Clinical Guides
Subdural Haematoma
A clinically focused guide separating acute traumatic from subacute and chronic subdural haematoma, with CT interpretation, neurosurgical escalation, anticoagulant reversal, operative options and appropriately limited discussion of middle meningeal artery embolisation in the Indian care context.
MedNext Academy | 14 min read
Subdural Haematoma
A clinically focused guide separating acute traumatic from subacute and chronic subdural haematoma, with CT interpretation, neurosurgical escalation, anticoagulant reversal, operative options and appropriately limited discussion of middle meningeal artery embolisation in the Indian care context.
Summary
A subdural haematoma (SDH) is blood between dura and arachnoid, usually caused by disruption of bridging veins, cortical vessels or an operative surface. The label covers biologically different problems. Acute traumatic SDH contains fresh clot, frequently accompanies contusion and cerebral swelling, and may cause rapid herniation. Chronic SDH develops through inflammatory membranes, fragile neovasculature and recurrent microbleeding over weeks; the initiating injury may have been minor or forgotten. Subacute and mixed-density collections lie between these categories, and acute bleeding can occur into a chronic cavity.
Presentation ranges from coma after major trauma to headache, gait decline, confusion or subtle unilateral weakness in an older adult. Initial GCS does not safely quantify the whole risk. Non-contrast CT identifies the collection, mass effect, midline shift, associated injury and often its age pattern. A crescent may cross cranial sutures but is restricted by dural reflections. Isodense bilateral chronic collections can be missed unless sulcal effacement, ventricular compression and clinical context are considered.
Every symptomatic or radiologically significant SDH merits prompt neurosurgical discussion. Acute mass lesions may require immediate craniotomy or decompressive craniectomy. Symptomatic chronic SDH is commonly treated by burr-hole evacuation with drainage, while small stable collections may be observed with defined imaging and neurological follow-up. Anticoagulant reversal is time-critical when bleeding is life-threatening or surgery is needed. Middle meningeal artery embolisation (MMAE) is an evolving selected therapy for nonacute disease; it must not delay decompression of dangerous mass effect.
How Common Is It?
The measured occurrence of SDH depends on which phenotype is counted. Acute SDH is embedded within traumatic-brain-injury registries and correlates with road traffic injury, falls and assault. Chronic SDH is increasingly encountered in ageing populations because cerebral atrophy stretches bridging veins, falls are common and antithrombotic exposure is widespread. Hospital series over-represent symptomatic and operated cases, while small conservatively managed collections and prehospital deaths may be missed. No single foreign incidence rate should be presented as a current Indian national figure.
Chronic SDH disproportionately affects older adults and men in many cohorts, but it also occurs in younger people with coagulopathy, intracranial hypotension, seizures, shunts or substantial trauma. Bilateral collections are clinically important because they may produce little midline shift despite marked intracranial volume. Recurrence after drainage is common enough that follow-up and return advice are essential, but recurrence estimates vary with imaging definition, surgical technique, drain use, antithrombotic practice and duration of observation.
India has both a high absolute trauma burden and rapidly growing older population, yet access to CT and neurosurgery varies greatly by district. These system features alter recorded incidence and outcome. For service planning, useful measures are time from injury or deterioration to CT, transfer acceptance, reversal availability, time to evacuation, postoperative re-imaging when indicated and unplanned reoperation. At the bedside, age or frequency should never replace examination: a low-energy fall followed days later by confusion can be as important as a dramatic high-speed collision.
Risk Factors
Acute SDH follows acceleration, deceleration or direct impact that tears bridging veins or surface vessels. High-energy road traffic trauma, falls from height and assault are obvious mechanisms, but an older person can develop substantial bleeding after a ground-level fall. Cerebral atrophy increases the distance traversed by veins and allows a collection to enlarge before symptoms appear. Alcohol use contributes through falls, thrombocytopenia, liver dysfunction and atrophy; the history must remain nonjudgmental and include withdrawal risk.
Anticoagulants increase expansion risk and change the urgency of CT and reversal. Record the exact drug, last dose, adherence, indication, renal function and interacting medicines rather than writing only “blood thinner.” Warfarin, factor-Xa inhibitors, dabigatran, heparins and antiplatelet agents require different responses. Thrombocytopenia, haemophilia, liver disease and haematological malignancy also matter. Prior craniotomy, CSF shunt, dialysis and spontaneous intracranial hypotension can predispose to nontraumatic or recurrent subdural collections.
Chronic SDH risk is increased by older age, recurrent falls, epilepsy, antithrombotics and prior SDH. The expanding outer membrane is biologically active, so recurrence is not simply a technical failure of drainage. In infants and children, SDH raises different concerns including birth-related bleeding, accidental high-energy injury, coagulation disorder and abusive head trauma; safeguarding assessment must be multidisciplinary and must not infer mechanism from the scan alone. Prevention includes falls review, vision and footwear assessment, alcohol support, appropriate antithrombotic indication review and safe home planning, never unsupervised cessation of stroke-prevention therapy.
Diagnosis
History
Determine the injury time and mechanism, loss of consciousness, amnesia, vomiting, seizure, headache and neurological trajectory. Ask witnesses whether collapse preceded the fall. For a delayed presentation, seek change in gait, cognition, continence, speech, hand use, sleepiness or personality over days to weeks. Establish baseline function and cognition. Record antithrombotic name, last dose, renal disease, liver disease, alcohol use, previous SDH, neurosurgery, shunt and repeated falls.
Examination
Use trauma ABCDE with cervical-spine protection when indicated. Record GCS as eye, verbal and motor components and repeat it; a two-point fall may be more informative than a single total. Examine pupils, gaze, speech, cranial nerves, pronator drift, power, sensation and coordination. Look for external injury, basal skull signs and other bleeding. In chronic SDH, assess walking, attention and comparison with family-described baseline. Check glucose, oxygenation, temperature and serial blood pressure.
Investigations
Non-contrast head CT is first-line. Acute blood is usually hyperdense and crescentic; chronic fluid is often hypoattenuating, while subacute or mixed acute-on-chronic collections may be isodense or layered. Report maximal thickness, midline shift, basal cisterns, ventricular compression, sulci, bilateral disease and associated contusions, fractures or SAH. CT criteria after head injury follow age, GCS, vomiting, seizure, focal deficit, skull signs, amnesia, mechanism and antithrombotic exposure. Obtain blood count, platelets, INR or appropriate coagulation studies, electrolytes, renal and liver function, group and crossmatch when surgery is plausible. Repeat CT is driven by deterioration, initial lesion, anticoagulation, operative planning and local protocol. MRI can clarify an isodense or alternative lesion but must not delay urgent CT or surgery.
Differential Diagnosis
Acute epidural haematoma is usually biconvex and limited by sutures, but shape alone is imperfect and both collections can coexist. Traumatic SAH tracks sulci and cisterns; contusions are intraparenchymal and frequently frontal or temporal. Diffuse axonal injury can produce severe coma with initially modest CT findings. Ischaemic stroke, spontaneous intracerebral haemorrhage, seizure with postictal weakness, intoxication, hypoglycaemia and cervical-spine injury may explain or accompany the presentation. A patient found after a fall may have fallen because of stroke, arrhythmia or SAH rather than trauma being the first event.
Chronic SDH commonly mimics dementia, delirium, normal-pressure hydrocephalus, brain tumour, depression, medication toxicity and subacute stroke. Fluctuation, headache, a new asymmetric deficit or decline after even minor trauma should lower the threshold for imaging. Bilateral collections can cause gait and cognitive symptoms without a large midline shift. Subdural empyema produces fever, headache, seizure and focal deficit and may show an enhancing collection; it is an infectious neurosurgical emergency, not a chronic haematoma. Hygroma contains CSF-like fluid and may follow trauma or surgery but can evolve or coexist.
Spontaneous intracranial hypotension can generate bilateral subdural fluid or haemorrhage with orthostatic headache and characteristic MRI changes. A dural metastasis, meningioma or postoperative change can resemble a collection. In an infant, metabolic disease and benign enlargement of subarachnoid spaces enter a specialist differential, but neither removes safeguarding obligations. Imaging density cannot date an injury precisely enough for forensic conclusions, and differing densities do not alone prove repeated trauma. Diagnosis should integrate symptoms, serial images, coagulation, mechanism and an expert neuroradiology or neurosurgical opinion.
Management
Acute SDH management begins with trauma resuscitation: prevent hypoxia and hypotension, protect the cervical spine when indicated, treat seizures, correct glucose and temperature, and avoid delays to CT and neurosurgical contact. If GCS is eight or less or airway reflexes fail, experienced airway management and ventilation are required. Elevate the head when haemodynamics permit, maintain neutral neck alignment and use hyperosmolar rescue only for suspected herniation under an emergency protocol. It is a bridge to definitive care, not a substitute for evacuation.
The Brain Trauma Foundation recommends evacuating an acute SDH thicker than 10 mm or with midline shift greater than 5 mm regardless of GCS; a comatose patient below those dimensions may still need surgery after GCS decline, pupillary abnormality or raised ICP. These thresholds support, not replace, urgent clinical judgement. Current ACS guidance emphasizes evacuating a large traumatic haematoma before deterioration and using a large trauma craniotomy for acute clot, with the bone flap left out when replacement would compress swollen brain. Operative candidates go to surgery as soon as possible.
For chronic SDH, small minimally symptomatic collections can sometimes be monitored with reliable supervision, a scheduled reassessment and clear triggers for repeat imaging. Neurological deficit, impaired consciousness, substantial mass effect or functional decline usually leads to drainage, commonly burr holes with a temporary drain. Twist-drill drainage or craniotomy has selected roles; organized membranes, solid components and recurrence influence choice. Correct coagulopathy and plan antithrombotic restart around both bleeding and thromboembolic indication. Rehabilitation and falls work begin early. MMAE may complement standard care for selected nonacute or recurrent disease, but trial populations and endpoints differ; it does not decompress quickly and must not delay surgery for life-threatening mass effect.
Prescribing Information
Reversal must be drug-specific and coordinated with neurosurgery, trauma, anaesthesia, haematology or a verified institutional pathway. For warfarin-associated life-threatening intracranial bleeding or emergent surgery, intravenous vitamin K plus four-factor prothrombin complex concentrate (4PCC) is generally preferred, with INR rechecked. Dabigatran is reversed with idarucizumab when indicated. Factor-Xa inhibitors may be reversed with andexanet alfa or 4PCC depending on drug, timing, availability and policy. Heparin exposure prompts protamine-based assessment. Renal function and time since last dose materially change benefit. Do not wait for a normal routine coagulation screen to exclude clinically relevant DOAC effect.
Antiplatelet management is not equivalent to anticoagulant reversal. Routine platelet transfusion for every patient taking aspirin or clopidogrel can expose patients to harm and is not supported; platelet-function testing and transfusion or desmopressin decisions are individualized, particularly around urgent neurosurgery. Correct severe thrombocytopenia and fibrinogen abnormalities through local major-haemorrhage guidance. Record the antithrombotic indication because mechanical valves, recent venous thrombosis or coronary stents alter restart risk. Restart timing requires a documented multidisciplinary decision, never indefinite omission by default.
Analgesia should permit examination and avoid respiratory depression or hypotension. Treat clinical seizures promptly. ACS guidance supports considering seven days of antiseizure prophylaxis in severe TBI with early-seizure risk factors, but prophylaxis beyond seven days does not prevent late post-traumatic epilepsy. Chronic SDH has no universally effective tablet that replaces indicated drainage. Dexamethasone is not routine disease-modifying treatment, and statins or tranexamic acid should not be advertised as standard outside an adopted protocol or trial. Avoid NSAIDs until bleeding risk is assessed. Every dose, reversal threshold and route requires local formulary verification.
When to Refer
Any CT-confirmed acute SDH should be discussed promptly with neurosurgery, even when the patient is initially alert. Immediate transfer is required when there is falling GCS, pupil asymmetry, focal deficit, seizure, significant mass effect, associated brain injury, anticoagulant exposure with bleeding, need for ICP-capable critical care or likely surgery. A normal initial examination does not justify delaying the image discussion. Send CT data electronically and report thickness, shift, cisterns, associated lesions and trajectory rather than the word “subdural” alone.
Before transfer, complete necessary resuscitation without allowing nonessential tests to become obstacles. Secure the airway when indicated, correct hypoxia and hypotension, start appropriate reversal, immobilize relevant injuries, crossmatch blood when surgery is likely and provide trained escort with monitoring and the ability to manage deterioration. The referring and receiving clinicians should agree destination, transport priority and interim plan. If the patient is too unstable because of uncontrolled extracranial bleeding, trauma and neurosurgical teams must coordinate rather than transferring to a unit unable to manage the whole injury.
Suspected chronic SDH also needs urgent assessment when there is new weakness, speech change, gait failure, confusion, repeated falls or progressive drowsiness. Stable small collections still require a named clinician, planned follow-up and explicit return precautions. Recurrence after drainage, persistent bilateral disease, inability to resume essential antithrombotics or consideration of MMAE belongs in a multidisciplinary neurosurgical and, where relevant, neurointerventional pathway. Children, unexplained injury and vulnerable adults require safeguarding referral alongside clinical care, without delaying treatment.
Red Flags
After head injury, a GCS below 15 that does not recover, a fall by two or more points, unequal or nonreactive pupils, new weakness, aphasia, repeated vomiting, worsening headache, seizure, bradycardia with hypertension, abnormal breathing or progressive agitation or drowsiness signals intracranial deterioration. Anticoagulant or antiplatelet treatment, age 65 or older, bleeding disorder, skull-fracture signs and dangerous mechanism lower the imaging threshold. A lucid interval does not belong exclusively to epidural bleeding and should never reassure.
In chronic SDH, families may notice the danger before the examination looks dramatic: new shuffling, repeated falls, confusion, reduced self-care, unilateral clumsiness, incontinence or excessive sleepiness. Bilateral collections can be large without marked midline shift. Acute headache or sudden deficit in a known chronic collection suggests fresh bleeding. Fever and inflammatory markers with a collection raise concern for empyema; orthostatic headache and bilateral fluid suggest intracranial hypotension. Each alternative requires its own urgent specialist pathway.
Process failures are also red flags. These include relying on INR to exclude DOAC effect, postponing reversal until transfer, accepting a poor GCS as inevitable without checking glucose or seizure, giving routine platelets for aspirin without an operative or laboratory rationale, or observing a patient where repeat examination and emergency CT are impossible. Do not let discussion of MMAE delay burr-hole drainage or craniotomy when there is dangerous mass effect. A stable scan does not overrule clinical deterioration, and a stable patient does not make a large acute lesion safe without neurosurgical input.
Indian Clinical Context
India's geography makes time to CT and neurosurgery highly variable. A primary centre should recognize high-risk head injury, protect physiology and move the patient to CT-capable emergency care; a CT-capable district facility must know which centre can provide 24-hour neurosurgery, ICU support and blood products. Current Ministry of Health and Family Welfare standard-treatment resources include major-trauma and critical-care guidance, but local teams must verify that the actual ambulance, scanner, radiologist, reversal stock and operating theatre match the written pathway.
For transfer, record injury and deterioration times, GCS components and trend, pupils, oxygenation, blood pressure, antithrombotic name and last dose, renal function, reversal, CT findings and associated injuries. Share DICOM images before departure when technology permits. If a private neurointerventional option exists but an affordable surgical pathway does not, MMAE should not be portrayed as the default solution: chronic SDH evidence comes from selected trial populations, material and expertise costs differ, and emergency decompression remains the priority for major mass effect.
Older patients may live far from family, have baseline cognitive impairment or lack someone able to monitor deterioration. Conservative management is unsafe unless follow-up and rapid return are credible. Language-accessible discharge instructions should describe weakness, speech change, worsening headache, vomiting, seizure, confusion, imbalance and drowsiness. Rehabilitation, fall-prevention, alcohol support and rational antithrombotic restart are part of treatment rather than optional extras. In infants or unexplained injuries, coordinate paediatrics, radiology, neurosurgery, ophthalmology and safeguarding according to law and local policy; do not use imaging density alone to assign timing or blame.
NMC Competency Mapping
The NMC CBME curriculum supports SDH through integrated trauma, neurological and anatomical outcomes rather than a claim that an undergraduate can independently manage neurosurgery. Relevant surgery learning includes primary trauma assessment, resuscitation, GCS documentation, recognition of raised intracranial pressure and head-injury investigation and referral. General-medicine cerebrovascular and altered-consciousness outcomes reinforce neurological localization and supportive care. Anatomy of dura, arachnoid, bridging veins, venous sinuses and dural reflections explains the crescentic pattern and potential for herniation. Pharmacology contributes rational use and reversal of antithrombotic drugs.
A graduating learner should perform ABCDE, state GCS components, recognize pupil and focal changes, select urgent non-contrast CT, describe an acute crescent and identify mass effect. They should distinguish acute from chronic presentation, know why anticoagulant history is exact and time-stamped, and make a structured neurosurgical referral. Applied questions should test the classic greater-than-10-mm thickness or greater-than-5-mm shift thresholds while rewarding the insight that clinical decline, pupils and ICP can mandate surgery below them.
The competence boundary is explicit. Reading cannot certify intubation, hyperosmolar prescribing, anticoagulant reversal, ICP monitoring, burr-hole drainage, craniotomy, craniectomy, MMAE or antithrombotic restart. Those decisions require supervised training and multidisciplinary authority. Simulation can assess recognition, closed-loop escalation, safe transfer and family communication. Formal curricula should verify the exact local 2024 code wording rather than copying older web tables, particularly because similarly numbered surgery competencies have changed across compilations. Safeguarding documentation in childhood injury is a professional duty but forensic conclusions require expert multidisciplinary assessment.
Key Exam Pearls for NEET PG
Acute SDH usually arises from torn bridging veins or cortical vessels and appears as a hyperdense crescent. It can cross sutures but not freely cross dural reflections such as falx and tentorium. Epidural blood is classically biconvex and suture-limited. Chronic SDH is commonly hypodense, subacute blood may be isodense, and mixed density suggests components of different age or rebleeding but cannot precisely date trauma. Cerebral atrophy, older age, alcohol exposure and antithrombotics are core associations.
The Brain Trauma Foundation operative rule is high yield: acute SDH thickness greater than 10 mm or midline shift greater than 5 mm warrants evacuation regardless of GCS. A comatose patient with smaller measurements may still need operation after a two-point GCS fall, asymmetric or fixed dilated pupils, or ICP above 20 mmHg. Modern ACS guidance emphasizes early evacuation of a large lesion and large trauma craniotomy; the bone flap may be left out when swelling makes replacement compressive.
Chronic SDH often presents with headache, cognitive decline, gait disturbance or focal deficit weeks after a minor injury. Symptomatic mass effect is commonly treated with burr-hole evacuation and a drain; recurrence requires reassessment, not repeated steroids by default. Reverse life-threatening anticoagulant-associated bleeding with an agent-specific pathway: vitamin K plus 4PCC for warfarin, idarucizumab for dabigatran, andexanet or 4PCC for factor-Xa inhibition as locally verified. MMAE targets vascularized chronic membranes and may reduce selected recurrence or treatment failure, but trial results and populations differ and it cannot rapidly decompress a herniating brain.
Frequently Asked Questions
Can an older adult develop a chronic subdural haematoma after a minor or forgotten fall?
Yes. Cerebral atrophy stretches bridging veins and creates room for a collection to enlarge gradually. Headache may be absent; relatives may instead notice gait decline, confusion, sleepiness, speech change or one-sided clumsiness. A delayed presentation does not make the condition benign. New functional or neurological change after even minor trauma warrants examination and usually urgent CT.
Does every subdural haematoma require immediate surgery?
No, but every symptomatic or significant collection needs prompt neurosurgical assessment. Large acute SDH, clinical deterioration, pupil change or major mass effect may require immediate evacuation. A small stable collection can sometimes be observed only when serial examination, appropriate repeat imaging, reliable supervision and rapid return are available. Chronic symptomatic collections are commonly drained through burr holes.
How is anticoagulation handled when SDH is life-threatening or surgery is urgent?
The team identifies the exact agent, last dose, renal function, indication and relevant tests, then uses a verified drug-specific reversal pathway. Warfarin generally needs intravenous vitamin K plus 4PCC; dabigatran has idarucizumab; factor-Xa inhibitors may use andexanet alfa or 4PCC. Reversal and later restart both require specialist risk balancing and documentation.
Can middle meningeal artery embolisation replace surgical drainage for chronic SDH?
Not when a patient needs rapid decompression for substantial mass effect or neurological decline. Randomized studies support benefit in selected nonacute populations, including adjunctive use, but they used different eligibility criteria, endpoints and standard-care choices, and longer-term safety and local generalizability remain important. MMAE should be selected by neurosurgical and neurointerventional teams, not offered as a universal substitute.
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