocaudal spinal cord motion pattern and an increased focal spinal cord motion among DCM patients were depicted by both MRI sequences (p < 0.01). Higher time-resolution resolved steeper and larger peaks, causing inter-center differences (p < 0.01). Comparison of different processing methods showed a high level of rating reliability (ICC > 0.86 at segments C2/C3 to C6/C7).

DISCUSSION

Craniocaudal spinal cord motion is a genuine finding. Differences between values were attributed to time-resolution of the MRI sequences. Automated processing confers the benefit of unbiased and consistent analysis, while data did not reveal any superiority.