Clinical Neurophysiology Flashcards
What are the main things done in Neurophysiology?
- Nerve conduction studies/Electromyography (EMG)
- EEG
- Evoked potentials
What is nerve conduction studies/Electromyography (EMG)?
To investigate problems of peripheral nerve and muscle
technique for evaluating and recording the electrical activity produced by skeletal muscles
What is an EEG?
Electrical activity within the brain, investigate epilepsy and states of altered consciousness
a test used to find problems related to electrical activity of the brain. An EEG tracks and records brain wave patterns
What are evoked potentials?
Visual and somatosensory, investigate problems in central pathways
What are nerve conduction studies used to examine?
•To examine nerve function:
- Conduction velocity
- Amplitude
record at one point then another and calculate the distance between them and therefore the time taken for the impulse to travel betweent the 2 points in order to see if there is a delay
What are sensory studies?
Similar technique stimulating the sensory nerve fibres in the fingers allows measurement of sensory and motor function separately
What is the site of ulnar neuropathy?
Most often at the elbow
Occasionally at the wrist
What are the effects of ulnar neuropathy?
- Ulnar distribution numbness - Note dorsal cutaneous branch
- Wasting of small muscles, esp FDI
What are we looking for on exmaination?
Conduction block/slowing due to demyelination
Where can the ulnar nerve be stimulated?
multiple points
How can we differentiate between a root and peripheral lesion?
Peripheal nerve lesion you loose both motor and sensory but if you damage it by the spinal cord level you loose the motor axons but the sensory nerve bodies live outside of the spinal cord so the patient cant feel anything but when you test it the sensory response is still normal due to this and this allows use to differentiate between a root lesion and a peripheral lesion
What does neurophysiology allow us to do?
Neurophysiology can investigate nerve function
Combining this with anatomy allows diagnosis of nerve entrapment and guides subsequent surgery
What is Myaesthenia Gravis?
Myasthenia gravis is a rare long-term condition that causes muscle weakness
It most commonly affects the muscles that control the eyes and eyelids, facial expressions, chewing, swallowing and speaking. But it can affect most parts of the body
Antibodies to post-synaptic ACh Receptor
Decrease effectiveness of released ACh and presents with weakness, fatigue, normal sensation
What weakness may be seen in Myaesthenia Gravis?
Weakness may be generalised
Often affects eyes:
- Diplopia
- Ptosis
What is the diagnosis of Myaesthenia Gravis?
Detect Antibodies (takes some weeks, only +ve in 70%)
Neurophysiology:
- Repetitive stimulation
- Single fibre EMG
What is EMG?
Routine EMG looks at action potentials from whole motor units
SF EMG uses filter, sensitivity and timebase settings to isolate the action potentials from individual muscle fibres within one motor unit
How is SF EMG useful?
Needle can be positioned to record from two fibres within the same motor unit
Normally little variation in time of firing between two such fibres
In NM junction disease, how does the tight relationship between fibres change?
In NM junction disease that tight relationship between the two is lost
Result is “jitter”.
Why is the tight relationship lost resulting in a jitter?
Basic physiology:
- EPSP
- Threshold
- AP firing
ACh causes EPSP until it reaches threshold then an AP is fired but if you begin to block some post synaptic potentials then decrease of amplitude. Slight variation in threshold potential greatly effects firing in time and begins to become more random and jumps around
Only get weakness when EPSP is to weak to even reach threshold and don’t get any second one firing at all and then get a clinical weakness
Neurophysiology can investigate the function of the ________________
Hence can diagnose conditions such as ________, ________ and guide medical treatment
Neurophysiology can investigate the function of the neuromuscular junction
Hence can diagnose conditions such as myaesthenia, botulism and guide medical treatment
What do EEGs do?
Assess brain function
Recording electrical activity generated by cortical neurons across multiple points on the scalp
What can we see on a EEG?
- Epileptic Activity
- States of consciousness - Sleep, stages of sleep
- Encephalopathy
EEGs look at brain function to allow the diagnosis of what?
- Epilepsy
- Altered states of consciousness
- Non-epileptic attacks
- Facilitate medical or surgical treatment for epilepsy
