Keywords
extradural hematoma - extradural empyema - extradural abscess
A patient may be asymptomatic after initial head injury. A few patients present later
with headache and warrant investigation. Most of such patients have normal imaging
findings, and symptom is ascribed to posttraumatic chronic headache. In some instances,
a chronic subdural hematoma is found, particularly in elderly individuals. Rarely
subacute/chronic hematoma may be seen. A chronic extradural hematoma (EDH) can also
be seen in patients, days after trauma due to resolution of blood clot. However, hypodense
EDH in subacute stage after trauma warrants further investigation. We describe a case
of head injury that presented later, and on investigation was found to have extradural
empyema within EDH.
Case
A 24-year-old man sustained head injury 12 days back. He was riding pillion, and had
a fall over his head. He was unconscious for about 1 hour after injury. He had bleeding
from his right ear and a scalp swelling over temporoparietal region. There was no
open scalp wound. His previous medical condition was good, and he did not have any
immunocompromised condition. The patient did not have history of middle ear infection.
As he recovered consciousness, he did not seek a medical consultation at that time.
He was asymptomatic after injury. He presented with a history of worsening headache
for past 4 days and increase in scalp swelling. On arrival at casualty, the patient
was afebrile and had normal vital parameters. A boggy tender swelling was felt over
his right temporoparietal scalp. He was conscious and did not have any neurologic
deficits. The routine hematologic and biochemical profile was normal. A computed tomography
(CT) scan of the head revealed a large biconvex hypodense lesion in extradural plane
in temporoparietal region. There was hypodense scalp swelling over the same region.
There was a linear fracture of temporal and parietal bone. The postcontrast study
revealed peripheral rim of enhancement of extradural lesion and scalp swelling. The
imaging diagnosis was extradural empyema ([Fig. 1]). A temporoparietal craniotomy was performed. The surgical findings were pus in
subgaleal and extradural plane. The pus was mixed with old EDH. Complete evacuation
of pus and extradural hematoma was done. The Gram stain of pus showed gram-negative
bacilli; however, the culture was sterile. A histopathologic examination of extradural
tissue was not done. He was treated with injectable ceftriaxone and amikacin for 4
weeks and did well. A repeat imaging after completion of medical treatment did not
reveal residual pus.
Fig. 1 CT scan of the head axial sections plain (A) and postcontrast (B) showing subgaleal collection and hypodense extradural collection with peripheral
rim of enhancement.
Discussion
The causes of hypodensity in an EDH are air, active bleeding, or chronic blood. Hypodense
bubbles in acute extradural hematoma are described in cases of active or fresh bleeding
from torn dural sinuses or transected meningeal vessels.[1]
[2] In a series of 13 cases of acute EDH as a result of injury involving the venous
sinuses, 6 cases had large hypodense bubbles within the hyperdense EDH. These hypodense
bubbles correlated with findings of liquid blood during surgery.[1] The CT scan appearance of hypodense bubbles and proximity of the clot to the venous
sinuses should alert the high probabilities of venous sinus tear. The other causes
of hypodensity are hyperacute lesions with ongoing active bleeding or coagulopathy.[3] The hyperacute EDH also shows patchy distribution of hyperdense and isodense blood
similar to “swirl sign” described by Zimmerman and Bilaniuk.[4] Hypodensity can be due to several foci of pneumocephalus if EDH is present adjacent
to fractured air sinuses.[5]
The unique finding in our case was hypodense EDH. Though it was after 12 days of trauma,
it was too early for a hematoma to become hypodense. The other causes of hypodensity
in an EDH such as air, active bleeding, or chronic blood were not thought of; hence
a contrast-enhanced CT scan was done. The contrast-enhanced CT scan was typical of
extradural empyema. At surgery, it was confirmed that the patient had EDH, which got
secondarily infected. Hypodensity due to pus formation within EDH is described in
our case, and it should be kept in mind when evaluating a patient who presents few
days after injury.
