Classification by Timing

• Mechanism: tearing of bridging veins between cortex and dural sinuses; blood collects between dura and arachnoid
• Acute SDH: high-velocity injury (falls, MVA, assault); 50–90% mortality in severe cases; often associated with underlying brain contusion
• Chronic SDH: elderly, anticoagulated, or brain atrophy patients; minor or unrecalled trauma; neomembrane with fragile vessels → recurrent bleeding and gradual enlargement
• Bilateral SDH: think coagulopathy, anticoagulation, alcohol use, or elderly with atrophy
• Isodense subacute SDH: easily missed — look for effaced sulci, midline shift without obvious mass, and medial displacement of the gray-white junction

Surgical Indications

Indications for Surgical Evacuation

• SDH thickness >10 mm
• Midline shift >5 mm
• GCS drop ≥2 points from time of injury to hospital arrival
• ICP >20 mmHg
• Posterior fossa SDH with any mass effect or neurological deterioration — very low threshold to operate

Surgical Approach

• Acute SDH → craniotomy: solid clot requires open evacuation and direct hemostasis; large bone flap for adequate exposure
• Chronic SDH → burr hole drainage: liquefied collection drains easily through 1–2 burr holes; subdural drain left for 24–48 h to prevent re-accumulation
• Subacute SDH: may require either approach depending on clot consistency (assessed on imaging)
• Timing: acute SDH should be evacuated within 4 hours of injury for best outcomes (mortality increases significantly with delays beyond 4 h)

Medical (Non-Operative) Management Criteria

• SDH thickness <10 mm AND midline shift <5 mm
• Neurologically stable (no GCS decline)
• ICP <20 mmHg (if monitored)
• No posterior fossa location
• Requires serial imaging every 6–12 h initially, then daily
• Correct coagulopathy; reverse anticoagulation; hold antiplatelets

Pathophysiology & Clinical Features

• Source: rupture of the middle meningeal artery (most common; ~85% arterial) — blood collects between dura and inner table of skull
• Less commonly: dural venous sinuses (especially posterior fossa EDH), diploic veins, or middle meningeal vein
• Location: temporal bone — thinnest part of the skull; temporal bone fracture crosses the MMA groove
• CT appearance: biconvex (lenticular) hyperdense collection; does NOT cross suture lines (dura is firmly adherent at sutures)
• EDH does cross the midline falx (unlike SDH which does not) but does not cross suture lines

Classic Lucid Interval

• Initial LOC from concussive impact → transient improvement (lucid interval) → rapid deterioration as expanding hematoma causes uncal herniation
• Present in only ~20–50% of EDH patients — but is a classic board scenario
• Deterioration: ipsilateral pupil dilation (CN III compression) → contralateral hemiparesis → coma → death
• Ipsilateral fixed dilated pupil + contralateral hemiparesis = classic uncal herniation sign (Kernohan notch phenomenon may produce ipsilateral hemiparesis — false localizing sign)

Surgical Indications

Indications for Urgent Craniotomy

• EDH thickness >15 mm
• Midline shift >5 mm
• GCS <9 with anisocoria (unequal pupils)
• Neurological deterioration (any GCS decline)
• Posterior fossa EDH with any mass effect
• This is a surgical emergency — one of the most time-critical neurosurgical conditions; outcomes are excellent if evacuated promptly

Conservative (Non-Operative) Criteria

• Thickness <15 mm
• Midline shift <5 mm
• GCS >8 without focal neurological deficit
• No posterior fossa location
• Requires close monitoring with serial CT every 6–8 h; neurosurgical standby
• Must have reliable neurological exam — intubated or sedated patients should not be managed conservatively

Monroe-Kellie Doctrine

• The cranial vault is a fixed, rigid compartment containing three components: brain parenchyma (~80%), CSF (~10%), and blood (~10%)
• An increase in the volume of any one component must be compensated by a decrease in another, or ICP rises
• Initial compensation: CSF displacement into spinal canal + venous blood displacement out of skull → maintains normal ICP
• Once compensatory reserves are exhausted, small additional volume increases cause exponential ICP rises (steep portion of the compliance curve)
• Normal ICP: <20 mmHg (7–15 mmHg in adults; <10 mmHg in children)
• CPP = MAP − ICP; target CPP 60–70 mmHg (Brain Trauma Foundation guidelines)

Stepwise ICP Management

Osmotherapy — Mannitol vs. Hypertonic Saline

Malignant MCA Infarction

• Definition: complete MCA territory infarction with progressive edema, midline shift, and impending herniation; typically peaks at 48–72 hours
• Affects ~10% of ischemic stroke patients; mortality up to 80% with medical management alone
• CT findings: hypodensity involving >50% of MCA territory, effacement of basal cisterns, midline shift

Landmark Trials

Indications — Malignant MCA Infarction

• Age <60 years (strongest evidence)
• Surgery within 48 hours of symptom onset (before maximal edema)
• Infarction >50% of MCA territory on imaging
• Clinical deterioration (decreasing consciousness) despite medical management
• Key counseling point: reduces mortality but increases the proportion surviving with moderate-severe disability (mRS 4)
• Age >60: discuss with family — survival benefit exists but most survivors are severely disabled (DESTINY II)

Refractory ICP in Traumatic Brain Injury

• Indication: ICP >20–25 mmHg refractory to maximum medical therapy (full ICP ladder exhausted)
• RESCUE-ICP trial (2016): decompressive craniectomy vs. continued medical management in TBI patients with refractory ICP >25 mmHg

RESCUE-ICP Results

• Surgery reduced mortality (26.9% vs. 48.9%)
• Surgery reduced ICP effectively
• BUT: increased the rate of vegetative state (8.5% vs. 2.1%) and severe disability
• At 12 months: more patients in surgery group had favorable outcomes (mRS 1–4) when vegetative state and death were grouped as unfavorable
• Bottom line: craniectomy is a life-saving procedure but must be weighed against quality-of-life outcomes; shared decision-making essential

Surgical Technique

• Bone flap must be large — at least 12 cm (anteroposterior diameter) for unilateral craniectomy
• Small craniectomies are harmful — brain herniates through the defect, causing venous infarction at bone edges
• Unilateral: standard for MCA infarction or unilateral TBI
• Bifrontal: for diffuse bifrontal edema or bilateral pathology
• Duraplasty (opening and expanding the dura) is performed to maximize volume expansion
• Cranioplasty (bone flap replacement) typically performed 6–12 weeks later once edema has resolved; bone stored frozen or synthetic implant used

Indications for Burr Holes

• Chronic subdural hematoma drainage — most common indication; 1–2 burr holes with subdural drain placement
• Emergent ventricular access: external ventricular drain (EVD) placement for acute hydrocephalus or ICP monitoring
• Brain biopsy: stereotactic needle biopsy through a burr hole for deep-seated or eloquent-area lesions
• Subdural empyema drainage
• ICP monitor placement: intraparenchymal bolt or fiberoptic monitor

Twist Drill vs. Burr Hole vs. Craniotomy

EVD Placement

• Landmark: Kocher point — 11 cm posterior to nasion (or 1 cm anterior to coronal suture), 3 cm lateral to midline
• Trajectory: aim toward the medial canthus of the ipsilateral eye in the coronal plane and the tragus of the ipsilateral ear in the sagittal plane → targets the frontal horn of the lateral ventricle
• Typical depth: 5–7 cm from the cortical surface
• Usually placed on the right side (non-dominant hemisphere in right-handed patients)
• Complications: infection (ventriculitis; ~5–10%), hemorrhage (~5%), malposition, overdrainage

Posterior Fossa Emergencies

• The posterior fossa is a small, non-compliant space — even small hematomas or infarctions cause rapid brainstem compression and obstructive hydrocephalus
• Cerebellar hemorrhage >3 cm or with brainstem compression or hydrocephalus → surgical evacuation (suboccipital craniectomy)
• Cerebellar infarction with edema: suboccipital decompressive craniectomy if deteriorating despite medical management
• Posterior fossa EDH: very low surgical threshold; rapid deterioration from brainstem compression; often venous (transverse/sigmoid sinus)
• EVD placement for acute obstructive hydrocephalus — but beware of upward herniation if CSF drained too rapidly without addressing the posterior fossa mass

Anticoagulation Reversal Before Surgery

Herniation Syndromes — Quick Reference