Changes In Cerebrospinal Fluid Pressure Research Articles

Upstream Effects: Intraoperative Migration of Intradural Extramedullary Tumor After Non–Adjacent Level Stenosis Decompression

A 74 year-old man with back pain, foot numbness, and hip/thigh radiculopathy was found to have an L1-2 intradural extramedullary (IDEM) neoplasm and severe L4-5 stenosis. He was taken to surgery for L4-5 minimally-invasive (MIS) laminectomy for decompression and concomitant L1-2 MIS laminectomy for tumor resection. The L4-5 laminectomy was completed first followed by the separate L1-2 laminectomy. Upon extensive intradural exploration at L1-2, no neoplasm was found. Immediate postoperative imaging showed that the IDEM tumor had migrated caudally by nearly a complete spinal level, presumably as a result of changes in cerebrospinal fluid pressure and resultant shift in intradural contents after the L4-5 laminectomy. The patient was taken back to surgery for successful resection of the IDEM, with improvement in his symptoms.

Effect of Inhaled Sevoflurane on Pediatric Cerebrospinal Fluid Pressure During Lumbar Puncture; Implications for Intracranial Hypertension.

Objective: To determine influence of sevoflurane on changes in cerebrospinal fluid pressure in children presenting for lumbar puncture. Methods: Cerebrospinal fluid pressure, end tidal carbon dioxide, and end tidal sevoflurane concentration measurements were obtained at 2-minute intervals for a total of 10 minutes (T0 to T5). Because of concerns regarding patient safety and comfort, the study measurements were completed at the end of the lumbar procedure, starting with the closing pressure and when sevoflurane was stopped. Results: As end tidal sevoflurane concentration decreased, cerebrospinal fluid pressure initially increased up to T2 before decreasing back to around the initial point. There was no significant correlation between sevoflurane level and cerebrospinal fluid pressure. Both weight status and presence or absence of optic edema did not have a significant impact on pressure over time. However, there was a statistically significant difference in the cerebrospinal fluid pressure over time between those with spontaneous respirations compared to those without. Conclusions: There was no significant correlation between the end tidal sevoflurane concentration and cerebrospinal fluid pressure. Assisted ventilation did produce a statistically significant increase in cerebrospinal fluid pressure and suggests that the most accurate measurements are in those with spontaneous respirations.

Commentary: The impact of yoga practice on glaucoma.

Yoga is the most popular form of complementary therapy being practiced to maintain one’s physical and mental wellbeing. While yoga traditionally comprises advice for ethical lifestyle and spiritual practice, it is most often associated with physical postures (asanas), breathing techniques (pranayama), and meditation (dhyana). While these exercises are routinely safe, there are risks involved for certain patients including those suffering from or at risk of glaucoma. The effects of yoga on intraocular pressure (IOP) have been found to be bidirectional, and the exact mechanisms are not yet fully understood. The authors have reviewed literature to study the effect of yoga on IOP and glaucoma. They have observed a reduction of IOP in patients of glaucoma through Jyoti tratak (candle meditation) and slow yoga breathing exercises and a rapid increase in IOP immediately after head-down posture yoga.[1] Tratak kriya is said to lead to contraction and relaxation of ciliary muscles, which may possibly increase the aqueous humor outflow and subsequently decrease the IOP.[2] Dada et al.[3] have evaluated the effect of yoga and meditation on IOP, quality of life, stress markers, neurotrophins, and gene expression in patients with primary open-angle glaucoma and found an improvement in all parameters. On the other hand, progressive glaucomatous optic neuropathy and field loss in patients who regularly practiced Sirsasana (Headstand) has also been identified.[1,4,5] Four yogasanas [Adho Mukha Savasana (downward-facing dog), Uttanasana (standing forward bend), Halasana (plough pose), and Viparita Karani (legs-up-the-wall)] showed a 20–73.7% increase in IOP in all study subjects.[1] Yoga with head-down positions was associated with a rapid rise in IOP in glaucoma and healthy eyes and with the body vertical, with a doubling of the IOP, remaining elevated as long as the position was maintained.[1] Mani Baskaran et al.[6] observed a twofold increase in IOP during Sirsasana, which was maintained during the posture in all age groups irrespective of their ocular characteristics. Valsalva maneuver is known to affect IOP; so it is expected that breath-holding yogic exercises are likely to cause IOP elevation. Forced unilateral nostril breathing has also been observed to affect IOP significantly.[7] Rakstyte et al.[8] studied an impact on IOP before, during, and after Matsyasana (fish yoga pose) and found an increased IOP in head- down position which returns to the initial value shortly after. A case series by Mehrdad Malihi et al.[9] to study the effect of different body and head positions on IOP shows a lower measurement while sitting with a neutral neck position and a rise in IOP in all other positions. Acute angle-closure glaucoma attacks often precipitated by prone-position yoga exercises suggest that this position probably increases pupillary block in “at risk” eyes by causing the lens to fall onto the iris, which has been the principle of the prone provocative test for decades. Certain questions, however, remain unanswered. It is unclear whether yoga has any sustained effects on the IOP and optic nerve. Further research is needed to fully comprehend the mechanisms by which yoga exerts its effects and determine the types, optimal duration, and frequency of yoga practice for glaucoma patients. Future studies are also warranted to ascertain whether yoga-associated IOP changes are associated with parallel changes in perimetry and nerve fiber thickness and changes in cerebrospinal fluid pressure, blood pressure in lamina cribrosa capillaries, and the ocular blood flow. It is difficult to establish direct causality between different yogic postures and glaucomatous progression, but in patients with pre-existing glaucomatous optic neuropathy, dramatic changes in IOP can definitely be harmful. Inquiring about the practice of yoga in cases of unexplained progression despite an apparently well-controlled IOP can, therefore, be an important consideration. Relaxation and meditative aspects of yoga may help to reduce stress and improve the overall well-being of an individual which can be indirectly beneficial. The key is to “keep the head above the heart at all times.” It is also important to note that yoga should not replace traditional glaucoma treatment but rather be practiced/advised as a complementary therapy and glaucoma patients should consult their healthcare provider before beginning any new exercise or relaxation program, including yoga.

Cerebrospinal fluid micro-volume changes inside the spinal space affect intracranial pressure in different body positions of animals and phantom.

Interpersonal differences can be observed in the human cerebrospinal fluid pressure (CSFP) in the cranium in an upright body position, varying from positive to subatmospheric values. So far, these changes have been explained by the Monroe–Kellie doctrine according to which CSFP should increase or decrease if a change in at least one of the three intracranial volumes (brain, blood, and CSF) occurs. According to our hypothesis, changes in intracranial CSFP can occur without a change in the volume of intracranial fluids. To test this hypothesis, we alternately added and removed 100 or 200 μl of fluid from the spinal CSF space of four anesthetized cats and from a phantom which, by its dimensions and biophysical characteristics, imitates the cat cerebrospinal system, subsequently comparing CSFP changes in the cranium and spinal space in both horizontal and vertical positions. The phantom was made from a rigid “cranial” part with unchangeable volume, while the “spinal” part was made of elastic material whose modulus of elasticity was in the same order of magnitude as those of spinal dura. When a fluid volume (CSF or artificial CSF) was removed from the spinal space, both lumbar and cranial CSFP pressures decreased by 2.0–2.5 cm H2O for every extracted 100 μL. On the other hand, adding fluid volume to spinal space causes an increase in both lumbar and cranial CSFP pressures of 2.6–3.0 cm H2O for every added 100 μL. Results observed in cats and phantoms did not differ significantly. The presented results on cats and a phantom suggest that changes in the spinal CSF volume significantly affect the intracranial CSFP, but regardless of whether we added or removed the CSF volume, the hydrostatic pressure difference between the measuring sites (lateral ventricle and lumbar subarachnoid space) was always constant. These results suggest that intracranial CSFP can be increased or decreased without significant changes in the volume of intracranial fluids and that intracranial CSFP changes in accordance with the law of fluid mechanics.

MRI-findings in idiopathic intracranial hypertension (Pseudotumor cerebri).

Pseudotumor cerebri, also known as idiopathic intracranial hypertension, is a disorder of increased intracranial pressure of unknown etiology. Main symptom is headache which has a characteristic similar to other headache diseases, therefore the idiopathic intracranial hypertension often remains undetected. The incidence is 1/100 000 with the number of unreported cases being much higher. This article highlights the essential role of MRI in the differential diagnosis. A literature search was carried out on idiopathic intracranial hypertension and Pseudotumor cerebri in English and German. Original and Review articles as well as case reports were taken into account. Since the main focus of the article is MRI diagnostics, some images were selected to illustrate the characteristic MRI morphological features. The diagnosis of idiopathic intracranial hypertension is based on an exclusion procedure. Most common syndromes are headache, transient visual obscurations, pulsatile tinnitus and nausea. In the presence of an underlying cause for the increased intracranial pressure one speaks of a secondary intracranial hypertension. The diagnostics include a detailed medical history, neurological and ophthalmic examination, lumbar puncture, and neuroradiological imaging procedures. MRI, in particular, has become increasingly important in recent years, since signs for changes in cerebrospinal fluid pressure are now detectable and well-defined. The therapeutic approaches are symptom-oriented and aim to lower the pressure. With a precise diagnosis and timely start of therapy, idiopathic intracranial hypertension has a good prognosis, especially with regard to the preservation of eyesight. · The idiopathic intracranial hypertension is an important differential diagnosis for unspecific headache and impaired vision. · Overweight women in childbearing age are particularly affected. · The most important component in diagnostics is MRI. · Juhász J, Hensler J, Jansen O. MRT-Befunde bei der idiopathischen intrakraniellen Hypertension (Pseudotumor cerebri). Fortschr Röntgenstr 2021; 193: 1269 - 1276.

A novel biomarker for increased intracranial pressure in idiopathic intracranial hypertension.

Changes in optic disc and peripapillary structures associated with optic nerve edema in idiopathic intracranial hypertension (IIH), can be evaluated with spectral domain optical coherence tomography (SD-OCT). We aimed to evaluate the association between increased cerebrospinal fluid (CSF) opening pressure and changes in peripapillary structures detected by SD-OCT and to determine whether these changes can be used to assess the changes in CSF pressure without performing lumbar puncture (LP). Retrospective study METHODS: We included 54 eyes of 28 patients with bilateral papilledema who had peripapillary SD-OCT imaging within 24h before the LP. Correlation between CSF pressure and peripapillary OCT parameters including maximal retinal thickness, maximal anterior retinal projection, maximal retinal nerve fiber layer (RNFL) thickness and Bruch membrane opening (BMO) was evaluated. Bruch Membrane openingand maximal RNFL thickness were significantly higher in patients with increased CSF pressure. There exist correlations between CSF pressure and BMO, maximal RNFL thickness and maximal retinal thickness. (Spearman's Rho: 0.791, 0.482 and 0.297, p < 0.001, < 0.001 and 0.029, respectively) The cut off value of BMO for the prediction of increased CSF pressure was 1785µm, with a sensitivity of 78.8% and a specificity of 81%. The cut off value for maximal RNFL thickness was 174µm, with a sensitivity of 75.8% and a specificity of 61.9%. Bruch membrane opening and maximal RNFL thickness can give an idea about increased CSF pressure values in IIH patients. Thus SD-OCT can be used to detect CSF pressure changes in these patients.

The mechanisms behind perivascular fluid flow.

Flow of cerebrospinal fluid (CSF) in perivascular spaces (PVS) is one of the key concepts involved in theories concerning clearance from the brain. Experimental studies have demonstrated both net and oscillatory movement of microspheres in PVS (Mestre et al. (2018), Bedussi et al. (2018)). The oscillatory particle movement has a clear cardiac component, while the mechanisms involved in net movement remain disputed. Using computational fluid dynamics, we computed the CSF velocity and pressure in a PVS surrounding a cerebral artery subject to different forces, representing arterial wall expansion, systemic CSF pressure changes and rigid motions of the artery. The arterial wall expansion generated velocity amplitudes of 60–260 μm/s, which is in the upper range of previously observed values. In the absence of a static pressure gradient, predicted net flow velocities were small (<0.5 μm/s), though reaching up to 7 μm/s for non-physiological PVS lengths. In realistic geometries, a static systemic pressure increase of physiologically plausible magnitude was sufficient to induce net flow velocities of 20–30 μm/s. Moreover, rigid motions of the artery added to the complexity of flow patterns in the PVS. Our study demonstrates that the combination of arterial wall expansion, rigid motions and a static CSF pressure gradient generates net and oscillatory PVS flow, quantitatively comparable with experimental findings. The static CSF pressure gradient required for net flow is small, suggesting that its origin is yet to be determined.

Cervical Vestibular Evoked Myogenic Potentials in Idiopathic Intracranial Hypertension.

Idiopathic intracranial hypertension (IIH) is raised intracranial pressure without any identifiable etiology. The inner ear structures are susceptible to cerebrospinal fluid (CSF) pressure changes because of connections between the CSF space and the labyrinth to explain the audiovestibular symptoms, such as pulsatile tinnitus or dizziness, reported in 50% to 60% of these patients. The aim of this study was to investigate the vestibular functions using cervical vestibular evoked myogenic potentials (cVEMPs) in IIH. cVEMPs were recorded in 30 patients with IIH before lumbar puncture. Thirty healthy volunteers constituted the control group. The latencies of peaks p13 and n23 and peak-to-peak amplitude of p13-n23 were measured. Responses were gathered bilaterally from all healthy controls. In 30 patients with IIH, 49 responses could be gathered from 60 tests (81.7%). The potential was absent bilaterally in five and unilaterally in one patient. When recorded, the latency and amplitude values of the responses of the patients were not significantly different from the healthy controls (P > 0.005). A correlation between CSF pressure and response persistence could not be determined. cVEMPs are affected in patients with IIH and the main finding is the absence of the responses. Increased intracranial pressure causing sound transmission changes within the inner ear can affect the saccular afferents and may end up with absent responses on air-conducted cVEMP recordings. To comment on the correlation between the CSF pressure and cVEMP changes, successive cVEMP recordings with longitudinal CSF pressure monitoring seem necessary.

Shock wave propagation along the central retinal blood vessels.

Retinal haemorrhage is often observed following brain injury. The retinal circulation is supplied (drained) by the central retinal artery (vein) which enters (leaves) the eye through the optic nerve at the optic disc; these vessels penetrate the nerve immediately after passing through a region of cerebrospinal fluid (CSF). We consider a theoretical model for the blood flow in the central retinal vessels, treating each as multi-region collapsible tubes, where we examine how a sudden change in CSF pressure (mimicking an injury) drives a large amplitude pressure perturbation towards the eye. In some cases, this wave can steepen to form a shock. We show that the region immediately proximal to the eye (within the optic nerve where the vessels are strongly confined by the nerve fibres) can significantly reduce the amplitude of the pressure wave transmitted into the eye. When the length of this region is consistent with clinical measurements, the CSF pressure perturbation generates a wave of significantly lower amplitude than the input, protecting the eye from damage. We construct an analytical framework to explain this observation, showing that repeated rapid propagation and reflection of waves along the confined section of the vessel distributes the perturbation over a longer lengthscale.

Peripapillary Retinal Pigment Epithelium Layer Shape Changes From Acetazolamide Treatment in the Idiopathic Intracranial Hypertension Treatment Trial.

PurposeRecent studies indicate that the amount of deformation of the peripapillary retinal pigment epithelium and Bruch's membrane (pRPE/BM) toward or away from the vitreous may reflect acute changes in cerebrospinal fluid pressure. The study purpose is to determine if changes in optic-nerve-head (ONH) shape reflect a treatment effect (acetazolamide/placebo + weight management) using the optical coherence tomography (OCT) substudy of the Idiopathic Intracranial Hypertension Treatment Trial (IIHTT) at baseline, 3, and 6 months.MethodsThe pRPE/BM shape deformation was quantified and compared with ONH volume, peripapillary retinal nerve fiber layer (pRNFL), and total retinal (pTR) thicknesses in the acetazolamide group (39 subjects) and placebo group (31 subjects) at baseline, 3, and 6 months.ResultsMean changes of the pRPE/BM shape measure were significant and in the positive direction (away from the vitreous) for the acetazolamide group (P < 0.01), but not for the placebo group. The three OCT measures reflecting the reduction of optic disc swelling were significant in both treatment groups but greater in the acetazolamide group (P < 0.01).ConclusionsChange in the pRPE/BM shape away from the vitreous reflects the effect of acetazolamide + weight management in reducing the pressure differential between the intraocular and retrobulbar arachnoid space. Weight management alone was also associated with a decrease in optic nerve volume/edema but without a significant change in the pRPE/BM shape, implying an alternative mechanism for improvement in papilledema and axoplasmic flow, independent of a reduction in the pressure differential. (ClinicalTrials.gov number, NCT01003639.)

Deformation of the Lamina Cribrosa and Optic Nerve Due to Changes in Cerebrospinal Fluid Pressure.

PurposeCerebrospinal fluid pressure (CSFp) changes are involved or implicated in various ocular conditions including glaucoma, idiopathic intracranial hypertension, and visual impairment and intracranial pressure syndrome. However, little is known about the effects of CSFp on lamina cribrosa and retrolaminar neural tissue (RLNT) biomechanics, potentially important in these conditions. Our goal was to use an experimental approach to visualize and quantify the deformation of these tissues as CSFp increased.MethodsThe posterior eye and RLNT of porcine eyes (n = 3) were imaged using synchrotron radiation phase-contrast micro-computed tomography (PC μCT) at an intraocular pressure of 15 mm Hg and CSFps of 4, 10, 20, and 30 mm Hg. Scans of each tissue region were acquired at each CSFp step and analyzed using digital volume correlation to determine 3-dimensional tissue deformations.ResultsElevating CSFp increased the strain in the lamina cribrosa and RLNT of all three specimens, with the largest strains occurring in the RLNT. Relative to the baseline CSFp of 4 mm Hg, at 30 mm Hg, the lamina cribrosa experienced a mean first and third principal strain of 4.4% and −3.5%, respectively. The corresponding values for the RLNT were 9.5% and −9.1%.ConclusionsCSFp has a significant impact on the strain distributions within the lamina cribrosa and, more prominently, within the RLNT. Elevations in CSFp were positively correlated with increasing deformations in each region and may play a role in ocular pathologies linked to changes in CSFp.

How Much Cerebrospinal Fluid Should We Remove Prior to Measuring a Closing Pressure?

The objective of this study was to identify a relationship between cerebrospinal fluid (CSF) volume removal and change in CSF pressure in children with suspected idiopathic intracranial hypertension (IIH). We performed a cross-sectional study of children 22 years and younger who underwent a lumbar puncture (LP) and had a documented opening pressure, closing pressure, and volume removed. Relationship between volume removal and pressure change was determined using a fractional polynomial regression procedure. In the 297 patients who met the inclusion criteria, CSF pressure decreased by 1 cm H2O for every 0.91 mL of CSF removed if the maximum change in pressure was less than 15 cm H2O ( R2 = 0.38). A linear relationship exists between the volume of CSF removed and the amount of pressure relieved when the desired pressure change is less than 15 cm H2O.

Efficacy and Security of Intrathecal with Methotrexate in the Treatment of Meningeal Carcinomatosis

背景与目的脑膜癌病是中枢神经系统转移瘤的一种少见类型。近年来，随着恶性肿瘤治疗疗效的提高，患者生存期延长，脑膜癌病的发病率逐年增加，目前尚缺乏有效的治疗手段。本研究旨在探讨鞘内注射甲氨蝶呤（methotrexate, MTX）治疗脑膜转移的疗效、安全性和预后。方法对27例脑膜转移患者的临床资料、脑脊液实验室检查进行回顾性分析，并分析鞘注化疗后的不良反应及预后。结果27例脑膜转移患者接受鞘注化疗后，70.4%获得临床症状缓解，但脑脊液压力和脑脊液生化改变无统计学差异。55.6%患者无不适，25.9%出现下肢麻木、轻微疼痛，无严重不可逆的不良反应发生。本组患者中位生存期4个月。结论鞘内注射MTX可改善脑膜癌病患者临床症状，无严重不良反应发生。

The Effect of Body Position on Intraocular and Intracranial Pressure in Rabbits.

The correlation between cerebrospinal fluid (CSF) and intraocular pressure (IOP) is still unclear. We compared CSF and IOP measured by the same invasive technique using a new experimental model in rabbits during changes of body position. Pressure changes were recorded in the lateral ventricle (LV), the cortical subarachnoid space (CSS), and the anterior ocular chamber of anesthetized rabbits (n = 12). Animals and measuring instruments were both fixed on a board at an adequate hydrostatic level. In a horizontal position, control IOP (15.1 ± 1.6 cmH2O) and CSF pressure in the LV (12.4 ± 0.6 cmH2O) and CSS (12.2 ± 0.9 cmH2O) were similar during the 60-min period. When changing the body position from horizontal to vertical (upright), CSF pressures decreased drastically (LV = -5.5 ± 2.6 cmH2O and CSS = -7.7 ± 2.3 cmH2O), while the IOP decreased moderately (IOP = 13.3 ± 0.5 cmH2O). Change in body position from horizontal to vertical causes drastic changes in CSF pressure and moderate changes in IOP. Thus, IOP is not reflected by the CSF pressure. In an upright position, the values of CSF pressure were equal to the hydrostatic distance between measuring points and the foramen magnum, which suggests that CSF pressure inside the cranium depends on its anatomical and biophysical features, and not on CSF secretion and absorption.

Intraocular Pressure Rise in Subjects with and without Glaucoma during Four Common Yoga Positions

PurposeTo measure changes in intraocular pressure (IOP) in association with yoga exercises with a head-down position.MethodsThe single Center, prospective, observational study included 10 subjects with primary open-angle glaucoma and 10 normal individuals, who performed the yoga exercises of Adho Mukha Svanasana, Uttanasana, Halasana and Viparita Karani for two minutes each. IOP was measured by pneumatonometry at baseline and during and after the exercises.ResultsAll yoga poses were associated with a significant (P<0.01) rise in IOP within one minute after assuming the yoga position. The highest IOP increase (P<0.01) was measured in the Adho Mukha Svanasana position (IOP increase from 17±3.2 mmHg to 28±3.8 mmHg in glaucoma patients; from 17±2.8 mmHg to 29±3.9 mmHg in normal individuals), followed by the Uttanasana position (17±3.9 mmHg to 27±3.4 mmHg (glaucoma patients) and from 18±2.5 mmHg to 26±3.6 mmHg normal individuals)), the Halasana position (18±2.8 mmHg to 24±3.5 mmHg (glaucoma patients); 18±2.7 mmHg to 22±3.4 mmHg (normal individuals)), and finally the Viparita Kirani position (17±4 mmHg to 21±3.6 mmHg (glaucoma patients); 17±2.8 to 21±2.4 mmHg (normal individuals)). IOP dropped back to baseline values within two minutes after returning to a sitting position. Overall, IOP rise was not significantly different between glaucoma and normal subjects (P = 0.813), all though glaucoma eyes tended to have measurements 2 mm Hg higher on average.ConclusionsYoga exercises with head-down positions were associated with a rapid rise in IOP in glaucoma and healthy eyes. IOP returned to baseline values within 2 minutes. Future studies are warranted addressing whether yoga exercise associated IOP changes are associated with similar changes in cerebrospinal fluid pressure and whether they increase the risk of glaucoma progression.Trial RegistrationClinicalTrials.gov #NCT01915680

Hearing loss in hydrocephalus: a review, with focus on mechanisms.

While neither hydrocephalus nor cerebrospinal fluid (CSF) shunt placement is traditionally considered in the differential diagnosis of hearing loss, there is substantial evidence that CSF circulation and pressure abnormalities can produce auditory dysfunction. Several indirect mechanisms may explain association between hydrocephalus and hearing loss, including mass effect, compromise of the auditory pathway, complications of prematurity, and genetically mediated hydrocephalus and hearing loss. Nevertheless, researchers have proposed a direct mechanism, which we term the hydrodynamic theory. In this hypothesis, the intimate relationship between CSF and inner ear fluids permits relative endolymphatic or perilymphatic hydrops in the setting of CSF pressure disturbances. CSF is continuous with perilymph, and CSF pressure changes are known to produce parallel perilymphatic pressure changes. In support of the hydrodynamic theory, some studies have found an independent association between hydrocephalus and hearing loss. Moreover, surgical shunting of CSF has been linked to both resolution and development of auditory dysfunction. The disease burden of hydrocephalus-associated hearing loss may be large, and because hydrocephalus and over-shunting are reversible, this relationship merits broader recognition. Hydrocephalic patients should be monitored for hearing loss, and hearing loss in a patient with shunted hydrocephalus should prompt further evaluation and possibly adjustment of shunt settings.

P6. Optic nerve sheath diameter measurement – A tool to identify high risk patients for spinal ischemia after endovascular thoracoabdominal aortic aneurysm repair?

Objective Thoracic endovascular aortic repair (TEVAR) is associated with a reasonable risk of spinal ischemia. As cerebrospinal fluid pressure (CSFP) is correlated with the rate of paraplegia, a non-invasive method to estimate CSFP could help to estimate the patient’s individual risk and guide the therapeutic approach. The quantification of the optic nerve sheath diameter (ONSD) using ocular sonography could be a suitable technique and was examined in the present study. Methods 28 patients with TEVAR were included. Five consecutive measurements of the ONSD were performed in each patient. The first before the intervention (“baseline”), the next immediately postinterventional at the intensive care unit (post1), measurements 3, 4 (post2, post3) on day 1 and 2 after the intervention and number 5 (post4) before discharge. Statistical analysis was done using the Wilcoxon-test. A p -value Results A significant increase between baseline and post1-measurements (right eye: p = 0.006; left eye: p = 0.02) could be detected. A significant decrease was detected between post1 and post3 (right eye: p = 0.02; left eye: p Conclusions The present study is the first to prospectively examine and prove the possibility to monitor CSFP changes in patients with TEVAR associated transient spinal edema using OCCS. Systematic factors as artificial ventilation and body positioning did not have a significant effect.

Optic Nerve Sheath Diameter Measurement to Identify High-Risk Patients for Spinal Ischemia after Endovascular Thoracoabdominal Aortic Aneurysm Repair.

Thoracic endovascular aortic repair (TEVAR) is associated with a reasonable risk of spinal ischemia. As cerebrospinal fluid pressure (CSFP) is correlated with the rate of paraplegia, a non-invasive method to estimate CSFP could help to estimate the patient's individual risk and guide the therapeutic approach. The quantification of the optic nerve sheath diameter (ONSD) using ocular sonography (OS) could be a suitable technique and was examined in the present study. 28 patients with TEVAR were included. Five consecutive measurements of the ONSD were performed in each patient. The first before the intervention ("baseline"), the next immediately postinterventional at the intensive care unit (post1), measurements 3, 4 (post2, post3) on day 1 and 2 after the intervention and number 5 (post4) before discharge. Statistical analysis was done using the Wilcoxon-test. A p-value < 0.05 was considered statistically significant. A significant increase between baseline and post1-measurements (right eye: p = 0.006; left eye: p = 0.02) could be detected. A significant decrease was detected between post1 and post3 (right eye: p = 0.02; left eye: p < 0.01). A group of 5 patients had an additional increase of ONSD from post1 to post2, one of these patients developed a permanent paraplegia. Patients with spinal catheters had significantly lower ONSDs at nearly all time points. The present study is the first to prospectively examine and prove the possibility to monitor CSFP changes in patients with TEVAR associated transient spinal edema using OS. Systematic factors as artificial ventilation and body positioning did not have a significant effect.

The role of low intracranial pressure in the development of glaucoma in patients with Alzheimer's disease

October 22, 2013Dear Editor,We read with great interest the paper by Janssen et al. (2013)entitled ‘The vast complexityof primaryopen angle glaucoma: Dis-ease genes, risks, molecular mechanisms and pathobiology.’ Theauthors deserve appreciation for their very informative reviewarticle.However,wewishtomakeacommentconcerningtheirdis-cussion of the potential role of intracranial pressure (ICP) in Alz-heimer’s disease (AD) and glaucoma.In the last section of their paper, Janssen and colleaguesdiscuss the potential relation between primary open angle glau-coma (POAG) and AD. As the authors mention, several studieshave found an increase in the occurrence of glaucoma in AD pa-tients. The authors state: “In our view, POAG damage could becaused by the net pressure over the optic disk, involving boththe aqueous humor pressure of the eye and cerebrospinal fluid(CSF) pressure of the brain, as described above. Also, CSF pressurechanges have been described in AD (Silverberg et al., 2006).Could these pressure changes underlie a relationship betweenPOAG and AD, and at the same time explain the apparently con-flicting association studies?” Further, the authors state: “We hy-pothesize that there is a strong association between normalpressure glaucoma and late AD, since both disease stages,following the ‘net pressure on the optic disk hypothesis’,arecharacterized by one single disease mechanism: an abnormallylow ICP.”Janssen et al. (2013) thus hypothesize that low ICP may play arole in the association between glaucoma and AD. We fully agreewith the authors since our group has previously presented this hy-pothesisforthefirsttime(Wostynetal.,2008,2009a).Intwoofourearlier manuscripts published in 2008 (Wostyn et al., 2008) and2009 (Wostyn et al., 2009a), we proposed low ICP occurring inAD as a factor leading to increased risk of glaucoma. Evidence forthishypothesiswasgainedfromCSFpressuremeasurementstudiesin AD patients and patients with glaucoma. The finding of a highoccurrence of reduced CSF pressure among patients with AD(Silverberg et al., 2006; Wostyn et al., 2009b) could be linked tothe high rate of reported comorbidity between AD and glaucoma(Bayer et al., 2002; Tamura et al., 2006), since it has been shownthat CSF pressure is lower in patients with glaucoma (Berdahlet al., 2008a, 2008b; Ren et al., 2010). This could result in anabnormally high trans-lamina cribrosa pressure difference andlead to glaucomatous damage. Given this previously advanced hy-pothesis, it was a great surprise when Janssen et al. (2013) recentlyhypothesized about the potential role of low ICP in glaucoma andAD without citing our earlier work (Wostyn et al., 2008, 2009a)or making clear the relevant precedents. The authors did cite oneof our papers, one largely focused on the high occurrence rate ofglaucoma among patients with normal pressure hydrocephalus(Wostyn et al., 2010), but this paper has no direct relevance tothe above hypothesis.Sincerely yours,Peter Wostyn, MDVeva De Groot, MD, PhDDebby Van Dam, PhDKurt Audenaert, MD, PhDPeter Paul De Deyn, MD, PhDReferences

Hearing loss following ventriculoperitoneal shunt in communicating hydrocephalus patients: A pilot study

Hearing loss can be associated with a decrease in cerebrospinal fluid (CSF) pressure because changes in CSF pressure induce changes in perilymph pressure. Hearing loss after neurosurgical procedures have been reported, but clinical information on hearing loss after the placement of ventriculoperitoneal (VP) shunts, the most commonly used CSF shunt for hydrocephalus patients, is limited. This study is aimed to show the relationship between VP shunt and hearing loss. Prospective study. Pure tone threshold and electrocochleography were preoperatively performed in nine patients (18 ears) undergoing elective VP shunt placement. Five-day and 1-month post-shunt placement hearing thresholds were compared with baseline data. A correlation analysis was conducted between the threshold and summating potential/action potential (SP/AP) ratio changes at 5 days and 1 month after shunt placement. Cochlear aqueduct dimensions measured by high-resolution CT were compared between ears with and without hearing loss. About 40% of subject ears showed hearing loss with a threshold elevation of at least 15 dB in one or more frequencies. After VP shunt placement, the mean threshold of all ears showed a significant increase in most frequencies and the pure tone average. The change in the SP/AP ratios was significantly correlated with the change in the pure tone average at both 5 days and 1 month after shunt placement. Cochlear aqueduct dimensions were not correlated with hearing loss occurrence. Hearing thresholds may increase following VP shunt placement, possibly due to secondary endolymphatic hydrops.