Why studying neurosciences?
• Neurological symptoms account for high % of
consultation in general practice.
• Accounts for 20% of acute admissions to
hospitals, trauma, critical illness, anesthesia &
surgery.
• Dx. is primarily clinical, based on history and
physical exam.
• Any investigations can only supplement but
never replace the process of clinical
assessment.
The brain
• The brain weighs 2 % of body weight.
• The brain utilizes 20% of total energy expenditure.
•
It contains about 100 billion neurons.
• Each neuron has about 10000 (200 – 200000) input.
• Single output (axon)
• brain is one of the most complex systems
The brain
Dinosaur
1600 KgBW,
0.07 Kg brain weight
0.004%
Human
70KgBW,
1.4Kg Brain weight
2%
The Symptomatology of a
nervous disease
1. Negative symptoms;
• Lesion to a center in the CNS may diminish or abolish
the function of that center.
2. Positive symptoms; Produced by;
•
Centers are liberated from the control of a damaged
center.
• or their activities intensified to compensate for the
missing function
• or because of unbalanced activities.
The Symptomatology of a
nervous disease
1. Negative symptoms;
paralysis blindness, deafness….
2. Positive symptoms;
epileptic focus, spasticity, Babinski sign,
rigidity, parasthesia and ataxia.
Babiniski Reflex
BABINSKI
http://medicine.ucsd.edu/clinicalmed/neuro3.htm
http://www.gen.umn.edu/courses/1135/lab/reflexlab/corticospinaltract.html
Dx. Of Neurological Diseases
1. Anatomical factors; It determines signs,
symptoms and localization of the lesion.
2. Non-anatomical factors; It helps to
determine the etiology of the disease.
Non – Anatomical factors
include;
1. The speed of development of signs and
symptoms (Acute, subacute or chronic)
2. The course of the signs and symptoms;
(progressive, fluctuating)
3. The outcome.
The disturbance of function
involves first;
1. The most recently acquired task.
e.g. native language versus acquired
language.
1. The most complex features.
e.g. writing, speaking, playing musical
instruments versus grasp reflex.
Signals within the CNS
Action potential
Electrotonic potential
http://fulton.edzone.net/cites/winkler-science/team1/chap8.html
http://www.neuro.wustl.edu/neuromuscular/pathol/nervenl.htm
Stimulus Strength
Compound Action Potential,
CAP
http://www.unmc.edu/Physiology/Mann/mann12.html
CAP: Conduction Velocity
• Conduction velocities: ~0.2m/s to >100m/s
• Give indication on health of nerve fiber
• Demyelination decreases velocity
Haines, Fundamental Neuroscience, Elsevier, Fig 3-11
Electroneurography(ENG(
Definition:
• ENG is the measurement of the speed of
conduction of impulses down a peripheral
nerve.
also known as
• nerve conduction studies (NCS(
• nerve conduction velocity (NCV(
EMG machine
Compound Motor Action Potential:
CMAP
Motor nerve is stimulated and muscle response is calculated. Latency
includes synaptic transmission etc. By subtracting the two latencies, the
conduction velocity can be calculated.
http://www.mmi.mcgill.ca/Dev/chalk/lect72p2.htm
SNAP:
Sensory Nerve Action Potential
Figure 2 Median orthodromic sensory study. The index finger digital nerves are stimulated
via ring electrodes and the response recorded over the median nerve at the wrist.
Mallik, A et al. J Neurol Neurosurg Psychiatry 2005;76:ii23-31ii
NCV disorders
• Demyelination is indicated if conduction
velocities have fallen below 50 % of
normal .
• Even significant loss of axons commonly
reduces conduction velocities by only
about 30 %based on a loss of the fastest
conducting fibers.
How do I approach a patient with
muscle weakness?
• Muscle
• Nerve
• Root
• Spinal Cord
• Brainstem
• Brain
What is your Dx.?