Usefulness of intravoxel incoherent motion MRI for visualizing slow cerebrospinal fluid motion.

BACKGROUND: In the cerebrospinal fluid (CSF) dynamics, the pulsations of cerebral arteries and brain is considered the main driving force for the reciprocating bidirectional CSF movements. However, measuring these complex CSF movements on conventional flow-related MRI methods is difficult. We tried to visualize and quantify the CSF motion by using intravoxel incoherent motion (IVIM) MRI with low multi-b diffusion-weighted imaging. METHODS: Diffusion-weighted sequence with six b values (0, 50, 100, 250, 500, and 1000 s/mm2) was performed on 132 healthy volunteers aged ≥ 20 years and 36 patients with idiopathic normal pressure hydrocephalus (iNPH). The healthy volunteers were divided into three age groups (< 40, 40 to < 60, and ≥ 60 years). In the IVIM analysis, the bi-exponential IVIM fitting method using the Levenberg-Marquardt algorithm was adapted. The average, maximum, and minimum values of ADC, D, D*, and fraction of incoherent perfusion (f) calculated by IVIM were quantitatively measured in 45 regions of interests in the whole ventricles and subarachnoid spaces. RESULTS: Compared with healthy controls aged ≥ 60 years, the iNPH group had significantly lower mean f values in all the parts of the lateral and 3rd ventricles, whereas significantly higher mean f value in the bilateral foramina of Luschka. In the bilateral Sylvian fossa, which contain the middle cerebral bifurcation, the mean f values increased gradually with increasing age, whereas those were significantly lower in the iNPH group. In the 45 regions of interests, the f values in the bilateral foramina of Luschka were the most positively correlated with the ventricular size and indices specific to iNPH, whereas that in the anterior part of the 3rd ventricle was the most negatively correlated with the ventricular size and indices specific to iNPH. Other parameters of ADC, D, and D* were not significantly different between the two groups in any locations. CONCLUSIONS: The f value on IVIM MRI is useful for evaluating small pulsatile complex motion of CSF throughout the intracranial CSF spaces. Patients with iNPH had significantly lower mean f values in the whole lateral ventricles and 3rd ventricles and significantly higher mean f value in the bilateral foramina of Luschka, compared with healthy controls aged ≥ 60 years.

Immune-related aseptic meningitis diagnosed by Cube FLAIR on enhanced magnetic resonance imaging for a lung cancer patient administered atezolizumab: A case report.

Immune checkpoint inhibitors (ICIs) can cause immune-related adverse events (irAEs), such as neurological toxicity. A 46-year-old man was diagnosed with squamous cell lung cancer. Lung cancer recurred 3 years after he experienced left segmental lung rejection. Therefore, he received atezolizumab as fourth-line chemotherapy. He experienced fever, headache, and decreased consciousness 10 days after the first dose of atezolizumab. Plain head computed tomography and cerebrospinal fluid examination showed no significant findings. Magnetic resonance imaging (MRI) with a Gadolinium (Gd)-enhanced Cube fluid-attenuated inversion recovery (FLAIR) sequence showed nodular abnormalities with contrast enhancement. Thus, aseptic meningitis caused by ICIs was suspected. His consciousness level gradually improved with glucocorticoid therapy. Moreover, most nodular abnormalities observed on cerebral MRI disappeared concurrently. Thus, Gd-enhanced Cube FLAIR sequence has the unique ability to reveal immune-related aseptic meningitis.

MRI-based assessment of acute effect of head-down tilt position on intracranial hemodynamics and hydrodynamics.

PURPOSE: To quantify the acute effect of the head-down tilt (HDT) posture on intracranial hemodynamics and hydrodynamics. MATERIALS AND METHODS: We evaluated the intracranial physiological parameters, blood flow-related parameters, and brain morphology in the HDT (-6° and -12°) and the horizontal supine (HS) positions. Seven and 15 healthy subjects were scanned for each position using 3.0 T magnetic resonance imaging system. The peak-to-peak intracranial volume change, the peak-to-peak cerebrospinal fluid (CSF) pressure gradient (PGp-p ), and the intracranial compliance index were calculated from the blood and CSF flow determined using a cine phase-contrast technique. The brain volumetry was conducted using SPM12. The measurements were compared using the Wilcoxon signed-rank test or a paired t-test. RESULTS: No measurements changed in the -6° HDT. The PGp-p and venous outflow of the internal jugular veins (IJVs) in the -12° HDT were significantly increased compared to the HS (P < 0.001 and P = 0.025, respectively). The cross-sectional areas of the IJVs were significantly larger (P < 0.001), and the maximum, minimum, and mean blood flow velocity of the IJVs were significantly decreased (P = 0.003, < 0.001, and = 0.001, respectively) in the -12° HDT. The mean blood flow velocities of the internal carotid arteries were decreased (P = 0.023). Neither position affected the brain volume. CONCLUSION: Pressure gradient and venous outflow were increased in accordance with the elevation of the intracranial pressure as an acute effect of the HDT. However, the CSF was not constantly shifted from the spinal canal to the cranium. LEVEL OF EVIDENCE: 2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2018;47:565-571.