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
2
Q
Site of LP?
A
- L3-L4 or L4-L5
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
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
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
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
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
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
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
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
11
Q
Xanthochromia - orange?
A
- blood breakdown products, high carotenoi ingestion
12
Q
Xanthochromia - pink?
A
- blood breakdown products
13
Q
Xanthochromia - green?
A
- hyperbilirubinemia, purulent CSF
14
Q
Xanthochromia - brown?
A
- meningeal melanomatosis (melanoma of CNS)
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
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
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)
