22.3 Epidural Hematoma, Subdural Hematoma, and Penetrating Injury (03.I.3–4, 7)

Blueprint items 03.I.3–4 and 03.I.7 are pattern-recognition plus a short list of cubic centimeters and millimeters. An epidural hematoma (EDH) is a skull-and-artery problem until proven otherwise. An acute subdural hematoma (aSDH) is a bridging-vein and high-energy problem. A chronic subdural hematoma (cSDH) is an elderly, atrophic, often anticoagulated problem whose recurrence you can reduce with a drain and, increasingly, middle meningeal artery (MMA) embolization. Penetrating injury adds a foreign body, a vascular tract, and a seizure and infection risk that blunt protocols under-treat.

Numbers below come from the 2006 surgical management of TBI guidelines (Bullock and colleagues), the Santarius drain trial (NEJM 2009), and 2024 MMA-embolization randomized trials. This is independent OpenExamPrep teaching, not a BTF handbook reprint.

Epidural hematoma: lucid interval and 30 mL

Classic EDH is a lacerated middle meningeal artery under a temporal or temporoparietal fracture (pterion). Venous EDH occurs at the vertex or in the posterior fossa from a torn sinus and can still kill if the posterior fossa fills. The textbook lucid interval — knocked out, wakes, talks, then collapses as the clot grows — is memorable and incomplete. Many patients never lucid. Many “lucid” patients have a mild concussion rather than a true talk-and-die EDH. Still, a deteriorating patient with a lentiform extra-axial clot is an operative emergency, not a steroid infusion.

CT shape: biconvex (lentiform), limited by cranial sutures (the dura is tacked at sutures), can cross the midline only if it is a vertex venous EDH that strips the sagittal sinus. Density is homogeneously hyperdense unless the patient is anemic or actively bleeding (swirl sign).

Surgical rules boards still use:

• Volume 30 mL or greater: evacuate regardless of GCS.
• Also operate for thickness over 15 mm, midline shift over 5 mm, anisocoria, or any neurologic decline referable to the clot.
• Nonoperative observation is reserved for under 30 mL, thickness under 15 mm, shift under 5 mm, GCS over 8, and no focal deficit, in a center that can repeat CT and reach an operating room immediately.

Anisocoria with an EDH is a herniation clock, not a reason to wait for a 30 mL recalculation. Posterior-fossa EDH has a lower volume tolerance because the brainstem is adjacent.

Acute subdural hematoma: crescent and 10 mm / 5 mm

Acute SDH layers over the hemisphere in a crescent, crosses sutures, and stops at the falx and tentorium. It is usually torn bridging veins after high-energy deceleration, or hemorrhagic transformation of a contused surface. The brain underneath is often more injured than the extra-axial millimeters suggest, which is why aSDH mortality exceeds EDH mortality even when the clot looks “smaller.”

Usual evacuation thresholds:

• Thickness 10 mm or greater, or midline shift 5 mm or greater, regardless of GCS.
• GCS 8 or less with ICP over 20 mm Hg attributable to the SDH.
• A drop of 2 or more GCS points between injury and hospital arrival.
• Asymmetric pupils or a motor posturing new deficit.

Technique (craniotomy versus decompressive craniectomy, bone flap size) is a neurosurgical call driven by swelling. Your job in the ICU is to reverse anticoagulants, keep the airway safe, treat ICP after the clot is out, and not delay the scanner-to-OR interval for a “complete” spine MRI in a herniating patient. Elderly, anticoagulated aSDH has a grim prognosis; that does not justify skipping reversal or skipping an operation in a previously independent patient who still has a salvageable exam.

Chronic subdural hematoma: drains and MMA embolization

cSDH presents days to weeks after often-minor trauma in older adults with atrophy, alcohol use, or antithrombotic therapy: gait failure, headache, fluctuating cognition, hemiparesis. CT is hypodense or mixed-density with septations. Burr-hole or minicraniotomy evacuation is first-line for symptomatic collections.

Santarius and colleagues (NEJM 2009) randomized burr-hole evacuation with versus without a subdural drain. Recurrence requiring redrainage was 9.3% with a drain versus 24% without. Six-month mortality was 8.6% versus 18.1%. Leaving a drain is not optional trivia; it is the highest-yield cSDH trial on the exam.

MMA embolization targets the dural blood supply that feeds the inflammatory cSDH membrane. Three 2024 randomized trials (EMBOLISE, MAGIC-MT, STEM) showed fewer recurrences when embolization is added to surgery or, in selected nonsurgical patients, used as primary therapy. Teach it as an emerging adjunct that reduces return-to-OR rates, not as a replacement for evacuating a patient who is already herniating. Antiplatelet or anticoagulant restart after cSDH is individualized once a stability scan is clean; the recurrence cost of staying off stroke-prevention drugs is real.

Penetrating brain injury

Do not remove a knife, arrow, nail, or bone fragment in the trauma bay. The object may be tamponading a vessel or a sinus. Stabilize it, protect the airway without levering the object, give blood products if the patient is in shock, and go to CT/CTA and then the operating room with a cerebrovascular plan.

Vascular imaging (CTA, then catheter angiography when the tract crosses a named artery, cavernous sinus, or dural venous sinus) looks for occlusion, pseudoaneurysm, dissection, and traumatic fistula. Delayed pseudoaneurysm can appear days later, so a negative admission CTA does not close the book on a tract that kissed the middle cerebral artery.

Infection is expected: scalp flora, bone fragments, and sinus violation. Start prompt intravenous antimicrobials; there is no single universally mandated cocktail, but delay is the error. CSF leak and retained organic material raise abscess and meningitis risk. Heroic removal of every deep metallic fragment is not required; remove what is accessible and contaminated, elevate compound depressed fractures, and evacuate mass lesions.

Seizure prophylaxis is more justified than in blunt TBI. Penetrating injury carries a high rate of early and late post-traumatic epilepsy. A time-limited antiseizure medication (often at least 7 days, sometimes longer depending on cortical violation and retained fragments) is reasonable. Blunt TBI prophylaxis stays at the 7-day early-seizure window and is not a license for months of levetiracetam in every concussion.

Extra-axial and penetrating comparison

Worked contrast: a 22-year-old talks after a baseball to the temple, then drops his GCS as a 35 mL lentiform temporal clot appears — that is EDH at the 30 mL rule, middle meningeal, tonight. An 80-year-old on apixaban with a 12 mm crescentic aSDH and 6 mm of shift meets thickness and shift criteria even if he still says his name. A 78-year-old who shuffles in 3 weeks after a ground-level fall with a 22 mm hypodense cSDH gets holes and a drain, and you mention MMA embolization to reduce the next admission. A construction worker arrives with a nail gun nail in the orbit pointing at the cavernous sinus: you tape the nail in place, call the endovascular team, and do not pull it in the bay.