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Neurology Adams > Diagnostics > Flashcards

Diagnostics Flashcards

1
Q

What are the possible complications of lumbar puncture? Give at least 3.

A

(1) Headache, especially in patients with migraine
(2) bleeding into the spinal/ epidural space
(3) infection, if technique is not sterile

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2
Q

What blood parameters can signify increased risk of bleeding into the spinal/epidural space in patients who are about to undergo lumbar puncture?

A

(1) patients on anticoagulation, with INR greater than 1.4
(2) patients with low platelet counts ( less than 50,000/ mm3)
(3) patients with impaired platelet function (as in alcoholism or uremia)

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3
Q

What is the normal CSF pressure in an adult in a lateral decubitus position?
How about in children?

What happens to the pressure at the lumbar sac when the patient is seated?

A

Adult in lateral decubitus position: 100-180 mm H2O or 8-14 mm Hg
Child in lateral decubitus position: 30-60 mm H2O

When seated, there is about 2x increase in pressure

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4
Q

When does the CSF look hazy pink to red? At what number of RBCs/ mm3?

A

At 1,000-6,000 RBCs per mm3, CSF may be hazy pink to red in color

At at least 200 RBC per mm3 it may only be hazy or ground glass

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5
Q

What are the ways to discriminate between a traumatic tap in Subarachnoid hemorrhage, based on CSF results?

A

First, you need multiple samples

(1) A traumatic tap will have decreasing number of RBCs per sample
(2) A traumatic tap would have normal CSF pressure, in SAH pressure may be increased
(3) In traumatic tap, blood may clot or form fibrinous webs, this does not happen in SAH CSF
(4) in SAH, RBCs hemolyze within a few hours, it becomes pink-red (erythrochormia); if the tap is taken a t least one day after the bleed, then the supernatant fluid will already be xanthochromic

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6
Q

What can cause xanthochormia in the supernatant of CSF?

A

(1) Subarachnoid hemorrhage
(2) traumatic tap with a lot of venous blood ( more than 100,000 per mm3)
(3) severe jaundice
(4) diseases with increased CSF protein (at more than 150 mg/100 mL)
(5) hypercarotenimia
(6) hemoglobinemia

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7
Q

What is the usual ratio of WBC to RBC in a traumatic tap, when serum hematocrit is normal?

A

1 - 2 WBC per 1,000 RBC

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8
Q

What is Froin syndrome?

A

High CSF protein ( at least 1,000 mg/dL), deeply yellow CSF, and CSF that clots readily (because of presence of fibrinogen)

Seen in cases of block to CSF flow, such as in tumor, mass, infection)

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9
Q

What is the normal protein content of CSF in adults at the level of the lumbar spine? basal cistern? ventricles?

How about children?

A

Normal CSF Protein in Adults:
At lumbar subarachnoid space: 45- 50 mg/dL
At basal cistern: 10-25 mg/dL
At ventricles: 5-15 mg/ dL

In children, lower than adults, less than 20 mg/dL at lumbar subarachnoid spac

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10
Q

In hemorrhages, particularly into the ventricles or subarachnoid space, how does the protein level change relative to the number of RBCs?

A

CSF protein should increase by 1 mg per 1,000 RBCs,

However, in SAH, CSF protein may be even higher due to the irritating effect of hemolyzed RBCs to the leptomeninges

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11
Q

What is the major immunoglobulin in CSF?
How much of the CSF total protein does it comprise of?
What is its distribution relative to blood?

A

The major immunoglobulin in CSF is IgG

IgG comprise about 12% of the total CSF protein. (This may be higher in MS, neurosyphillis, SSPE, chronic viral meningitides)

Gamma globulin fraction in CSF is approx. 70% that of serum

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12
Q

What is the normal CSF glucose?

What is the normal proportion of CSF glucose to blood glucose levels?

How is this ratio affected by hypo or hyperglycemia?

A

Normal CSF glucose if 45-80 mg/dL

Normally, CSF glucose if 2/3 or 0.6 to 0.7 of blood glucose concentrations

In marked hyperglycemia, the ratio decreases to 0.5 to 0.6, in hypoglycemia, it increases to 0.85

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13
Q

What conditions can cause a false positive CALAS?

A

High titers of rheumatoid factor

High titers of antitreponemal antibodies

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14
Q

What conditions can cause false positive VDRL or RPR?

A

Collagen disease
Malaria
Yaws

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15
Q

What is the average osmolality of CSF? how does it compare to blood?

A

The average osmolality of CSF is 295 mOsm/L

This is similar to plasma

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16
Q

What isoenzyme of lactate dehydrogenase is present in the CSF of patients with bacterial meningitis but not aseptic or viral meningitis?

In what other condition can CSF LDH be elevated?

A

LDH Isoenzyme 4 and 5

LDH is also elevated in meningeal tumor infiltration, particularly in lymphoma.
(N.B. CEA is also elevated in meningeal tumor infiltration, but not in bacterial meningitis)

17
Q

What pigments color the CSF in SAH? How can they be used to determine how old the hemorrhage is?

A

Oxygemoglobin- appears within several hours after the hemorrhage, becomes maximal in approx 36 hours, diminishes over a 7-9 day period.

Bilirubin- begins to appear in 2-3 days, increase in amount as oxygemoglobin decreases

Methemoglobin- appears when blood is loculated or encysted and isolated from the flow of CSF

18
Q

At what GFR should IV contrast for CT scan be witheld to avoid inducing nephropathy?

A

Do not administer IV CT contrast for patients with GFR less than 30 ml/min/1.73 m2.
If GFR is between 30-60, may give CT contrast after hydration and discontinuation of nephrotoxic medications such as NSAIDS, cisplatin containing chemotherapy, aminoglycosides

19
Q

How long after IV contrast for CT scan is given should you wait before repeating a contrast study?

A

Repeat infusion of IV contrast should be avoided if there is exposure to contrast in the last 72 hours

20
Q

What are the possible complications of overexposure to radiation, ie in CT scans?

A

Alopecia, leukomalacia, neoplasia

21
Q

Which atom’s signal does the MRI use to make images from?

A

Hydrogen. The MRI image is essentially a map of hydrogen content of tissue

22
Q

What condition is a rare but severe possible complication of gadolinium?
How long after contrast administration can this occur?

A

Nephrogenic Systemic Fibrosis- this is a severe cutaneous sclerosing disease, it occurs mostly in patients with preexisting renal failure.
Kidney sclerosis may appear from several days to 2 months after procedure

23
Q

How does fat appear in CT scan? MRI T1? T2?

A

Fat is black in the CT scan, White on MRI T1, Black on MRI T2

24
Q

What marker in the MR spectroscopy indicate neuronal integrity?
In what conditions is it decreased?

A

N-acetylaspartate (NAA)
It is decreased in destructive lesions and in conditions where there is reduction in the density of neurons (ex. edema or glioma that increases distance between neurons)

25
Q

What is choline a marker of in MR spectroscopy?

How does it change in glioma?

A

Choline is a marker for membrane turnover

It is elevated in some rapidly dividing tumors, including gliomas.

26
Q

What is the usual incidence of complications from conventional angiography?

A

2.5%, this usually comprise of worsening of the vascular lesion or complications on the arterial puncture site
Rare but disastrous complication of angiography: myelopathy (ex. cervical myelopathy in vertebral artery angiography- precise mechanism unknown)

27
Q

What is the frequency of the waves used in ultrasonography?

How about transcranial doppler

A

The ultrasound transducer converts electrical energy to ultrasound waves of frequency ranging from 5-20 kHz
Transcranial doppler uses 2 MHz pulsed signals

28
Q

What is the composition and size of EEG electrodes?

A

EEG electrodes are silver or silver chloride discs, 0.5 cm in diameter

29
Q

What is the proper rate of hyperventilation for EEG?

What is the frequency of photic stimulation, and how far should the light source be?

A

Hyperventilation: 20 deep breaths per minute for 3 minutes

Photic stimulation: frequency of 1-20 per second, with light source about 15 inches from the patient’s eyes.

30
Q

What is the frequency of the dominant rhythm in infants?

At what age does the occipital alpha rhythm appear?

At what age is the adult frequency reached?

A

Frequent dominant rhythm in infants is typically about 3 Hz

Alpha rhythm appears by age 6 years

Adult frequency is reached by age 10-12 years

31
Q

How are spike and sharp waves differentiated in terms of time period?

A

Spike waves: 20-70 ms

Sharp waves: 70-200 ms

32
Q

At what voltage is an EEG said to be isoelectric?

A

At 2uV
This may indicate brain death, in the absence of nervous system depressants or extreme hypothermia, and if patient has no brainstem reflexes nor spontaneous respiratory or muscular activity

33
Q

What is the characteristic EEG finding in Herpes simplex encephalitis?

A

Periodic high voltage sharp and slow wave complexes at intervals of 1-3 per second in the temporal regions are characteristic of herpes simplex encephalitis

34
Q

What is the expected latency of the P100 in PSVER?
What is the upper limit?
What is the interside difference between 2 eyes?

A

P100 expected latency is 100 ms
Upper limit is 118 ms
If difference in latency is greater than 9 ms, then there is involvement of one optic nerve

35
Q

Which areas of the auditory tract is correlated with each wave in the BAER?

A 
Wave 1: auditory nerve
Wave 2: cochlear nuclei (pons)
Wave 3: superior olivary nucleus
Wave 4: lateral lemniscus
Wave 5: Inferior colliculus (midbrain)
Wave 6: Medial geniculate (?)
Wave 7: Auditory radiations (?)
36
Q

What are the mean and upper limit of the interwave latencies in the BAER?

A

Between wave I and III: mean 2.1 ms, upper limit 2.6 ms
Between wave III and V: mean 1.9 ms, upper limit 2.4 ms
Between wave I and V: mean 4.0 ms, upper limit 4.7 ms

Interside difference for most latencies: mean 0.1 ms, upper limit 0.4 ms

37
Q

What are the different points/ latencies measured in the SSEP of the upper and lower extremities?

A

Upper extremity
* Erb’s point : mean 9.7 ms, upper limit 12 ms
* P/N 13 (cervicomedullary area)
* N19/P 21 (parietal cortex)
Interwave latency
* Erb’s to N13, mean 3.8 ms, upper limit 5.2 ms
* P/N13 to N19, mean 5.5 ms, upper limit 6.8 ms
Interside difference
* P/N13- N19, mean 0.3 ms, upper limit 1.1 ms

Lower extremity (stimulation from ankle, in a 165 cm height person)
* Lumbar point (cauda): mean 20 ms, upper limit 25 ms
* N/P 37 (cortex)
Interwave latency
* Lumbar - N/P 37: mean 16.4 ms, upper limit 21.6 ms
Interside difference
* Lumbar- N/P 37: mean 0.7 ms, upper limit 1.9 ms

Neurology Adams (3 decks)

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