Neuro Diagnostics Flashcards
What is an electroencephalogram (EEG)?
Safe, painless recording of cortical electrical activity
8-16 electrodes applied to scalp
Stressors of EEG
Sleep deprivation
Hyperventilation
Indications for EEG
Seizure disorders (may be normal, they are episodic) Metabolic encephalopathy (distinguish focal from generalized slowing) Distinguish b/w cortical and subcortical Tumors (see focal slowing or spike discharges)
How to distinguish b/w cortical and subcortical on EEG
Cortical: see neglect, aphasia, hemianopia
Subcortical: see motor hemiparesis
Rhythms seen on EEG
Alpha: 8-12 Hz (normal awake adult)
Beta: >12 Hz
Theta: 4-8 Hz
Delta: 0-4 Hz
What does this EEG finding suggest: epileptiform activity
Seizures
What does this EEG finding suggest: focal discharges/spikes c/w focal problem
Tumor, infarct, scar tissue
What does this EEG finding suggest: generalized changes/slowing c/w metabolic disorders
Encephalopathy, anoxia
What does this EEG finding suggest: normal EEG with presence of seizure activity
Psychogenic seizures (inpt monitoring is helpful)
Contraindications to EEG
No major ones
What is an electromyogram (EMG)?
Clinical examination of the electrical activity of muscle fibers/ motor unit
Define location of problems affecting peripheral nerves
What can an EMG do?
Differentiate primary muscle conditions from muscle weakness caused by neurologic disorders
Technique for EMG
Needle electrodes inserted into skeletal muscle to record electrical potentials and look for abnormals (electrode on the needle detects electrical activity given off by muscles)
Makes graphs, sounds or numerical values
When to measure electrical activity with EMG
Needle insertion
Spontaneous activity at rest
Slight muscle contraction
Full muscle contraction
Indications for EMG
Lower motor neuron diseases (ALS)
NMJ disease (myasthenia gravis)
Muscle disease (myopathy)
Peripheral nerve disorders (carpal tunnel, peripheral neuropathies)
(alcohol neuropathy, brachial plexopathy, cervical spondylosis, denervation, guillain barre, nerve dysfunction, polymyositis)
What does an EMG show for myasthenia gravis (NMJ disease)?
Fatigability
What does EMG show for myopathy?
Decreased amplitude of motor response
What are nerve conduction studies used for?
Assess rate of conduction and amplitude of response of peripheral nerves (usually with an EMG!)
Electrical stimulation of peripheral nerve will produce muscle contraction or a sensory response
Recording electrode and stimulating electrodes over nerve or muscle
Indications for nerve conduction studies
Differentiate between primary nerve and muscle disorders
Differentiate lower motor neuron diseases from peripheral neuropathy
Detect abnormalities in sensory nerves
Axonopathy (decreased amplitude)
Demyelinating process (decreased conduction rate)
NCV and carpal tunnel syndrome
Used to check integrity of sensory and motor pathways
Can help determine when surgery is needed
Types of neuroimaging
Plain films CT scan MRI U/s Angiograph/MRA Myelography
Indications for plain films
Degenerative disease (osteophyte, decreased disk space, alignment-kyphosis/scoliosis)
Trauma (fracture, dislocation)
Malignancy
Lumbar spine films for spondylolisthesis
Flexion and extension views indicated to evaluate degree of instabiity
First line to look for spinal fractures with or without associated dislocations
Plain films (compression fractures)
What must be done after plain films to define presence of soft tissue injuries
CT or MRI
Indications for plain skull films
Trauma
Metabolic disease
Malignancy
Indications for CT
Trauma Stroke (ischemia or hemorrhagic) Hydrocephalus Suspicious HAs AMS For spine (trauma, degenerative) Loss of consciousness Persistent neuro dysfunction Persistent vomiting GCS <8 or deteriorating Retrograde or antegrade amnesia Post traumatic seizures
Epidural vs subdural hematoma on CT scan
Epidural: lens shaped
Subdural: crescent shaped
What is mandatory to rule out hemorrhagic stroke before administering thrombolytic meds?
Non contrast head CT
Indications for MRI
Tumors Vascular disease Inflammation/infection Multiple sclerosis Degenerative disease (spine)
T1 vs T2 MRI
T1: reflects uptake of magnetic energy better for normal anatomy
T2: reflects release of magnetic energy better for pathology
CSF/water is dark on T1 and white on T2
Diagnostic study of choice for tumors
MRI with gadolinium (look for mass effect, surrounding edema and pattern of enhancement)
What is a diffusion MR?
Measures microscopic motion of water
Most sensitive test when suspect acute ischemic stroke or brain or spinal cord
Diffusion MR (also good for encephalitis or abscess)
What is seen on MRI in multiple sclerosis?
Periventricular plaques
CT/MRI indications for new deficit
Acute onset of: New vision loss Aphasia Mental status changes Sensory abnormalities Motor paralysis Vertigo with HA, diplopia, focal deficit, ataxia or dysarthria
CT/MRI indications for headache
Worst HA of life
New HA in pts with cancer of HIV
HA with papilledema, neuro deficit, mental status changes
Worsens with exertion, positionally related, awaken pts from sleep or changes over time
Recommended study for head trauma
CT
Recommended study for new onset sxs
CT (do MRI if CT is negative and pt has neuro deficit)
Indications for MRI of the spine
Radiculopathy (persistent/progressive) High impact trauma New or progressive deficit Suspected tumor or infection Neurogenic claudication New onset of back pain in a pt with cancer
Carotid ultrasound
Reflective sound waves can determine velocity through blood vessel
Assess degree of stenosis
When is angiography indicated?
When definitive anatomy needed (pre-op like CEA or aneurysm repair)
What is myelography used for?
Detects spinal cord pathology/compression (herniated disks or spinal stenosis)
Radiopaque dye injected into thecal space
Has been replaced by MRI
When can LP not be performed?
If papilledema or increased ICP
