Cerebral Cortex Involvement in Neuromyelitis Optica Spectrum Disorder

Updates in NMOSD and MOGAD Diagnosis and Treatment: A Tale of Two Central Nervous System Autoimmune Inflammatory Disorders

Aquaporin-4-IgG positive neuromyelitis optica spectrum disorder (AQP4+NMOSD) and myelin-oligodendrocyte glycoprotein antibody-associated disease (MOGAD) are antibody-associated diseases targeting astrocytes and oligodendrocytes, respectively. Their recognition as distinct entities has led to each having its own diagnostic criteria that require a combination of clinical, serologic, and MRI features. The therapeutic approach to acute attacks in AQP4+NMOSD and MOGAD is similar. There is now class 1 evidence to support attack-prevention medications for AQP4+NMOSD. MOGAD lacks proven treatments although clinical trials are now underway. In this review, we will outline similarities and differences between AQP4+NMOSD and MOGAD in terms of diagnosis and treatment.

Understanding the Pathophysiology and Magnetic Resonance Imaging of Multiple Sclerosis and Neuromyelitis Optica Spectrum Disorders

Magnetic resonance imaging (MRI) has been extensively applied in the study of multiple sclerosis (MS), substantially contributing to diagnosis, differential diagnosis, and disease monitoring. MRI studies have significantly contributed to the understanding of MS through the characterization of typical radiological features and their clinical or prognostic implications using conventional MRI pulse sequences and further with the application of advanced imaging techniques sensitive to microstructural damage. Interpretation of results has often been validated by MRI-pathology studies. However, the application of MRI techniques in the study of neuromyelitis optica spectrum disorders (NMOSD) remains an emerging field, and MRI studies have focused on radiological correlates of NMOSD and its pathophysiology to aid in diagnosis, improve monitoring, and identify relevant prognostic factors. In this review, we discuss the main contributions of MRI to the understanding of MS and NMOSD, focusing on the most novel discoveries to clarify differences in the pathophysiology of focal inflammation initiation and perpetuation, involvement of normal-appearing tissue, potential entry routes of pathogenic elements into the CNS, and existence of primary or secondary mechanisms of neurodegeneration.

Cortical ischemic lesions from atrial myxoma as a mimic of disease activity in an RRMS antiCD20-treated patient

Cortical lesions (CLs) detected with double inversion recovery (DIR) magnetic resonance imaging (MRI) are very helpful in differentiating multiple sclerosis (MS) from other neuroinflammatory diseases of the central nervous system (CNS), that is, neuromyelitis optica spectrum disorders (NMOSDs). Furthermore, CLs are closely related to motor and cognitive impairment. We report a case of a 48-year-old female MS patient who developed several CLs during anti-CD20 therapy. Some CLs disappeared during follow-up MRIs. In the suspicion of a treatment failure, the screening for the autologous hematopoietic stem cell transplant (AHSCT) was performed with the evidence of an atrial myxoma. In MS patients with new CLs, a comorbid ischemic pathology should be considered and carefully investigated.

Overlap syndrome of anti-aquaporin-4 positive neuromyelitis optica spectrum disorder and systemic lupus erythematosus: A systematic review of individual patient data

BACKGROUND

Neurological involvement can occur in systemic lupus erythematosus (SLE) due to co-existing neuromyelitis optica spectrum disorder (NMOSD). The symptoms can mimic those of neuropsychiatric manifestations of SLE. Pathogenic anti-aquaporin-4 (AQP4) antibodies, commonly found in NMOSD, are responsible for the neuroinflammatory response and secondary demyelinating lesions. These anti-AQP4 antibodies can be the drivers of neuroinflammatory process in SLE patients, which is distinct from the immunopathogenesis seen in traditional neuropsychiatric SLE. The clinical course is often a relapsing one and is managed differently. In this review, we describe and outline the clinical course and outcomes of AQP4+ NMOSD/SLE overlap cases.

METHODS

To investigate the co-existence of SLE with AQP4+NMOSD, we conducted a systematic review of individual patient data from case reports and case series reported in major databases. The study extracted clinic-demographic features, imaging and laboratory profiles, treatment approaches, and outcomes of these patients. Inclusion criteria for the review required patients to have positivity for AQP4 or NMO in the blood and/or cerebrospinal fluid (CSF) and exhibit at least one manifestation of both NMOSD and SLE.

RESULTS

In this overlap between SLE and AQP4+NMOSD, a high female preponderance was observed, with 42 out of 46 patients (91.3%) being female. Nearly half of the NMOSD cases (47.8%) had onset after lupus, with a median of 5 years between the two diagnoses. Hematological manifestations were seen in the majority of patients (63%), as well as longitudinally extensive transverse myelitis (87%), and brainstem involvement on imaging (29.6%). Cerebrospinal fluid analysis showed a dominantly lymphocytic pleocytosis, with oligoclonal bands being reported scarcely. Although cyclophosphamide was the most common steroid sparing agent used for maintenance, robust evidence for both efficacy and safety in AQP4+NMOSD is available for mycophenolate mofetil, azathioprine, and rituximab. The majority of reported cases showed a relapsing course, while one patient had a monophasic course.

CONCLUSION

AQP4+NMOSD in SLE patients is a relapsing and neurologically disabling disorder that can mimic neuropsychiatric manifestations, frequently occurs after the onset of lupus or may predate, responds to immunosuppressants, and necessitates indefinite treatment.

Breast cancer-associated paraneoplastic neuromyelitis optica with cervical cord compression and spondylosis requiring laminectomy: A case report

Neuromyelitis optica, an autoimmune inflammatory disorder affecting the central nervous system, can occur in a paraneoplastic context, although rare. We report an intriguing case of a 71-year-old woman with a history of triple-negative infiltrating ductal breast carcinoma, manifesting with paraneoplastic neuromyelitis optica that led to significant respiratory failure and required a cervical laminectomy. The patient presented with pain in the left breast, weakness in the lower extremities, and neck pain. The neurological evaluation showed 2/5 muscle strength in all extremities, diffuse hyperreflexia, and loss of multimodal sensation below the shoulder. She developed acute respiratory failure that required mechanical ventilation. Magnetic resonance imaging highlighted a diffuse abnormal increase in T2 signal intensity throughout the posterior and central portion of the cervical and thoracic spinal cord consistent with longitudinally extensive transverse myelitis, and significant cervical cord compression at C3-C4. Magnetic resonance imaging of the brain showed non-enhancing T2/fluid-attenuated inversion recovery (FLAIR) white matter hyperintensities and cerebellar hemispheres. The serum cell-based assay study demonstrated a high anti-aquaporin-4 immunoglobulin G titer (>1:160) confirming the diagnosis of neuromyelitis optica. She was taken for bilateral laminectomy from C3 to C6. Despite intravenous methylprednisolone and plasmapheresis treatment, no significant recovery was achieved, necessitating tracheostomy and percutaneous endoscopic gastrostomy. Subsequent rituximab treatment led to a mild improvement, with no new lesions on repeat magnetic resonance imaging. This case raises suspicion of the potential for neuromyelitis optica to occur as a paraneoplastic phenomenon, strengthening the need for vigilance in patients with malignancies.

Update on the diagnosis and treatment of neuromyelits optica spectrum disorders (NMOSD) - revised recommendations of the Neuromyelitis Optica Study Group (NEMOS). Part I: Diagnosis and differential diagnosis

The term 'neuromyelitis optica spectrum disorders' (NMOSD) is used as an umbrella term that refers to aquaporin-4 immunoglobulin G (AQP4-IgG)-positive neuromyelitis optica (NMO) and its formes frustes and to a number of closely related clinical syndromes without AQP4-IgG. NMOSD were originally considered subvariants of multiple sclerosis (MS) but are now widely recognized as disorders in their own right that are distinct from MS with regard to immunopathogenesis, clinical presentation, optimum treatment, and prognosis. In part 1 of this two-part article series, which ties in with our 2014 recommendations, the neuromyelitis optica study group (NEMOS) gives updated recommendations on the diagnosis and differential diagnosis of NMOSD. A key focus is on differentiating NMOSD from MS and from myelin oligodendrocyte glycoprotein antibody-associated encephalomyelitis (MOG-EM; also termed MOG antibody-associated disease, MOGAD), which shares significant similarity with NMOSD with regard to clinical and, partly, radiological presentation, but is a pathogenetically distinct disease. In part 2, we provide updated recommendations on the treatment of NMOSD, covering all newly approved drugs as well as established treatment options.

MRI Patterns Distinguish AQP4 Antibody Positive Neuromyelitis Optica Spectrum Disorder From Multiple Sclerosis

Neuromyelitis optica spectrum disorder (NMOSD) and multiple sclerosis (MS) are inflammatory diseases of the CNS. Overlap in the clinical and MRI features of NMOSD and MS means that distinguishing these conditions can be difficult. With the aim of evaluating the diagnostic utility of MRI features in distinguishing NMOSD from MS, we have conducted a cross-sectional analysis of imaging data and developed predictive models to distinguish the two conditions. NMOSD and MS MRI lesions were identified and defined through a literature search. Aquaporin-4 (AQP4) antibody positive NMOSD cases and age- and sex-matched MS cases were collected. MRI of orbits, brain and spine were reported by at least two blinded reviewers. MRI brain or spine was available for 166/168 (99%) of cases. Longitudinally extensive (OR = 203), "bright spotty" (OR = 93.8), whole (axial; OR = 57.8) or gadolinium (Gd) enhancing (OR = 28.6) spinal cord lesions, bilateral (OR = 31.3) or Gd-enhancing (OR = 15.4) optic nerve lesions, and nucleus tractus solitarius (OR = 19.2), periaqueductal (OR = 16.8) or hypothalamic (OR = 7.2) brain lesions were associated with NMOSD. Ovoid (OR = 0.029), Dawson's fingers (OR = 0.031), pyramidal corpus callosum (OR = 0.058), periventricular (OR = 0.136), temporal lobe (OR = 0.137) and T1 black holes (OR = 0.154) brain lesions were associated with MS. A score-based algorithm and a decision tree determined by machine learning accurately predicted more than 85% of both diagnoses using first available imaging alone. We have confirmed NMOSD and MS specific MRI features and combined these in predictive models that can accurately identify more than 85% of cases as either AQP4 seropositive NMOSD or MS.

Magnetic resonance imaging in neuromyelitis optica spectrum disorder

Neuromyelitis optica spectrum disorder (NMOSD) is an inflammatory disease of the central nervous system (CNS) associated with antibodies to aquaporin-4 (AQP4), which has distinct clinical, radiological and pathological features, but also has some overlap with multiple sclerosis and myelin oligodendrocyte glycoprotein (MOG) antibody associated disease. Early recognition of NMOSD is important because of differing responses to both acute and preventive therapy. Magnetic resonance (MR) imaging has proved essential in this process. Key MR imaging clues to the diagnosis of NMOSD are longitudinally extensive lesions of the optic nerve (more than half the length) and spinal cord (three or more vertebral segments), bilateral optic nerve lesions and lesions of the optic chiasm, area postrema, floor of the IV ventricle, periaqueductal grey matter, hypothalamus and walls of the III ventricle. Other NMOSD-specific lesions are denoted by their unique morphology: heterogeneous lesions of the corpus callosum, 'cloud-like' gadolinium (Gd)-enhancing white matter lesions and 'bright spotty' lesions of the spinal cord. Other lesions described in NMOSD, including linear periventricular peri-ependymal lesions and patch subcortical white matter lesions, may be less specific. The use of advanced MR imaging techniques is yielding further useful information regarding focal degeneration of the thalamus and optic radiation in NMOSD and suggests that paramagnetic rim patterns and changes in normal appearing white matter are specific to MS. MR imaging is crucial in the early recognition of NMOSD and in directing testing for AQP4 antibodies and guiding immediate acute treatment decisions. Increasingly, MR imaging is playing a role in diagnosing seronegative cases of NMOSD.

Contrasting the brain imaging features of MOG-antibody disease, with AQP4-antibody NMOSD and multiple sclerosis

Background:

Identifying magnetic resonance imaging (MRI) markers in myelin-oligodendrocytes-glycoprotein antibody-associated disease (MOGAD), neuromyelitis optica spectrum disorder-aquaporin-4 positive (NMOSD-AQP4) and multiple sclerosis (MS) is essential for establishing objective outcome measures.

Objectives:

To quantify imaging patterns of central nervous system (CNS) damage in MOGAD during the remission stage, and to compare it with NMOSD-AQP4 and MS.

Methods:

20 MOGAD, 19 NMOSD-AQP4, 18 MS in remission with brain or spinal cord involvement and 18 healthy controls (HC) were recruited. Volumetrics, lesions and cortical lesions, diffusion-imaging measures, were analysed.

Results:

Deep grey matter volumes were lower in MOGAD (p = 0.02) and MS (p = 0.0001), compared to HC and were strongly correlated with current lesion volume (MOGAD R = −0.93, p < 0.001, MS R = −0.65, p = 0.0034). Cortical/juxtacortical lesions were seen in a minority of MOGAD, in a majority of MS and in none of NMOSD-AQP4. Non-lesional tissue fractional anisotropy (FA) was only reduced in MS (p = 0.01), although focal reductions were noted in NMOSD-AQP4, reflecting mainly optic nerve and corticospinal tract pathways.

Conclusion:

MOGAD patients are left with grey matter damage, and this may be related to persistent white matter lesions. NMOSD-AQP4 patients showed a relative sparing of deep grey matter volumes, but reduced non-lesional tissue FA. Observations from our study can be used to identify new markers of damage for future multicentre studies.

Extensive Cerebral Cortical Involvement in Aquaporin 4 Antibody Positive Neuromyelitis Optica Spectrum Disorder

Neuromyelitis optica spectrum disorders (NMOSDs) usually manifest with features of long-segment myelitis and/or optic neuritis. Area postrema involvement presents with nausea, vomiting, and intractable hiccups. Cerebral cortical involvement is a relatively uncommon phenomenon. This report describes an interesting case of aquaporin 4 antibody positive NMOSD with extensive cerebral cortical involvement in addition to area postrema and cervicomedullary lesions observed on magnetic resonance imaging. Following immunosuppressive therapy, good clinical response and near-complete resolution of brain imaging abnormalities were observed.

Assessment of lesions on magnetic resonance imaging in multiple sclerosis: practical guidelines

MRI has improved the diagnostic work-up of multiple sclerosis, but inappropriate image interpretation and application of MRI diagnostic criteria contribute to misdiagnosis. Some diseases, now recognized as conditions distinct from multiple sclerosis, may satisfy the MRI criteria for multiple sclerosis (e.g. neuromyelitis optica spectrum disorders, Susac syndrome), thus making the diagnosis of multiple sclerosis more challenging, especially if biomarker testing (such as serum anti-AQP4 antibodies) is not informative. Improvements in MRI technology contribute and promise to better define the typical features of multiple sclerosis lesions (e.g. juxtacortical and periventricular location, cortical involvement). Greater understanding of some key aspects of multiple sclerosis pathobiology has allowed the identification of characteristics more specific to multiple sclerosis (e.g. central vein sign, subpial demyelination and lesional rims), which are not included in the current multiple sclerosis diagnostic criteria. In this review, we provide the clinicians and researchers with a practical guide to enhance the proper recognition of multiple sclerosis lesions, including a thorough definition and illustration of typical MRI features, as well as a discussion of red flags suggestive of alternative diagnoses. We also discuss the possible place of emerging qualitative features of lesions which may become important in the near future.

Diagnosis and Prediction of Relapses in Susac Syndrome: A New Use for MR Postcontrast FLAIR Leptomeningeal Enhancement

BACKGROUND AND PURPOSE

Leptomeningeal enhancement can be found in a variety of neurologic diseases such as Susac Syndrome. Our aim was to assess its prevalence and significance of leptomeningeal enhancement in Susac syndrome using 3T postcontrast fluid-attenuated inversion recovery MR imaging.

MATERIALS AND METHODS

From January 2011 to December 2017, nine consecutive patients with Susac syndrome and a control group of 73 patients with multiple sclerosis or clinically isolated syndrome were included. Two neuroradiologists blinded to the clinical and ophthalmologic data independently reviewed MRIs and assessed leptomeningeal enhancement and parenchymal abnormalities. Follow-up MRIs (5.9 MRIs is the mean number per patient over a median period of 46 months) of patients with Susac syndrome were reviewed and compared with clinical and retinal fluorescein angiographic data evaluated by an independent ophthalmologist. Fisher tests were used to compare the 2 groups, and mixed-effects logistic models were used for analysis of clinical and imaging follow-up of patients with Susac syndrome.

RESULTS

Patients with Susac syndrome were significantly more likely to present with leptomeningeal enhancement: 5/9 (56%) versus 6/73 (8%) in the control group (P = .002). They had a significantly higher leptomeningeal enhancement burden with ≥3 lesions in 5/9 patients versus 0/73 (P < .001). Regions of leptomeningeal enhancement were significantly more likely to be located in the posterior fossa: 5/9 versus 0/73 (P < .001). Interobserver agreement for leptomeningeal enhancement was good (κ = 0.79). There was a significant association between clinical relapses and increase of both leptomeningeal enhancement and parenchymal lesion load: OR = 6.15 (P = .01) and OR = 5 (P = .02), respectively.

CONCLUSIONS

Leptomeningeal enhancement occurs frequently in Susac syndrome and could be helpful for diagnosis and in predicting clinical relapse.

Brain and cord imaging features in neuromyelitis optica spectrum disorders

OBJECTIVES

To validate imaging features able to discriminate neuromyelitis optica spectrum disorders from multiple sclerosis with conventional magnetic resonance imaging (MRI).

METHODS

In this cross-sectional study, brain and spinal cord scans were evaluated from 116 neuromyelitis optica spectrum disorder patients (98 seropositive and 18 seronegative) in chronic disease phase and 65 age-, sex-, and disease duration-matched multiple sclerosis patients. To identify independent predictors of neuromyelitis optica diagnosis, after assessing the prevalence of typical/atypical findings, the original cohort was 2:1 randomized in a training sample (where a multivariate logistic regression analysis was run) and a validation sample (where the performance of the selected variables was tested and validated).

RESULTS

Typical brain lesions occurred in 50.9% of neuromyelitis optica patients (18.1% brainstem periventricular/periaqueductal, 32.7% periependymal along lateral ventricles, 3.4% large hemispheric, 6.0% diencephalic, 4.3% corticospinal tract), 72.2% had spinal cord lesions (46.3% long transverse myelitis, 36.1% short transverse myelitis), 37.1% satisfied 2010 McDonald criteria, and none had cortical lesions. Fulfillment of at least 2 of 5 of absence of juxtacortical/cortical lesions, absence of periventricular lesions, absence of Dawson fingers, presence of long transverse myelitis, and presence of periependymal lesions along lateral ventricles discriminated neuromyelitis optica patients in both training (sensitivity = 0.92, 95% confidence interval [CI] = 0.84-0.97; specificity = 0.91, 95% CI = 0.78-0.97) and validation samples (sensitivity = 0.82, 95% CI = 0.66-0.92; specificity = 0.91, 95% CI = 0.71-0.99). MRI findings and criteria performance were similar irrespective of serostatus.

INTERPRETATION

Although up to 50% of neuromyelitis optica patients have no typical lesions and a relatively high percentage of them satisfy multiple sclerosis criteria, several easily applicable imaging features can help to distinguish neuromyelitis optica from multiple sclerosis. ANN NEUROL 2019;85:371-384.

Unusual cortical involvement in aquaporin-4 antibody-positive patients: An analysis with double inversion recovery and phase-sensitive inversion recovery imaging

BACKGROUND

Previous studies strongly suggested the absence of cortical involvement in neuromyelitis optica spectrum disorder.

METHODS

We describe two patients with anti-aquaporin-4 antibody and cortical lesions.

RESULTS

A 58-year-old and a 61-year-old woman presented with status epilepticus and right leg numbness, respectively. Double inversion recovery (DIR) and phase-sensitive inversion recovery (PSIR) imaging, magnetic resonance imaging sequences that enable the clear delineation of gray matter, revealed intracortical lesions and lesions located across the cortex and subcortex.

CONCLUSION

Although rare, cortical involvement may exist in aquaporin-4 antibody-positive patients. DIR and PSIR MRI can help to determine the exact location of the lesion.

Neuromyelitis Optica Spectrum Disorders: Spectrum of MR Imaging Findings and Their Differential Diagnosis

Neuromyelitis optica (NMO) is an autoimmune demyelinating disorder for which the aquaporin-4 (AQP4) water channels are the major target antigens. Advances in the understanding of NMO have clarified several points of its pathogenesis, clinical manifestations, and imaging patterns. A major advance was the discovery of the AQP4 antibody, which is highly specific for this disorder. Descriptions of new clinical and radiologic features in seropositive patients have expanded the spectrum of NMO, and the term NMO spectrum disorder (NMOSD) has been adopted. NMOSD is now included in a widening list of differential diagnoses. Acknowledgment of NMOSD imaging patterns and their mimicry of disorders has been crucial in supporting early NMOSD diagnosis, especially for unusual clinical manifestations of this demyelinating disease. This pictorial review summarizes the wide imaging spectrum of NMOSD and its differential diagnosis, as well as its historical evolution, pathophysiology, and clinical manifestations. ^©RSNA, 2018.

Cortical blindness and not optic neuritis as a cause of vision loss in a Sjögren's syndrome (SS) patient with the neuromyelitis optica spectrum disorder (NMOSD): Challenges of ascribing demyelinating syndromes to SS: a case report

RATIONALE

The conception that multiple sclerosis may be challenging to distinguish from demyelinating manifestations of Sjögren's syndrome (SS) was introduced more than 30 years ago. However, it is now recognized that the neuromyelitis optica spectrum disorder (NMOSD) may occur more frequently in SS as opposed to multiple sclerosis. Characteristic NMOSD features can include severe attacks of optic neuritis, myelitis which is frequently longitudinally-extensive (spanning at least three vertebral segments on magnetic resonance imaging [MRI]), and an association with anti-aquaporin-4 antibodies. In addition, whereas NMOSD was initially thought to spare the brain, it is now recognized that brain lesions occur in a majority of NMOSD patients. Therefore, it is important for the multi-disciplinary team of physicians who care for SS patients to understand this widening spectrum of NMOSD as encompassing brain lesions. In this case-report we describe clinical features, radiographic findings, and treatment of a SS NMOSD patient presenting with severely decreased visual acuity, visual hallucinations, and encephalopathy.

PATIENT CONCERNS

The SS NMOSD patient presented with rapid, bilateral onset of severely decreased visual acuity and was therefore suspected as having bilateral optic neuritis.

DIAGNOSIS

However, the patient lacked stigmata of optic neuritis, instead had visual hallucinations and encephalopathy suggestive of cortical blindness, and was noted to have occipital lobe lesions on brain MRI. Other radiographic findings included simultaneous enhancement of brainstem and periventricular lesions.

INTERVENTIONS

The patient was initially treated with methylprednisolone with no change in her neurological deficits. She was then treated with plasma exchange therapy.

OUTCOMES

The patient had resolution of decreased visual acuity, visual hallucinations, encephalopathy, and contrast-enhancing brain lesions in response to plasma exchange therapy.

LESSON

We provide the first example of severely decreased visual acuity in a NMOSD patient due to cortical blindness and not bilateral optic neuritis. This finding expands the spectrum of central nervous system syndromes and brain lesions which may occur in NMOSD. The synchronous enhancement of a brainstem lesion (known to occur in NMOSD) with occipital lobe lesions also suggests that our patient's occipital lobe findings were due to NMOSD. All of our patient's findings had an excellent clinical and radiographic response to plasma exchange therapy.

Complexity and wide range of neuromyelitis optica spectrum disorders: more than typical manifestations

Neuromyelitis optica (NMO), considered to be mediated by autoantibodies, often cause severely disabling disorders of the central nervous system, and predominantly cause optic nerve damage and longitudinally extensive transverse myelitis. Remarkable progress has been made in deciphering NMO pathogenesis during the past decade. In 2015, the International Panel for NMO Diagnosis proposed the unifying term "NMO spectrum disorders" (NMOSD) and the updated NMOSD criteria reflects a wide range of disease and maintains reasonable specificity. Moreover, cumulative findings have indicated that NMOSD are frequently associated with multiple autoimmune diseases, thereby presenting complex clinical symptoms that make this disease more difficult to recognize. Notably, most neurologists do not heed these symptoms or comorbid conditions in patients with NMOSD. Whereas previous reviews have focused on pathogenesis, treatment, and prognosis in NMOSD, we summarize the present knowledge with particular emphasis on atypical manifestations and autoimmune comorbidities in patients with NMOSD. Furthermore, we emphasized the identification of these atypical characteristics to enable a broader and better understanding of NMOSD, and improve early accurate diagnosis and therapeutic decision making.

Research into the Physiology of Cerebrospinal Fluid Reaches a New Horizon: Intimate Exchange between Cerebrospinal Fluid and Interstitial Fluid May Contribute to Maintenance of Homeostasis in the Central Nervous System

Cerebrospinal fluid (CSF) plays an essential role in maintaining the homeostasis of the central nervous system. The functions of CSF include: (1) buoyancy of the brain, spinal cord, and nerves; (2) volume adjustment in the cranial cavity; (3) nutrient transport; (4) protein or peptide transport; (5) brain volume regulation through osmoregulation; (6) buffering effect against external forces; (7) signal transduction; (8) drug transport; (9) immune system control; (10) elimination of metabolites and unnecessary substances; and finally (11) cooling of heat generated by neural activity. For CSF to fully mediate these functions, fluid-like movement in the ventricles and subarachnoid space is necessary. Furthermore, the relationship between the behaviors of CSF and interstitial fluid in the brain and spinal cord is important. In this review, we will present classical studies on CSF circulation from its discovery over 2,000 years ago, and will subsequently introduce functions that were recently discovered such as CSF production and absorption, water molecule movement in the interstitial space, exchange between interstitial fluid and CSF, and drainage of CSF and interstitial fluid into both the venous and the lymphatic systems. Finally, we will summarize future challenges in research. This review includes articles published up to February 2016.