Prediction & Mechanisms of Recovery Following IEDS
- Conditions
- Decompression Sickness
- Registration Number
- NCT06370897
- Lead Sponsor
- University of Plymouth
- Brief Summary
Inner Ear Decompression sickness (IEDS) accounts for 20% of all types of decompression sickness (the bends) in divers. The condition commonly affects the peripheral vestibular system (inner ear). IEDS results in acute symptoms of dizzyness (vertigo) and imbalance. Even with the recommended treatment of hyperbaric oxygen therapy some people do not recovery fully. However, even in the presence of a permanent vestibular deficit many people can show a behavioural recovery where symptoms improve over time. Recovery can be aided by vestibular rehabilitation (VR) which is now routine for acute IEDS but was not provided before 2021, and is not widespread across the UK (United Kingdom) or world, meaning people may have a suboptimal recovery.
This project will investigate if and how people recover after an acute episode of IEDS and whether people who had IEDS in the past show changes in the central (brain) processing of vestibular function and in symptoms of dizziness, balance and posture.
This project has two main parts. Part one is a prospective observational study where people with an acute onset of IEDS are serially monitored while they are receiving hyperbaric treatment and VR over 10-14 days. Part two is a retrospective observational study where who have had IEDS in the past 15 years are re-assessed in a one-off session. The tests in both parts involve clinical tests and specialist eye movement recordings that assess vestibular function. We will also determine the site of any vestibular pathology by using selective stimulation of the vestibular end organ or nerve and assess whether there are any changes in how the structure and function of central vestibular pathways in the brain. In people with chronic IEDS with vestibular symptoms we will offer participants a course of VR over 12 weeks and assess whether this is associated with any improvement in symptoms.
- Detailed Description
Decompression sickness after diving can occur following a rapid ascent. Here, nitrogen, absorbed by the body when breathing compressed air at depth, comes out of solution and forms microbubbles in the blood. Inner ear decompression sickness (IEDS) accounts for approximately 20% of all cases of decompression sickness. The vestibular system is involved in \~85% cases of IEDS resulting in symptoms of vertigo, nausea, vomiting and unsteadiness with hearing loss and tinnitus.
The strong association of IEDS with a patent foramen ovale (50-73% of cases) suggests that a shunted venous gas embolism causes damage to the vestibular apparatus, which is particularly vulnerable due to its low perfusion and thus slow inert gas washout, compared to the cochlea and other brain structures. It is hypothesised that the nitrogen bubbles within the blood vessels trigger an inflammatory reaction in the endothelium with a coagulation cascade that leads to hypoxic injury and/or that there is direct damage to the membranous labyrinth. Animal models of rapid decompression suggest that it can cause a haemorrhage within the labyrinth with ectopic bone growth and fibrosis occurring over the next month. Advances in the imaging of the inner ear using a gadolinium-based contrast agent (GBCA) allow us to explore structural changes in human divers. Imaging can also help to differentially diagnose another potential cause of diving induced dizziness, superior structural dehiscence syndrome
Decompression sickness and the subsequent inflammatory response requires emergency treatment using with hyperbaric oxygen. The effects of hyperbaric therapy and rehabilitation are not uniform across participants, factors affecting recovery include a high clinical score on admission and a delay in hyperbaric recompression of over 6 hours. Complete recovery is seen in only about 30% of cases. Previous studies have highlighted that people who do not fully recover can have a variety of symptoms that can affect work, hobbies and well-being. These include feelings of instability in some situations (working at a height and with movement) and imbalance in the dark or when changing position.
In people with permanent vestibular pathology, symptoms can still improve due to central adaptive processes within the brain termed vestibular compensation. Clinical studies in other types of peripheral vestibular dysfunction show that it is possible to facilitate the compensation process and symptom recovery through vestibular rehabilitation. Early access to vestibular rehabilitation is now routine practice at the Diving Diseases Research Centre (DDRC) where patients are treated in the South-West UK. This is coupled to diagnosis and monitoring of vestibular function using objective laboratory tests (rotary testing) and clinical tests.
Animal studies highlight the mechanisms underlying vestibular compensation following a peripheral nerve lesion. These focus on changes in the interconnections between brainstem nuclei (e.g. vestibular nuclei) and the cerebellum and re-weighting of the relative importance of multi-sensory sensory inputs. Human studies in chronic peripheral dysfunction also suggest there are recovery-related changes in cortical areas that normally process vestibular information over time. Functional changes in the acute stages include an increase in contralesional activity in the parietoinsular vestibular cortex as well as interlinked subcortical areas (posterolateral thalamus, anterior cingulate gyrus, pontomesencephalic brainstem, hippocampus) with a decrease in activity was seen in the visual, somatosensory and auditory cortices. Structural changes over the first 3 months post lesion include increases in grey matter volume in the vestibular cortex, bilateral hippocampus, visual cortices and the cerebellum.
Within the DDRC vestibular rehabilitation has only been routinely undertaken for people diagnosed with IEDS since 2021. As complete recovery is seen in only about 30% of cases \[9\]; this suggests that there may be a cohort of patients with residual vestibular symptoms. In surveys of the aural and vestibular effects of diving, including those conducted by the DDRC, 79% (of 790 respondents) have reported aural related problems after learning to dive. Of those with reported problems 46% did not seek any medical advice and 39% specifically reported dizziness / vertigo. In total this suggests that at least 14% of all divers may have undiagnosed vestibular problems that could benefit from vestibular rehabilitation. A case review highlights that since 1999 there have been 79 cases of clinically diagnosed IEDS at the DDRC. Therefore, there is a need to assess and provide rehabilitation support to people with past IEDS and potentially in the future a larger cohort of divers with previously undiagnosed symptoms.
This study plans to:
undertake a prospective observational study where people with acute onset IEDS are followed up. This will include the current battery of clinical and laboratory (rotary) tests but also additional optional clinical and physiological testing (Vestibular Evoked Myogenic Potentials VEMPs), imaging (Diffusor Tensor Imaging DTI and functional Magnetic Resonance Imaging f MRI) and semis-structured interviews in the acute (1-14 days) and chronic (3 months and 12 months) stage.
We will also:
undertake a retrospective cross-sectional study of people who have previously been managed for IEDS by the DDRC. Here we will undertake the same battery of tests as for the prospective study which includes measures of potential risk factors and patient reported outcome measures. We will also take this opportunity to explore people's symptoms post IEDS and their views on future rehabilitation trials. In those with remaining vestibular symptoms and signs we will provide advice on vestibular rehabilitation by qualified personnel with follow up as required. We will compare our data to a cohort of healthy controls of a similar age and gender distribution.
Recruitment & Eligibility
- Status
- NOT_YET_RECRUITING
- Sex
- All
- Target Recruitment
- 41
Not provided
Not provided
Study & Design
- Study Type
- OBSERVATIONAL
- Study Design
- Not specified
- Primary Outcome Measures
Name Time Method Side of peripheral vestibular damage: Prospective cohort T0=baseline within 24 hours of IEDS in the prospective cohort Side (left or right) of vestibular dysfunction as determine by video head impulse test (v HIT) testing
Extent of peripheral vestibular damage: Prospective cohort T0=baseline within 24 hours of IEDS in the prospective cohort VOR gain (unit less) as measured by v HIT at T0 (Range 0-1 higher values are better outcome)
Site of peripheral vestibular damage: Prospective cohort T0=baseline within 24 hours of IEDS in the prospective cohort Site of dysfunction: semi-circular canals affected as determine by v HIT testing. One or a combination of Horizontal, anterior or posterior canals.
Side of peripheral vestibular damage: Retrospective cohort 1 time point: 0-10 years post injury Side (left or right) of vestibular dysfunction as determine by video head impulse test (v HIT) testing
Extent of peripheral vestibular damage:Retrospective cohort 1 time point: 0-10 years post injury VOR gain (unit less) at T0 (Range 0-1 higher values are better outcome)
Site of peripheral vestibular damage:Retrospective cohort 1 time point: 0-10 years post injury Site of dysfunction: semi-circular canals affected as determine by v HIT testing.One or a combination of Horizontal, anterior or posterior canals.
- Secondary Outcome Measures
Name Time Method Vestibular Evoked myogenic Potentials latency: Prospective Study 7-10 days , 3 months and 12 months post injury Change from baseline (T0) in Galvanic and Auditory Vestibular Evoked myogenic Potentials (VEMPs) will be assessed and the latency of evoked responses measured in milliseconds.
VOR Time constant:Prospective Study 7-10 days , 3 months and 12 months post injury Change from baseline (T0)in VOR time constant in response to a step rotation (initial 140°/s acceleration/deceleration and a 60°/s fixed-chair velocity) stimulus . Time constant (seconds) where a higher time constant is clinically better. Range 0-40s.
Clinical measure of walking: Prospective Study 7-10 days , 3 months and 12 months post injury Change from baseline (T0) in Dynamic Gait Assessment (DGA). Eight tasks scored 0-3. Total range = 0-24 with a higher score indicating better walking ability.
Clinical measure of balance: Prospective Study 7-10 days , 3 months and 12 months post injury Change from baseline (T0) in Clinical measures of balance sharpened Romberg (tandem stance). The length of time a person is able to stand in the eyes open, tandem stance position is recorded up to a maximum of 30 seconds.
Patient reported outcome measure: Prospective Study 7-10 days , 3 months and 12 months post injury Change from baseline (T0) in PROM (patient reported outcome measure) vertigo severity scale.15 questions rated 0-4. Score range =0-60 where lower scores indicate a better clinical outcome
Vestibular Evoked myogenic Potentials amplitude: Prospective Study 7-10 days , 3 months and 12 months post injury Change from baseline (T0) in Galvanic and Auditory Vestibular Evoked myogenic Potentials (VEMPs) will be assessed and the amplitude of evoked responses measured in millivolts.
VOR gain: Retrospective Study 7-10 days , 3 months and 12 months post injury VOR gain assessed through sinusoidal rotation in the dark . Gain is unit less and range from 0-1 where higher values indicate a better clinical outcome.
Perception of verticality: Retrospective Study 1 time point: 0-10 years post injury Rod and Disk test: The ability to orientate a line to vertical is assessed with / without visual distractors. The error from vertical is recorded in degrees. Outcomes range from 0-180 degrees where lower numbers indicate better verical perception.
Posturography: Prospective Study 7-10 days , 3 months and 12 months post injury Change from baseline (T0) in Postural sway quotient. Postural sway (mm/s) is measured via force plates. The ratio of the sway with eyes open and eyes closed is calculated (unitless ratio).
Perception of verticality: Prospective Study 7-10 days , 3 months and 12 months post injury Change from baseline (T0) in Rod and Disk test: The ability to orientate a line to vertical is assessed with / without visual distractors. The error from vertical is recorded in degrees. Outcomes range from 0-180 degrees where lower numbers indicate better verical perception.
Patient reported outcome measure: Retrospective Study 1 time point: 0-10 years post injury PROM (patient reported outcome measure) vertigo severity scale.15 questions rated 0-4. Score range =0-60 where lower scores indicate a better clinical outcome
Clinical measure of balance: Retrospective Study 1 time point: 0-10 years post injury Clinical measures of balance sharpened Romberg (tandem stance). The length of time a person is able to stand in the eyes open, tandem stance position is recorded up to a maximum of 30 seconds.
VOR gain v HIT: Prospective Study 7-10 days , 3 months and 12 months post injury Change from baseline (T0) in VOR gain assessed through V HIT test . Gain is unit less and range from 0-1 where higher values indicate a better clinical outcome.
VOR gain: Prospective Study 7-10 days , 3 months and 12 months post injury Change from baseline (T0) in VOR gain assessed through sinusoidal rotation in the dark . Gain is unit less and range from 0-1 where higher values indicate a better clinical outcome.
VOR Time constant: Retrospective Study 1 time point: 0-10 years post injury VOR time constant in response to a step rotation (initial 140°/s acceleration/deceleration and a 60°/s fixed-chair velocity) stimulus . Time constant (seconds) where a higher time constant is clinically better. Range 0-40s.
Functional MRI response to an optokinetic stimulus: Retrospective Study 1 time point: 0-10 years post injury Regions of interest will also assess changes in activation with an optokinetic stimulus compared to rest in cortical and subcortical sites that process vestibular information namely the insulo-parietal cortex and hippocampus and sites that process other sensory information namely the visual cortex and somatosensory cortex
Vestibular Evoked myogenic Potentials amplitude: Retrorospective Study 1 time point: 0-10 years post injury Galvanic and Auditory Vestibular Evoked myogenic Potentials (VEMPs) will be assessed and the amplitude of evoked responses measured in millivolts.
Posturography: Retrospective Study 1 time point: 0-10 years post injury Postural sway quotient. Postural sway (mm/s) is measured via force plates. The ratio of the sway with eyes open and eyes closed is calculated (unitless ratio).
Functional MRI response to an optokinetic stimulus: Prospective Study 7-10 days , 3 months and 12 months post injury Change from baseline (T0) in Regions of interest will also assess changes in activation with an optokinetic stimulus compared to rest in cortical and subcortical sites that process vestibular information namely the insulo-parietal cortex and hippocampus and sites that process other sensory information namely the visual cortex and somatosensory cortex
Clinical measure of walking: Retrospective Study 1 time point: 0-10 years post injury Dynamic Gait Assessment (DGA). Eight tasks scored 0-3. Total range = 0-24 with a higher score indicating better walking ability.
Vestibular Evoked myogenic Potentials latency: Retrospective Study 1 time point: 0-10 years post injury Galvanic and Auditory Vestibular Evoked myogenic Potentials (VEMPs) will be assessed and the latency of evoked responses measured in milliseconds.