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Neuro > Neuordiagnostics > Flashcards

Neuordiagnostics Flashcards

1
Q

Indications for lumbar puncture?

A
  • when CSF is needed for biochemical analysis, cellular exam and culture
  • also done to introduce drugs into subarachnoid space for tx of cancer or to introduce contrast agents

-emergent indications:
suspected CNS infection,
supected subarachnoid hemorrhage in pt with neg CT scan

general indications:
dx of CNS malignancies, demylenating diseases, Guillain-Barre syndrome

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2
Q

Site of LP?

A
  • L3-L4 or L4-L5
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3
Q

Technique of LP?

A
  • pt in left lateral decubitus fetal position or sitting upright with spine curved forward
  • entry through L3-L4 or L4-L5 space using sterile technique
  • measure opening pressure with manometer (best if pt in recumbent position)
  • collect 8-15 cc of CSF in 4 tubes for lab studies
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4
Q

What are some relative CIs to LP?

A
  • local skin infections over proposed puncture site (absolute CI)
  • IICP, exception is pseudotumor cerebri (cause herniation of brain)
  • suspected spinal cord mass or intracranial mass lesion (based on lateralizing neuro findings or papilledema)
  • uncontrolled bleeding diathesis, thrombocytopenia, or anitcoag
  • spinal column deformities (osteoarthritis) (may reqr fluoroscopic assistance)
  • lack of pt cooperation
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5
Q

Complications of LP?

A
  • post lumbar puncture HA (10-30% of pts): CSF leak - go away when lying down
  • infection
  • bleeding: spinal hematoma
  • cerebral herniation (fatal)
  • minor neuro sxs (radicular pain or numbness)
  • late onset epidermoid tumors of the theca sac
  • back pain
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6
Q

What pts should undergo a CT of head prior to LP?

A 
- pts that you want to R/O mass lesion:
altered mentation
focal neuro signs
papilledema
seizure w/in previous week
impaired cellular immunity (cancer)
  • some places have protocols where CT is done on all pts prior to LP
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7
Q

CSF normal values?

A
  • pressure: 70-180 mmH2O (can be up to 250 in obese people)
  • appearance: clear, colorless
  • total protein: 15-45 mg/dL
  • glucose: 45-85 mg/dL or greater than 2/3 of serum blood glucose
  • cell count and diff: WBCs - 0-5 cells/microL, 0 RBCs
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8
Q

Opening pressure - CSF analysis?

A
  • normal: 70-180 mmH2O but increases with BMI
  • need to be in lateral decubitus position to measure accurately
  • elevated ICP can be present in meningitis, ICH, tumors
  • will be on high end in obese pts
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9
Q

Appearance - CSF analysis?

A
  • normal is crystal clear
  • may be cloudy from infection, bloody or colored:
    bloody tap or
    xanthochromia = yellow, orange, or pink from lysis of RBCs (occurs w/in 2 hrs, last 2 weeks) - subarachnoid hemorrhage, increased protein levels, elevated bilirubin
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10
Q

Different causes of Xanthochromia? yellow?

A
  • blood breakdown products, hyperbilirubinemia, CSF protein greater than 150 mg/dL, greater than 100,000 rbcs/mm3
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11
Q

Xanthochromia - orange?

A
  • blood breakdown products, high carotenoi ingestion
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12
Q

Xanthochromia - pink?

A
  • blood breakdown products
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13
Q

Xanthochromia - green?

A
  • hyperbilirubinemia, purulent CSF
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14
Q

Xanthochromia - brown?

A
  • meningeal melanomatosis (melanoma of CNS)
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15
Q

CSF anaylsis: protein?

A
  • CSF protein concentration is one of most sensitive indicators of pathology within CNS
  • newborns: up to 150 mg/dL
  • adults (15-45 mg/dL), same for kids at 6-12 months
  • can diff protein types for conditions such as Guillan Barre and MS
  • low: repeated LPs, CSF leak, acute water intoxication
  • elevated: infections, ICH, Guillain Barre, malignancy, some endocrine abnormalities, inflammatory conditions
  • falsely elev in traumatic tap: correction factor - subtract 1 mg/dL for q 1000 RBCs
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16
Q

CSF analysis - glucose?

A
  • glucose level is about 2/3 serum glucocse measured during preceding 2-4 hrs
  • normal: can be normal in CNS viral infection
  • low: CNS bacterial infection, neoplasm or fungal infection
  • high: when peripheral glucose levels are elevated, above a serum glucose of 300 the CSF glucose doesn’t increase that much
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17
Q

CSF analysis - WBCs

A
  • WBCs:
    0-5 mm3 adults, up to 20 mm3 in newborns
  • meningitis: less than 1000 likely viral, and greater than 1000 likely bacterial
  • increased post seizure, ICH, malignancy, inflammatory conditions
18
Q

CSF analysis - cell diff?

A
  • normal WBC 70% lymphocytes, 30% monocytes
  • in meningitis: predominance of neutrophils= bacterial
  • in meningitis: predominance of lymphocytes = viral, fungal or TB
  • increased eosinophils = parasitic infection
19
Q

CSF analysis - RBCs?

A
  • traumatic tap: measure cell counts in 3 consecutive tubes and number of RBCs should decrease with each
  • if RBCs don’t decrease then assume from intracranial hemorrhage!!!
20
Q

Microscopic exam?

A
  • gram stain
  • acid fast stain for TB
  • india ink stain positive in cryptococcus
  • wright or giemsa stain + in toxoplasmosis
21
Q

Other tests with LP (latex agglutination, PCR)?

A
  • send for culture
  • latex agglutination: allows for rapid detection of bacterial antigens in CSF, variable sensitivity and specificity
  • PCR: high sensitivity and specificity, fast, particularly useful in viral meningitis, HSV-1, EBV, enterovirus, CMV, TB, acute neurosyphilis
22
Q

Expected LP results in bacterial meningitis?

A
  • pressure of over 300 mmH20
  • cloudy, purulent
  • increased total protein
  • decreased glucose
  • greater than 1000 cell count, greater than 80% are neutrophils
23
Q

Expected LP results in viral (aseptic meningitis)?

A
  • over 200 mmH2O
  • clear
  • increased total protein
  • normal glucose
  • increased cell count, but less than 1000 (lymph up to 50%)
24
Q

Expected LP results in fungal meningitis?

A
  • over 300 mmH2O
  • clear or cloudy
  • increased total protein
  • decreased glucose
  • increase but less than 500 cell count, lymph up to 50%
25
Q

Multiple sclerosis findings in LP?

A
  • normal pressure
  • clear color
  • increased total protein
  • increased WBC 0-20 (lymph)
26
Q

Guillian-Barre findings in LP?

A
  • normal pressure
  • clear or xantho colore
  • increased total protein
  • normal glucose
  • normal or elevated cell count
27
Q

2 diff types of nerve conduction studies?

A
  • Nerve Conduction Velocity (NCV):
    measures how well and how fast the peripheral nerves send the signals
  • eval of entrapment neuropathies and Guillian Barre
  • electromyelography (EMG): measures the electrical activity of muscles during rest and contraction
28
Q

What are nerve conduction studies?

A
  • test the peripheral nerves only and can dx a focal or generalized disorder
  • used to diff muscle disorders from nerve disorders
  • Use to figure out if the nerve signal is adequate but muscle isn’t responding vs altered nerve signals and intact muscle response
29
Q

Indications of nerve conduction studies?

A
  • eval of paresthesias of arms and legs
  • eval of weakness of arms and legs
  • some disorders that can be dx by nerve conduction studies: carpal tunnel, ulnar neuropathy, spinal disc herniation, Guillian Barre, peripheral neuropathy
  • myasthenia gravis
30
Q

Classification of nerve fibers?

A
  • A-alpha: large, myelinated fibers, touch, vibration and position
  • A-delta: small myelinated fibers, cold and pain sensation
  • C-fibers: unmyelinated fibers, warm and pain
31
Q

What is NCV?
What does it study? Limitations?
Useful in testing for what diseases?

A
  • only study the largest A-alpha fibers: touch, vibration and position
  • tests motor and sensory nerves
  • can appear normal in polyneuropathies with primarily small fiber involvement
  • stim of motor or sensory nerve at diff pts and calculation of velocity of conduction of propagated impulse
  • measures velocity of fastest conducting fibers
  • normal velocity if myelin is intact
  • slow conduction velocity if demylenation or destruction of large fibers
  • Useful in studying demyelinating polyneuropathy (Guillain-Barre syndrome) or focal demyelination (entrapment neuropathies such as carpal tunnel syndrome)
32
Q

Indications for EMG?

A
  • find diseases that damage msucle tissue, nerves, or junctions b/t nerve and muscle
  • herniated disc, amyotrophic lateral sclerosis (ALS) or myasthenia gravis
  • involves cooperative pt who can voluntarily contract muscles when needed (it does hurt!)
  • needle electrodes are used (surface EMG unreliable)
33
Q

Mechanism of EMG?

A
  • needle is placed into muslce (motor unit)

- electrical stimulus delivered and a motor unit AP is created

34
Q

Use of nerve conduction tests?

A
  • should always be ordered together (EMG and NCV)
  • may be used to dx or follow progression of various diseases
  • consider for eval of peripheral weakness and or parasthesias
  • characterizes disorders of motor neuron, neuromuscular jxn, primary nerve disorder or nerve root disorders
  • ** these shouldn’t be first tests ordered but should be used to confirm a dx or judge severity of disease
35
Q

Clinical utility of EEG?

A
  • to distinguish epileptic seizures from:
    psychogenic spells, syncope, movement disorders, migraine variants
  • diff organic causes of encephalopathy or delirium from psychiatric causes
  • testing for brain death
  • determining whether or not to wean anti-epileptic meds (not having seizures anymore)
36
Q

Setup of electrodes in an EEG?

A
  • consists of 10-20 electrodes and a nasopharyngeal lead that is placed in nose and advanced to pharynx near the temporal lobe
  • electrodes on the scalp record synaptic activtiy of the brain
  • electrical activity is recorded as a wave form
  • the wave forms are labeled according to their amplitude: delta - 0.4 Hz, theta 4-8 Hz, alpha 8-12 Hz, beta is greater than 12 Hz
37
Q

What does increased slow wave activity in an awake person mean?

A
  • may be focal brain lesion
    theta and delta wves
  • increased slow waves - abnormal
  • focal delta activity is usually irregular in configuration and is termed polymorphic delta activity (PDA- usually indicative of focal brain lesion)
38
Q

What is EEG a sensitive test for?

A
  • for encephalopathy
  • gen. theta and delta activity is an indication of encephalopathy
  • also very useful in dx of seizure disorders, epileptiform d/c’s are common b/t overt seizures as well as during seizures
39
Q

What events can induce seizures, thus increasing EEG test sensitivity?

A
  • hyperventilation, photic stimulation, sleep, sleep deprivation, drugs
40
Q

When is an EEG used?

A
  • commonly used to work up seizure disorder
  • able to dx seizures, encephalopathy, focal brain lesions
  • However, normal EEG doesn’t rule out epilepsy (possible to miss infrequent epileptic activity - try for multiple recordings)

Neuro (19 decks)

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