Neuro Flashcards
Where is CSF made?
In the ependymal cells of the choroid plexus in the lateral ventricles.
- The choroid plexus is essentially the blood-brain barrier. It is only one cell thick and prone to hemorrhage.
- Normally, 20-30mL/hr of CSF is made.
*About 500mL of CSF is made every day and reabsorbed into superior saggital sinus via the arachnoid granulations.
Name some of the functions of the CSF:
- Transports nutrients, chemical messengers and waste products.
- Supports and cushions the brain.
- Interchanges with interstitial fluid of the brain.
- Surrounds all exposed surfaces of the CNS.
What is normal ICP?
5-15mm/Hg
Anything above 20mm/Hg is considered for treatment.
Basic functions of the cerebellum…
Coordination of voluntary movement
Balance/equilibrium
Muscle tone
Basic functions of the basal ganglia
Controls movement, even blinking. Because we are always moving, the BG has a high metabolic demand. Therefore, it functions poorly in hypoxic states.
Parkinson’s effects the BG.
What is the tentorium?
- A prominent fold in the dura mater that separates the upper brain (supratentorium) from the lower brain (infatentorium) at the level of the cerebellar/occipital interface.
- The only communication between the infa and supra is the channel that connects the third and fourth ventricle.
Basic functions and cranial nerves of the Pons…
Reticular Activating System (RAS)
Contains CNs IV, V, VI, VII and VIII
Dysfunction occurs in infratentorial herniation due to proximity to cerebellar tonsils.
Basic functions and cranial nerves of the medulla oblongata…
Regulates autonomic functions such as HR, BP and digestion.
Contains CNs IX, X, XI and XII, and the respiratory center.
CN I
Olfactory
Transmits sense of smell from nose to brain
CN II
Optic nerve
Transmits visual information from retina to occiput via the midbrain.
Communicates directly with CN III. A bright light is sensed by CN II, then both pupils should constrict in response to stimuli from CN III.
Located in midbrain
CN III
Oculomotor
Eye movement, pupillary constriction, upper eyelid move’t
Located in midbrain
Will be affected by supratentorium ICP since it will be compressed by the uncus (uncal herniation).
CN IV
Trochlear
Allows eye to look down and inward
Located in anterior, superior pons
CN V
Trigeminal Has three branches at different levels of the face (V1 ophthalmic, V2 maxillary, V3 mandibular) that sense facial stimulation. Mastication Assessed via corneal reflex Located in superior, anterior pons
CN VI
Abducens
Allows eye to turn outward
CN VII
Facial
Facial muscle movement
Assessed via corneal reflex
Located in mid pons
CN VIII
Vestibulochlear/Accoustic
Transmits sounds and equilibrium information from the inner ear to the brain.
Assessed via doll’s eye test.
Located in inferior pons
CN IX
Glossopharyngeal
Muscle control of pharynx (assists with swallowing)
Gag reflex
Located in superior medulla.
Will be compressed by cerebellar tonsils in cases of infratentorium pathology.
CN X
Vagus
- Sensory innervation of pharynx, larynx, thoracic and abdominal viscera, heart, GI tract and tongue.
- Motor innervation to pharyngeal and laryngeal muscles.
- Provides parasympathetic innervation to the thoracic and abdominal viscera including the heart, GI tract and most abdominal organs.
- Gag and cough reflex
- Loacated in superior medulla, just above the respiratory center.
CN XI
Accessory/Spinal Accessory
- Cranial branch controls muscles of soft palate and pharynx.
- Spinal branch controls trapezius and SCMs.
CN XII
Hypoglossal
Innervation muscles of tongue
Trace right side cerebral blood flow from LV to brain…
Anterior
Aorta -> brachiocephalic -> right common carotid -> internal carotid -> circle of Willis -> MCA/AComm/ACA
Posterior
Aorta->brachiocephalic -> right vertebral artery-> basilar -> PCA/PComm
Trace left sided cerebral blood flow…
Anterior
Aorta -> left common carotid -> left internal carotid -> circle of Willis -> MCA/AComm/ACA
Posterior
Aorta->left subclavian -> left vertebral -> basilar -> PCA/PComm
The internal carotid arteries account for approximately how much of the cerebral blood flow?
40% each.
The vertebral arteries account for 10% each.
What lobes does the MCA supply and what does its stroke syndrome look like?
Stems from the Circle of Willis. It is the largest of the cerebral arteries and is the one most often associated with CVAs. It feeds the temporal, parietal and some of the frontal lobes.
Of the cortical homunculus, it supplies the face and arms.
Facial droop, arm hemiparesis
Global aphasia - trunk of L MCA
Broca’s aphasia - anterior branch of L MCA
Wernicke’s aphasia - posterior branch of L MCA
List the vessels that stem from the Circle of Willis
MCAs
PCAs
ACAs
If collateral circulation exists, how long can a penumbra remain salvageable for?
6-8 hours
What percentage of CVAs are ischemic?
87%
(70% thrombotic [clot forms at site], 30% embolic [clot travels from elsewhere and lodges in vessel])
*The remaining 13% of CVAs are hemorrhagic
There are three types of aneurysms (fusifor, saccular and berry). What is the most common type?
Berry
(Berry shaped aneurysm at bifurcation)
*The ACommA is a common site for berry aneurysms and SAH.
How can you tell the difference between a CVA and a focal hemi-seizure?
- A person having a CVA will have a left sided lesion that causes right side deficits but will a have left sided gaze. (Looking toward the lesion).
- A focal seizure from the left brain could also have a right side deficits, but will have a right sided gaze along with it (looking away from the stimulus).
What type of strokes are associated with sudden onset dizziness, gaze palsy, nystagmus, N/V, ataxia, gait disturbance and incontinence?
Cerebellar CVAs.
They are generally severe and associated with high rates of mortality due to compression of the medulla.
Full occlusion of the basilar artery can result in what syndrome?
Locked In Syndrome (total muscle paralysis).
The basilar artery supplies the brainstem with 100% of its CBrDO2.
If someone has face, arm and leg hemiparesis, what is the most likely cause of the CVA?
It will likely be a deep tissue site in the internal capsule. Another possible source is carotid artery occlusion.
What lobe(s) does the ACA supply and what would its stroke syndrome look like?
Frontal lobe.
It includes the leg of the cortical homunculus.
Dysarthria, dysphasia, urinary incontinence.
Leg/shoulder hemiparesis > arm/hand/face hemiparesis
What lobe(s) does the PCA supply?
Occiput
Vision loss will occur if occluded.
What lobe(s) does the basilar artery supply?
It supplies 100% of the brainstem and RAS.
Occlusion will result in CN dysfunction, seizures and locked in syndrome.
*Seizures with CN dysfunction (facial palsies, occulomotor dysfunction, abnormal V/S) is a vestibular-basilar stroke until proven otherwise.
Where does CSF leave the CNS?
At the superior sagittal sinus at the top of the brain. If ICP rises, CSF is forced out but the fluid is still in the cranial vault since it needs to descend down the venous system.
Key features of uncal herniation…
- Ipsilateral pupillary dilation to site of insult
- Contralateral hemiparesis
Myp’s step by step (superior to inferior brainstem) cranial nerve exam…
- Open eyes, assess symmetry and size (midbrain CN II, III)
- Constriction x 2 pupils in response to light (midbrain CN II, III)
- Corneal reflex - eyes should blink (superior pons; middle pons CN V, VII)
- Doll’s eyes test - if no c-spine (inferior pons CN VIII)
- Gag reflex (superior medulla CN IX)
- Cough reflex (superior medulla CN X)
- Respiratory drive (middle medulla)
Post cardiac arrest, the patient is demonstrating roving eyes. What is this indicative of?
CN III, IV, VI are functioning and receiving input from the cortex.
When reporting on a neuro patient, what are three things that are important to communicate?
- Confounders such as sedation, hypothermia
- Brainstem reflexes, including any apneic periods
- GCS, especially motor exam
Score a GCS - M6
- Obeys commands. Can look right/left, stick out tongue and give a thumbs up or wiggle fingers/toes. Squeezing the hands is a primitively response so avoid assessing it.
- Indicates cortex is intact.
Score a GCS - M5
- Place arms at pt’s side and provide a pain stimulus (trap squeeze, supraorbital pressure). Pt’s contralateral arm must move across midline.
- Indicates cortex is intact, but dysfunctional.
Score a GCS - M4
Withdraws
- Place pt’s hands on abdo and provide constant fingernail stimuli. Pt’s hand must curl and pull away.
- Indicates severe cortical dysfunction.
Score a GCS - M3
Abnormal Flexion
- Place pt’s hands on abdo and provide constant pressure to fingernail. Pt’s hand must supranate and bicep will flex.
- Indicates deep brain damage and cortex is fucked.
Score a GCS - M2
Abnormal Extension
- Place pt’s hands on abdo and apply constant fingernail pressure. Pt’s arms must fully extend with flexed triceps and hands rotated outwards. Feet will point down.
- Indicates brainstem pathology.
List the five reflexes and associated spinal roots
Bicep - C5 Brachioradialus - C6 Tricep - C7 Knee - L4 Achilles - S1 Grade on a scale of absent->normal->brisk.
The plantar reflex is a upper motor neurone sign. If the toes point up, is it a good thing or a bad thing?
Bad thing. Toes should point down.
What’s the difference between dysarthria and dysphasia?
Dysarthria can still comprehend and produce writing. Dysarthia means your tongue isn’t working due to loss of brain input. Dysphasia means your brain is fucked and make you no words good.
Is monitoring pupillary response a solid clinical finding for cerebellar pathology?
No. CN II and III are located in the superior portion of the midbrain and will not be effected in the case of cerebellar ICP increases.
Describe the Monro-Kellie Doctrine:
The cranial vault is made up of 80% parenchyma, 10% CSF and 10% arteries and veins. If the mass of one increases, there must be a reduction in one or two of the other. Since veins and CSF are the only low pressure compartment, fluid must shift out of these compartment.
What is the approximate volume of the cranial vault and its contents?
1600mL
Parenchyma: 1300mL
Vessels: 150mL
CSF: 150mL
What is the intracranial compliance curve?
In regards to the Monro-Kellie doctrine, intracranial compliance worsens as pathological mass increases. CSF and venous blood are shunted out of the cranium as ICP is driven upwards. The curve eventually plateaus when the parenchyma starts to herniate.
List the three waves in an ICP waveform:
P1: arterial pulsation (gets smaller with ICP increase)
P2: venous/parenchymal bulk (gets larger with ICP increase)
P3: closure of the aortic valve
How does mannitol work? How is it different from HTS?
Osmolar diuretic. It draws fluid out of brain parenchymal cells, thus reducing the volume of parenchyma. The extra fluid is then diuresed by the kidneys. It is a volume contractor whereas HTS is a volume expander and a better agent in hypovolemic states.
How much will elevation HOB and loosening collars reduce ICP by?
HOB: 5-10mmHg
Collar: 5-10mmHg
How does appropriate sedation facilitate a reduction in ICP?
Decreases cellular metabolism which decreases CBF via flow-metabolic coupling.
How much change in ICP does one mmHg of PaCO2 affect?
Every 1 mmHg of PaCO2 will change CBF by 2-3%. Since there is only 150mL of intracranial blood, small changes in PaCO2 can drastically affect CBF.
Target PaCO2 to 35-40mmHg
When using mannitol, how much fluid do you put back in?
Measure urinary output and replace fluid (normal saline) at a 1:1 ratio.
What is the caveat to using 3% HTS?
It has an osmolarity of 512mmol. If urine osmolarity is greater, it won’t work. Use 5% HTS if you can get it.
HTS is incompatible with almost all drugs so it must go through it’s own IV line. It is not contraindicated for I/O.
How much does one degree of temperature change affect CBF?
20%.
If patient’s are hyperthermic, it is likely due to hypothalamic dysfunction. Acetaminophen won’t work well, so actively cool the patient instead.