L15: Neurodiagnostics Flashcards by Jeri Sheldon (AZ PA Mast 20)

Safe, painless recording of the cortical electrical activity

8-16 pairs of electrodes applied to the scalp

EEG

Electroencephalogram

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Alpha rhythm on EEG

8-12 Hz

Normal awake adult

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Beta rhythm on EEG

> 12 Hz

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Theta rhythm on EEG

4-8 Hz

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Delta rhythm on EEG

0-4 Hz

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Contraindications to EEG

None

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Indications for EEG

Seizure disorders → may be normal; seizures are episodic events

Metabolic encephalopathy → distinguish focal
from generalized slowing

Cortical vs subcortical
• Cortical: see neglect, aphasia and hemianopia
• Sub cortical: see motor hemiparesis

Tumors → see focal slowing/spike discharges

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Epileptiform activity on EEG

seizures

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Focal discharges or spikes on EEG (consistent with a focal problem)

Tumor
Infarct
Scar tissue

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Generalized changed on EEG

Slowing consistent with metabolic disorders:
Encephalopathy
Anoxia (no O2)

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Psychogenic seizures

Normal EEG

Pt has seizures that don’t show up on EEG, aka its “all in their head” (psychological)

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Clinical examination of the electrical activity of

muscle fibers/motor uni

EMG (electromyogram)

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EMG can….

Define location of problems affecting peripheral
nerves
Differentiates primary muscle conditions from muscle
weakness caused by neurologic disorders

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EMG evaluates electrical activity of the muscle during

Needle insertion
Spontaneous activity at rest
Slight muscle contraction
Full muscle contraction

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Example of a LMN disease that can be seen on EMG

Amyotrophic lateral sclerosis (ALS)

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Myasthenia Gravis on EMG

Fatiguability

A NMJ disease

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Muscle diseases/myopathy shows _____ on EEG

EMG consistent with ↓ amplitude of motor

response

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Examples of peripheral nerve disorders which can be seen on EMG

Carpel tunnel

Peripheral neuropathies

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Assess rate of conduction and amplitude of response of peripheral nerves
Usually in conjunction with EMG

Nerve conduction studies

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How is a nerve conduction study performed?

Electrical stimulation of peripheral nerve→ muscle contraction or a sensory response
Recording electrode and stimulating electrodes over
nerve or muscle

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Nerve conduction studies are indicated for _____

•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)
Carpal Tunnel Syndrome
• Can check integrity of sensory and motor pathways
• Determine when surgery is needed

What information does a nerve conduction study give us?

The nerve conduction velocity

Indications for plain films

Degenerative disease
Osteophytes
Decreased disk space
Alignment
Kyphosis, scoliosis
Trauma
Fracture/dislocation
Malignancy

Plain skull films:
Trauma
Metabolic disease
Malignancy, Multiple Myeloma

Spondylolisthesis requires _____ views to evaluate _____

flexion and extension views to evaluate for degree of instability
(L3-S1)

First line imaging for spinal fractures with or without associated dislocations (compression fractures)

Plain films Followed by CT or M

Indications for CT

``` Trauma • Stroke→ Ischemic vs hemorrhagic • Hydrocephalus • Suspicious headaches • Altered mental status • For spine→ Trauma, Degenerative Loss of consciousness • Persistent neurologic dysfunction • Persistent vomiting • GCS < 8 or deteriorating • Retrograde or anterograde amnesia • Post-traumatic seizures ```

What might a non-contrast CT of a gunshot wound show?

soft tissue swelling hemorrhagic track across brain (bullet pathway) blood in ventricles air bubbles in ventricles. (Blood=white)

CT: Lens shaped bleed between dura and skull

Epidural bleed

CT: Crescent shaped bleed between dura and arachnoid

Subdural bleed

How do you rule out a hemorrhagic stroke before administering thrombolytic medications?

Non-contrast head CT

Hydrocephalus on CT

Dilated ventricles

Indications for MRI

``` Tumors Vascular disease Inflammation/ infection Multiple sclerosis Degenerative disease (spine) ```

T1 MRI vs T2 MRI

T1: water/CSF dark T2: water white (T2 shows H20)

Test of choice for brain tumors

MRI with gadolinium Shows: Mass effect, surrounding edema, pattern of enhancement

On MRI, Multiple Sclerosis will show

Periventricular plaques

Measures microscopic motion of water→ most sensitive for acute ischemic Stroke of the brain and/or spinal cord. Encephalitis Abscess

Diffusion MR

Indications for imaging (CT/MRI) of a new deficit

``` Acute onset of: •New vision loss •Aphasia •Mental Status changes •Sensory abnormalities •Motor paralysis •Vertigo w/HA, diplopia, focal deficit, ataxia, dysarthria ```

Indications for Imaging for a headache (CT/MRI)

``` “Worst HA of my life” (SAH) New HA in patients with cancer or HIV Papilledema Neurologic deficit Mental status changes Worsens w/exertion, positionally related, awakens pt. from sleep, changes over tim ```

On a CT, blood appears _____

Opaque

A suspected TIA or CVA should get ___ imaging

A suspected brain tumor should get ___ imaging

MRI

Recommended study for New onset symptoms

Do ____ if the CT (-) and the patient has new onset symptoms with a neurologic deficity

MRI

Do an MRI for dizziness if _____

Brainstem or cerebellar CVA or mass suspected

Indications for an 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 patient with cancer ```

Reflective sound waves determine velocity through vessel | Assess degree of stenosis by percentage

Carotid ultrasound

Detect spinal cord pathology/ compression→ herniated disks, spinal stenosis Radiopaque dye injected into thecal space Patient tilted for imaging: X-ray or CT

Myelography

Myelography was replaced by

MRI

Lumbar puncture contraindications you should really know by now

Cannot be performed if papilledema or increased intracranial pressure

IV injection of contrast medium→ traditional, CTA, or MRA | Vascular access via femoral vessels

Angiography

Angiography indications

Indicated when definitive anatomy needed: pre-op CEA, aneurysm repair