| • The arrows show a poorly defined reddish-brown lesion
of the cerebellum.
• The center is granular and contains fragmenting tissue. |
| • The arrows show a poorly defined reddish-brown lesion
of the cerebellum.
• The center is granular and contains fragmenting tissue. |
| Abscess |
| Etiology |
•An abscess arises from septic emboli or direct exposure
of the brain to outside organisms through head trauma
or erosion of an infection through the bone as in
sinusitis and mastoiditis. •Both bacteria and fungi can cause abscesses. |
| Pathogenesis |
•In parenchymal abscesses, an area of microvascular
damage due to a septic embolus causes a small area of
necrosis due to the influx of neutrophils and bacteria
or fungi into the area. •The surrounding tissue begins
to form inflammatory granulation tissue about the
area of necrosis in a few days. •Within a week or two
if the necrotic area does not spread a collagenous
capsule infiltrated by neutrophils, lymphocytes, plasma
cells and macrophages surrounds the necrotic center
with an astrocytic border and chronic inflammation.
•This is one of the two lesions in the brain that is surrounded by connective tissue, most brain lesions are surrounded by astrocytic fibers only. |
| Epidemiology |
•Brain abscesses are seen most often in patients who have
lung abcesses or bronchiectasis, head trauma or, less
often, with sinusitis or mastoiditis. •Abscesses are seen
also in patients with bacterial endocarditis or intracardiac shunts. •It is the second most common intracranial
infection and can occur in the epidural and subdural
space or intraparenchymally. •Abscesses can be seen at all ages. |
| Clinical |
•The intraparenchymal, subdural, or epidural abscess
acts as a mass lesion and can cause cerebral edema and
herniation, along with neurological signs such as a
hemiparesis, seizures, or other signs depending on
where it is localized. •Herniation can lead to death as can rupture of the abcess into ventricles and meninges. |
| General Gross Description |
•Early on the abscess appears as an area of necrosis which
is relatively circumscribed. •As time goes by, if the abscess does not spread producing a larger area of necrosis, it is surrounded by a firm capsule. This can rupture and cause a spreading cerebritis or rupture into a ventricle producing ventriculitis or meningitis. |
| General Micro Description |
•Microscopically, the abscess has a center full of
necrotic debris, neutrophils, macrophages and organisms. •The second layer about this is made up of proliferating
fibroblasts and capillaries with a more chronic
inflammatory reaction. •The third layer is of reactive astrocytes with plump pink cytoplasm as well as chronic inflammatory cells such as lymphocytes and plasma cells. |
| Reference |
• Poirer J et.al. Manual of basic neuropathology. Philadelphia: Saunders, 1990, pp. 105. • Cotran RS, Kumar V, Robbins SL: Robbins Pathologic Basis of Disease. 5th ed. Philadelphia, W.B. Saunders, 1994, pp. 1316-1317.
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