2. Special Techniques For Neurologic Diagnosis Flashcards
T/F: LP should generally be preceded by CT or MRI whenever elevation of ICP is suspected.
True
Indications for lumbar puncture:
- To obtain pressure measurements & procure a sample of CSF for cellular, cytologic, chemical, & bacteriological examination
- To aid in therapy by the administration of spinal anesthetics & occasionally, antibiotics or antitumor agents, or by reduction of CSF pressure
- To inject radiopaque substance, as in myelography, or a radioactive agent, as in radionuclide cisternography
Corticosteroids are particularly useful in situations in which increased ICP is caused by __________
Vasogenic cerebral edema
LP is easiest to perform at _____ interspace.
L3-L4
L3-L4 interspace corresponds to __________
The axial plane of the iliac crests
The most common complication of LP
Headache
Normal opening pressure in an adult:
100-180 mm H2O or 8-14 mm Hg
LP opening pressure reflecting increased ICP:
> 200 mm H2O
LP opening pressure indicating intracranial hypotension:
</= 50 mm H2O
Test which confirms the presence of a spinal subarachnoid block confirmed by jugular venous compression (tests for rapid rise in pressure within a few seconds after release of pressure on the vein):
Queckenstedt test
How much RBCs imparts a hazy or ground glass appearance to CSF?
200/mm^3
How much RBCs imparts a hazy pink to red color of the CSF?
1000-6000/mm^3
Distinguish a traumatic lumbar tap from subarachnoid hemorrhage:
Traumatic tap:
1) decreasing number of RBCs on 2nd & 3rd tubes
2) CSF pressure is usually normal
3) it will clot
In SAH, RBCs begin to hemolyze within a few hours giving a pink-red discoloration to the supernatant fluid. This is called __________
Erythrochromia
In SAH, if the supernatant fluid from a lumbar tap is left to stand for a day or more, the fluid becomes yellow brown. This is called __________
Xanthochromia
The pigments that discolor the CSF following SAH are:
Oxyhemoglobin
Bilirubin
Methemoglobin
This pigment appears within several hours of hemorrhage, becomes maximal in approximately 36 h, & diminishes over a 7- to 9-day period:
Oxyhemoglobin
This pigment begins to appear in 2-3 days & increases in amount as oxyhemoglobin decreases:
Bilirubin
This pigment appears when blood is loculated or encysted & isolated from the flow of CSF:
Methemoglobin
Protein content of lumbar spinal fluid:
</= 45-50 mg/dL
A combination of:
1) CSF protein content of >/= 1000 mg/dL, indicating a block to CSF flow
2) fluid is deeply yellow
3) clots readily due to presence of fibrinogen
Froin syndrome
What is the major immunoglobulin in normal CSF?
IgG
What is the normal CSF glucose concentration?
45-80 mg/dL (about 2/3 of that in the blood)
T/F: As a rule, viral infections of the meninges and brain lower the CSF glucose
False
What is the average osmolality of the CSF?
295 mOsm/L (identical to that of plasma)
What is the normal pH of the CSF?
7.31 (slightly lower than arterial blood: pH 7.41)
T/F: In T1-weighted images, CSF appears dark while in T2-weighted images, CSF appears white
True
This is a type of susceptibility technique in MRI which is especially sensitive to blood & its breakdown products
Gradient-echo (GRE) sequences
An MRI technique which gives a high signal for parenchymal lesions & a low signal for CSF
FLAIR (fluid-attenuated inversion recovery)
A paramagnetic agent that enhances the process of proton relaxation during the T1 sequence of MRI, which permits even sharper definition & highlights regions surrounding many types of lesions where the BBB has been disrupted
Gadolinium
A procedure that has been invaluable in detecting the earliest stages of ischemic stroke (generally within 2 hrs or less of onset) & also useful in distinguishing between cerebral metastases & abscesses
Diffusion-weighted imaging (DWI)
This is the main technique used in functional MRI (fMRI), which measures the difference between oxy- & deoxyhemoglobin, which reflects blood delivery to the region
Blood-oxygen level dependent (BOLD) signal
8- to 12-per-second sinusoidal waves in both occipital & parietal regions that wax & wane spontaneously & are attenuated or suppressed completely with eye opening or mental activity
Alpha waves
Faster than 12 Hz & of lower amplitude (10-20 mV) that are normally recorded from the frontal regions
Beta waves
Waves below 4Hz with amplitudes from 50-350 mV
Delta waves
Waves with frequency of 4-7 Hz
Theta waves
Transient high-voltage waveforms that have a pointed peak at recording speeds & duration of 20-70 ms & 70-200 ms
Spikes or sharp waves
Spikes or sharp waves that occur interictally in people with epilepsy or in individuals with a genetic disposition to seizures
Epileptiform discharges
3-per-second spike-and-wave complexes that characteristically appear in all leads of the EEG simultaneously & disappear almost as suddenly at the end of the seizure are associated with what type of seizure?
Absence seizures
The most pathologic EEG finding
Electrocerebral silence
