The translaminar pressure gradient in sustained zero gravity, idiopathic intracranial hypertension, and glaucoma

Berdahl, John P.; Yu, Dao‐Yi; Morgan, William H.

doi:10.1016/j.mehy.2012.08.009

Cited by 76 publications

(75 citation statements)

References 48 publications

(64 reference statements)

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“…16,17 In space, it is thought that the CSF is distributed evenly within the subarachnoid space compartments, which would increase the effective CSF pressure posterior to the lamina cribrosa, whereas their IOP remains unchanged. 15 The existing case reports, and the two new patients we add to the literature, provide strong evidence that IOP can be an important factor in disc swelling. Both of our cases provide evidence that lowering IOP may "unmask" disc swelling from elevated ICP, by altering the translaminar pressure gradient: our second case corroborates this phenomenon that has previously been reported following trabeculectomy surgery.…”

Section: Discussionmentioning

confidence: 77%

“…15 Under normal earth gravitational force, CSF pools in the lower spine, and CSF pressure at the eye level is on average 13 mm Hg lower than that location. 16,17 In space, it is thought that the CSF is distributed evenly within the subarachnoid space compartments, which would increase the effective CSF pressure posterior to the lamina cribrosa, whereas their IOP remains unchanged.…”

Section: Discussionmentioning

confidence: 99%

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Asymmetrical Intraocular Pressures and Asymmetrical Papilloedema in Pseudotumor Cerebri Syndrome

Lawlor

Zhang

Virgo

et al. 2016

Neuro-Ophthalmology

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This report is of two cases of asymmetrical papilloedema in patients with asymmetrical intraocular pressures (IOPs). The first patient presented with headaches, transient visual obscurations (TVOs), and elevated IOPs, and was found to have increased intracranial pressure caused by a torcula meningioma. He developed papilloedema after his IOPs were pharmacologically lowered; the papilloedema resolved after the IOP became elevated again after stopping his glaucoma drops, and then again returned as the IOP reduced when the drops were restarted. The second patient with a history of Sturge-Weber syndrome requiring previous left trabeculectomy, presented with left-sided TVOs, photopsia, and pulsatile tinnitus caused by idiopathic intracranial hypertension. Asymmetrical papilloedema was observed, worse in the eye with the lower IOP following trabeculectomy. These cases suggest that asymmetric IOP may be one factor that can influence the development of asymmetric papilloedema. Ophthalmologists finding disc swelling at low normal pressures should ask about symptoms of raised ICP, and neuro-ophthalmologists confronted with asymmetrical disc swelling should routinely measure IOP. ARTICLE HISTORY

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Section: Discussionmentioning

confidence: 77%

Section: Discussionmentioning

confidence: 99%

Asymmetrical Intraocular Pressures and Asymmetrical Papilloedema in Pseudotumor Cerebri Syndrome

Lawlor

Zhang

Virgo

et al. 2016

Neuro-Ophthalmology

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“…in microgravity. One case of particular interest is the visual impairment syndrome seen in astronauts on long-duration space missions [35, 36] where an ICP disturbance is believed to be the main cause [37]. …”

Section: Discussionmentioning

confidence: 99%

Human jugular vein collapse in the upright posture: implications for postural intracranial pressure regulation

Holmlund

Johansson

Qvarlander

et al. 2017

Fluids Barriers CNS

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BackgroundIntracranial pressure (ICP) is directly related to cranial dural venous pressure (P dural). In the upright posture, P dural is affected by the collapse of the internal jugular veins (IJVs) but this regulation of the venous pressure has not been fully understood. A potential biomechanical description of this regulation involves a transmission of surrounding atmospheric pressure to the internal venous pressure of the collapsed IJVs. This can be accomplished if hydrostatic effects are cancelled by the viscous losses in these collapsed veins, resulting in specific IJV cross-sectional areas that can be predicted from flow velocity and vessel inclination.MethodsWe evaluated this potential mechanism in vivo by comparing predicted area to measured IJV area in healthy subjects. Seventeen healthy volunteers (age 45 ± 9 years) were examined using ultrasound to assess IJV area and flow velocity. Ultrasound measurements were performed in supine and sitting positions.ResultsIJV area was 94.5 mm2 in supine and decreased to 6.5 ± 5.1 mm2 in sitting position, which agreed with the predicted IJV area of 8.7 ± 5.2 mm2 (equivalence limit ±5 mm2, one-sided t tests, p = 0.03, 33 IJVs).ConclusionsThe agreement between predicted and measured IJV area in sitting supports the occurrence of a hydrostatic-viscous pressure balance in the IJVs, which would result in a constant pressure segment in these collapsed veins, corresponding to a zero transmural pressure. This balance could thus serve as the mechanism by which collapse of the IJVs regulates P dural and consequently ICP in the upright posture.Electronic supplementary materialThe online version of this article (doi:10.1186/s12987-017-0065-2) contains supplementary material, which is available to authorized users.

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“…These subjects have increased intracranial pressure, which persists for months and years after their return to earth. The explanation for this phenomenon is likely to involve the fact that in microgravity there is a cephalad fluid shift with increased venous pressures and impaired lymphatic flow around the head 69 70. Both factors may conspire to impede CSF outflow and lead to an increased average CSFP, which is not reduced or ameliorated by postural changes, that is, by standing.…”

Section: Abnormal Anatomymentioning

confidence: 99%

Cerebrospinal fluid pressure and the eye

et al. 2015

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Cerebrospinal fluid pressure (CSFP) interacts with intraocular pressure (IOP) and blood pressure to exert a major influence upon the eye, particularly the optic nerve head region. There is increased interest regarding the influence of CSFP upon disorders affecting this region, in particular glaucoma and idiopathic intracranial hypertension. Additionally, a high proportion of astronauts develop features similar to idiopathic intracranial hypertension that persist for years after returning to Earth. The factors that affect the CSFP influence upon the optic nerve and globe are likely to influence the outcome of various ophthalmic disorders.

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The translaminar pressure gradient in sustained zero gravity, idiopathic intracranial hypertension, and glaucoma

Cited by 76 publications

References 48 publications

Asymmetrical Intraocular Pressures and Asymmetrical Papilloedema in Pseudotumor Cerebri Syndrome

Asymmetrical Intraocular Pressures and Asymmetrical Papilloedema in Pseudotumor Cerebri Syndrome

Human jugular vein collapse in the upright posture: implications for postural intracranial pressure regulation

Cerebrospinal fluid pressure and the eye

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