Middle Meningeal Artery (MMA) Embolization for Patients With Chronic Subdural Hematoma (cSDH)
Conditions: Chronic Subdural Hematoma
Sponsor: Washington University School of Medicine

 
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Middle meningeal artery (MMA) embolization for patients with chronic subdural 
hematoma (cSDH) 
 
PI: Joshua Osbun, MD 
Institution: Washington University School of Medicine, St. Louis, MO 
June 2, 2020 
 
Background 
 
Chronic subdural hematoma (CSDH) is one of the most common diseases in neurosurgery. 
Though conventional surgical methods like burr-hole irrigation and craniotomy have been the 
mainstay of treatment, middle meningeal artery (MMA) embolization has recently emerged as a 
promising adjunctive or alternative treatment, especially in patients with intractable CSDH or in 
patients where anticoagulation or antiplatelet therapy cannot be stopped.  
  
The MMA gives rise to capillary feeders of hematomas. Embolization of this artery is thought to 
inhibit blood flow into pathological structures, control bleeding from the CSDH membrane, and 
enhance spontaneous resolution of the hematoma, thus potentially providing a minimally 
invasive alternative or adjunct to conventional surgical techniques.  
 
Chronic subdural hematoma (CSDH) occurs in approximately 14 patients per every 100,000 
people and becomes more prevalent in older patients, with an occurrence of 18 patients per every 
100,000 between the ages of 71-80. It is currently one of the most common diseases treated by 
neurosurgeons, and as the population ages, the incidence of CSDHs is expected to double in 
slightly over 25 years. There is significant morbidity and mortality associated with this common 
disease.  
  
Recent studies have shown the efficacy of endovascular MMA embolization in treating CSDH. 
There is emerging data to suggest that this minimally invasive therapy may be more efficacious 
and equally as safe compared to conventional more invasive surgery. If these results can be 
supported by more vigorous clinical data, this represents a revolutionary change in the treatment 
of this common disease in the elderly with major morbidity and mortality.  
 
Prior Research 
From recent meta-analysis, three dual-armed studies that compared embolization and 
conventional surgery groups and six single-armed case series were identified and analyzed. 
Hematoma recurrence rate was significantly lower in the embolization group compared to the 
conventional treatment group (2.1% vs 27.7%, OR .087, 95% CI .026-.292, p<.001, I2=0%), 
whereas surgical complication rates were similar between the two (2.1% vs 4.4%, OR 0.563, 
95% CI 0.107-2.96, p=.497, I2 =27.5%). Number of patients with mRS>2 in the embolization 
(12.5%) versus conventional treatment (9.1%) groups also showed no statistical difference 
(p=.689). A composite hematoma recurrence rate of 3.6% was found after summing the six-
case series. Composite recurrence and complication rates in the embolization cohorts of the dual-
armed studies as well as the case series were also lower than literature values for conventional 
surgical treatments. Since then, there has been one study with 60 embolizations showing a 90% 
success rate of avoiding subsequent surgery with no procedural-related complications.  
 

 
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Objective 
Through the use of a prospective dual cohort, this study seeks to assess the safety and efficacy of 
middle meningeal artery embolization for subdural hematoma in addition to standard treatments, 
which include observation and surgical evacuation. Middle meningeal artery embolization has 
emerged recently as a minimally invasive and successful method of preventing re-accumulation 
of subdural hematoma, particularly for patients that are not obvious surgical candidates or those 
with recurrent or refractory hematomas. We will compare the outcomes of these two groups of 
patients who undergo middle meningeal artery embolization to matched historical controls from 
the past four years.  
 
Specific Aim 1:  
Determine the efficacy of middle meningeal artery embolization vs observation alone 
 
The recurrence rate of patients that undergo the middle meningeal artery procedure will be 
compared to a number of medically managed patients that experience a clinically significant 
persistent or recurrent hematoma. This endpoint will be determined through a series of 
neurologic assessments and follow up imaging. Patients will be followed for 90 days. 
Secondarily, the number of patients in each treatment group that experience persistence or 
recurrence to the degree that surgical evacuation is required will be compared. Patients who 
prospectively undergo middle meningeal artery embolization will be compared to retrospective 
matched controls of patients that underwent medical management. We hypothesize that patients 
who undergo MMA embolization as compared to simple observation alone will be less likely to 
ultimately need surgery and have a higher likelihood of SDH resolution after 90 days.  
 
Specific Aim 2:  
Determine the safety and efficacy of middle meningeal artery embolization for recurrent and 
refractory subdural hematomas after initial surgical evacuation. 
 
MMA embolization has emerged as an adjunct treatment for patients who experience recurrent 
or refractory SDH after initial surgical evacuation. These patients will require surgical 
evacuation of the hematoma for their condition regardless of the use of MMA embolization. For 
patients with a residual SDH or who develop recurrent SDH within 30 days of initial standard of 
care surgery, the patients that have adjunct treatment with MMA embolization will be compared 
to historical patients that are managed with continued observation versus repeat surgery. We 
hypothesize that patients who undergo MMA embolization will have a higher likelihood of 
demonstrating radiographic improvement of the SDH and have a lower rate of requiring 
additional surgery.  
 
Methodology 
Participants 
Approximately 200 patients with chronic subdural hematoma are treated at Barnes-Jewish 
Hospital annually. Patients aged 18+ of any race, sex, and socioeconomic status undergoing 
treatment for subdural hematoma will be identified by screening of the inpatient neurosurgical 
units or identification by an investigator. Patients will be approached regarding enrollment in the 
study at the time a decision is made to treat the subdural hematoma. If a patient expresses 
interest, an investigator or coordinator will provide the written consent form and explain the 

 
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information gathered, time frame of participation, potential benefits, and risks of participation, 
including the risks of undergoing an interventional neuroradiology procedure. Treatment with 
middle meningeal artery embolization will be offered in addition to the standard surgical 
evacuation or observation by the physician in consideration of the patient’s medical history and 
current condition. If patients are unable to provide informed consent, consent from the next of 
kin will be obtained in accordance with Missouri Statute Title XXVII, Section 431.064. 
 
Patients will have as much time as they desire to think about the study, ask questions, and 
discuss with family. Any patient requiring emergent intervention or experiencing sudden 
neurologic deterioration is excluded from this study. The consent documentation contains a 
statement that consent is freely given, that the patient understands the potential risks and benefits 
of entering the study, and that the patient is free to withdraw from the study at any time. As the 
patient may experience a direct benefit from the study, the patient must initial yes/no to 
permission for future use of their data per policy. Patients who agree will then sign the IRB 
approved consent form prior to undergoing the procedure. The original signed consent will be 
maintained in a binder in a locked office. A copy will be given to the patient, with contact 
numbers if the patient has further questions or wishes to withdraw their consent. The expected 
duration of patient participation in the study is 90 days. 
 
Based on a review of prior literature, we expect an effect size of 20% patients to meet the 
endpoint of recurrent or refractory subdural hematoma requiring surgery. With the addition of 
MMA embolization, we expect that only 5% of patients will meet this outcome. With equal 
numbers of patients in each arm, we estimate that 124 patients will be needed for a power of 
80% using a two tailed alpha set at 0.5. In order to account for study dropout, we plan to study 
200 patients who undergo MMA embolization. These patients will be compared to an additional 
400 historical matched controls obtained via retrospective chart view from January 1st 2014 to 
December 31st 2018.   
 
Inclusion/Exclusion Criteria 
Must meet the following criteria for inclusion to undergo MMA embolization: 
1.   
Patients 18 years or older undergoing treatment for a new diagnosis of chronic or acute 
subdural hematoma (cSDH) 
or 
Patients 18 year or older who have undergone surgical evacuation of a subdural 
hematoma and have a significant residual hematoma status post-surgery or who develop a 
recurrent subdural hematoma. 
2. Minimal symptoms such as headache, altered mental status, or mild neurological deficit 
only  
3. Ability to understand and sign written informed consent by patient or LAR 
 
If any of the following criteria are met, the individual will be excluded from 
participation: 
1. Significant midline shift and/or neurologic symptoms requiring urgent decompression.   
2. Common carotid stenosis of over 50%.  
3. Significant contraindication to angiography (eg. kidney failure, difficult anatomy).  

 
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4. SDH related to underlying condition 
 
 
Groups: 
1. Embolization Only 
a. Patients with new chronic or acute SDH with minimal symptoms only, or who are 
poor surgical candidates (dual antiplatelet therapy or systemic anticoagulation, 
ASA Class 4 or greater) 
 
2. Embolization + Standard of Care Evacuation 
a. Patients with chronic or acute SDH who failed conventional surgery at any point 
needing additional intervention, not requiring urgent evacuation 
b. Recurrent SDH 
3. Medical Management (Historical Cohort) 
4. Surgery Alone (Historical Cohort) 
 
Study Procedure 
Middle meningeal artery embolization is ideal for patients with minimal symptoms or that are 
poor surgical candidates due to the need for continued anticoagulant or antiplatelet therapy. For 
patients who meet inclusion criteria, MMA embolization as an adjunct treatment will be offered. 
For patients that are medically managed, they will undergo MMA embolization to prevent 
growth or recurrence of the hematoma and have standard imaging follow up. For patients that 
require evacuation of the hematoma due to size or symptoms, they will undergo standard of care 
surgery via burr hole or craniotomy at the treating neurosurgeon’s discretion and then at a later 
date during the same hospitalization receive MMA embolization. These patients may have 
already had multiple surgical evacuations with recurrence of the hematoma.  
 
Once consented and enrolled, patients will undergo MMA embolization in the neuro-
angiography suite via selective MMA catheterization and embolization with 150-250 micron 
polyvinyl alcohol (PVA) particles. The neurointerventional radiology department at BJH is a 
high volume center. Physicians and staff are experienced in neurovascular embolization for a 
variety of indications.  
 
Middle meningeal artery embolization is a minimally invasive angiography procedure completed 
either under general anesthesia or conscious sedation (per preference of the performing 
physician) with use of fluoroscopy. Access is obtained through the femoral or radial artery and a 
catheter is advanced to the MMA. Polyvinyl alcohol particles are then injected to seal off this 
portion of the artery and prevent any further blood flow into the subdural hematoma. All 
catheters are then removed and hemostasis is obtained at the access site.  
Patients will be followed post-procedure for 90 days to track any complications or recurrence/ 
persistence of the subdural hematoma. Further treatment following standard of care will be 
offered if the patient develops worsening symptoms or presents with radiographic recurrence or 
persistence of the subdural hematoma. 
 
A head CT, NIHSS, and modified Rankin Score will be repeated on the following schedule. 
These non-invasive procedures are detailed in the consent:  

 
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 Pre-Procedure 
 30 days (±7) post procedure 
 90 days (±10) post procedure 
Data Points 
Patient demographic data including but not limited to age, sex, race, comorbidities, previous 
neuro history, and relevant medical history will be gathered from Epic and Clindesk. Pre-
procedure information gathered about the current admission include the use of anticoagulants, 
date of presentation with the SDH, size and hemisphere of SDH, neurologic presenting 
symptoms, head CTs, and neuro exams, including mRS and NIHSS. 
 
Post-procedure data gathered include the time to embolization, time to follow up, procedural 
complications, neuro exam results, head CTs and angiography images. Date of surgery and need 
for surgical removal of recurrent hematoma will be documented if relevant. 
The modified Rankin Score (mRS) is a well-established scale used to classify outcomes on a 0 to 
6 point scale where outcome is classified as: 0- no neurological deficits, 1-no significant 
disability, 2- slight disability, 3-moderate disability  (requires assistance with activities of daily 
life, but able to walk unassisted), 4-moderately severe disability (requires assistance in activities 
of daily life and unable to walk unassisted), 5-severe disability (bedridden, incontinent), or 6-
deceased. 
The National Institutes of Health Stroke Scale (NIHSS) is an objective measure of impairment 
caused by a stroke. Eleven items are evaluated, with a potential score ranging from 0 to 42, with 
a higher score indicating more impairment.  
 
Privacy/Data Protection 
Patients will be assigned a unique study identification number at the time of consent. This 
number will link to identifying protected health information in a separate locked database 
accessible only to relevant research team members. Clinical study data will be entered into a 
secure database on RedCap under the study ID number to maintain patient data confidentiality. 
 
Screening: 
Study 
ID 
MRN 
Last 
Name 
First 
Name 
Admit 
Date 
Enrolled 
Y/N 
Date 
Consent 
Signed 
Signed 
By 
Patient/ 
LAR
Exclusion 
 
Initial Data: 
Study 
ID 
Birth 
Year 
Sex 
Race 
(relevant 
comorbidities) 
Use 
Anticoagulant 
y/n 
Name of 
Med 
(aspirin, 
warfarin)
Procedure 
Date 
Presenting 
neuro 
symptoms 

 
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Any neuro 
history 
NIHSS 
Presentation 
Baseline 
mRS 
Size of SDH 
at 
Presentation 
Laterality 
of SDH 
Left 
Right 
bilateral
Procedural 
Complications
 
 
Follow up: 
Study 
ID 
Date of 
Follow Up
Time Point (30, 
90 days) 
NIHSS mRS 
Size of SDH 
at follow up
Neuro Deficit 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Analysis 
Endpoints 
Two primary endpoints will be analyzed, related to the two main aims of the study. Aim 1 is to 
establish if middle meningeal artery embolization is more effective than observation alone at 
preventing recurrence of subdural hematoma. Aim 2 is to determine if adding on middle 
meningeal artery embolization reduces the need for further surgery in patients that initially 
undergo evacuation. The number of patients that experience a recurrent or refractory subdural 
hematoma will be compared, as well as the number of patients in each group that require surgery 
after undergoing embolization.  
 
Primary Endpoints: 
Recurrent or progressive SDH  
Secondary surgical evacuation required 
 
Secondary Endpoints: 
Change in size of SDH at follow up  
Procedure-related complications 
New neuro deficit 
NIHSS/mRS at follow-up intervals 
 
Statistical Analysis 
Statistical comparisons will be made for the number of patients that experience a recurrent or 
refractory subdural hematoma, as well as the number of patients in each group that require 
evacuation surgery after undergoing embolization, an indication that the embolization procedure 
failed. These primary endpoints will be compared with simple t-test. The secondary endpoint of 
the change in the size of the subdural hematoma on radiographic imaging will be analyzed by 
repeated measures ANOVA. Change in score on NIH Stroke Scale pre and post embolization 
will be compared to determine the functional outcome of the procedure. For a safety analysis, the 
rate of procedure-related complications between embolized patients and surgical controls will be 
compared by t-test. Rankin Score at the follow up intervals will be compared with a Chi Square 
analysis. 

 
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Safety Monitoring Plan 
 
Research will be performed according to protocols approved by the Institutional Review Board 
at Washington University in St. Louis School of Medicine. An application to the IRB is currently 
pending. 
 
Patients with subdural hematoma present with symptoms including confusion or altered mental 
status, decreased consciousness, weakness or numbness on one side of the body, headache, 
seizure, and difficulty with speech, swallowing, or walking.  
 
During this study, assessment of medical history and physical examination will be performed at 
baseline and at stated follow up intervals to ascertain neurologic status, change in functional 
baseline, and occurrence of any AEs. Prior to interventional procedures, patients have 
coagulation tests performed to assess risk of bleeding. If the patient has an allergy to iodinated 
contrast, they will receive standard pre-medication. During the embolization procedure, patients 
undergo continuous vital sign monitoring and are assessed frequently by a dedicated, ACLS-
certified procedural nurse. The patient will be monitored as an inpatient in the neuroICU or 
stepdown unit for a minimum of 24-48 hours after the procedure.  
 
Adverse Events 
An adverse event (AE) is any untoward medical occurrence in a subject during participation in 
the clinical study or with use of the experimental agent being studied. An adverse finding can 
include a sign, symptom, abnormal assessment (laboratory test value, vital signs, 
electrocardiogram finding, etc.), or any combination of these. 
A serious adverse event (SAE) is any adverse event that results in one or more of the following 
outcomes: 
 Death 
 A life-threatening event 
 Inpatient hospitalization or prolongation of existing hospitalization 
 A persistent or significant disability/incapacity 
 A congenital anomaly or birth defect 
 An important medical event based upon appropriate medical judgment 
AEs will be labeled according to severity, which is based on their impact on the patient. An AE 
will be termed “mild” if it does not have a major impact on the patient, “moderate” if it causes 
the patient some minor inconvenience, and “severe” if it causes a substantial disruption to the 
patient’s well-being. AEs will be categorized according to the likelihood that they are related to 
the study intervention. Specifically, they will be labeled definitely unrelated, definitely related, 
probably related, or possibly related to the study intervention.  
 
Unanticipated events and deaths will be reported to the IRB within 10 days per institutional 
policy. Individual adverse events will be summarized and reported at continuing review without 
any subject level identifiable information. Any updates to study risks or benefits based on 
analysis of this study data or other new published research will be reported as a modification 
during continual review and may require updated consent.  Determination of severity, SAE, and 

 
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unexpected event status will be decided by the PI. Adverse event documentation will be prepared 
and compiled by the research coordinator utilizing a standardized WUSTL reporting template.  
 
Risks 
Conventional burr hole craniotomy has a literature reported complication rate of 9%. The meta-
analysis of middle meningeal artery embolizations demonstrated a composite complication rate 
of 2.1% in double arm studies21, especially significant as a greater proportion of embolization 
patients are maintained on anticoagulant medications. The largest individual study to date 
included 60 embolizations with no procedural related complications15. A meta-analysis including 
15 studies with 193 procedures additionally reported no procedure-related complications25.  
 
Expected risks to the subject due to the interventional procedure are minor pain and bruising at 
the catheter insertion site. About 5% of subjects may develop a hematoma, a collection of blood 
that may cause more bruising and pain than normal and may require intervention. Less likely, 
more serious risks of embolization procedures (<1%) include temporary neurologic deficits, 
blindness or cranial nerve palsy, or an anaphylactic reaction to the contrast dye.  
 
There is a small risk (0.3%) of carotid artery dissection and/or stroke with permanent neurologic 
deficit from catheter injury or clot formation. Arterial perforation or brain hemorrhage is a life 
threatening but rare complication. Insertion site infection is exceedingly rare.  
 
When procedures are performed through the radial artery, a combination of medications are used 
to prevent radial artery occlusion, which may be asymptomatic or may cause hand ischemia and 
the loss of the hand. Radial subjects receive a TR band at the conclusion of the procedure to 
maintain patent hemostasis. Radial artery occlusion is rare with these prevention measures. 
Femoral access subjects receive manual compression or a closure device and must be maintained 
on strict bedrest for 6 hours to prevent hematoma formation.  
 
These risks are addressed in the consent form and are considered to be minimal or outweighed by 
the risk of multiple invasive surgical procedures or the risk to the patient by reaccumulation of 
the hematoma. Patients with known contraindications to angiography or comorbid conditions 
placing them at higher risk of procedural complications are excluded from study participation. 
The neurointerventional radiology department at BJH is a high volume center with experienced 
physicians and staff. Approximately 1200 outpatient diagnostic cerebral angiograms are 
performed each year and over 300 interventional procedures. 
 
Study subjects will be followed for research purposes for 90 days and may continue long term 
follow up with their outpatient neurosurgeon. Study follow up visits occur at 30 days (±7) post 
procedure, and 90(±10) days post procedure. At each of these time points the subject will receive 
a head CT scan, neurologic assessment, and assessment of adverse events. Adherence to follow 
up visits will be tracked and reported. 
 
The original signed consent will be maintained in a binder in a locked office. Subjects will be 
assigned a unique study identification number at the time of consent. Subject level hard copies of 
documents will be maintained in subject binders in a locked office with no personal identifying 
information, only the subject ID number. This number will link to identifying protected health 

 
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information in a separate locked database accessible only to relevant research team members. 
Clinical study data will be entered into a secure database on RedCap under the study ID number 
to maintain patient data confidentiality. Only engaged research team members will have access 
to the RedCap database.  
 
Safety and Analysis  
Study progress and safety, including patient recruitment, retention/attrition, and AEs, will be 
reviewed quarterly (or more frequently if needed). An Annual Report will be compiled and will 
include a list and summary of AEs. In addition, the Annual Report will address (1) whether AE 
rates are consistent with pre-study assumptions; (2) reason for dropouts from the study; 
(3) whether all participants met entry criteria; (4) whether continuation of the study is justified 
on the basis that additional data are needed to accomplish the stated aims of the study; and 
(5) conditions whereby the study might be terminated prematurely. This report will be made 
available to the IRB at continuing review.  
 
No external monitoring committee will be utilized due to the nature of the study. The study will 
be collectively monitored for safety and adverse events by the three interventional 
neuroradiology faculty. Any adverse events will be reviewed at both the Department of 
Neurosurgery and Department of Radiology QA/QI committee meeting. Additionally any 
adverse events will be reported to the HSR QA/QI review board at Washington University. Each 
faculty reports to the Conflicts of Interest Review Committee (CIRC) at Washington University, 
and currently none have any financial conflicts of interest relevant to this study and are unlikely 
to develop any during the study duration given there is no funding source for the project and no 
industry sponsored product being utilized. Should any FCOI arise, that research member will be 
removed from study participation in accordance with policies recommended by CIRC.    
 
Based on a review of prior literature, we expect an effect size of 20% of patients to meet the 
endpoint of recurrent or refractory subdural hematoma requiring surgery. With the addition of 
MMA embolization, we expect that only 5% of patients will meet this outcome. With equal 
numbers of patients in each arm, we estimate that 124 patients will be needed for a power of 
80% using a two tailed alpha set at 0.5. In order to account for study dropout, we plan to study 
200 patients who undergo MMA embolization. 
 
This study will be stopped prior to its completion if: (1) the intervention is associated with 
adverse effects that call into question the safety of the intervention; (2) difficulty in study 
recruitment or retention will significantly impact the ability to evaluate the study endpoints; 
(3) any new information becomes available during the trial that necessitates stopping the trial; or 
(4) other situations occur that might warrant stopping the trial. 
 

 
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