NEUROLOGY
STROKES
(i)
Hypertension causing strokes/Haemorrhage
is questionable as according to MRC trials, 1423 hypertensive patients if treated, 1 stroke is prevented. Also it is now considered inadvisable to reduce the high BP in an acute stroke as this may reduce the cerebral
perfusion. The high BP is probably a beneficial autonomic response.
(ii)
After occlusion of cerebral
Artery, anastomotic channels open up and cerebral O2 extraction is increased. Therefore
there may be no infarction. Infarction is worsened by acidic tissue pH by anaerobic
production of lactic acid. If Ischemic
damage has occurred to the capillary endothelium then restoration of circulation by lysis of the embolus (either natural or
by thrombolysis as in AMI) causes haemorrhage through the endothelium(causing reperfusion injuries). Hence in stroke in evolution, no anticoagulation with Heparin, etc is of any proven value.
(iii)
In stroke due to thrombosis/ICH
75% patients survive and 80% recovery of function is a rule within 3 months.
(iv)
In subarrachnoid Haemorrhage,
50% die immediately and rest get a recurrence within 6 months.
COMA
occurs
when the insult to the brain affects the cerebrum and Reticulo Activating system sparing the vital brain stem thus preserving
respiratory and cardiovascular centres and functions.
Metabolism
of the tissues, muscle and brain is reduced to bare minimum placing a very small demand on the failed organs.
Reduced
Lactic Acid production from muscles along with increased Renal blood flow due to the supine position aid in shifting the pH
to the higher side which is clearly beneficial for recovery of neuronal tissue.
Increased
venons return helps in maintaining adequate cardiac output.
Swallowing
reflexes depend on Brain stem which is usually spared in comas which can be otherwise reversed in Hospital. Usually Brain
stem reflexes are preserved allowing reflex swallowing of liquids.
Coma
usually wavers in depth from stupor to deep coma depending on cerebral oedema, increased Intracranial tension, hydration,
BP, Blood volume, etc. Whenever coma depth decreases, the Brain stem reflexes
increase and swallowing reflexes are enhanced permitting a bypass from expertise dependent RT feeding and Parenteral fluid
& electrolyte balance.
PARKINSON’S DISEASE
The
fine tremor occurs only at rest and does not interfere with movement.
The
rigidity when combined with tremor causes a jerky movement in addition.
Akinesia
or slowing of movement occurs. The disease is very slowly progressive with a
usual course of 10-15 years.
Treatment
with Levodopa should only be started if there is significant disability. Side effects are plenty like vomiting, confusion
and hallucinations.
Fluctuations
in the response to treatment causes improvement alternating with severe immobility (freezing and falling). C
horea
and dystonea start developing at the end of the duration of action of each dose and more and more dosage is required.
And
Levodopa does not alter the natural progression of the disease and hence should not be started unless absolutely necessary.
EPILEPSY
per say is harmless and it is the momentary loss of consciousness which may make activities
such as driving, swimming, sports dangerous.
INCREASED INTRA
CRANIAL TENSION
Deteoriation of conciousness
only comes in as a serious and late consequence of high increased ICT.
Recumbency increases
ICT which is followed by headache & vomiting.
Vomiting serves to
decrease ICT.
The increase in ICT causes compensatory fall in CSF prodn & increase in CSF absorption as well as vasoconstriction
of cerebral Aa causing decrease in intracranial blood volume creating more space.
SUBDURAL HEMATOMA
Small hematomas resolve.
The increased intra cranial tension
itself serves to seal off the bleed.
Cysts form only rarely which
may be chronic.
Asymptomatic Hematomas in the
young respond badly to surgery.
Infection can be dangerous.
General anaesthesia & sedatives
may act adversely causing drowsiness & coma post surgery.
