Subdural Hematoma Surgery
- Author: Herbert H Engelhard III, MD, PhD, FACS; Chief Editor: Allen R Wyler, MD more...
Overview
A subdural hematoma (SDH) is a common neurosurgical disorder that often requires surgical intervention. It is a type of intracranial hemorrhage that occurs beneath the dura (essentially, a collection of blood over the surface of the brain) and may be associated with other brain injuries (see the images below).
A left-sided acute subdural hematoma (SDH). Note the high signal intensity of acute blood and the (mild) midline shift of the ventricles. 
A left-sided chronic subdural hematoma (SDH). Note the effacement of the left lateral ventricle. Subdural hematomas (SDHs) can be associated with high mortality and morbidity rates, even with the best medical and neurosurgical care. They are usually caused by trauma but can be spontaneous or result from a procedure (eg, lumbar puncture).[1] Anticoagulation, such as with heparin or warfarin (Coumadin), may be a contributing factor.
Historical information
The practice of trephination of the head (ie, chipping or drilling a hole through the skull) has been traced back to ancient times. In 1840, the French author Balzac described a case of chronic subdural hematoma (SDH), including its traumatic origin and surgical treatment.[2]
In the late 19th century, with the rise of medicine, development of aseptic technique and anesthesia, and establishment of the basic principles of neurologic localization, surgery for intracranial lesions (including subdural hematoma [SDH]) became more common and, later, survival rates improved.
In 1883, Hulke first described successful neurosurgical treatment of chronic subdural hematoma (SDH).[3] Although cerebral angiography could be used to localize subdural hematomas (SDHs) in the early–to–mid-20th century, the development of computed tomography (CT) scanning in the late 1970s represented another leap in patient care.
See also Subdural Hematoma, Emergent Management of Subdural Hematoma, Imaging in Subdural Hematoma, Closed Head Trauma, Head Injury, and Forensic Autopsy of Blunt Force Trauma.
Anatomy
As the name implies, the subdural space is under the dura but above the pia-arachnoid that is intimately associated with the cortical surface. Subdural hematomas (SDHs) are usually hemispheric in location, but they may occur along the falx, the tentorium, or in the posterior fossa.
A subdural hematoma (SDH) usually forms after the rupture of a bridging vein. These run from the cortical surface to the dura. Bridging veins are most commonly found along the sagittal sinus and around the anterior tip of the temporal lobe. The source of bleeding may or may not be found at the time of surgery.
Surgical Indications
The nature and timing of neurosurgical intervention depends on multiple factors, including the size, age, and location of the hematoma and the medical and neurologic condition of the patient. Surgery may be urgently required, yet even emergency surgery does not guarantee a satisfactory outcome.
Surgical evacuation via craniotomy is often considered in patients with an acute subdural hematoma (SDH) thicker than 5 mm (as measured with axial computed tomography [CT] scanning) and who have any neurologic signs, such as lethargy or other change in mental status, or a focal neurologic deficit. Bullock et al reported that "an acute [subdural hematoma] SDH with a thickness greater than 10 mm, or a midline shift greater than 5 mm on computed tomography (CT) scan should be surgically evacuated, regardless of the patient's Glasgow Coma Scale (GCS) score."[4]
Surgery for chronic subdural hematoma (SDH) may also be indicated if the subdural hematoma (SDH) is symptomatic or is producing significant mass effect, as evaluated with diagnostic imaging. Diagnostic imaging that shows an expanding hematoma may also indicate the need for surgery, even in some patients whose neurological status is near normal. See the following images.
An isodense subdural hematoma (SDH). Note that no sulcal markings are below the inner table of the skull on the right side. 
An acute subdural hematoma (SDH) as a complication of a craniotomy. Note the significant mass effect with midline shift. Surgical Contraindications
Contraindications to surgery are determined on a case-by-case basis, depending on factors that relate to the patient's neurologic and medical condition. For example, a patient with a massive subdural hematoma (SDH) may not be a surgical candidate if he or she has concomitant brain death, anticipated severe neurologic damage, coexisting brain lesions (eg, infarction), or a medical condition that contraindicates general anesthesia or surgery (eg, coagulopathy before correction). In addition, what is known of the patient's and family's beliefs and instructions may play a role in this decision.
At the other end of the spectrum, small acute subdural hematomas (SDHs) thinner than 5 mm on axial computed tomography (CT) images without sufficient mass effect to cause midline shift or neurologic signs may be able to be observed clinically. Magnetic resonance imaging (MRI) may be more sensitive than CT scanning in detecting small SDHs (see the following image).
Isodense subdural hematoma (SDH) as pictured with magnetic resonance imaging (MRI). MRI can more readily reveal smaller SDHs, and, on MRI, the imaging of the blood products change characteristically over time. A chronic subdural hematoma (SDH) with minimal or no mass effect on imaging studies and no neurologic symptoms or signs except mild headache is often observed with serial scans and may resolve without surgical intervention.
Surgical Considerations
Although surgical intervention may be able to successfully remove the hematoma itself, patients with acute subdural hematomas (SDHs) are often difficult to treat and may have a poor outcome due to underlying brain injury. The medical issues, especially in older patients with subdural hematomas (SDH), may be complex.
Regarding surgical timing, the adage "the sooner the surgery is done, the better" may not always be accurate. This is for various reasons, and it depends on the individual case.[5] Even 2 decades ago, Wilberger and colleagues concluded that "the time from injury to operative evacuation of the acute [subdural hematoma] SDH in regard to outcome morbidity and mortality was not statistically significant when examined at hourly intervals."[6] However, in patients with acute subdural hematoma (SDH) and indications for surgery, surgical evacuation should be performed as soon as possible.[4]
Surgery for Acute Subdural Hematoma
Craniotomy and craniectomy are briefly discussed in this section.
Craniotomy
Surgery to manage an acute subdural hematoma (SDH) usually consists of a large craniotomy (centered over the thickest portion of the clot) to decompress the brain; to stop any active subdural bleeding; and if indicated, to evacuate intraparenchymal hematoma in the immediate vicinity of the acute subdural hematoma (SDH). A subdural hematoma (SDH) usually has a consistency that is too firm to allow removal through burr holes alone.
Including the sylvian fissure in the craniotomy exposure should be considered, as this is a likely location of a ruptured cortical vessel. If brain injury and edema are associated with the subdural hematoma (SDH), an intracranial pressure (ICP) monitor may need to be placed. Bullock and colleagues stated that "all patients with acute [subdural hematoma] SDH in coma (Glasgow coma scale [GCS] score less than 9) should undergo intracranial pressure monitoring."[4]
Craniectomy
Craniectomy (ie, the removal of the bone plate or flap) is also sometimes required, such as when increased ICP is present or anticipated. Different methods for storing the bone flap for possible later replacement exist.
Surgery for Chronic Subdural Hematoma
Various surgical techniques for the treatment of chronic subdural hematoma (SDH) have been described.
Trephination
Liquefied chronic subdural hematomas (SDHs) are commonly treated with drainage through 1 or 2 burr holes. The burr holes are placed so that conversion to a craniotomy is possible, if needed. A closed drainage system is sometimes left in the subdural space for 24-72 hours postoperatively.
Bilateral chronic hematomas (see the following image) may require drainage from both sides, usually during the same operation by means of burr holes placed on each side of the head.
Chronic subdural hematomas (SDHs) are commonly bilateral and have areas of acute bleeding, which result in heterogeneous densities. Note the lack of midline shift due to the presence of bilateral hematomas. Twist-drill craniotomy
Drainage via twist-drill craniotomy at the bedside has also been described.[7, 8]
A relatively new system, the Subdural Evacuating Port System (SEPS), was introduced in the mid-2000s, with initial encouraging results.[9] In 2010, Kenning et al and Rughani et al published their results in using this system to treat subdural hematomas (SDHs).
Kenning et al found that SEPS was not only safe and effective in the treatment of subacute and chronic subdural hematomas (SDHs) but that it would be ideal for patients unable to tolerate general anesthesia (eg, elderly, sick patients).[10] In addition, SEPS was more effective in draining subdural hematomas (SDHs) that were hypodense on computed tomography (CT) scans than it was in evacuating mixed-density SDHs. Although 1 patient required urgent surgical subdural collection evacuation following iatrogenic injury, Kenning et al noted that significant bleeding was uncommon with SEPS insertion.[10]
Rughani et al reported that SEPS treatment for chronic subdural hematoma had a similar efficacy and safety compared to other twist-drill methods, and its efficacy was also statistically similar to trephination (burr hole), as measured by radiographic worsening or for need for another procedure.[11] There was a trend toward higher recurrence using SEPS but no difference in mortality or other adverse outcomes.[11]
Craniotomy
Under certain circumstances, craniotomy is recommended for chronic subdural hematoma (SDH), depending on factors such as recurrence, the consistency of the hematoma, and the presence of membranes.
Perioperative Details
In general, a poor preoperative neurologic status in a patient with acute or chronic subdural hemorrhage (SDH) may be a harbinger of a poor outcome.
Preoperative
Phenytoin (Dilantin) is administered to decrease the risk of developing early posttraumatic seizures (within the first 7d after the injury).[12] Patients have an estimated risk of greater than 20% for developing posttraumatic epilepsy after an acute subdural hematoma (SDH). Whether this risk is modifiable with prophylactic anticonvulsants remains debatable.
Intraoperative
The surgical technique for removing an acute subdural hematoma (SDH) is well described in most standard texts of neurosurgery. When an acute subdural collection is evacuated, intraoperative ultrasonography may be helpful for locating intraparenchymal clots, which also may require evacuation, depending on the risks and benefits involved.
Perioperative antibiotics may be administered to decrease the risk of postoperative infection.
Postoperative
Elevated intracranial pressure (ICP) postoperatively indicates a poor prognosis and may indicate the severity of the underlying brain injury (eg, trauma, secondary infarction).
Acute subdural hematoma
After the evacuation of an acute subdural (SDH), medical treatment is aimed at controlling the ICP below 20 mm Hg and maintaining the cerebral perfusion pressure above 60-70 mm Hg. If elevated ICP is an issue postoperatively, an urgent computed tomography (CT) scan should be obtained to look for a new intracranial mass lesion or reaccumulation of the subdural hematoma (SDH) (see the image below).
An acute subdural hematoma (SDH) as a complication of a craniotomy. Note the significant mass effect with midline shift. Serial neurologic examinations are used to determine the patient's subsequent clinical course (whether the patient is stable, improving, or deteriorating). Depending on the severity of the neurologic injury, patients may require physical therapy, occupational therapy, long-term rehabilitation, or even nursing-home placement.
A follow-up CT scan is usually obtained within 24 hours of acute subdural collection removal and as needed to monitor for residual hematoma and recurrence. Although CT imaging alone is usually sufficient for short-term management, a brain magnetic resonance image (MRI) is sometimes used (after a patient is stabilized) to look for associated brain injuries.
Serial imaging studies may be necessary to confirm that the acute subdural hematoma (SDH) has fully resolved; a residual hematoma could become a symptomatic chronic subdural collection. This transformation can occur regardless of whether the hematoma has been managed surgically or conservatively.
Postoperative coagulation studies (prothrombin time [PT], activated partial thromboplastin time [aPTT]) and platelet counts should be observed closely and, when possible, adjustments made to lessen the risk of additional bleeding.
Chronic subdural hematoma
After the evacuation of a chronic subdural hematoma (SDH), adequate patient hydration is needed to help reexpand the brain. In addition, the patient may be maintained on bedrest with the head of the bed flat to aid brain reexpansion by increasing the intracranial venous pressure.
As with acute subdural hematoma (SDH), serial neurologic examinations are used and coagulation parameters may need to be followed. Serial CT scans are used to document the resolution of the chronic subdural collection.
Depending on the patient, physical therapy, occupational therapy, long-term rehabilitation, or even nursing home placement may be needed.
For patients who were on anticoagulation therapy preoperatively, no solution is perfect regarding when to restart anticoagulation therapy. The risks and benefits of anticoagulation must be weighed against the risks of rebleeding to determine when to restart therapy.
The mortality rate for chronic subdural hematoma (SDH) within 30 days of surgery is 3.2-6.5%.
Complications
Postoperative complications for acute and chronic subdural hematoma (SDH) are briefly discussed below.
Acute subdural hematoma
Parenchymal brain injury is commonly associated with acute subdural hematoma (SDH) and can lead to increased intracranial pressure (ICP). Residual neurologic problems, as well as secondary events, can result from these associated injuries.
As with every medical condition and treatment, inherent risks exist. Postoperatively, recurrent or residual hematoma might be present, which, if symptomatic, may require repeat operative intervention. As many as one third of patients experiences posttraumatic seizures after a severe head injury. Wound infection and cerebrospinal fluid (CSF) leak are possible after craniotomy. Meningitis or cerebral abscess can occur after any intracranial procedure, and constitutional signs of infection, delayed neurologic deterioration, or signs of meningeal irritation may require further evaluation.
A long list of potential complications may also be related to anesthesia and hospitalization but are not discussed here.
Chronic subdural hematoma
Among patients with chronic subdural hematoma (SDH) who underwent surgical drainage, 5.4-19% experience medical or surgical complications. Medical complications, including seizures, pneumonia, empyema, and other infections, occur in 16.9% of cases. Surgical complications, including acute subdural collection formation, intraparenchymal hematoma, or tension pneumocephalus, occur in 2.3% of cases.
Following surgery for chronic subdural hematoma (SDH), even with normalization of ICP, a persistent space may exist between the brain and dura (see the image below), as the brain may not expand to fill this space. Residual hematoma has been found on 92% of postoperative computed tomography (CT) scans within 4 days of operation; however, clinical improvement may proceed regardless of the size of this collection.
Atrophy of the brain, resulting in a space between the brain surface and the skull, increases the risk of subdural hematoma (SDH). Reoperation rates for reaccumulation of hematoma have been reported to be from 12% to 22%. When the reoperation for burr-hole drainage was compared with craniotomy drainage, similar rates of 18.5% and 12.5%, respectively, were found.[13] However, the total number of craniotomies performed in this series was small. Of the patients who require a second operation to drain a reaccumulated hematoma, 26.6% (a total of 4 patients) required a third procedure to drain reaccumulated hematoma; 2 of these 4 patients who underwent 3 operations developed subdural empyema.[13] In another series, contralateral hematomas formed in 4% of patients who underwent drainage of unilateral chronic subdural collections.[14] These occurred from 3 days to 6 weeks postoperatively.[14]
Postoperative seizures have been reported in 3-10% of patients. Whether prophylactic anticonvulsants therapy can decrease this risk is debatable. Subdural empyema, brain abscess, and meningitis have been reported to occur in less than 1% of patients after operative drainage of a chronic subdural hematoma (SDH). In these patients, numerous potential complications are also related to anesthesia, hospitalization, patient age, and concurrent medical conditions.
Outcomes
Outcome, in general and following surgical intervention, for acute and chronic subdural hematoma (SDH) are briefly discussed below.
Acute subdural hematoma
The mortality rate of acute subdural hematoma (SDH) has been reported to range from 36% to 79%. Many survivors do not regain previous levels of functioning, especially after an acute subdural collection (SDH) severe enough to require surgical drainage. Favorable outcome rates after acute subdural hematoma (SDH) range from 14% to 40%.
Several series have shown an increase in favorable outcome in younger patients.[15] Ages younger than 40 years were associated with a mortality rate of 20%, whereas ages of 40-80 years were associated with a mortality rate of 65%. Ages older than 80 years carried a mortality rate of 88%.
Findings demonstrated by computed tomography (CT) scan (or magnetic resonance image [MRI]) may help indicate prognosis. Such findings may include the thickness or volume of the hematoma, the degree of midline shift, the presence of associated traumatic intradural lesions, and the compression of the brainstem or basal cisterns.[16] The first CT scan may underestimate the size of parenchymal contusions.
Elevated intracranial (ICP) postoperatively indicates a poor prognosis and may indicate the severity of the underlying brain injury (eg, trauma, secondary infarction). Additionally, generally, a poor preoperative neurologic status may be a harbinger of a poor outcome.
Other poor prognostic indicators for acute subdural hematoma (SDH) have been reported to include the initial and postresuscitation Glasgow coma scale (GCS), the GCS motor score on admission, pupillary abnormalities, alcohol use, injury by motorcycle, ischemic damage,[17] hypoxia or hypotension, and overall ability to control ICP.[16, 6, 5]
Chronic subdural hematoma
Outcome after drainage of a chronic subdural hematoma (SDH) has also been found to correlate with preoperative neurologic status. Early diagnosis before a significant neurologic deterioration may correlate with a more favorable prognosis. No correlation has been found between preoperative CT scan findings and postoperative outcome.
The mortality rate within 30 days of surgery is 3.2-6.5%. About 80% of patients resume their prehematoma level of function, and favorable outcomes occur in 61% of patients aged 60 years or younger and in 76% of patients older than 60 years.
In a series by Mori and Maeda, 89.4% of patients with chronic subdural hematoma (SDH) who were treated with a closed drainage system had a good recovery and 2.2% worsened.[18] Old age, preexisting cerebral infarction, and subdural air after surgery correlated with poor brain expansion.[18] Stanisic et al reported a 14.9% postoperative recurrence rate[19] ; various factors were associated with this.
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