Sudural haemorrhage: a bleed on the brain
This is a guest article I wrote for Brainbook; check out the original on their site.
Why does an intracranial bleed matter?
The skull is an inflexible bony box. It has limited space inside, which is fully occupied by the brain, its covering layers, blood vessels, and a cushioning fluid known as CSF (cerebrospinal fluid). A bleed (or any extra mass) inside the skull quickly raises the intracranial (inside-skull) pressure, squishing these structures. This causes all sorts of neurological mayhem as the flow of blood and CSF is impaired.
After a head injury with bleeding inside the skull (intracranial haemorrhage), symptoms relate to the raised intracranial pressure (ICP). These include a progressive headache, nausea/vomiting, loss of consciousness, and seizures. When the bleed is large or ongoing, death will ultimately result from a stroke (reduced blood flow to an area of the brain), or herniation (bulging of brain outside its normal boundaries) – more on this later.
A subdural haemorrhage is one type of intracranial bleed. The name simply describes the location of the bleed under (sub) the dura (tough membrane on the inside of the skull).
Transverse slice of the skull showing a subdural haemorrhage. Note the bleed (red) is between the dura (blue) and brain (pink) surface. You can see the ‘mass effect’ of the bleed pushing the brain tissue away from it.
How do they present?
Luckily there are operations neurosurgeons can perform to relieve this pressure and stop persisting bleeding. First however, the bleed needs to be discovered. The story given by the patient (or a witness to the head injury) may hint they are suffering from an intracranial haemorrhage. Patients may be unconscious at the point of injury, or ‘talk and deteriorate’, where they are initially alert but fall unconscious as the bleed progresses.
When the injury is unwitnessed, and patient is already unconscious by the time medics are involved, there are some important clinical clues to hint a significant head injury thus potential bleed has occurred:
A bump, bruise, or wound on the head to suggest trauma
Focal neurology: evidence of new sensorimotor disturbance e.g. a fixed, dilated pupil (sometimes called a ‘blown pupil’). This will not constrict (shrink) when light is shone in the eye, as would be the normal response.
Signs of a base of skull fracture, including rhinorrhoea (CSF leak from the nose), otorrhoea (CSF leak from the ear), battle sign (bruising over the mastoid process behind the ear), and raccoon eyes (bruising around the eyes).
Signs of raised intracranial pressure: headache, vomiting, visual disturbances, confusion, drowsiness, unconsciousness, seizures.
Environmental clues such as a broken handrail with a bloodstain, banana skin on the floor, vomit nearby, etc
Known potential significant trauma e.g. involvement in a car crash, assault, or fall from height
Known use of anticoagulation: taking blood thinning medication like Aspirin, Apixaban or Warfarin make significant bleeding more likely
A 'blown pupil', which is fixed and dilated, i.e. unresponsive to light. This can indicate raised intracranial pressure compressing the occulomotor nerve (cranial nerve 3).
When a bleed is suspected we can use a CT scan to look for it. Xray radiation from lots of angles is used to build up a 3d image of the anatomy, which radiologists then interpret in 2d ‘slices’.
If a bleed progresses and the intracranial pressure rises too much, then ‘herniation’ can occur. This is when parts of the brain are squished out of their normal locations into places they shouldn’t be. For example, one cause of death in head trauma is ‘coning’, where the cerebellum of the brain is pushed out of the skull through the foramen magnum (big-hole) in the base of the skull. There isn’t room to spare here, and this extra mass compresses the brainstem, stopping it from sending signals to the heart & lungs. These then quickly stop beating and breathing respectively and the patient dies.
Emergency neurosurgery: craniotomy decompression
Rising ICP quickly becomes a medical emergency, and requires decompression to relieve in order to prevent disability and death. One way to decompress the skull is surgery where ‘burr holes’ are drilled, allowing CSF fluid and blood to spill out, relieving pressure. This can be extended to a craniotomy, where a section of the skull is removed. This allows large blood clots to be taken away, and an injured swollen brain to expand.
Leave it out or put it back?
The ‘bone flap’ cut away can be put back on after the clot is removed and bleed has stopped. It is not always safe to do this immediately, as the brain may be very swollen. It can be left out for weeks or months if needed, and the defect (gap) reconstructed later when the injury has settled. This is done with plates, screws, and sometimes 3D printed materials. It’s not always clear if it is safer to leave the bone flap off, or replace it after removing a clot. If replaced and the brain continues to swell the patient will need further surgery to decompress the swelling. If the brain does not swell and the bone is left out, the patient will need a surgery later down the line to reconstruct the defect. To find out what action is best when the best option is unclear, there is a large study going on to see which has better patient outcomes. This is called the Rescue ASDH trial, which you can read more about here, or watch a video on here.
The Rescue ASDH trial is studying whether leaving the bone flap out, or replacing it, is the better option in ambiguous cases of craniotomy decompression of ASDH.
Conclusion
Time is of the essence when diagnosing a bleed on the brain, and doing the simple things well leads to early detection, and fast-tracking these patients to Neurosurgeons to fix the problem before it results in permanent disability or death.
I’ve been working hard with the team at Brainbook, and After Everything Entertainment on a great case video on acute subdural haemorrhage, where you can see the operation involved from the surgeons’ perspective. Check it out here.
I’d like to give a shout out of thanks to the Global Health Research Group on Neurotrauma, whose support has allowed this wonderful collaboration of Medical Illustration, Neurosurgery, and Videography to share information in a unique way globally and freely.
Also props to Mr Alex Alamri, Neurosurgery Registrar at Barts Health NHS Trust, the man who puts the brain in Brainbook, bringing diverse specialities together to create these exciting resources.