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

http://www.gen.umn.edu/courses/1135/lab/reflexlab/corticospinaltract.htmlhttp://www.gen.umn.edu/courses/1135/lab/reflexlab/corticospinaltract.html

http://medicine.ucsd.edu/clinicalmed/neuro3.htmhttp://medicine.ucsd.edu/clinicalmed/neuro3.htm

BABINSKIBABINSKI

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://www.neuro.wustl.edu/neuromuscular/pathol/nervenl.htmhttp://fulton.edzone.net/cites/winkler-science/team1/chap8.html

Compound Action Potential, CAP

http://www.unmc.edu/Physiology/Mann/mann12.html

Stim

ulus

Str

engt

h

CAP: Conduction Velocity

Haines, Fundamental Neuroscience, Elsevier, Fig 3-11

• Conduction velocities: ~0.2m/s to >100m/s• Give indication on health of nerve fiber• Demyelination decreases velocity

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

Mallik, A et al. J Neurol Neurosurg Psychiatry 2005;76:ii23-31ii

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.

SNAP: Sensory Nerve Action Potential

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.

• MuscleMuscle

• NerveNerve

• RootRoot

• Spinal CordSpinal Cord

• BrainstemBrainstem

• BrainBrain

How do I approach a patient with muscle weakness?

What is your Dx.?