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Flashcards in principles of clincal neurophysiology Deck (22):
1

instrucments

• We can record from
– Brain - EEG/ECoG/MEG
– Spinal cord - SSEPs/MEP
– Nerves - NCS
– Muscles - EMG
– Retina - ERG
– Optic nerve - VEP
– Brainstem/Cochlea - BSAEPs

2

testing the brain?

The brain is a biological network of
electrical circuits
• It is possible to record individual cortical
neurons
• Usually we measure the effect of all the
positive and negative charges in a
population of axons.

3

eeg

• Electroencephalography EEG
– Recording from the scalp
– Comparing the activity in different parts of the
brain
– Look at synchronicity
– Look at rhythms
– Focal changes

4

ecog

• Electrocorticography
ECoG
– Recording from the
cortex
– Comparing the activity
in very small area of
the brain
– Look for focal lesions

5

meg

Magnetoencephalography (MEG) is a technique for mapping brain activity by recording magnetic fields produced by electrical currents occurring naturally in the brain, using very sensitive magnetometers. Arrays of SQUIDs (superconducting quantum interference devices) are currently the most common magnetometer, and SERF being investigated for future machines. Applications of MEG include basic research into perceptual and cognitive brain processes, localizing regions affected by pathology before surgical removal, determining the function of various parts of the brain, and neurofeedback.

6

pic of spinalcord

A image thumb
7

sematosensory provoked testing

• Testing Dorsal

Column
• Give electrical
impulse to peripheral
nerve
• Record passage up
limb, spine and into
somatosensory cortex

8

motor evoked potential?

Motor evoked potentials (MEP) are recorded from muscles following direct stimulation of exposed motor cortex, or transcranial stimulation of motor cortex, either magnetic or electrical. Transcranial magnetic MEP (TCmMEP) potentially offer clinical diagnostic applications. Transcranial electrical MEP (TCeMEP) has been in widespread use for several years for intraoperative monitoring of pyramidal tract functional integrity.
During the 1990s there were attempts to monitor "motor evoked potentials", including "neurogenic motor evoked potentials" recorded from peripheral nerves, following direct electrical stimulation of the spinal cord. It has become clear that these "motor" potentials were almost entirely elicited by antidromic stimulation of sensory tracts—even when the recording was from muscles (antidromic sensory tract stimulation triggers myogenic responses through synapses at the root entry level). TCMEP, whether electrical or magnetic, is the most practical way to ensure pure motor responses, since stimulation of sensory cortex cannot result in descending impulses beyond the first synapse (synapses cannot be backfired).
TMS-induced MEPs have been used in many experiments in cognitive neuroscience. Because MEP amplitude is correlated with motor excitability, they offer a quantitative way to test the role of various types of intervention on the motor system (pharmacological, behavioral, lesion...) TMS-induced MEPs may thus serve as an index of covert motor preparation or facilitation, e.g., induced by the mirror neuron system when seeing someone's else actions.[23] In addition, MEPs are used as a reference to adjust the intensity of stimulation that need to delivered by TMS when targeting cortical regions whose response might not be as easily measurable, e.g., in the context of TMS-based therapy.

 

• A small electric impulse is given over 
nerve
• The response is measured downstream
over the nerve (if sensory) or muscle (if
motor)

9

erve conduction potential

A image thumb
10

what is nerve conduction studies used for?

• Localisation of nerve damage
• Typing of nerve problem – local/general
– Axonal / demyelinating
• Prognosis

11

cmmon conduction onditions

• Carpal tunnel syndrome
• Ulnar nerve entrapment
• Neuropathies
• Radial nerve entrapment
• Tarsal tunnel syndrome
• Peroneal Foot drop
• Radiculopathies

12

carpel tunnel syndrome?

• Median n compression
• Risks
– Age & Sex
– Obesity
– Occupation
– Most arthritides
– Diabetes
– Hypothyroidism
– Pregnancy

13

eletromyography?

• Uses
– Confirm motor axon loss
– To identify early nerve repair
– To identify myopathy
– To identify muscle inflammation (myositis)

14

what does re-innervation look like?

A image thumb
15

other neurological diseases

• Guillain Barre
Syndrome
• Myasthenia Gravis
• Lambert Eaton
Myasthenic
Syndrome
• MND
• Critical illness
neuropathy/myopathy
• Botulism
• Phrenic palsies
• Myotonic dystrophy
• Brachial plexus
injuries
• Nerve entrapments

16

how to diagnose myasthenia gravis?

• Diagnosis autoantibodies
to the Ach receptor / anti
MuSk antibodies
• Tensilon test (60%) –
edrophonium
• Repetitive NS
• Treated with
pyridostigmine, iv Ig,
longterm
immunosuppression

17

myas gravis trains?

A image thumb
18

lambert eaton?

• Proximal weakness
• Only 15% respiratory
• Improves with brief
exercise!
• 80% have cancer
• Rep Stim results in
increment after
exercise or 50Hz train

19

mnd/polio

• Mixture of upper and lower motor neurone
signs
• Wasting and weakness, with brisk reflexes
• EMG essential - evidence of activity at rest
and reduced recruitment

20

myotnic dystrophy?

• Failure of relaxation of skeletal m
• Improves with exercise
• Due to Na channel disorder
• Some need
NIV

21

reading from ear

 

• BSAEP – clicking noise

A image thumb
22