The authors herby declare that, although Prof. Eshel Ben-Jacob is a PLOS ONE Editorial Board member, this does not alter the authors' adherence to all the PLOS ONE policies on sharing data and materials.
Conceived and designed the experiments: SE GF IK NG HG. Performed the experiments: SE GF YB JB MF. Analyzed the data: SE OV KK EB-J HG. Wrote the paper: SE EB-J HG. Performed the experiments (brain SPECT): OV. Performed the experiments (neurological evaluation part): IK. Performed the experiments (brain imaging part): HG.
Recovery after stroke correlates with non-active (stunned) brain regions, which may persist for years. The current study aimed to evaluate whether increasing the level of dissolved oxygen by Hyperbaric Oxygen Therapy (HBOT) could activate neuroplasticity in patients with chronic neurologic deficiencies due to stroke.
A prospective, randomized, controlled trial including 74 patients (15 were excluded). All participants suffered a stroke 6–36 months prior to inclusion and had at least one motor dysfunction. After inclusion, patients were randomly assigned to "treated" or "cross" groups. Brain activity was assessed by SPECT imaging; neurologic functions were evaluated by NIHSS, ADL, and life quality. Patients in the treated group were evaluated twice: at baseline and after 40 HBOT sessions. Patients in the cross group were evaluated three times: at baseline, after a 2-month control period of no treatment, and after subsequent 2-months of 40 HBOT sessions. HBOT protocol: Two months of 40 sessions (5 days/week), 90 minutes each, 100% oxygen at 2 ATA. We found that the neurological functions and life quality of all patients in both groups were significantly improved following the HBOT sessions while no improvement was found during the control period of the patients in the cross group. Results of SPECT imaging were well correlated with clinical improvement. Elevated brain activity was detected mostly in regions of live cells (as confirmed by CT) with low activity (based on SPECT) – regions of noticeable discrepancy between anatomy and physiology.
The results indicate that HBOT can lead to significant neurological improvements in post stroke patients even at chronic late stages. The observed clinical improvements imply that neuroplasticity can still be activated long after damage onset in regions where there is a brain SPECT/CT (anatomy/physiology) mismatch.
ClinicalTrials.gov
Intensive functional therapy and rehabilitation programs for post stroke patients are considered essential for maximizing the patients' quality of life
Years of clinical experience revealed that the dramatic spontaneous recovery from stroke occurs mainly within the first 30 days, though moderate and severe stroke survivors continue to improve for at least 90 days
Many physiological pathways, each with a different characteristic time, are spontaneously activated following the onset of stroke. Therefore, a challenging question to be addressed considers the optimal time lapse after stroke to start the HBOT procedure. It should also be kept in mind that signals and chemical cues associated with cell death during the acute stage of stroke might, in fact, promote repair during recovery
The study was performed as a prospective, randomized, controlled, two-group trial. The population included patients of ages 18 years or older, who had either ischemic or hemorrhagic stroke 6–36 months prior to their inclusion. All patients had to have at least one motor dysfunction. Exclusions were based on chest pathology incompatible with HBOT, inner ear disease, claustrophobia and inability to sign informed consent. Additional exclusions were based on dynamic neurologic improvements during the last month (based either on objective measurements by external evaluator or on subjective statement by the patients). Smoking was not allowed during the study. All patients signed written informed consent; the protocol was approved by the local Helsinki committee. The study was conducted in the hyperbaric and research units of Assaf-Harofeh Medical Center, Israel.
After signing an informed consent form, the patients were invited for baseline evaluations. Included patients were randomized into two groups (1∶1 randomization): a treated group and a cross group. The neurologic functions as evaluated by National Institutes of Health Stroke Scale (NIHSS)
The clinical severity of the stroke was blindly assessed by a trained physician according to the NIHSS
Brain single photon emission computed tomography (SPECT) was conducted with 925–1,110 MBq (25–30 mCi) of technetium-99methyl-cysteinate-dimmer(Tc-99m-ECD)at 40–60 min post injection using a dual detector gamma camera (ECAM or Symbia T, Siemens Medical Systems) equipped with high resolution collimators. Data was acquired in 3-degree steps and reconstructed iteratively with Chang method (
More specifically, the assessment was done independently by two nuclear medicine physicians who compared the scans and graded them as either: 1 = no change, 2 = mild change and 3 = significant change. This was done “blindly” (without pre-conditioned information about the patients). “No change” was assigned to no visual difference in the number or size of perfusion deficits; “mild change” to a reduction in number or size of perfusion defects; “significant change” to a global perfusion increment in addition to diminution of defect numbers or size. Differences in evaluation were resolved after mutual reviewing. A comparison of the SPECT results with anatomical imaging CT was conducted in order to evaluate the extent of perfusion deficit in relation to the anatomical lesion. All SPECT analysis were done while blinded to the laboratory and clinical data.
Quality of life was evaluated by the EQ-5D questionnaire
The statistical analysis considerations are detailed in Appendix A. SAS software (version 9.1; SAS Inc.) was used. Continuous data is expressed as means ± STD (standard deviation) and compared by unpaired t-test for inter-group comparison and by paired t-test for intra-group comparison. Categorical data is expressed in numbers and percentages and compared by chi-square test. P values<0.05 were considered statistically significant. All randomly allocated patients were included in the safety analysis and those who had post-baseline assessment were included in efficacy analyses.
The analysis aims to better quantify and compare changes in the clinical scores, while taking into consideration the high patient-to-patient variability. The idea was to inspect, for each patient at each time stage, the scaled relative differences in each of the clinical scores. More specifically, we calculated for a specific patient (j) the scaled relative difference SRDj, defined as:
Where SFj is the value of a clinical score at the end of the time stage (either treatment or control), and SIj is the score at the beginning of the time stage. We note that the symbol<> indicates average over the values of the patients in the group. For example, <SFj> means the average of SFj over all patients (j) that belong to the group. The abbreviation STD means the standard deviation between the values of the patients in the group. This analysis enables quantitative inspection of the changes in the clinical scores as is further explained and illustrated in
The study included 74 patients (August 2008-October 2010). 7 patients from the treated group and 8 patients from the cross group were excluded: 8 refused the SPECT, 3 had no measurable paresis, 1 had a medical problem, 1 had a stroke during the control period, and 2 refused to quit smoking (
Twenty four patients (80%) from the treated group had a history of ischemic stroke; of those, 17(71%), 3(13%), 2(8%) and 2(8%) patients were classified as TOAST 1, 2, 3 and 4, respectively. Twenty five patients (86%) from the cross group had ischemic stroke; of those, 18(72%), 3(12%), 2(8%) and 2(8%) patients were classified as TOAST 1, 2, 3 and 4, respectively; p = 0.8 for comparison of the TOAST classification between the groups. Of the 6 patients (20%) in the treated group that had hemorrhagic stroke, 5(83%) had anterior circulation stroke; and of the 4 patients with hemorrhagic stroke in the cross group, 3(75%) had anterior stroke. Baseline patients’ characteristics are summarized in
Treated Group(n = 30) | Cross Group(n = 29) | P Value | |
Age (years) | 61±12 | 63±6.3 | 0.28 |
Males/Females | 22/8 | 17/12 | 0.23 |
Years of education | 14.2±3.7 | 15.1±3.3 | 0.39 |
Time from Stroke (years) | 1.49±0.83 | 1.48±0.79 | 0.94 |
Ischemic stroke | 24 (80%) | 25 (86%) | 0.8 |
Hemorrhagic stroke | 6 (20%) | 4 (14%) | 0.75 |
Diabetes | 10 (33.3%) | 12 (41.4%) | 0.52 |
Hypertension | 24 (80%) | 22 (75.9%) | 0.7 |
Ischemic heart disease | 6 (20%) | 6 (20.7%) | 0.94 |
Hyperlipidemia | 24 (80%) | 24 (82.8%) | 0.8 |
History of convulsions | 5 (16.7%) | 2 (6.9%) | 0.09 |
History of smoking | 10 (33.3%) | 9 (31%) | 0.7 |
|
|||
Aspirin | 11 (36.7%) | 14 (48.3%) | 0.24 |
Clopidrogel | 10 (33.3%) | 7 (24.1%) | 0.43 |
Warfarin | 3 (10%) | 5 (17.2%) | 0.91 |
Statins | 23 (76.7%) | 23 (79.3%) | 0.8 |
Anti-convulsive | 6 (20%) | 3 (10.3%) | 0.14 |
Anti-Hypertensive | 21 (70%) | 22 (75.8%) | 0.43 |
Glucose lowering drugs | 9 (30%) | 10 (34.5%) | 0.7 |
Anti-Depressants | 7 (23.3%) | 9 (31%) | 0.13 |
Data presented as Mean ± standard deviation.
The results of the neurological evaluations, including the NIHSS and the ADL and the quality of life estimates EQ-5D and EQ-VAS, are summarized in
(
Treatment group | Cross group | ||||||||
Baseline | Post HBOT | P1 | P2 | Baseline | Control period | Post HBOT | P1 | P3 | |
|
8.53±3.62 | 5.52±3.59 | <0.0001 | 0.004 | 8.71±4.11 | 8.34±4.25 | 5.85±3.44 | 0.43 | <0.0001 |
|
16.1±6.52 | 12.77±7.26 | <0.0001 | 0.02 | 17.38±9.49 | 17.45±9.53 | 13.82±8.75 | 0.42 | <0.0001 |
|
9.3±1.36 | 7.67±1.33 | <0.0001 | 0.009 | 8.78±1.55 | 8.64±1.69 | 7.57±1.51 | 0.122 | <0.0001 |
|
4.93±1.62 | 6.45±1.50 | <0.0001 | 0.016 | 5.14±2.25 | 5.34±2.27 | 6.79±1.85 | 0.053 | <0.0001 |
Data presented as Mean ± standard deviation.
P1 = p value compared to baseline in the same group. P2 = p value compared to the cross group after the control period. P3 = p valus compared to the 2nd evaluation at the end of the control period.
Clinical evaluations revealed statistically significant improvements in the NIHSS measures following treatment both in the HBOT-treated group (
Clinical evaluations revealed statistically significant improvements in the ADL score following treatment both in the HBOT-treated group (
The statistical significance of the improvements following the treatment periods is noticeable in the scatter plot analysis represented in
The scatter plot shows changes in the NIHSS and ADL scores in terms of the scaled relative differences as is defined in the methods section (averaged difference (<SFj–SIj>) is not divided by STD(SFj−SIj)). The color code is – changes during the treatment periods for the HBOT treated group (red diamonds), changes during for the HBOT-treated cross group (red circles) and changes during the control (non-treatment) period of the HBOT-treated cross group (blue circles).
The effect on the quality of life is summarized in
All brain SPECT evaluations were completed for 29 patients in the treated group and for 28 in the cross group. Comparison of brain activity improvement following the HBOT revealed that 55% of the treated group had significant improvement after HBOT and 35% had mild improvement. In the cross group, during the first (control) period 36% had mild improvement and only 6.2% had significant improvement (p<0.001). After HBOT, the cross group demonstrated 43% significant improvement and 29% mild improvement (p<0.001) (data not shown in tables).
The improvements in the SPECT were mostly in regions showing noticeable discrepancy between the CT and SPECT–the earlier mentioned stunned regions of low activity living cells. The following examples of three typical patients illustrate the associations between the improvements in the patients’ clinical conditions and evaluations and the changes in their brain activity (indication of the activation of neuroplasticity) as reflected by changes in their corresponding SPECT images:
Baseline brain SPECT images demonstrating hypoperfusion in the right fronto-parietal region, right postero-medial frontal and posterior-parietal perfusion lesions with no significant changes after the control period (
The results are of a patient in the cross group, suffering from left hemiparesis due to ischemic stroke that occurred 1 year prior to inclusion in the study. Baseline and control volume rendered brain perfusion views show diffuse hypoperfusion in the right hemisphere involving the fronto-parietal region and right postero-medial frontal (right motor cortex), right medial parietal and posterior-parietal (sensory cortex and associative motor cortex) (red circles). The HBOT SPECT scan done at the end of HBOT treatments shows disappearance of the perfusion deficits that were still demonstrated at the end of the control period. In addition, a significant global cortical and subcortical (basal ganglia and thalamic nuclei) perfusion improvement is seen.
The results are of a patient in the treated group, suffering from right hemiparesis due to ischemic stroke that occurred 14 months prior to her inclusion in the study. Comparison of pre- and post-hyperbaric treatment SPECT scans. These SPECT images demonstrate significant improvement of perfusion deficits in the left hemisphere involving the medial and posterolateral frontal area (motor cortex, red circles) and lateral inferior frontal region (Broca's area, blue circles) in comparison to the baseline SPECT. HBOT SPECT findings correlate positively with the patient's improved motor and verbal functions.
These SPECT images are of a 61y old woman from the cross group, suffering from left hemiparesis due to ischemic stroke that occurred 1 year prior to inclusion. Baseline NIHSS showed minor facial paresis, no ability to hold her left hand against gravity, some ability to hold her left leg against gravity for less than 5 seconds and mild-to-moderate sensory loss. In ADL, she needed help in bathing, dressing and climbing stairs. She was unable to do any housework. After HBOT, she was able to hold her hand and leg against gravity without significant sensory loss. She could move her fingers, was independent in bathing, dressing, shopping and cooking.
SPECT images at the end of HBOT demonstrating significant improvement of perfusion deficit in the left hemisphere (
SPECT images demonstrating improvement in the peri-infarct region following HBOT. The images are of a 64y old woman from the treated group suffering from right hemiparesis due to ischemic stroke that occurred 26 months prior to inclusion. After treatment, the leg hemiparesis was resolved, her hand function improved significantly but she did not regain all fine motor skills.
The results are of a patient in the treated group suffering from left hemiparesis due to ischemic stroke that occurred 26 months prior to inclusion in the study. The brain perfusion maps (upper two images) show the infracted brain (deep blue color) involving the right antero-postero-lateral frontal, right superior-parietal and right parieto-occipital regions. Curved sagittal view in CT MIP reconstruction of the brain shows the anatomical stroke area (left lower image, V = posterior horn of right ventricle). The peri-infarct region show improved perfusion as demonstrated by HBOT image (right upper image). Quantitation of the cerebral blood flow (CBF) change (delta between baseline and HBOT) is demonstrated in the right lower image.
Six patients had mild-moderate barotrauma of the middle ear. After several days of rest they returned and completed the protocol. Two patients with a history of epileptic seizures prior to their inclusion in the study had mild episodes of convulsion (consciousness was fully maintained) during the study. Both patients were already treated with anti-epileptic drugs prior to their inclusion.
In the current study, the effect of HBOT on chronic neurological deficiency due to stroke was evaluated in a prospective, randomized controlled study. Statistically significant improvements were obtained following treatment for almost all treated patients from both the HBOT-treated group and the HBOT-treated cross group (with no false negative), as was evaluated by NIHSS, ADL, brain SPECT and life quality. The significance of the improvements in this chronically debilitated population of patients is further noticeable when compared to the lack of improvement during the control (no-treatment) period of the cross group (with no false positive).
This is the first prospective, randomized clinical study evaluating the effect of HBOT in the late post-stroke period (6 months to 3 years after the acute event). There are two major reasons for selecting this study population. First, by carefully selecting patients with chronic stable neurological deficiency we were able to avoid unexpected changes in their condition. In this regard, the selection proved very useful since the control group demonstrated neurological stability with no outliers. The second reason was, as discussed in the introduction, to test our hypothesis that the optimal time for the HBOT procedure should be during the regenerative and not during the degenerative stage. While it is not possible to mark a clear line between the regenerative and the degenerative phases
The issue of “how to handle the control group” was discussed by a multidisciplinary team including physicians specializing in hyperbaric medicine, physicists specializing in neuronal-glia interactions and the ethics committee. The patients can tell if pressure is increased or not, so the pressure must be increased also in the control group. The only way to administer “placebo” of HBOT is to bring the patients to the hyperbaric chamber and to increase the environmental pressure to an extent that the patients will feel it in their ears. The minimal pressure needed to gain such a feeling should be 1.3 ATM. Henry’s law states: “the amount of a given gas dissolved in a given type and volume of liquid is directly proportional to the pressure of that gas in equilibrium with that liquid”. Thus, hyperbaric environment significantly increases the dissolved oxygen pressure even if a person holding his breath
Since increasing the pressure even without adding oxygen can also increases the dissolved oxygen partial pressure, the only way to maintain normal (placebo) levels of dissolved oxygen is to supply air with lower than normal level of oxygen, which we deemed unethical. To partially compensate for this inherent limitation, the patients in the cross group started with a two-month control period of no treatment, at the end of which they were crossed to two months of HBOT sessions. To gain better validity of the results, we used the scatter plot analysis of the changes in the combined neurological evaluations. The scatter plots (
During most of the 20th century, there was an ongoing debate about the time window available for induction of neuroplasticity. The improvements in the chronic late stage reported here support the view that neuroplasticity can be activated months to years after the acute event when a proper brain stimulation (such as HBOT) is applied. More specifically, the current study included patients that underwent stroke more than 6 months prior to treatment and after their condition reached a steady state (no improvements were monitored for at least a month). These important and unexpected findings arein agreement with other recent findings revealing that many aspects of the brain remain plastic even at adulthood
Current imaging technologies reveal that the stunned brain areas (regions of high anatomy-physiology mismatch) may persist for months and years after an acute brain event
In any case, the observed reactivation of neuronal activity in the stunned areas imply that increasing the plasma oxygen concentration with hyperbaric oxygenation is a potent means of delivering to the brain sufficient oxygen for tissue repair: HBOT might initiate a cellular and vascular repair mechanism and improve cerebral vascular flow
To conclude, in this study we provide, for the first time, convincing results demonstrating that HBOT can induce significant neurological improvement in post stroke patients. The neurological improvements in a chronic late stage demonstrate that neuroplasticity can be operative and activated by HBOT even long after acute brain insult. Thus, the findings have important implications that can be of general relevance and interest in neurobiology. Although this study focused on stroke patients, the findings bear the promise that HBOT may serve as a valuable therapeutic practice in other neurological disorders exhibiting discrepancy between the anatomical and functional evaluation of the brain.
Clinical Study Protocol.
(DOCX)
CONSORT 2010 checklist.
(DOCX)
Informed consent form (English translation).
(PDF)
Statistical, Randomization and Placebo Considerations.
(DOCX)
Scatter plot analysis of the clinical scores.
(DOCX)
We are thankful Dr. Alexander Vol and Dr. Orna Gribova for enlightening discussions regarding the neurophysiology and oxygen related processes in brain recovery. Special thanks to Dr. Hanna Levi for valuable help with the statistics and data analysis. We thank Michal Ben-Jacob for her significant help in editing the manuscript. We thank the following individuals for their important contribution in patients’ management during this study: Alona Esterin, Mazi Aski-Sela, Angela Chanimov, Malca Katovski, Lea Shkolnic, Eyal Malca. Vitali Triban.