Page 895 - Textbook of Pathology, 6th Edition

B. Intracranial haemorrhage: 879
a) Haemorrhage in the brain parenchyma (intracerebral
haemorrhage)
b) Haemorrhage in the subarachnoid space (subarachnoid
haemorrhage).
The stroke syndrome is the cardinal feature of cere-
brovascular disease. The term stroke is used for sudden and
dramatic development of focal neurologic deficit, varying
from trivial neurologic disorder to hemiplegia and coma.
Other less common effects of vascular disease include:
transient ischaemic attacks (TIA), vascular headache (e.g. in
migraine, hypertension and arteritis), local pressure of an
aneurysm and increased intracranial pressure (e.g. in
hypertensive encephalopathy and venous thrombosis).
A few important forms are discussed below.

A. ISCHAEMIC BRAIN DAMAGE
Figure 30.6 Neurocysticercosis. The sliced surface of the cerebral Ischaemic necrosis in the brain results from ischaemia caused
hemisphere of the brain shows may tiny whitish nodules and cysts about by considerable reduction or complete interruption of blood
1 cm in diameter.
supply to neural tissue which is insufficient to meet its
Grossly, the changes are too rapid to become noticeable metabolic needs. The brain requires sufficient quantities of
but brain atrophy may be seen in long-standing cases. oxygen and glucose so as to sustain its aerobic metabolism,
Microscopically, the hallmark is spongiform change i.e. mainly by citric acid (Krebs’) cycle which requires oxygen.
there are small round vacuoles in the neuronal cells. These Moreover, neural tissue has limited stores of energy reserves
changes are predominantly seen in the cortex and other so that cessation of continuous supply of oxygen and glucose
grey matter areas. Spongiform changes result in neuronal for more than 3-4 minutes results in permanent damage to CHAPTER 30
loss and glial cell proliferation but significantly without neurons and neuroglial cells.
any inflammation or white matter involvement.
Deprivation of oxygen (anoxia) to the brain may occur in
4 different ways:
Fungal and Protozoal Encephalitis
1. Anoxic anoxia, in which there is low inspired pO .
2
Mycotic diseases of the CNS usually develop by blood stream 2. Anaemic anoxia, in which the oxygen-carrying haemo-
from systemic deep mycoses elsewhere in the body. They globin is reduced.
are particularly more common in immunosuppressed 3. Histotoxic anoxia, in which there is direct toxic injury as
individuals such as in AIDS, patients of lymphomas and occurs in cyanide poisoning.
other cancers. Some of the fungi which may disseminate to 4. Stagnant (ischaemia) anoxia, in which the damage is caused The Nervous System
the CNS are Candida albicans, Mucor, Aspergillus fumigatus, by cessation of blood with resultant local accumulation of
Cryptococcus neoformans, Histoplasma capsulatum and metabolites and changes in pH.
Blastomyces dermatitidis. These fungal infections may produce
one of the three patterns: fungal chronic meningitis, vasculitis In all these different forms of anoxia, the end-result is
and encephalitis. ischaemic brain damage which may have one of the following
Besides fungal infections, CNS may be involved in two patterns:
protozoal diseases such as in malaria, toxoplasmosis, 1. Global hypoxic-ischaemic encephalopathy, resulting from
amoebiasis, trypanosomiasis and cysticerosis (Fig. 30.6). generalised cerebral hypoperfusion.
2. Cerebral infarction, resulting from severe localised
CEREBROVASCULAR DISEASES reduction or cessation of blood supply.

Cerebrovascular diseases are all those diseases in which one Global Hypoxic-Ischaemic Encephalopathy
or more of the blood vessels of the brain are involved in the
pathologic processes. Various pathologic processes commonly The brain receives 20% of cardiac output for maintaining its
implicated in cerebrovascular diseases are: thrombosis, vital aerobic metabolism. A number of factors determine the
embolism, rupture of a vessel, hypoxia, hypertensive maximum length of time the CNS can survive irreversible
arteriolosclerosis, atherosclerosis, arteritis, trauma, aneurysm ischaemic damage. These are as under:
and developmental malformations. These processes can result i) Severity of the hypoxic episode.
in 2 main types of parenchymal diseases of the brain: ii) Presence of pre-existing cerebrovascular disease.
iii) Age of the patient.
A. Ischaemic brain damage: iv) Body temperature.
a) Generalised reduction in blood flow resulting in global In normal individuals, the brain continues to be perfused
hypoxic-ischaemic encephalopathy adequately up to systolic arterial pressure of 50 mmHg by
b) Local vascular obstruction causing infarcts. an auto-regulatory vascular control mechanism. However,