Imaging for central nervous system (CNS) interstitial fluidopathy: disorders with impaired interstitial fluid dynamics

Abstract

After the introduction of the glymphatic system hypothesis, an increasing number of studies on cerebrospinal fluid and interstitial fluid dynamics within the brain have been investigated and reported. A series of diseases are known which develop due to abnormality of the glymphatic system including Alzheimer's disease, traumatic brain injury, stroke, or other disorders. These diseases or disorders share the characteristics of the glymphatic system dysfunction or other mechanisms related to the interstitial fluid dynamics. In this review article, we propose "Central Nervous System (CNS) Interstitial Fluidopathy" as a new concept encompassing diseases whose pathologies are majorly associated with abnormal interstitial fluid dynamics. Categorizing these diseases or disorders as "CNS interstitial fluidopathies," will promote the understanding of their mechanisms and the development of potential imaging methods for the evaluation of the disease as well as clinical methods for disease treatment or prevention. In other words, having a viewpoint of the dynamics of interstitial fluid appears relevant for understanding CNS diseases or disorders, and it would be possible to develop novel common treatment methods or medications for "CNS interstitial fluidopathies."

Keywords: Cerebrospinal fluid; Glymphatic system; Interstitial fluid dynamics; Interstitial fluidopathy; Pathophysiology.

Fig. 1

Overview of “CNS Interstitial Fluidopathy”. Different etiology including mechanical force, distribution of hemorrhagic products, and other abnormality results in impaired interstitial dynamics

Fig. 2

Traumatic brain damage. A 5th decade female with a history of traumatic subdural hemorrhage who underwent surgical treatment, following which she gradually developed gait disturbance. T2-WI shows dilated perivascular space especially in the region adjacent to the old traumatic brain contusion (arrow)

Fig. 3

A case of small vessel disease diagnosed as CADASIL (cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy) a FLAIR image, b T2-WI. A 5th decade male with severe migraine like symptom. Skin biopsy revealed GOM deposition and was diagnosed as CADASIL. His father had developed cerebral infarction in his 6th decade. Axial FLAIR image and coronal T2WI showing subcortical abnormal signal suggesting dilated perivascular space and surrounding gliosis

Fig. 4

Migration of intraocular silicone oil into the brain. a, b CT, c T1-WI, d T2-WI. A 6th decade male who has silicone oil tamponade in vitreoretinal surgery for retinal detachment. After 10 years of the surgery, brain CT revealed high density material in his lateral ventricle. MRI showed chemical shift on both T1 and T2-WI, indicating silicone oil transport into the brain. The migration of the silicone oil is speculated to have taken place via the subarachnoidal space around the optic nerve

Fig. 5

MRI of endolymphatic hydrops in Meniere's disease. a, b MR cisternography, c, d Hybrid of reversed image of positive endolymph signal and native image of positive perilymph signal (HYDROPS) image. Healthy (a, c) and a Meniere’s disease ear (b, d) are presented. MR cisternography (a, b) shows a high signal both for the inner ear labyrinthine endolymph and perilymph. On HYDROPS image obtained 4 h after intravenous administration of single-dose gadolinium-based contrast agent (GBCA) (c, d), endolymph is delineated as low signal since GBCA does not transit into endolymph. In Meniere’s disease ear, dilatation of endolymphatic space in cochlea and vestibule is clearly visualized (d: arrows)

Fig. 6

A case with migraine with dilated perivascular space. a, b T2-WI (axial), c, d T2-WI (magnified view of a and b). Fifteen years old female, who has severe headache. T2-WI showed high signal in occipital white matter. There are no other abnormalities on MRA, contrast enhanced MRI, perfusion study, diffusion images or MR spectroscopy, and the case clinically diagnosed as migraine. Note dilated perivascular space on Magnified view (arrows)

Fig. 7

Dilated perivascular space in mucopolysaccharidoses. a T2-WI (axial), b T2-WI (coronal). Four years old boy, who has contracture of joints, hearing disability and facial dysmorphism. He has been diagnosed as Hunter syndrome by urinary glycosaminoglycans analysis. Axial and coronal T2WI shows periventricular abnormal signal suggesting dilated perivascular space (arrows).