Neurodiagnostic Eval Flashcards
Uses highly collimated x-ray beams that are rotated over many diff angles to obtain a differential absorption pattern across various rays through a slice of the body
Computed Tomography
levels of density in the image in a CT scan is measured in
Hounsfield units
most hyperdense tissue according to hounsfield units
bone c 400+ HU
type of CT most useful for identifying acute hemorrhage
Non-contrast CT
non contrast CT is invaluable in
assessment of acute neurotrauma
NCCT is used for Mx of acute stroke by
- determining cause of signs & Sx
- r/o stroke mimics
- select pts to be started on RTPA
The sign when there is hyperattenuating vessel filled with acute thrombus
dense MCA & dot sign
CT findings in a pt c stroke
- dense MCA sign & dot sign
- loss of gray-white matter differentiation
- loss of insular cortex (insular ribbon sign)
- decreased density of the basal ganglia (disappearing basal ganglia sign)
this enhances differences in tissue density, demonstrate vasculature and vascular pathology and detect areas of BBB breakdown
contrast enhanced CT
what imaging method to use on pts who had a recent head trauma
CT scan
a pt who is medically unstable is supposed to be checked for any brain affectation, what would be the best imaging to use?
CT scan
In CECT, allergic reactions are
normal
possible condition that may develop in pts c renal dysfunction that underwent CECT
contrast induced nephropathy
Limitations of CT scan
- imaging of posterior fossa - linear artifacts
- ionizing radiation - pregnant
common indications for CT
- acute/chronic Functional Neurologic Disorders
- head/facial trauma
- headache (abrupt/worsening, SAH traumatic/nontraumatic)
- change in mental status
- new-onset seizure
this allows quantitative measures of cerebral BV, cerebral mean transit time, time to peak, and cerebral blood flow
CT perfusion
limitation of CT angiography
time-consuming process requiring to edit and generate renderings
repeating scan during a bolus of IV contrast produces dynamic set of images that are real time 4D images of blood flow through the intracranial vessels
CT angiography
produces functional images of the brain parenchymal blood floow
CT perfusion
uses hydrogen nuclei that consist of a single proton that is constantly spinning
Magnetic Resonance Imaging
this has the ability to distinguish different STs and identify pathologic abnormalities
Magnetic Resonance Imaging
contrast agent in MRI scans
gadolinium chelates
gadolinium chelates causes what?
deposition in tissues resulting in fibrosis in pts c renal dysfunction (nephrogenic systemic fibrosis)
MRI sequence used to display brain and spinal cord anatomy & evaluate subacute hemorrhage, lipids, paramagnetic metals, or proteinaceous composition of lesions
T1-Weighted MRI
MRI sequence used to display brain and spinal cord pathology as evidenced by inc tissue water content
T2-weighted MRI
in T2W, white matter is ____, gray matter is ____, and CSF is ____
dark; bright; bright
used in highlighting subtle brain pathology; specifically useful for white matter diseases and lesions near CSF compartments
fluid attenuated inversion recovery (FLAIR)
demonstrates non-enhancing tumor components, as well as associated mass effect and edema
fluid attenuated inversion recovery
MRI sequence used to eliminate signal from fat and is useful in diagnosing lipoma and dermoid cyst
short tau inversion recovery (STIR)
useful in detecting early ischemic brain injury
Diffusion Weighted Imaging (DWI)
this characterizes tissue components such as calcification or iron content; sensitivity to small amounts of blood & blood breakdown products
gradient recalled echo (GRE)
this signifies breakdown of BBB and characterize lesions from brain tumors, metastases to infectious and inflammatory
gadolinium contrast enhancement
contraindications for gadolinium contrast enhancement
- severe allergy
- renal failure; NSF
MRI sequence used to identify/diagnose stenosis, thrombosis, dissections, aneurysms
Magnetic Resonance Angiography
CE MRA is used to:
evaluate neck vasculature
used to evaluate for patency of dural venous sinuses in venous sinus stenosis/thrombosis
magnetic resonance venography
this uses MRI for localization of cerebral activation and is used to obtain functional info by visualizing cortical activity
functional MRI
detects subtle changes in Blood Flow/Oxygenation in response to stimuli/actions
Functional MRI
MRI technique that measures water molecule diffusion and its direction
diffusion tensor imaging (DTI)
clinical application for DTI
- assess white matter tract integrity
- presurgical and pretherapeutic planning
used as a problem solving technique in attempt to differentiate lesions
MR spectroscopy
N-acetylaspartate signifies what:
normal neuronal tissue/integrity
what is the marker of astrocytes/astrogliosis seen in MS when undergoing MRS
inositol/myoinositol
this MRI technique is done by quantifying blood flow through biologic tissues
MR perfusion imaging
clinical applications of MR perfusion imaging
- cerebrovascular diseases (e.g. stroke or vasospasm)
- brain tumors and metastases
diagnostic imaging that does not use radiation
MRI
molecular imaging used to better understand the biochemical process that underline diseases
positron emission tomography (PET) and single-photon emission computed tomography (SPECT)
imaging done in real-time, is noninvasive, comprehensive, affordable, repeatable, harmless, and portable
neurovascular ultrasound
US used to screen extracranial carotid and vertebral arteries for atherosclerosis
extracranial ultrasound (duplex ultrasound/color doppler)
in extracranial US, what does plaque surface irregularity imply
there is an increased risk of stroke
in extracranial US, what does echoluscent carotid plaque signify
increased risk of stroke/MI
give 2 indications for extracranial ultrasound examination
Evaluation of:
- cerebral ischemia, stroke, or TIA
- pts c cervical bruit
- pulsatile mass in the neck
- blunt neck trauma
- post-op carotid endarterectomy/carotid stenting
- suspected carotid/VA dissection
- pre-operative eval of pts undergoing major cardiovascular or other major surgical procedures
- drop attacks or syncope
- vasculitis of extracranial arteries
non-invasive US technology that monitors blood flow velocity and direction in large intracranial arteries
intracranial ultrasound
high resolution images of extracranial and intracranial vasculature and is the gold standard for viewing cerebral blood vessels
cerebral angiography
advantages of cerebral angiography
- improved temporal resolution
- functions as both diagnostic and therapeutic
conditions diagnosed/treated by cerebral angiography
- occluded/stenotic vessels
- arterial dissection
- aneurysms
- ateriovenous malformation and other vascular malformations
- vasculitic narrowing
- dural venous sinus thrombosis
possible complications of cerebral angiography
- artery puncture
- dislodged plaque (cerebral or systemic ischemic lesions)
- dissection
- thombus formation over catheter tip
- vasospasm
- disruption of BBB
these measure spontaneous electrical activity generated by neural structures
electroencephalography and evoked potentials
this reflects electrical currents flowing in the extracellular spaces of the brain and are summated effects of innumerable excitatory and inhibitory potentials of the cortical neurons
electroencephalography
what are the 4 stages of sleep
N1 - low voltage slower activity, presence of vertex sharp waves
N2 - sleep spindles, K complexes, positive occipital sharp transients of sleep (POSTS)
N3 - slow waves of sleep
REM - resemble EEG of drowsiness c REM and general atonia
clinical applications of EEG
- epilepsy
- focal brain lesion/dysfunction
- diffuse brain dysfunction or injury
- intraoperative neuromonitoring
these are generated by the nervous system in response to stimuli
evoked potentials
composed of stereotyped sequence of waveforms that are labelled by their polarity and their peak latency from the time of stimulation
evoked potentials
absence of waveforms in evoked potentials is caused by
complete interruption of conduction/destruction of the neural generators
evoked potential elicited by light electrical stimulation of peripheral nerves
somatosensory evoked potentials
EP obtained by stimulation c an alternating checkerboard pattern of black and white squares
visual EP
VEPs are used in pts c
- acute optic neuritis
- demyelinating diseases
- ischemic optic neuropathy
- optic nerve compression
- retinal diseases
This EP consists of 7 waveforms and is done by delivering auditory stimulus to one ear, and is recorded through scalp electrodes and superimposed on each other
Brainstem Auditory Evoked Potentials (BAER)
This tests the integrity of motor pathways
Motor Evoked Potentials
this is the transcutaneous stimulation of motor/sensory nerves and recording of an elicited response in terms of CMAP/SNAP
nerve conduction studies
what does NCS measure
speed and strength of an electrical impulse conducted along a peripheral nerve
what produces SNAP waveforms
large type Ia axons
where are the electrodes placed in assessing motor nerves
motor enplate region
what does recording electrodes capture
electrical potential generated by depolarization of the muscle (CMAP)
this is the latency and distance between the stimulus and recording electrode
conduction velocity
time difference between the stimulus and waveform onset
latency
summated number of responsive axons
amplitude
latency and conduction velocity are dependent on
intact myelinated nerves
amplitude depends on
number of functioning axons within the nervr
what does slowed conduction velocity and prolonged latency imply
there is demyelination
what does decreased CMAP/CNAP amplitude imply
there is axonal loss
the cumulative time for impulses to reach SC via sensory fibers, synapse c the anterior horn cells, and to be transmitted through motor fibers to stimulate
H reflex
the supramaximal stimulus of a mixed nerve/pure motor nerve and is the result of impulses that travel antidromically in the motor nerves to the AHC
F response
how is needle electromyography activated
voluntary contraction at different levels of effort
brief burst of electrical activity provoked by EMG needle as it moves through the muscle
insertional activity
hallmark of denervation
fibrillations, sharp waves
t/f: normal resting muscle is electrically silent
true
how to determine chronic neurogenic injury using needle EMG
reinnervation high amplitude, long duration, and polyphasic MUPs
characteristics of myopathies under needle EMG
reduced MUPs, short duration, low amplitude and polyphasic; high pitched cracking sound like rainfall on a tin roof
characteristics of denervation under needle EMG
reduced number but normal MUPs
trains of 4-10 waveforms are evaluated for decrease in area and amplitude
repetitive nerve stimulation (RNS)
in EMG, this is the interval between stimulus and response, varies with each stimulus
Jitter
in neuromuscular junction dysfunction, what is the seen jitter
increase in jitter
EMG wherein a single muscle fiber AP is measured
single fiber EMG (SFEMG)
this uses light scattering to produce cross sectional images of the retina, allowing evaluation of the different layers
optical coherence tomography
normal measurement in audiograms
better than 8dB
what is electronystagmography/videonystagmography used for?
balance testing
give an indication for lumbar puncture
- obtain pressure measurements and procure CSF sample
- instillation of anesthetics, antibiotics, antitumor agents
- drainage to reduce CSF pressure
- injection of radio-opaque substances in myelography
level for lumbar puncture
L3-L4 interspace
most common complication of LP
headache
why is headache the most common complication of lumbar puncture
upright position d/t reduction of CSF pressure from leakage of fluid at the puncture site and tugging on cerebral vessels
t/f: viral infections of the meninges and brain do not lower csf glucose
true
what is checked in CSF analysis
- gross appearance
- CSF cells
- CSF protein and glucose
- CSF microscopy
- CSF serology
- CSF cytology and flow cytometry
- CSF oglioclonal bands/content of gamma globulin
clinical applications of nerve biopsy
- vasculitis
- sarcoid neuropathy
- amyloidosis
- leprous neuropathy
- other peripheral neuropathies
most commonly used nerve in nerve biopsies
sural nerve
