• Korean Journal of Radiology
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• v.21 no.11
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• pp.1199-1209
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• 2020

The glymphatic system hypothesis is a concept describing the clearance of waste products from the brain. The term "glymphatic system" combines the glial and lymphatic systems and is typically described as follows. The perivascular space functions as a conduit that drains cerebrospinal fluid (CSF) into the brain parenchyma. CSF guided to the perivascular space around the arteries enters the interstitium of brain tissue via aquaporin-4 water channels to clear waste proteins into the perivascular space around the veins before being drained from the brain. In this review, we introduce the glymphatic system hypothesis and its association with fluid dynamics, sleep, and disease. We also discuss imaging methods to evaluate the glymphatic system.

• Journal of the Korean Society of Radiology
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• v.83 no.3
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• pp.538-558
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• 2022

The perivascular space (PVS) of the brain, also known as Virchow-Robin space, consists of cerebrospinal fluid and connective tissues bordered by astrocyte endfeet. The PVS, in a word, is the route over the arterioles, capillaries, and venules where the substances can move. Although the PVS was identified and described first in the literature approximately over 150 years ago, its importance has been highlighted recently after the function of the waste clearing system of the interstitial fluid and wastes was revealed. The PVS is known to be a microscopic structure detected using T2-weighted brain MRI as dot-like hyperintensity lesions when enlarged. Although until recently regarded as normal with no clinical consequence and ignored in many circumstances, several studies have argued the association of an enlarged PVS with neurodegenerative or other diseases. Many questions and unknown facts about this structure still exist; we can only assume that the normal PVS functions are crucial in keeping the brain healthy. In this review, we covered the history, anatomy, pathophysiology, and MRI findings of the PVS; finally, we briefly touched upon the recent trials to better visualize the PVS by providing a glimpse of the brain fluid dynamics and clinical importance of the PVS.

• Dementia and Neurocognitive Disorders
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• v.22 no.3
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• pp.87-99
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• 2023

Background and Purpose: According to the amyloid cascade hypothesis, fibrillary amyloid-beta load in the brain causes Alzheimer's disease (AD) with toxic effects. Recently, perivascular spaces (PVSs), fluid-filled cavities around small penetrating arterioles and venules in the brain, and the glymphatic system relationship with type 2 diabetes mellitus (DM2) and AD has been an important research topic from a physiopathological point of view. There are two types of PVSs that are associated with sporadic atherosclerosis and cerebral amyloid angiopathy. In this study, we evaluated the relationship between the number and localization of enlarged PVSs in AD. Methods: A total of 254 patients with AD and 125 healthy controls were included in this study All the patients were evaluated with neurological and cognitive examinations and magnetic resonance imaging (MRI). PVSs on MRI were graded by recording their number and location. The study was a retrospective study. Results: In our study, the number of white matter convexity-central semiovale localized PVSs was higher in patients than in the control group. In addition, the number of PVSs in this localization score was higher in patients with DM2. Cerebral PVS counts were higher in patients with AD than in the control group. Conclusions: These results suggest the important role of cerebral amyloid angiopathy, one of the vascular risk factors, and the glymphatic system in the pathogenesis of AD. In addition, the results of our study suggest that the evaluation of PVSs levels, especially at the (centrum semiovale), using imaging studies in AD is a potential diagnostic option.

• Korean Journal of Veterinary Research
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• v.24 no.2
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• pp.173-181
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• 1984

This paper dealt with the histopathological observations of the perirenal edema in pigs and rabbits administered with Amaranthus retroflexus, based on the clinical and pathological observations of the porcine perirenal edema naturally occurred in Korea. The results observed are summarized as follows; In the natural case, clinical signs were trembling, weakness and incoordination of the hindquarters, followed by sternal recumbency, coma and death. Death usually occurred within 24 hours after the signs of illness appeared. In gross findings, the grayish yellow fluid in the perirenal area was observed in each case. In some cases, the amount of fluid in the thoracic and abdominal cavities was increased and the yellowish red color of the hydrothorax and ascites was seen. When the renal capsule was incised, the kidneys were enlarged and congested and petechiae on the cortical surface and blood clots on the capsule appeared. In microscopical findings, there were cloudy swelling, hyaline droplets and necrosis of the convoluted tubules containing proteinaceous casts and a few oxalate crystals. In addition, interstitial and perivascular edema, distention of the Bowman's space and the convluted tubules and hemorrhages were recognized. In the weanling pigs and the adult pig fed various weeds, including Amaranthus retroflexus, Euxolus blitum and Portulaca oleracea, the pigs fed Amaranthus retroflexus appeared clinical signs and pathological findings of perirenal edema usually seen in the pigs of natural cases. In the pigs fed Euxolus blitum or fed Portulaca oleracea, neither clinical signs nor pathological changes were seen. It was regarded that this disease was affected with Amaranthus retroflexus, but there was no sensitivity in the adult pigs.

• Korean Journal of Veterinary Service
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• v.29 no.3
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• pp.309-316
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• 2006

This is a case report on the occurrence of caprine arthritis-encephalitis (CAE) disease among dairy goats in a local farm located in Yeongdong-gun, Chungbuk. Previously, it was reported that the farm experienced intermittent deaths numbering 15 of the 97 goats raised for 5 months. Most of the goats less than 6 months of age were suffering from ataxia and posterior paresis, body tremor and abnormal head posterior. Affected animals frequently had stunted growth and had a rough coat. Goats more than 6 months of age were affected with an insidious, chronic arthritis characterized by articular swelling ('big knee') of the carpal, hock, and stifle joints. Necropsy revealed severely swollen mesenteric lymph nodes, under- flow of 2-3ml synovial fluid in the articular space and fibrous proliferation of synovial membrane. Histopathological examination showed perivascular accumulations of mononuclear inflammatory cells in the white matter of the brain, proliferative synovitis characterized by villous hypertrophy, synovial cell hyperplasia and infiltration by mononuclear inflammatory cells. Pulmonary lesions consists of patchy interstitial pneumonia with hyperplasia of lymphoid tissues and an extensive mononuclear inflammatory cell infiltration into the alveolar septa. Confirmation by nested PCR involves amplification of a 296 bp (lst PCR) and 184 bp (2nd PCR) fragments corresponding to the gag region of the CAE virus. This is the first time CAE has been reported in a local farm in Korea and emphasizes the importances of developing preventive measures against CAE.

• Korean Journal of Radiology
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• v.24 no.6
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• pp.564-573
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• 2023

Objective: To investigate the feasibility of assessing the viscoelastic properties of the brain using magnetic resonance elastography (MRE) and a novel MRE transducer to determine the relationship between the viscoelastic properties and glymphatic function in neurologically normal individuals. Materials and Methods: This prospective study included 47 neurologically normal individuals aged 23-74 years (male-to-female ratio, 21:26). The MRE was acquired using a gravitational transducer based on a rotational eccentric mass as the driving system. The magnitude of the complex shear modulus |G^*| and the phase angle 𝛗 were measured in the centrum semiovale area. To evaluate glymphatic function, the Diffusion Tensor Image Analysis Along the Perivascular Space (DTI-ALPS) method was utilized and the ALPS index was calculated. Univariable and multivariable (variables with P < 0.2 from the univariable analysis) linear regression analyses were performed for |G^*| and 𝛗 and included sex, age, normalized white matter hyperintensity (WMH) volume, brain parenchymal volume, and ALPS index as covariates. Results: In the univariable analysis for |G^*|, age (P = 0.005), brain parenchymal volume (P = 0.152), normalized WMH volume (P = 0.011), and ALPS index (P = 0.005) were identified as candidates with P < 0.2. In the multivariable analysis, only the ALPS index was independently associated with |G^*|, showing a positive relationship (β = 0.300, P = 0.029). For 𝛗, normalized WMH volume (P = 0.128) and ALPS index (P = 0.015) were identified as candidates for multivariable analysis, and only the ALPS index was independently associated with 𝛗 (β = 0.057, P = 0.039). Conclusion: Brain MRE using a gravitational transducer is feasible in neurologically normal individuals over a wide age range. The significant correlation between the viscoelastic properties of the brain and glymphatic function suggests that a more organized or preserved microenvironment of the brain parenchyma is associated with a more unimpeded glymphatic fluid flow.