Neuro Flashcards
Where is CSF absorbed? Produced?
Absorbed in the arachnoid villi in superior saggital sinus
CMR02
3-3.8mL/02/100 g brain tissue/min
60% electrical activity, 40% cell integrity/housekeeping
CMR02 ↓ 7% for each 1C temp ↓
Locations of cell bodies of spinothalamic neurons
1st order neuron: Dorsal root ganglion
2nd order neuron: Dorsal horn
3rd order neuron: Thalamus
Posterior circulation of brain
Vertebral, basilar a.
Aorta → subclavian → vertebral → basilar → posterior fossa, cervical spinal cord
Anterior circulation of brain
Carotid
Aorta → carotid → internal carotid → O of Willis → hemispheres
CBF
45-55mL/100g tissue/min (global)
<20= evidence of ischemia
15=complete cortical suppression
<15=membrane failure and cell death
Determined by: CMR02 CPP Venous pressure PaC02 Pa02
Most common site of transtentorial herniation?
Temporal uncus
With ↑ ICP, temporal uncus is forced from supratentorial space → infratentorial space. This ↑ pressure on the midbrain..
..CNIII (oculomotor) originates from the midbrain and crosses near the tentorium. Herniation here puts pressure on the nerve, making it ischemic. Clinically, this manifests as a fixed and dilated pupil.
Cushing’s triad
HTN, bradycardia, irregular respiration’s
HTN: ↑ ICP → ↓ CPP. BP ↑ in effort to preserve CPP
Brady: reflex brady from HTN
Irregular resp: Compression of medulla → irregular breathing
Anticonvulsants that → thrombocytopenia, anemia?
Thrombocytopenia: Valproic acid (kids>adults), Carbamazepine
Aplastic anemia: Phenytoin, Carbamazepine
Dorsal column (medial lemnsical)
SENSORY
Mechanoreceptive sensations:
- fine touch, proprioception, vibration, pressure
- capable of 2 point discrimination
- large, myelinated, fast fibers
Perfused by posterior blood supply
Meds to avoid with Parkinson’s
Anything that antagonizes dopamine
Metoclopramide
Butyrophenones (hallow and droperidol)
Phenothiazines (promethazine)
Alfentanil: May cause acute dystonic reaction
Ketamine is controversial
Sux and NDMBs both actually OK
Only 3 conditions definitively linked to MH
- King Denborough syndrome
- Central core disease
- Multiminicore disease
ALSO: families from Wisconsin, WV, Michigan appear to be at higher risk. Males, and youth as well.
4 Determinants of CBF
CMR02 (3.5 mL/02/100g brain tissue/min)
CPP [(MAP-ICP or CVP, whichever higher)] - intracranial tumors, head trauma, VAs abolish autoregulation
Venous pressure (↑ VP → ↓ cerebral drainage → ↑ volume)
PAC02
Pa02
Bleeding, vasospasm with cerebral aneurysm
Arterial bleeding is usually subarachnoid
Venous bleeding is usually subdural
Corticospinal tract (pyramidal)
MOTOR: most important motor pathway
- lateral corticospinal tract decussates in medulla
- ventral corticospinal tract fibers remain on ipsilateral side as they descend via ventral corticospinal tract, and cross over to the contralateral side of spinal cord in cervical or thoracic area
BABINSKI’S sign is a test of the integrity of the corticospinal tract.
Difference between upper motor neurons and lower motor neurons
Upper motor neurons: cortex → ventral horn
- If an injury occurs above the level of decussation in the medulla, paralysis will be contralateral
- If an injury occurs below the level of decussation in the medulla, paralysis will be ipsilateral
- Upper motor neuron injury presents as hyperreflexia and spasticity
Lower motor neurons: ventral horn → NMJ
- These are the fibers that link the spinal cord to a muscle
- Injury to lower motor neuron → ipsilateral paralysis
- Lower motor neuron injury presents with impaired reflexes and flaccid paralysis
Spinothalamic tract (anterolateral)
SENSORY
Pain, temperature, crude touch, tickle, itch, sexual sensation
- cannot do 2-point discrimination
- Smaller, slower fibers, but they are still myelinated
Laminae
Grey matter is subdivided into 9 laminae
- Laminae I-VI (1-6) = dorsal = sensory
- Laminae VII-IX (7-9) = ventral = motor
-pain neurons synapse in the substantia gelatinosa in laminae II, III
Types of peripheral mechanoreceptors that comprise dorsal column/medial lemniscal system
Meissner’s corpuscles: Two point discriminative touch, vibration
Merkel’s discs: Continuous touch
Ruffini’s endings: Proprioception , prolonged touch and pressure
Pacinian corpuscles: Vibration
How can you tell if its neurogenic shock or hypovolemic shock in a trauma?
Neurogenic → bradycardia, hypotension, hypothermia with pink, warm extremities
Hypovolemic → tachycardia, hypotension, cool clammy extremities
Where is the BBB not present/not great?
ANATOMY: CRTZ Posterior pituitary Pineal gland Parts of hypothalamus
PATHOLOGY: Tumor TBI Infection Ischemia Poorly developed in neonates
Order of CSF flow
Lateral ventricles → Foramen of Monro → 3rd ventricle → Aqueduct of Sylvius → 4th ventricle → BLL paired foramen of Luschka, midline foramen Magendie → subarachnoid space (brain and SC) + central canal of SC → superior saggital sinus (absorption)
Relationship between PaC02 and CBF
Linear.
PH of the CSF around the arterioles controls the CVR.
- at PaC02 40mmHg, CBF = 50mL/100g/min
- 1mmHg ↑ = CBF ↑ 1-2 (max vasodilation at PaC02 80-100)
- 1mmHg ↓ = CBF ↓ 1-2 (max vasoconstriction at PaC02 25)
Metabolic acidosis does not affect CBF because H+ does not pass thru BBB. Only C02 does.
How does Pa02 affect CBF?
- Pa02 below 50-60mmHg → cerebral vasodilation → ↑ CBF
- Pa02 above 60mmHg, no effect on CBF.
