Extradural hematoma (EDH) can be the most satisfying case for a
neurosurgeon and constitutes a major source of preventable mortality in
the head injured.
Epidemiology:
It
occurs in all age groups, but mostly in under the age of 40 years and
commoner in males. It is the most common post-traumatic intracranial
hematoma in children and follows SDH and ICH in adults. 10% of fatal
injuries in Glasgow autopsy series, 1-4% of imaged craniocerebral trauma,
and less than 2% of admitted craniocerebral trauma have EDH.
Aetiology:
It is
the result of an impact injury
most common in road traffic accidents, assaults, and fall from a
height. Occasionally, it may present as a post operative event or as a
result of bleeding from a dural AVM.
Pathophysiology:
The
potential extradural space needs to be stripped off the inner table before
the meningeal vessels bleed. In children under 3 years and in the older
age group, the dura is adherent to the inner table and hence the EDH is
less frequent.
In
more than 50% of EDHs, the source of bleeding is a ruptured middle
meningeal artery. In 33%, it is a ruptured middle meningeal vein. The rest
is from venous sinuses and diploic veins. The extravasated blood separates
the dura from the bone, leading to detachment of further vessels thus
aggravating the bleeding; the stripping do not cross the suture lines.
Over 80% of them are associated with a fracture.
In 67%,
the involved site is temporo-parietal region, and in about 10%, the site
is frontal. Occasionally it is bilateral.
Posterior fossa EDHs are uncommon, but the clinical deterioration is
rapid. A fracture at the region of transverse sinus or a diastasis of the
lambdoid or occipito-mastoid suture should alert the surgeon. A collection
of 15ml of blood in the subtentorial space results in severe functional
disturbance. Obstructive hydrocephalus is an ever present possibility.
Clinical features:
|
The
volume is not always directly proportional to the severity of the
clinical symptoms. 25 ml of hematoma is considered significant. The
clinical picture depends on location, rapidity of hematoma formation,
associated intradural and other injuries, and internal decompression
through fractures (blood & CSF leakage).
The
classical triad of head injury with lucid interval, ipsilateral
mydriasis and contralateral paresis occurs only in 18% of cases and
mainly in hematomas of the parieto-temporal hematomas.
Often, the clinical
picture is a combination of the above. There are no definite
symptoms of epidural hematomas. The clinical course may the same
in acute SDHs, ICHs, and temporal and frontal contusions. |
|
In acute EDHs,
the frequency of the clinical presentations is as follows: |
|
hyperacute course (up to 10 hours) |
10% |
|
acute course (up to 24 hours) |
38% |
|
short LOC followed by lucid interval (classical type) |
18% |
|
irritability, headaches, nausea |
84% |
|
GCS<7 from the onset with progressive deterioration |
31% |
|
ipsilateral anisocoria |
50% |
|
contralateral anisocoria |
4% |
|
contralateral hemiparesis |
62% |
|
ipsilateral hemiparesis (kernohan's phenomenon) |
3% |
|
|
In
subacute or chronic types, the lucid interval may last for days
and weeks.
In
children, seizures, vomiting, irritability, lethargy are common. The
onset of symptoms may be delayed, but deterioration may be rapid. Fracture
is uncommon. Blood volume lost to the extradural space in an infant may be
enough to produce a clinical picture of shock.
|
Investigations:
X-rays
of the skull may reveal a fracture, suggesting the site of the EDH.
CT scan
is the investigation of choice. The minimal volume required for
visualization in CT is about 25ml. Initial CT may be negative in about
30% of cases. The hematoma is seen as a biconvex, hyperdense,
nonenhancing extraparenchymal lesion. Heterodensity (Glacier effect)
suggests active/ fresh bleed. |
 |
| Hypodense
bubbles within the hematoma suggest venous tear. |
Biconvex EDH-CT |
|
The
hematoma may become isodense in about 2 weeks. Obliteration of
cerebral sulci may give a clue.
A
chronic EDH may reveal a contrast enhancing periphery.
Associated parenchymal injury, and a midline shift of >8mm suggest a
bad prognosis. |
 |
|
MRI scans show better
delineation of the pathology. The displaced dura
|
Fracture & contra-coup EDH-CT |
| appear as
a thin low signal intensity between the hematoma and brain.
Ultrasound
is useful in children with open fontanels and cost effective during
conservative treatment and follow-ups.
Management:
Non
operative management
may be tried when an EDH is an incidental finding and
small (<1cm) with no suggestion of raised ICP or focal deficit.
|
 |
|
Close observation with serial CT scanning is a must.
|
Post.fossa EDH-CT |
Prolonged hospitalization may be required.
In
an emergency when clinical symptoms develop rapidly and an urgent CT
scanning is not available, exploratory burrholes on
the site of fracture or soft tissue injury and/or in the temporal region
on the side of pupillary dilatation are carried out. Frontal and
parietal burrholes may be done if the other burrholes do not reveal a
clot. It is advised to explore the opposite side as well. However,
burrholes usually do not lead to radical removal of the EDH.
A
craniotomy allows radical removal of the EDH and control of the
bleeding; the dura may be opened if associated SDH is suspected. Bony
decompression is advised by some surgeons. Some surgeons prefer to leave a
drain. A ventricular drainage may be required in posterior fossa lesions.
Massive
(malignant) cerebral edema following evacuation is assumed to be due
to loss of cerebral autoregulation. It is usually associated with delayed
evacuation and very difficult to treat.
Post operative
intensive management with attention to metabolic, respiratory, and
infective complications associated with prolonged unconsciousness
determines the final outcome. ICP monitoring helps to detect
reaccumulation of the EDH.
Prognosis:
It
depends on the extent of secondary brain injury and associated injuries.
The nature of the first aid given and the timing of the surgery determine
the prognosis. The longer the period of lucid interval, the greater are
the chances of full recovery. GCS at the time of surgery, and the volume
of EDH also determine the outcome.
The
overall mortality ranges from 20-40% in various series. Children do
better. Faster transportation of the head injured, earlier recognition of
the clot, improved neurosurgical services, and the availability of CT
scans have greatly improved the prognosis.
