Intracranial Pressure and Brain Function: Effects of Head Down Tilt Upon Brain Perfusion and Cognitive Performance

Study Overview
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Brief Summary
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The aim of the study is to understand the relationship between intracranial pressure regulation, cerebral tissue oxygenation and cognitive functioning. More specifically, the study tests the hypothesis that head down tilt will increase intracranial pressure (not measured in this study, but demonstrated in previous studies), will induce venous congestion and facial swelling, decrease intracranial tissue oxygenation and hamper brain functioning. The objectives of the study therefore are to assess young healthy people during head-down tilt (HDT), and to assess cognitive brain functioning, cerebral tissue oxygenation (non-invasively), frontal skin thickness, cerebral perfusion and neuronal functioning via event-related potentials.

Official Title
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Intracranial Pressure and Brain Function: Effects of Head Down Tilt Upon Brain Perfusion and Cognitive Performance

Conditions
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Intracranial Hypertension

Intervention / Treatment
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* Other: 12° head down tilt


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Physically and mentally healthy male test subjects that are able and declare in writing their willingness to participate in the entire study and successfully passed the psychological and medical screening Aged between 18-55 years old with a Body Mass Index (BMI) of 20-28 kg/m2, weight between 65-100 kg, and a height between 158-195 cm Demonstrable medical insurance and official certificate of absence of criminal record Exclusion Criteria: Inability to sleep on the back Drug, medication or alcohol abuse (regular consumption of more than 20-30 g alcohol/day) Smoking within the past 6 months prior to study commencement Migraine or other chronic head aches Previous psychiatric illness Subjects suffering from weak concentration History of psychological or central nervous disorders Hiatus hernia Gastro-oesophageal reflux Diabetes mellitus Pronounced orthostatic intolerance (< 10 min standing) Kidney disorder: deviations from normal values for creatinine in plasma. (Normal value: Creatinine < 1.20 mg/dl) Thyroid gland disorder: deviations from normal values for thyroid stimulating Hormone (TSH) in plasma. (Normal range: TSH 0.55-4.80 mUnits/l) Anaemia: Hb under normal values (Normal values of Hb for men: 13.5-17.5 g/l) Elevated risk of thrombosis High likelihood of coagulopathy assessed by a clinical standard questionnaire Chronic back complaints History of lumbar surgery History of lumbar spine trauma Motor or sensory deficits as assessed by neurological examination Contraindications against MRI Imprisoned at the time of the study Taking medications that may impair cognitive function, autonomic function or any of the study procedures Ophthalmological conditions including glaucoma, retinopathy, severe cataracts, eye trauma or implants Any other medical condition that the investigators consider a contraindication to the study procedures that would make it unsafe or confound the measurements.

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 55 Years

Sexes Eligible for Study
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Male

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| No Intervention: Horizontal<br>Subjects will be in horizontal supine Position for 21 hours | |
| Experimental: -12° head down tilt<br>Subjects will be in 12° head down supine Position for 21 hours | Other: 12° head down tilt<br>* supine head down tilt<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in cognitive test battery score | The test battery includes sensomotoric speed, psychomotor vigilance, visual analysis of items, abstract thinking and mathematical processing | Twice at baseline, and 30 minutes and 20 hours after starting the intervention | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in mid cerebral artery blood flow velocity | Transcranial Doppler measurements | Twice at baseline, and 10 minutes and 19 hours after starting the intervention | 
| Change in cerebral tissue oxygenation | Near-infrared measurement | Twice at baseline, and 10 minutes and 19 hours after starting the intervention | 
| Magnetic resonance Imaging: Change in cerebral blood flow | Magnetic resonance imaging will be performed in order to gain information about intracranial blood flow. | Once at baseline, and 2 and 19 hours after starting the intervention | 
| Magnetic resonance Imaging: Change in resting state functional MRI (fMRI) | Magnetic resonance imaging will be performed to assess resting state functional MRI. | Once at baseline, and 2 and 19 hours after starting the intervention | 
| Magnetic resonance Imaging: Change in fMRI Response to decision task | Magnetic resonance imaging will be performed in order to assess functional MRI during a decision task combing a reaction time test using a visual stimulus. | Once at baseline, and 2 and 19 hours after starting the intervention | 
| Change in jugular vein filling | Conventional Imaging ultrasound from jugular veins veins will be used to assess vein cross sections | Once at baseline, and 10 minutes and 19 hours after starting the intervention | 
| Change in frontal vein filling | Conventional Imaging ultrasound from the frontal veins will be used to assess vein cross sections | Once at baseline, and 10 minutes and 19 hours after starting the intervention | 
| Change in P-300 | P-300 will be assessed via an EEG electrode during cognitive test battery | Twice at baseline, and 30 minutes and 20 hours after starting the intervention | 
| Change in sleep effectiveness | Polysomnographic recordings | over the entire intervention night | 
| Change in total sleep time | Polysomnographic recordings | from 22:00 until 6:00 in all nights | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Cognitive functioning, Brain tissue oxygenation, cerebral perfusion, head down tilt