principles of clincal neurophysiology

Question 1

instrucments

Answer 1

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

Question 2

testing the brain?

Answer 2

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.

Question 3

eeg

Answer 3

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

Question 4

ecog

Answer 4

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

Question 5

meg

Answer 5

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.

Question 6

pic of spinalcord

Answer 6

Question 7

sematosensory provoked testing

Answer 7

• Testing Dorsal

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

Question 8

motor evoked potential?

Answer 8

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)

Question 9

erve conduction potential

Answer 9

Question 10

what is nerve conduction studies used for?

Answer 10

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

Question 11

cmmon conduction onditions

Answer 11

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

Question 12

carpel tunnel syndrome?

Answer 12

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

Question 13

eletromyography?

Answer 13

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

Question 14

what does re-innervation look like?

Answer 14

Question 15

other neurological diseases

Answer 15

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

Question 16

how to diagnose myasthenia gravis?

Answer 16

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

Question 17

myas gravis trains?

Answer 17

Question 18

lambert eaton?

Answer 18

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

Question 19

mnd/polio

Answer 19

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

Question 20

myotnic dystrophy?

Answer 20

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

Question 21

reading from ear

• BSAEP – clicking noise

Answer 21