Subdural Haemorrhage



In the UK, 700,000 people visit A&E annually with the presentation of a head injury.1 Head injuries can be divided into mild and severe, with severe representing the scope of bleeding.2

Extra-axial haemorrhages are classified based on the separation of blood by the compartments and fascial layers of the brain (Figure 1).

A subdural haemorrhage (SDH; also known as a subdural haematoma), is defined as “a collection of blood between the dural and arachnoid coverings of the brain.”3



A cross-section of the layers covering the brain. The layers can be remembered using the mnemonic SCALP - Skin, Connective Tissue, Epicranial Aponeurosis, Loose Connective Tissue and Periosteum.
Figure 1: Layers covering the brain. 4 The layers of the scalp can be remembered using the mnemonic SCALP – Skin, Connective Tissue, Epicranial Aponeurosis, Loose Connective Tissue, Periosteum. The following lies deep to the scalp- Bone, Dura Mater, Arachnoid Mater, Pia Mater and Brain Parenchyma. Subdural haemorrhage happens between the dura and arachnoid layers in the subdural space.



By far the most common cause of subdural haemorrhage is trauma. The classic clinical case is a blow to the temporal side of the head, rupturing the bridging cranial veins.

However, other causes are as follows, and should be investigated thoroughly: ³

  • Trauma
  • Rupture of a cerebral aneurysm
  • Rupture of an arteriovenous malformation (AVM)
  • Cerebral hypotension
  • Malignancy (rare)


History and Examination

Subdural haemorrhages can be divided into acute (<3 days) and chronic (>21 days).3 When taking a history from a patient whom you suspect has a subdural haemorrhage (if you are able), it is important to identify risk factors that make the diagnosis more likely. Examples of risk factors include:2,3

  • History of trauma (e.g. a fall, road traffic accident, blow to the head)
  • Co-morbidities that make a patient vulnerable to falls (i.e. dementia and delirium)
  • Age (>65)
  • Anticoagulant use: Many patients are on warfarin, a lifelong monitored anticoagulant. Check their compliance, INR recordings and recent dosage amendments.
  • History of coagulopathy
  • Loss of consciousness

A complete neurological examination of the upper and lower body should be performed, along with a cranial nerve examination. In addition, an on-the-spot assessment of the patient’s Glasgow Coma Score (GCS) should be performed. ² Patients can present with a broad range of signs and symptoms, depending on the severity of neurological injury. The most common include:

Signs and Symptoms ²,³

  • Headache
  • Nausea/vomiting
  • Confusion/decreased mental alertness
  • Peripheral neurological deficit
  • Altered mental state i.e. irritability (common presentation in children)
  • Post-traumatic seizure
  • Focal neurological signs (much more common in acute SDH)
    • CN I: Loss of smell
    • CN II: Loss of vision
    • CN III, CN IV, CN VI: Double vision, problems with eye movements and pupil constriction/dilation
    • CN V: Loss of corneal reflex, impaired facial sensation, weak muscles of mastication
    • CN VII: Loss of taste in the anterior two-thirds of the tongue, weak muscles of facial expression
    • CN VIII: Loss of hearing, loss of balance
    • CN IX: Loss of taste in the posterior third of the tongue, impaired swallowing
    • CN X: Impaired autonomic functions
    • CN XI: Loss of head movements
    • CN XII: Loss of tongue movements


Coupled with features in the patient’s history/examination, imaging plays a crucial role in distinguishing subdural haemorrhage from other genres of brain bleeds. A non-contrast CT needs to be urgently sought if there is suspicion of an intracranial bleed (Figure 2). An MRI is not recommended unless in cases to ascertain the patient’s prognostic factors.2

Make sure to also check out our guide to CT head interpretation.

Figure 2A: A non-contrast CT scan depicting an acute SDH. 5 The hyperdense signal in acute SDH represents recently clotted blood. The outline (red) is characteristically crescent-shaped.


Figure 2B. A non-contrast CT scan depicting a chronic SDH. 6 The hypodense in chronic SDH represents the dissolution of cellular elements into liquid. Along with the timeline of the patient’s history, at the basic level, acute vs. chronic SDH can be differentiated by “hyperdense (white)” vs. “hypodense (black)” signals.7 The outline (red) of both is characteristically crescent- shaped.

Differentiating Types of Brain Haemorrhages

Sub-types of intracranial haemorrhage differ in their clinical presentation and radiological appearance. This list is not exclusive but will help you in differentiating different types of haemorrhages when it comes time for final exams and OSCEs (Table 1, Figure 3).


Table 1. Characteristic Differences of Brain Bleeds


Figure 3. Radiological Appearance of Different Brain Bleeds



Initial management of a patient with a suspected subdural haemorrhage should focus on resuscitation and stabilisation of vitals, following the ABCDE method.2 As soon as an intracranial bleed is suspected, the input of the senior doctor responsible for the patient, a neurosurgeon and potentially an anaesthetist should be sought.


  • C-spine stabilisation- important in the context of trauma to minimise spinal cord/nerve root damage
  • Ensure airway is patent
  • Assess any trauma to the head/neck


  • Effort and symmetry- accessory muscle use?
  • Respiratory rate
  • O2 saturation: give 15L/min oxygen in a non-rebreather mask if <94%, take ABG if <93%
  • Chest expansion
  • Chest palpation: include trachea position for co-morbid tension pneumothorax
  • Chest auscultation: perform chest x-ray if respiratory pathology suspected



  • Colour and skin temperature
  • Capillary refill time: normal= <2 seconds
  • Pulse: normal= 60-100bpm
  • Blood pressure: normal= 120/80 mmHg
  • If indicated, assess ECG, JVP and heart sounds


  • Calculate GCS (Glasgow Coma Scale) or AVPU score
  • Check pupil response
  • Monitor glucose levels
  • Check tympanic temperature



  • Essentially a head-to-toe assessment for any further injuries
  • Make sure to check behind the head and neck


Clinical Context

  • Be aware of the clinical context and interpret your clinical findings with this in mind
  • Context can be gained from reading the patient’s notes and speaking to witnesses

Criteria for Hospital Admission ²

  • GCS<15
  • New, clinically significant abnormalities seen on imaging
  • Persistent concerning signs (for example, vomiting or a severe headache)
  • CT unavailable/ patient is uncooperative (lacking capacity)
  • External concerning signs (i.e. intoxication or meningism)


Management Once SDH Confirmed ³

After confirmation of a subdural haemorrhage by non-contrast CT, the following management principles can be followed, as guided by the BMJ; 3, however, a neurosurgeon will chiefly use the patient’s clinical status as an indicator for management strategies. Prophylactic antibiotics may be considered in all cases but the evidence is contentious.11


Acute (<3 days)

The management depends on the size of the haemorrhage.

For bleeds <10mm size (midline shift <5mm non-expansile without significant neurological dysfunction):

1. Admit, observe and monitor. Have a follow-up CT in 2-3 weeks.

2. Prophylactic antiepileptics, such as IV phenytoin, IV phenobarbital or oral/IV levetiracetam

3. Intracranial pressure monitoring if GCS is <9

4. Correct coagulopathies (i.e. vitamin K)

5. Lower intracranial pressure (ICP)

For bleeds with one or more of the following: ≥10mm size; with midline shift >5mm; expansile or significant neurological dysfunction, surgical intervention would be required first. This would be a decompressive craniectomy, which involves removing part of the skull, in order to relieve the added pressure on the brain.

Chronic (>21days)

Management is as follows:

1. Antiepileptic medication (IV phenytoin, IV phenobarbital, oral/IV levetiracetam

2. Surgery for symptomatic patients- i.e. burr hole irrigation and drainage, craniotomy

3. Correct coagulopathy- i.e. with vitamin K

4. Lower ICP


Follow-up care may include the following: ³

1. Repeat CT Scan 2-3 weeks after discharge

2. Consult with cardiologist or haematologist to restart anticoagulants (if applicable)

3. Symptomatic relief



Complications that follow subdural haemorrhage result from damage from the bleed itself in addition to the standard post-op complications from surgical management. Examples of complications include:2,3  

  • Neurological deficits
  • Coma
  • Seizure
  • Infection
  • Recurrent haemorrhage


Edited by

Samantha Strickland

Reviewed by

Mr Arif Zafar, Neurosurgery Specialty Registrar



1. Brain Injury Group. Brain Injury- The Facts [Internet]. The BIG Network Ltd. 2018 [cited 2018 Jun 10]. Available from:

2. Guidance N. Head Injury: Assessment and early management [Internet]. NICE Clinical Knowledge Summaries. [cited 2018 Jun 10]. Available from:

3. Grande AJ. Subdural Haematoma [Internet]. BMJ Best Practice. [cited 2018 Jun 10]. Available from:

4. staff (2014). “Medical gallery of Blausen Medical 2014“. WikiJournal of Medicine1 (2). DOI:10.15347/wjm/2014.010ISSN 2002-4436. Scalp [Internet]. Wikipedia. 2018 [cited 2018 Jun 17]. Available from:

5. Case courtesy of Dr Craig Hacking, Available from:

6. Case courtesy of Dr Jeremy Jones, Available from:

7. CT Brain Image Gallery- SDH acute v. chronic [Internet]. Radiology Masterclass. 2018 [cited 2018 Jun 17]. Available from: _chronic_ct_brain#top_1st_img

8. Case courtesy of Dr Sandeep Bhuta , Available from:

9. Case courtesy of Dr David Cuete, Available from:

10. Case courtesy of Dr Farzad Pirzad,  Available from:

11. Lewis A, Sen R, Hill TC, James H, Lin J, Bhamra H, et al. Antibiotic prophylaxis for subdural and subgaleal drains. J Neurosurg [Internet]. 2017;126(3):908–12. Available from:


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