Discussion
Subdural empyema is a rare and fatal intracranial complication of
chronic otitis media with a mortality rate of 12.2% to
28%.11,17 The predisposing risk factors include
neglected middle ear infections, lack of access to health care and
availability of imaging modalities such as CT scan and/or MRI,
immunosuppression, and poor economic status.7,10,18,19Over the past years, the incidence of complications of otitis media have
decreased with the use of antibiotics, improved imaging studies, the
introduction of the pneumococcal vaccine, and multidisciplinary
management.6,7
Clinical presentation : The symptoms and signs in patients with
subdural empyema are due to pus collection and the mass effect on the
brain. The classical triad of presentation which include headache, fever
and vomiting is present only in 36% to 50% of the patients. Showing
that the triad is not very sensitive in diagnosing subdural abscess. To
emphasise this fact, as was already mentioned above in the case study,
the patient had only fever from the so called ‘classic triad’.
Therefore, it is generally agreed that the symptom complex of fever,
headache, vomiting, and altered mental status is rather more
precise.8,16,20 Even with this, due to the rarity of
the condition, the diagnosis is often delayed if not missed. Therefore,
physicians need to have a high index of suspicion in patients who have
history of COM.
Investigation : Radio-imaging using CT scan or MRI is required
to confirm the diagnosis. In the early stages of the disease however, CT
scan can be normal in 63% of the cases.8 As MRI can
identify intracranial edema better than CT scan, it is more preferable
to use MRI for earlier diagnosis of intracranial
complication.6 Similarly MRI is better in recognizing
the extension of the empyema into the interhemispheric fissure and the
posterior fossa.14 Hence, in suspected cases of
intracranial subdural empyema for accurate diagnosis MRI is the gold
standard with a sensitivity of 93%.8,12 Laboratory
analysis of blood shows elevated WBC, ESR, and C-reactive
protein.6 Culture and sensitivity of intraoperative
pus should be done, even though often empyema is sterile and has no
yield in 50% of the cases.6,8,16 It was similar in
our case. This is due to the administration of antibiotics before the
diagnosis is made.
Management : The mainstay treatment of subdural empyema includes
the use of antibiotics and surgical evacuation of the pus. There should
be immediate initiation of broad spectrum antibiotics. A combination of
oxacillin/nafcillin, a third-generation cephalosporin and metronidazole
covers the most common pathogens. Due to the increasing presence of
penicillin resistant Streptococcus pneumoniae andStaphylococcus aureus the use of vancomycin instead of oxacillin
is preferred.6,8,15,16,21 This was done in our case
and the outcome was satisfactory. Most recommend a minimum 2 weeks of IV
antibiotics while others suggest continuation for 6 weeks. In our case,
the two weeks of IV antibiotics were found to be adequate. But almost
all agree that IV antibiotics must be followed by 6 weeks of oral
antibiotics.6,8,15,22
Surgical drainage of the subdural pus is the next crucial step following
the initiation of antibiotics. The surgical procedure can either be
craniotomy or burr whole. Craniotomy is preferred as it allows adequate
exploration; complete removal of pus, loculations, and the possible
calcifications on the abscess wall, and effective decompression of
increased intracranial pressure.8,11,14,16 Moreover,
recurrence of subdural empyema is more common in Burr hole (almost 40%)
as compared to craniotomy.15,16,20 However, in the
weak patients or those in septic shock or when the empyema is
parafalcine, Burr hole is the preferred procedure. The surgical
intervention should be done as soon as possible, since any delay results
in worsening of outcome. Disability reaches as high as 70% in those who
were operated after 72 hours of presentation as compared to the 10% in
those who were operated within 72 hours.11,15,17
Administration of prophylactic anticonvulsants is advised as seizures
occur in 32% to 44% of patients with subdural
empyema.15,16,20 Moreover mannitol should be given
preoperatively and postoperatively to reduce the increased intracranial
pressure.6,15,21 After the patient stabilizes the
chronic otitis media and mastoiditis should be properly treated by the
ENT specialists.3,6,10 Similarly our patient was later
on transferred to the ENT department where her chronic otitis media was
properly addressed.
Factors such as age of the patient, delay in presentation, extent of the
sepsis, and the subdural empyema along with level of consciousness at
presentation significantly affect the outcome of the
patient.16 Morbidities such as sensorineural hearing
loss, residual neurological deficits including seizures and hemiparesis
are seen in about 28% of the survivors.3,11 Therefore
to achieve good results early diagnosis, immediate surgical
intervention, and appropriate antibiotic therapy are of paramount
importance.