ASET Q&A Flashcard Study System for EEG Card Set 1 4th edition

The meninges are the outer coverings of what structures?

Brain and SC

Name the three meninges starting with the outermost layer.

1) Dura mater-outermost layer, strongest and thickest
2) Arachnoid mater-middle layer, thin membrane encloses the subarachnoid space
3)Pia mater-innermost layer, follows contour of cortex, composed of 2 layers; highly vascular and sheaths blood vessels as they enter the brain

What is the cerebrospinal fluid (CSF) filled space between the arachnoid mater and pia mater?

subarachnoid space

Where is the primary motor cortex (Brodmann's area 4) located in the brain?

The primary motor cortex (Brodmann's area) is the precentral gyrus in the frontal lobe. This gyrus is directly anterior to the central sulcus (Rolandic fissure); it is the cortical area from which movements are most easily elicited and the source of about a third of the corticospinal tract

Where is the motor speech area (Broca's area) located in the brain?

The motor speech area (Broca's area) is located in the inferior frontal gyrus in the frontal lobe in the dominant hemisphere (usually the left hemisphere)

Where is the primary somatosensory cortex located in the brain?

This is the postcentral gyrus of the parietal lobe. This gyrus is directly posterior to the central sulcus (Rolandic fissure)

Where is the receptive speech area (Wernicke's area) located in the brain?

The receptive speech area (Wernicke's area) is located in the supramarginal and angular gyri of the parietal lobe, also includes adjoining regions of the temporal and occipital lobes, in the dominant hemisphere (usually left hemisphere)

What does the corpus callosum connect?

right and left cerebral hemispheres

Name the main structures that compose the brainstem.

The brainstem contains nuclei for most of the cranial nerves and connects critical pathways in the brain and spinal cord to the entire body. It is subdivided into the:
1)Medulla
2)Pons
3)Midbrain

The central sulcus is the boundary between what 2 lobes?

The central sulcus (Rolandic fissure) is the boundary between the frontal and parietal lobes, and the transition zone between primary motor and primary somatosensory cortex

The basal ganglia is composed of __.

a group of subcortical nuclei, most prominently including the putamen, globus pallidus, and caudate nucleus

Where is the primary visual cortex (Brodmann's area 17) located?

calcarine sulcus

What artery supplies blood to the anterior and middle cerebral arteries?

internal carotid artery

What large vessel is formed by the union of the two vertebral arteries?

basilar artery

What large arteries are formed by the bifurcation of the common carotid artery?

external carotid artery and internal carotid artery

What arteries account for most of the blood supply to the brain?

The two internal carotids account for 85% of cerebral blood flow and thus supply most of the blood to the brain

The middle cerebral artery supplies what areas of the brain?

the insula, most of the lateral surface of the cerebral hemisphere, and the anterior tip of the temporal lobe

The anterior cerebral artery supplies to what areas of the brain?

the frontal lobes and the medial aspects of the parietal and occipital lobes

The posterior cerebral artery supplies what areas of the brain?

the rostral midbrain, posterior thalamus, medial occipital lobe, and inferior and medial surfaces of the temporal lobe

Where does the vertebral artery enter the skull?

Originates at the first branch of the subclavian, runs through foramina in cervical vertebrae C6, enters the base of the skull through the foramen magnum, and ascends along the medulla

Name the arteries that form the Circle of Willis

Consists of parts of the internal carotid artery, the anterior and posterior cerebral arteries, interconnected by the anterior and posterior communicating arteries

What structure makes collateral circulation to the brain possible due to a vascular anastomosis at the base of the brain?

Circle of Willis

The interventricular foramen is also known as _

the Foramen of Monro

The Aqueduct of Sylvius (aka, cerebral aqueduct) connects what two ventricles?

the third and fourth ventricles

What is the opening between each lateral ventricle and third ventricle?

Foramen of Monro (interventricular foramen)

CSF is mainly produced by what structure?

the choroid plexus in the lateral, third, and fourth ventricles

What 2 openings allow CSF to flow into the subarachnoid space?

the foramina of Luschka and the foramen of Magendie

Where does the absorption of CSF into the blood stream take place?

in the superior sagittal sinus through structures called arachnoid villi

State the pathway for the flow of CSF through the ventricular system starting at the lateral ventricles.

Lateral ventricles, interventricular foramen, third ventricle, cerebral aqueduct, fourth ventricle, lateral and median apertures, subarachnoid space, arachnoid villi, subdural sinuses, venous blood

What is the main function of CSF?

To protect the brain and spinal cord by acting as a shock absorber. CSF is contained in the four ventricles, the subarachnoid space, and the central canal of the spinal cord

Define hydrocephalus

"water on the brain;" occurs when there is an increase of volume of CSF. Due to the closed skull there is no place for CSF to expand, if pressure becomes too high ,the brainstem is forced to try to escape (herniate) through the foramen magnum

Name the 2 types of hydrocephalus

1. Communicating Hydrocephalus-Nonobstructive; occurs with a defect in excretion through the subarachnoid space; most commonly caused by meningitis

2. Non-communicating Hydrocephalus-Obstructive; an obstacle prevents the flow of CSF through the ventricles because of tumor, infection, or congenital malformation

What supporting cells, found only in the ventricles, are responsible for creation and circulation of CSF?

ependymal cells

What are the main functions of the temporal lobe?

primary and association auditory, primary and association olfaction, recent memory, and receptive speech (dominant hemisphere)

What are the main functions of the occipital lobe?

visual functions

What are the main functions of the frontal lobe?

primary and association motor, eye movements, expressive speech (dominant hemisphere), and the processing of intellectual thought and cognitive functions

What are the main functions of the parietal lobe?

primary and association somatosensory (body sensations) and receptive speech (dominant hemisphere)

What are the main functions of the limbic system (limbic lobe)?

evoked emotions responses and higher autonomic control responses like recognizing fear, hunger, libido, and others

What are the main functions of the insula?

primary and association gustatory senses (taste sensations)

What are the main functions of the cerebellum?

critical structure for motor activities of an automatic nature such as walking, talking, balance/posture, coordination

What are the main functions of the diencephalon?

It includes the thalamus (relay station for information on its way to the cerebral cortex) and the hypothalamus (controls the autonomic nervous system and many aspects of drive related behavior)

What ion is found predominantly in intracellular fluid during the resting state of a neuron?

potassium (K)

The chemical structure of a neuron is dependent upon what three major ions?

sodium (Na), potassium (K), and chloride (Cl)

A neuron depolarizes only when excitatory influences reach a __

threshold

Cells in which an action potential can be triggered are considered _

excitable

When a nerve is stimulated, the electrical potential changes inside the nerve changes from

negative to positive

What is the approximate resting membrane potential of a neuron?

-70 mV

What electrophysiological events are thought to generate the EEG signal?

both excitatory postsynaptic potentials (EPSPs) and inhibitory postsynaptic potentials (IPSPs)

Action potentials develop in nerve and muscle fibers in response to _

depolarization

Define cerebrovascular accident

a focal neurologic deficit of sudden onset caused by central nervous system ischemia or hemorrhage

Define transient ischemic attack (TIA)

a focal neurological deficit of sudden onset caused by transient ischemia and resolving within 24 hours

Define agnosia

inability to recognize objects, people, sounds, shapes or smells. Symptoms common to tumors of the parietal lobes

Define aphasia

a complete loss of language function like speaking, writing, or ability to understand spoken or written language

Define apraxia

inability to perform a previously learned set of coordinated movements, not related to paralysis or lack of comprehension

Define dysnomia

difficulty naming objects or finding the desired words

Define dysphasia

inability to speak words which one has in mind or to think of correct words, or inability to understand spoken or written words. Symptoms common to tumors of the dominant cerebral hemisphere, particularly the frontal , temporal, and parietal lobes

Define hemiparesthesia

loss of sensation to one side of the body

Define hemiparesis

muscular weakness or partial paralysis to one side of the body

Define coma

a state in which a person is unaware of self and surroundings, even if stimulated from the outside

Define decorticate posturing

flexion of the wrist and arms and extension of the legs and indicates hemispheric dysfunction

Define decerebrate posturing

extension of all four extremities and internal rotation of the shoulders and indicates pathology of the midbrain or pontine levels

Define dementia

clinical state characterized by a significant loss of function in multiple cognitive domains that is not due to an impaired level of arousal

Name a disease caused by a prion

Creutzfeldt-Jakob disease

Define acoustic neuroma

tumor that arises from the eighth cranial nerve

Do patients with neurofibromatosis (Von Recklinghausen's disease) have an increased incidence of the tumors?

have an increased incidence of acoustic neuromas as well as other intracranial and spinal tumors

What are the clinical findings during a simple partial seizure?

include motor findings such as jerking or stiffening of a limb; sensory findings such as a sensation of tingling or pain, hearing a sound, smelling an odor or seeing brightly colored shapes; psychic features such as sweating or palpitations or autonomic finding such as fear or deja vu

How do the clinical findings differ in a simple vs a complex partial seizure?

During a simple partial seizure, the patient remains alert and aware. During a complex partial seizure, the patient has altered/diminished consciousness or responsiveness

Define epileptic aura

A subjective sensation that precedes the onset of a seizure. Sensations can be diverse such as hearing a buzzing sound, deja vu, or nausea

How do EEG patterns of partial seizures differ from EEG patterns of generalized seizures?

Partial seizures have EEG patterns that start in focal subsets of the brain. EEG patterns of generalized seizures involve all brain areas at once

Define automatism

seen during complex partial seizures. examples include fumbling of the hands, running fingers through hair, or making humming sounds

What are the differences between a typical and an atypical absence seizure?

Both have same clinical features of staring and unresponsiveness. Atypical absence seizures differ in that onset and termination of the episodes both clinically and electrographically are less clear and firing rates are slower

Describe the clinical features and EEG correlations seen with a myoclonic seizure.

lightening like or shock like contraction of the muscles driven by an epileptic discharge. EEG correlations: most commonly a high voltage polyspike-wave discharge which may occur in brief repetitive bursts

Describe the clinical features and EEG correlations seen with a clonic seizure

repetitive clonic jerks in nearly any skeletal muscle group in the body. EEG correlations: because each clonic jerk is driven by an EEG discharge a simultaneous spike wave discharge is expected with each clonic jerk

Describe the clinical features and EEG correlations seen with a tonic seizure

tonic stiffening of a limb, several limbs or the whole body. EEG correlations: most often a spray of rapid spikes in the affected area; other EEG correlates are not uncommon including an abrupt desynchronization (flattening) of the EEG

Describe the clinical features and EEG correlations seen with a generalized tonic-clonic seizure.

whole body stiffening followed by clonic jerking. EEG correlations: abrupt onset of generalized rapid spikes which then slow in frequency to manifest a clearer spike wave morphology

Describe the clinical features and EEG correlations seen with an atonic seizure.

loss of tone, could be slumping of shoulders or head drop or collapse to the ground. EEG correlations: many possible including slow spike-wave discharges, desynchronization (flattening) or polyspikes followed by flattening

Define differential amplifier

amplifies only the difference in voltage between the 2 inputs. Doesn't amplify equal (common) voltages at the 2 inputs. The more the inputs vary in voltage the more there is to amplify

Define input impedance

NOT the impedance between the scalp and the electrodes. It's impedance between components of the differential amplifier. It must be high for optimal functioning of the amplifier. Must be at least 10 megaohms

Define common mode rejection (CMRR)

Set by the EEG instrument manufacturer and not controlled by the user. Compares what is common to the amplifiers to what is amplified and should be at least 10,000:1

Describe the polarity convention of an EEG instrument.

????

The rule in the design of EEG instruments is that if input 1 is positive with respect to input 2, the deflection of that channel will be

down

The rule in the design of EEG instruments is that if input 1 is negative with respect to input 2, the deflection of that channel will be

up

Define gain

The ratio of output signal to input signal. Gain has no units of measurement

Define sensitivity

a measure of how much voltage is required to cause a deflection of a certain distance; in EEG usually uV/mm; S=V/A

Define amplifier

a combination of electronic components designed to increase the voltage

Define time constant

time required for the waveform to fall to 37% of the peak deflection. Describes the effect of the low frequency filter on square wave pulses like calibration square wave pulse

Name possible situations in which you may need to use a LFF of 5 Hz

To emphasize fast components such as spikes or sleep spindles by minimizing slow activity. In case of sweat artifact which cannot be controlled by any other means, the filter can minimize the baseline sway

Define filter

Used to exclude waveforms that are out of range so that waveforms of most importance can be recorded without distortion

Name possible situations in which you may need to use a LFF of 0.3-0.1 Hz

to emphasize low amplitude slowing; in association with 15 mm/sec timebase; during ECI recording to make sure there is no slow activity

Name possible situations in which you may need to use a HFF of 35 or 15 Hz

excessive muscle artifact that can't be removed by any other means

A high filter setting of 15 Hz will not show significant information at

50 Hz; the faster the frequency the more the 15 Hz filter will attenuate the signal. Viewing a frequency response curve shows that a 15 Hz HFF will greatly attenuate a 50 Hz wave

Which of the following is most attenuated by a time constant of .01 seconds?

The slowest wave, 0.3 Hz will be attenuated the most

Which of the following is attenuated by a low pass filter of 15 Hz?

20 Hz; a 15 Hz filter passes through the low/slow frequencies so it does not affect the 1, 5, or 10 Hz signals

Which filter setting will record the greatest amplitude of a 70 Hz wave

70 Hz

Which filter setting will record the greatest amplitude of a .4 Hz wave?

0.1 Hz; the slower the LFF setting (or the longer the time constant), the more voltage of the slow frequencies will be recorded

Which one of the following frequencies is most attenuated by a low filter of 5 hz?

0.1 Hz

Which time constant will record the greatest amplitude of a 1 Hz wave?

1 second; the longer the time constant, the more voltage of the slow activity will be recorded

Which one of the following frequencies is most attenuated by a low filter of 0.1 Hz?

3 Hz; the faster the slow activity, the more it will be attenuated by a LFF

Which filter setting will record the greatest amplitude of a 50 Hz wave?

70 Hz

Which low filter setting will most faithfully record the amplitude of a 1.5 Hz slow wave?

0.1 Hz; the slower the LFF setting ( or the longer the time constant), the more voltage of the slow frequencies will be recorded