Epidural or subdural hematomas, on the other
hand, may develop acutely or subacutely and
can be a diagnostic problem.
Epidural Hematoma
Because the external leaf of the dura mater
forms the periosteum of the inner table of the
skull, the space between the dura and the skull
is a potential space that accumulates blood only
when there has been an injury to the skull itself.
Epidural hematomas typically result from head
trauma with a skull fracture that crosses a groove
in the bone containing a meningeal vessel (see
Figure 4–1). The ruptured vessel may be either
arterial or venous; venous bleeding usually de-
velops slowly and often is self-limiting, having a
course more similar to subdural hematomas,
which are discussed below. On rare occasions,
epidural hematomas may result from bleeding
into skull lesions such as eosinophilic granulo-
ma,
1
metastatic skull or dural tumors,
2
or cra-
niofacial infections such as sinusitis.
3
Arterial bleeding is usually under high pres-
sure with the result that the vessel may not seal
and blood continues to accumulate. Thus, in-
stead of causing symptoms that develop slowly
or wax and wane over days or weeks, a patient
with an epidural hematoma may pass from hav-
ing only a headache to impairment of con-
sciousness and signs of herniation within a few
hours after the initial trauma.
Although epidural hematomas can occur
frontally, occipitally, at the vertex,
4
or even on
the side opposite the side of trauma (contre-
coup),
5
the most common site is in the lateral
temporal area as a result of laceration of the
middle meningeal artery. Trauma sufficient
to cause such a fracture may also fracture the
skull base. For this reason, it is necessary for
the examiner to be alert to signs of basal skull
fracture on examination, such as blood behind
the tympanic membrane or ecchymosis of the
skin behind the ear (Battle’s sign) or around
the eyes (raccoon eyes). The epidural hemor-
rhage pushes the brain medially, and in so do-
ing stretches and tears pain-sensitive menin-
ges and blood vessels at the base of the middle
fossa, causing headache. However, the head-
ache is often attributed to the original head
injury, and unless the lesion causes sufficiently
increased intracranial pressure (ICP) to pro-
duce nausea and vomiting, the condition may
Table 4–1 Examples of Structural Causes of Coma
Compressive Lesions
Destructive Lesions
Cerebral hemispheres
Cerebral hemispheres
Epidural and subdural hematomas, tumors,
and abscesses
Subarachnoid hemorrhages,
infections (meningitis), and tumors
(leptomeningeal neoplasms)*
Intracerebral hemorrhages, infarcts, tumors,
and abscesses
Hypoxia-ischemia
Hypoglycemia
Vasculitis
Encephalitis
Leukoencephalopathy
Prion diseases
Progressive multifocal
leukoencephalopathy
Diencephalon
Diencephalon
Basal ganglia hemorrhages, tumors,
infarcts, and abscesses*
Pituitary tumor
Pineal tumor
Thalamic infarct
Encephalitis
Fatal familial insomnia
Paraneoplastic syndrome
Tumor
Brainstem
Brainstem
Cerebellar tumor
Cerebellar hemorrhage
Cerebellar abscess
Infarct
Hemorrhage
Infection
*Both compressive and destructive.
Specific Causes of Structural Coma
121
not be recognized. Subsequently, the hema-
toma compresses the adjacent temporal lobe
and causes uncal herniation with gradual im-
pairment of consciousness. Early dilation of
the ipsilateral pupil is often seen followed by
complete ophthalmoparesis and then impair-
ment of the opposite third nerve as the herni-
ation progresses.
6
Motor signs often occur late
in such cases.
In many patients the degree of head trauma
is less than one might expect to cause a frac-
ture. In Jamieson and Yelland’s series, for exam-
ple, of 167 patients with epidural hematoma,
nearly one-half had no initial loss of con-
sciousness,
7
and in Gallagher and Browder’s
equally large series, two-thirds of such patients
had an initial injury too mild to command
hospital attention.
8
This is particularly true in
children, one-half of whom have suffered a fall
of less than one-half meter, and many of whom
complained of nonspecific symptoms.
9
Only
15% to 20% of patients had the ‘‘classic’’ his-
tory of traumatic loss of consciousness, fol-
lowed by a lucid interval and then a relapse into
coma (patients who ‘‘talk and die’’).
10
Thus,
even though most epidural hematomas are
identified by computed tomography (CT) scans
performed acutely in emergency departments
on trauma patients by using current evidence-
based decision paradigms,
11,12
the examiner
must remain alert to the possibility of an epi-
dural hematoma that develops or rapidly en-
larges after an apparently negative CT. It is
therefore important to review the CT scan
of trauma patients with attention directed to
whether there is a skull fracture that crosses
the middle meningeal groove. The hematoma
appears as a hyperdense, lens-shaped mass be-
tween the skull and the brain (i.e., the hema-
toma is convex on both surfaces; subdural he-
matomas, by comparison, are concave on the
surface facing the brain; see Figure 4–1). A
vertex hematoma may be missed on a routine
axial CT scan,
13
but a coronal reconstruction
should identify the lesion.
4
A magnetic reso-
nance imaging (MRI) scan is not required for
evaluation of an epidural hematoma, but may
be necessary to evaluate contusions and edema
in the underlying brain. In addition, mass le-
sions outside the brain may cause hyperdensity
Figure 4–1. A pair of computed tomography scans showing an epidural hematoma. The image in (A) shows the lens-
shaped (biconvex), bright mass along the inner surface of the skull. In (B), the skull is imaged with bone windows, showing
a fracture at the white arrow, crossing the middle meningeal groove.
122
Plum and Posner’s Diagnosis of Stupor and Coma