Subdural hematoma can usually be diagnosed
by CT scanning. Depending on the age of the
bleeding, the contents of the mass between the
dura and the brain may be either hyperdense or
isodense (Figure 4–2). Acute subdural hema-
tomas are hyperdense, with the rare exception of
those occurring in extremely anemic patients and
those in whom CSF has entered the subdural
space, diluting the blood. Although the hema-
toma may become isodense with brain after 2 to
3 weeks, it may still contain areas of hyperdense
fresh blood, assisting with the diagnosis. How-
ever, if the entire mass is isodense and contrast
is not given, the subdural hematoma may be
Figure 4–2. A series of magnetic resonance imaging scans through the brain of Patient 4–1 demonstrating bilateral
subdural hematomas and their evolution over time. In the initial scan from 6/19/02 (A, B), there is an isodense subdural
hematoma of 11.5 mm thickness on the right (left side of image) and 8 mm thickness on the left. The patient was treated
conservatively with oral prednisone, and by the time of the second scan 1 month later (C, D), the subdural hematomas
were smaller and hypodense and the underlying brain was less edematous. By the end of the second month (E, F), the
subdural hematomas had been almost completely resorbed.
Specific Causes of Structural Coma
125
difficult to distinguish from brain tissue, partic-
ularly if the hematomas are bilaterally symmet-
ric and do not cause the brain to shift. The lack
of definable sulci in the area of the hematoma
and a ‘‘supraphysiologic’’-appearing brain in an
elderly individual (i.e., a brain that lacks atro-
phy and deep sulci, usually seen with aging) are
clues to the presence of bilateral isodense sub-
dural hematomas. Chronic subdurals may be-
come hypodense. A CT scan with contrast clearly
defines the hematoma as the membranes, with a
luxuriant, leaky vascular supply, enhance pro-
fusely. MRI scanning can also define the hema-
toma, but the density is a complex function of
the sequence used and age of the hemorrhage.
Lumbar puncture is potentially dangerous
in a patient with a subdural hematoma. If the
brain is balanced on the edge of herniation, the
sudden relief of subarachnoid pressure from
below may further enhance the pressure cone
and lead to frank herniation. In such patients,
the CSF pressure may be low, due to the block-
age at the foramen magnum, leading to a false
sense of security. Hence, all patients who have
an impaired level of consciousness require an
imaging study of the brain prior to lumbar pun-
cture, even if meningitis is a consideration.
33
This issue is discussed further in the section on
meningitis on page 133.
The treatment of subdural hematomas has
traditionally been surgical.
34
Three surgical pro-
cedures, twist drill drainage, burr hole drainage,
and craniotomy with excision of membranes,
are used.
34,35
The procedure chosen depends
on whether the subdural hematoma has de-
veloped membranes, requiring more extensive
drainage, or is complex and compartmentalized,
requiring excision of the membranes. The out-
come of treatment varies in different series and
probably reflects differences in the patient pop-
ulation.
34
Although there have been no randomized
clinical trials of medical treatment of subdural
hematomas, many patients who have modest-
sized subdural hematomas with minimal symp-
toms (typically only a headache) and consider-
able ventricular and cisternal space, so there is
no danger of herniation, can be treated conser-
vatively with corticosteroids for several months
until the hematoma resorbs.
31,36
However, sub-
dural hematomas have a tendency to recur after
both medical and surgical therapy, and patients
must be followed carefully for the first several
months after apparently successful treatment.
Patient 4–1
A 73-year-old professor of art history developed
chronic bifrontal, dull headache. He had no his-
tory of head trauma, but was taking 81 mg of as-
pirin daily for cardiovascular prophylaxis. He felt
mentally dulled, but his neurologic examination
was normal. CT scan of the brain disclosed bilat-
eral chronic (low density) subdural hematomas of
8 mm depth on the left and 11.5 mm on the right.
He was started on 20 mg/day of prednisone with
immediate resolution of the headaches, and over
a period of 2 months serial CT scans showed that
the hematoma resolved spontaneously (see Figure
4–2). Repeat scan 3 months later showed no re-
currence.
Epidural Abscess/Empyema
In developing countries, epidural infections are
a feared complication of mastoid or sinus in-
fection.
37
In developed countries, neurosurgi-
cal procedures,
38
particularly second or third
craniotomies in the same area, and trauma are
more likely causes.
39
Sinusitis and otitis, if in-
adequately treated, may extend into the epidu-
ral space, either along the base of the temporal
lobe or along the surface of the frontal lobe.
The causative organisms are usually aerobic and
anaerobic streptococci if the lesion originates
from the ear or the sinuses, and Staphylococ-
cus aureus if from trauma or surgery. The pa-
tient typically has local pain and fever. Vomiting
is common
37
; focal skull tenderness and me-
ningism suggest infection rather than hemor-
rhage. The pathophysiology of impairment of
consciousness is similar to that of an epidural
hematoma, except that epidural empyema typ-
ically has a much slower course and is not asso-
ciated with acute trauma. CT scan is character-
ized by a crescentic or lentiform mass between
the skull and the brain with an enhanced rim.
Diffusion is restricted on diffusion-weighted
MRI, distinguishing it from hematomas or effu-
sions where diffusion is normal or increased.
40,41
Antibiotics and surgical drainage are effective
treatments.
38
The causal organisms can usually
be cultured to allow appropriate selection of
antibiotics. Some children whose epidural ab-
scess originates from the sinuses can be treated
126
Plum and Posner’s Diagnosis of Stupor and Coma