2.1 Neurophysiology Diagnostics Flashcards
Electrodes in EEG are connected from the head to the recording system, which are attached to the scalp according to a standardized system of electrode placement
Ten Twenty Placement
Where does the electrical signals come from?
Pyramidal cells of cerebral cortex
What type of EEG has standard 30 minute recording of awake and sleep EEG activity that can extend to 24 hrs recording video?
Surface/ scalp EEG
An EEG can determine changes in brain activity that may be useful in diagnosing brain disorders like:
Epilepsy or other seizure disorder Brain tumor Head injury Brain dysfunction Brain death in a persistent coma
Procedure: Pt will be ask not to sleep at night before the procedure or to stay up late or wake up early
Sleep deprivation test
Occurs often during sleep and are seizures originating in front of the brain that produces unusual symptoms that appear to be related to psychiatric problem or sleep disorder
Frontal lobe seizure
3Ps of frontal lobe seizure:
Pedaling motion
Pelvic thrusting
Profanity screams
How do you distinguished the left brain from right brain in an EEG?
RELO
Right side Even numbers
Left side Odd numbers
A test that detects electrical activity in the brain using small discs attached to the scalp.
Electroencephalography (EEG)
Different EEG activation procedures
S- leep deprivation H- yperventilation E- ye opening/ E-ye closure P- hotic stimulation S- ensory stimuli
Characteristics of normal sleep EEG
P- POST
S- Spindle
V- Vertex wave
Commonly seen on EEG and have been said to be more common during daytime naps than nocturnal sleep. Commonly seen in adolescents and middle aged adults
Positive Occipital Sharp Transient of Sleep
Powerful strobe of light is placed about 15 in from pt’s eyes and fleshed at frequencies of 1 to 20 per sec with the pt’s eyes open and close
Photic stimulation
Common procedure used in the EEG lab in children and adults using strobe of flashing lights at different frequencies to detect abnormal epileptogenic sensitivity to flickering light
Intermittent photic stimulation (IPS)
Patient is asked to breathe in and out deeply and rapidly 20x for 3 to 5 minutes
Hyperventilation
Considered most specific and sensitive test confirming a diagnosis of absence seizures
Generalized spike and wave pattern
Hyperventilation brings out seizures called
Staring spells or abscence
The pt is instructed to open and close his eyes. Then determine whether there are certain responses during closure or opening of the eye
Eye opening/ eye closure
Closing of the eyes indicate:
Opening of the eyes indicate:
Closed: negative wave deflection
Open: positive wave deflection
During EEG, the pt is instructed to raise his hands during the procedure or the pt is instructed to close and open his fists
Sensory stimuli
Abnormal EEG pattern seen in sensory stimuli
Spike and polyspike wave pattern or sharp transient of waves
Is used to evaluate the function esp. the ability of electrical conduction of the motor and sensory nerve. It also determine nerve damage and destruction
Nerve conduction studies (NCS)
How many electrodes are placed on the skin over the nerve in NCS
2; 1 electrode stimulates the nerve with a very mild electrical impulse and the second electrode records it
Is calculated by measuring the distance between electrodes and the time it takes for electrical impulses to travel between electrodes in NCS
Nerve conduction velocity
Usual nerves tested in NCS all have motor and sensory function except
Sural nerve (only sensory)
Develops after injury to axon and myelin, as in transection of the nerve. Muscle atrophy is seen
Wallerian degeneration
Develops after damage to the myelin sheath or schwann cell. Muscle is not denervated therefore no atrophy develops, with poor nerve conduction velocity
Segmental demyelination
Develops when damage to cell body of the neuron results in distal dying of the axon and subsequent loss of myelin. Muscle is denervated, muscle atrophy develops
Neuronal (axonal) degeneration
Follow segmental demyelination
Segmental remyelination
Associated with formation of clusters of small and thin myelinated fibers
Axonal regeneration
Decrease amplitude of CMAP/ SNAP and normal conduction velocity
Axonal nerve damage
Normal amplitude and slower conduction velocity
Demyelinating nerve damage
Result of damage to a single nerve or nerve group by trauma, injury, local compression, prolonged pressure or inflammation
Mononeuropathy
Damage to multiple nerves in roughly the same areas on both sides of the body. E.g is GBS
Poly neuropathy
Used in the presence of unexplained weakness based on the defect of neuromuscular transmission (sarcolemmal membrane or nerve terminal abnormality). CMAPs are recorded during repetitive stimulation of motor nerve.
Repetitive nerve stimulation
10% decremental response confirms:
Myasthenia gravis
10% incremental response after exercise confirms:
Lambert Eaton Syndrome
Usually performed in pts with bell’s palsy
Facial nerve or blink reflex
Assess the health of muscles and nerve cells that control them. Motor neurons transmit electrical signals that cause muscles to contract. Contraction can be recorded by needle electrodes
Electromyography
Four things to remember about EMG:
ISMR I: insertional activity S: spontaneous activity M: motor unit action potentials R:recruitment
_________ insertional activity is seen in denervated muscle or muscle that is being reinnervated
Increased
_______ of insertion activity found after prolonged denervation when muscle fibers have been replaced by connective tissue with fibrosis
Reduced
To view waveforms and to listen to muscular activity use an:
Ocsilloscope
EMG: ISMR I: increased S: fibrillation positive wave M: large unit limited recruitment R: reduced fast firing rate
Lower motor neurogenic lesion
Measure the electrophysiologic responses of the nervous system to a variety of stimuli. Study the more proximal segments of sensory pathway
Evoked potential
Electrophysiologic assessment of large fiber sensory pathways of peripheral nerves, spinal cord and brain (AL system and dorsal column).
Used to judge conduction velocity and demyelination in the posterior funiculus or to predict outcome for coma pt
Somatosensory evoked potentials
Used in the assessment of the clinical state of the cochlea, auditory nerve and the middle portion of the brainstem. Has 8 peaks generated on click stimulation
Brainstem auditory evoked potentials
Peaks I-V are clinically useful such as:
I auditory nerve II cochlear nucleus III superior olivary nucleus IV lateral lemniscus V inferior colliculus Others: VI medial geniculate VII thalamocortical connection
Lesions in the upper to middle pons tend to lead to _______ BAEP abnormalities
Ipsilateral
Measures cognitive factors such as attention, memory, language and others. Use in the diagnosis of dementia.
Cognitive event related potentials
Event related potential component elicited in the process of decision making.
P300 wave
____________ = cognitive slowing
Prolonged P300 latency
Test the function of the visual pathway from the retina to the occipital cortex. Most useful for testing optic nerve function
Visual evoked potentials
VEP usually measure the amplitude and latency of:
P100 wave
