II. LESIONS IN MENINGES AND VENTRICULAR SYSTEM
A. Epidural Hemorrhage
- 1. Epidural hemorrhage results in most cases from tearing of
the middle meningeal artery (less often may occur from tearing of
other vascular branches or venous sinuses). This event is usually associated
with skull fracture, often of the temporal bone
- 2. Epidural hemorrhage is a rapidly expanding space occupying
lesion and death may occur 2-12 hours after injury (bleeding is slower
if the middle meningeal artery is not involved). The hematoma often causes
uncal herniation and/or downward displacement of brainstem structures.
- 3. The classical clinical picture involves initial unconsciousness
due to concussion, a lucid interval (seconds to hours) and progression
to coma. However, the lucid interval does not occur in many cases and patients
remian unconsious from the time of injury. Symptoms may include focal signs
and/or indications of increased intracranial pressure.
- 4. Pathological examination shows a fresh epidural clot at autopsy.
B. Subdural Hemorrhage
- 1. Blood accumulates between the dura and arachnoid as a result
of shearing of bridging veins. Subdural hemorrhage is often associated
with blunt trauma without skull fracture and results from rotation of brain.
- 2. The rate of progression is variable - subdural hemorrhage
may be classified as acute or chronic and (and sometimes subacute) depending
on the rate of accumulation of blood and thus rate of progression of symptoms.
Acute and chronic conditions will be discussed separately.
- 3. Acute subdural hemorrhage is associated with obvious
trauma and is usually accompanied by contusion and cerebral artery tearing
(leading to subarachnoid hemorrhage and bloody CSF). Symptoms develop within
a few days (the onset of symptoms is slower than for epidural hemorrhage).
The hemorrhage acts as a space-occupying lesion and symptoms may be focal
and/or those of increased intracranial pressure. Consequences depend on
the rapidity of surgical drainage and severity of concomitant damage to
|| This coronal section illustrates compression of one cerebral hemisphere
by an acute subdural hemmorage.|
4. Chronic subdural hemorrhage is common in infants, the
elderly, alcoholics, epileptics and demented individuals. Contributing
factors include frequent head trauma and an enlarged subdural space (due
to cerebral atrophy), providing less support for veins traversing this
space. Chronic subdural hemorrhage follows mild trauma (sometimes forgotten
by the patient) and symptoms may not occur for weeks to months after the
trauma due to the slow rate of blood accumulation. Symptoms include seizures,
headaches, confusion, behavioral changes, and signs of increased intracranial
pressure; neurological signs may mimic those of degenerative disorders
or neoplasms. CSF may or may not show evidence of concomitant old subarachnoid
hemorrhage or of reactive meningitis. Among diagnostic tests, CT scan or
MRI is the most useful.
- 5. Pathology. For chronic subdural hematoma, the hematoma
is encapsulated after several weeks, by a pseudomembrane composed of granulation
tissue derived from the inflammatory reaction in the dura. The membrane
forms initially at the clot surface facing the dura and is called the outer
membrane. It extends around the clot to the surface facing the arachnoid,
to form the thinner inner membrane. Subsequent episodes of rebleeding may
occur, expanding the mass, followed by reorganization with a decrease in
size. (Waxing and waning of neurological signs may correspond to the changes
in hematoma size).
C. Subarachnoid Hemorrhage
- Accumulation of blood in the subarachnoid space to a greater or lesser
degree is a consistent accompaniment of cerebral contusions. Upon lumbar
puncture, grossly bloody CSF may be detected. In some cases in which a
medium-sized superficial vessel is torn, subarachnoid hemorrhage may be
the direct cause of symptoms; in most cases, bleeding arises from small
vessels and is part of the surface bruising associated with fracture of
the skull. Hydrocephalus may result if the subarachnoid bleeding or subsequent
fibrosis obstructs CSF flow in the subarachnoid space.