Neurology

Question 1

How does cisatracurium work?

Answer 1

Competes with acetylcholine binding at postsynaptic nicotinic receptors on motor end plate; acetylcholinesterase inhibitors such as neostigmine reverse neuromuscular blockade

Degraded in plasma by ester hydrolysis and Hofmann elimination (pH and temperature dependent - acidotic and hypothermic patients have longer half life)

Laudanosine is a metabolite of cisatracurium, can accumulate with repeated dosing or during continuous infusion, can cause hypotension

Question 2

List the normal EEG waves

Answer 2

Normal awake/asleep = alpha and beta (high frequency low amplitude); burst suppression = low frequency high amplitude

Question 3

Symptoms of epidural hematoma

Answer 3

60% of adults have a lucid period, less common in kids

Headache, nuchal rigidity, ipsilateral pupillary dilation, contralateral hemiparesis, coma

Question 4

List 3 types of dystrophinopathy

Answer 4

1. Duchenne muscular dystrophy
2. Becker muscular dystorphy
3. X-linked dilated cardiomyopathy

Question 5

How does Emery-Dreifuss muscular dystrophy present?

Answer 5

Early childhood, joint contractures (elbows, ankles, cervical spine), later skeletal muscle weakness

Mutationes in genes encoding emerin, lamin A, lamin C, nesprin (EMD, FHL1, LMNA)

Question 6

What impact does hypothermia have on neuromuscular blockade?

Answer 6

Prolonged duration of action – doubles for each 2 degree drop below 36.5 C

Question 7

What percent of kids with VP shunt malfunction have a negative CT scan?

Answer 7

13 to 30%

Question 8

Treatment for acute dystonia resulting from haldol

Answer 8

Diphenhydramine or benztropine

Dystonia is an unpredictable adverse effect of antipsychotic meds characterized by abnormal and prolonged contraction of the muscles of eyes, head, neck, limbs, or trunk; excess nigrostriatal dopamine blockade leading to excess cholinergic output

Question 9

What are the symptoms of infant botulism?

Answer 9

Generalized weakness, hypotonia, decreased activity, poor feeding, constipation, cranial nerve palsy, sluggish pupils, hypoventilation with shallow rapid breaths, occasional respiratory failure; no fever

Symmetric descending paralysis, fatiguability with repetitive stimulation of muscle contraction (e.g. repeatedly assess pupillary light reflex over 1-3 min)

Enema with sterile water for sample to detect toxin, treat with botulism immune globulin

Question 10

What is Nusinersen?

Answer 10

Treatment for spinal muscular atrophy (SMA) type 1

Intrathecal, binds specific sequence in SMN2 gene, increases production of functional SMN protein

Question 11

CSF in botulism vs. guillane barre?

Answer 11

Botulism: normal
GBS: high protein

Question 12

Hemodynamic impact of sevoflurane?

Answer 12

Hypotension (low SVR), cerebral vasodilation, decreases cerebral metabolic rate, preserves cerebral autoregulation

Question 13

Goal cerebral perfusion pressure by age?

Answer 13

Infant >40
Child >50
Adult >60

Question 14

How do reversal agents work?

Answer 14

Neostigmine - acetylcholinesterase inhibitor, so makes ACh last, but if there’s still NMB around can have re-paralysis (“recurarization”), can cause bradycardia - procholinergic

Sugammadex - noncompetitive, reverses vec and roc only, encapsulates the aminosteroid through chelation

Sugammadex WON’T reverse succinylcholine or atracurium/cisatracurium (those degraded in plasma)

There is no reversal for succinylcholine

Question 15

Ketamine

Answer 15

Dissociative state (sedation), amnesia, and analgesia without cardiac or respiratory depression

Bronchial smooth muscle dilation

N-methyl-D-aspartate receptor antagonism and u-opioid receptor agonism

Causes release of catecholamines, blocks reuptake of norepinephrine; also has direct myocardial depressant activity, use with caution in catecholamine-depleted patients

Contraindicated: hypertension, aneurysm, thyrotoxicosis, psychotic disorders

Question 16

Haloperidol

Answer 16

Typical antispychotic agent

QTc prolonging, extrapyramidal effects, drowsiness, dystonia, tremor

Butyrophenone class, nonselective blockade of brain postsynaptic dopaminergic D2-receptors

Question 17

Review the cellular pathways involved in neuronal injury following oxygen deprivation

Answer 17

Three phases of injury:
1. Exhaustion of cells energy stores

2. Excitatory neurotransmitters, inflammation, ROS, necrosis (encephalopathy and seizure)
   >Glutamate binds NMDA and AMPA receptors, persistent stimulation causes excitotoxicity - damage to neurons with glutamate receptors
   >AMPA receptors assist with removal of Mg from NMDA channel allowing influx of Ca; persistent glutamate activation of some AMPA receptors allowing Ca and Zinc in cause injury, increased expression of these receptors on surviving neurons
3. Neuronal apoptosis long after initial injury
   >Reperfusion injury causes delayed death via generation of ROS which cause further damage
   >Zinc contributes to chronic neuronal injury after HIE - depletion in presynaptic and accumulation in postsynaptic neurons (both depletion and accumulation of zinc can cause apoptosis)

Question 18

What are the three mechanisms of action of methadone?

Answer 18

Mu receptor
NMDA receptor antagonist
Blocks serotonin and norepinephrine reuptake

Question 19

Review neuromuscular blockade depolarizing/nondepolarizing mechanisms of action

Answer 19

Depolarizing (succinylcholine): bind to and activate ACh receptors to cause initial dpolarization, not hydrolyzed by acetylcholinesterase so stays bound, prevents new action potential – flaccid paralysis after the fasciculation

Good: rapid onset (30-60 sec), short duration of <5min; RSI
Bad: bradycardia (muscarinic ACh receptor activation), can give with atropine or glycopyrrolate, can also get rhabdo, hyperK - risk of cardiac arrhythmia

–

Nondepolarizing (roc, vec, cis): Competitively block ACh receptors, can be reversed by acetylcholinesterase inhibitors such as neostigmine (can cause bradycardia), also sugammadex - binds roc and vec

Question 19

How does dexmedetomidine work?

Answer 19

Selective alpha-2 agonist

Sympatholytic effect - reduces norepinephrine release

Sedative effect - reduces activity in locus coeruleus in CNS where there are a large number oa alpha2 adrenoceptors

Mild analgesic properties - good adjunct

Hypo/hypertension; hyper tension most often in younger patients who get a bolus (reflexive bradycardia), caused by peripheral alpha2 stimulation with vasoconstriction

Question 20

Equation for cerebral blood flow (CBF)

Answer 20

CBF = CPP/CVR
CPP = (MAP - ICP)

CBF of infant is > adult, peaks at age 4 years, then declines to adult levels

Question 21

Effect of O2 and CO2 on cerebral blood flow

Answer 21

CO2: changes in brain periartriolar pH lead to NO synthase activity > cGMP, linear increase in CBF for increase in PaCO2 between 20-80 (4% per mmHg)

O2: flat curve except at PaO2<50 mmHg

Question 22

What is Dravet syndrome

Answer 22

Severe Myoclonic Epilepsy of Infancy

Prolonged seizures, developmental delay, hypotonia, ataxia, speech impairment

SCN1A mutations, increased sodium into neurons

First line: clobazam, valproic acid
Second line: topiramate, stiripentol
Third line: clonazepam, keppra, zonisamide
Other: ketogenic diet, medical marijuana, fenfluramine (over age 2)

Avoid medications that bind to sodium channels: phenytoin, cabamazepine, oxcarbazepine, lamotrigine (worsen seizures by lowering GABA inhibitory tone)

Also avoid: phenobarbital, vigabatrin

Question 23

Miller Fisher variant of GBS symptoms

Answer 23

ataxia, areflexia, ophthalmoplegia

Question 24

Diagnostic findings in GBS (MRI, CSF)

Answer 24

MRI: normal to nerve root enhancement

CSF: high total protain otherwise normal (albuminocytologic dissociation)

Question 25

ICP readings falsely elevated or decreased by transducer position change?

Answer 25

If head is below transducer, falsely low, decreased drainage

If head is above transducer, falsely high, too much drainage

Question 26

Criteria for serotonin syndrome?

Answer 26

Spontaneous clonus
Inducible clonus with agitation or diaphoresis
Ocular clonus with agitation or diaphoresis
Tremor and hyperreflexia
Hypertonia and temperature over 38 °C and ocular or inducible clonus

can cause rhabdo

Question 27

MELAS

Answer 27

Mitochondrial Encephalomyopathy with Lactic Acidosis and Stroke-like Episodes

-mitochondrial disorders usually affect the aerobic tissues - heart, muscles, and nervous system
- typically have stroke-like events

Question 28

cerebral edema types

Answer 28

Oncotic edema is a process by which Starling forces drive water to enter contused neurons (which have increased osmolarity), causing edema in the affected brain. Vasogenic edema occurs as a result of the disruption of the tight junctions of the blood brain barrier. Cytotoxic edema is caused by adenosine triphosphate (ATP) depletion, which disrupts ion channels. This disruption allows water to enter and causes cellular swelling.

Question 29

Glasgow Coma Scale intubated

Answer 29

Eye and motor only, max 10T, min 2T

Question 30

Pharmacokinetic properties of etomidate?

Answer 30

Highly protein bound so in protein deficiency there will be more free etomidate available

Most significant adverse effect is adrenal suppression - dose dependent inhibition of 11-beta-hydroxylase lasting 6-12 hrs (makes cortisol); contraindicated in sepsis for that reason

Binds to GABA sites, increases affinity for GABA

Minimal hemodynamic and ICP effects

Question 31

Symptoms of spinal muscle atrophy

Answer 31

Degeneration of anterior horn cells

Regression of motor milestones, tongue fasciculations, areflexia, hypotonia, extremity weakness (proximal)

SMN1 mutation, meaning patient has to rely on reduced production by SMN2

Nusinersen alters the pre-messenger RNA splicing, promoting increased production of full-length SMN

Onasemnogene is adenovirus-associated vector that replaces nonfunctioning SMN1 gene

Type 0 (worst/earliest) to Type 4 (Adult onset)

Question 32

Train of four with non-depolarizing vs. depolarizing neuromuscular blockade?

Answer 32

Non-depolarizing shows fade, number of twitches correlates to percent of receptors blocked (1 twitch 90%, 2 twitches 85%, 3 twitches 80%, 4 twitches 75% or less)

> You want a train of four ratio (fourth to first twitch amplitude) >0.9 before extubation

Depolarizing shows equal but lower amplitude

Question 33

Risk of lots of lorazepam IV?

Answer 33

Propylene glycol, osmolar gap anion gap acidosis

Question 34

Likely ingestion with toxidrome of somnolence, hypotension, bradycardia, hypothermia, normal-sized pupils (+/- miosis), normal urination

Answer 34

clonidine

Question 35

Typical age of presentation of AVM

Answer 35

Often around puberty, may be influenced by hormonal changes, maybe genetics

Not associated: stimulant use, tobacco use, physical activity

Question 36

Neuroleptic malignant syndrome vs. Malignant hyperthermia

Answer 36

NMS: fever, AMS, rigidity with HYPOreflexia; extrapyramidal symptoms - tremor, chorea; CK high, leukocytosis

Occurs through blockade of dopamine receptor - typical and atypical antispychotics or rapid withdrawal of agonists (levodopa)

Rx: supportive, dantrolene, bromocriptine

–
Serotonin syndrome has clonus, HYPERreflexia

Malignant hyperthermia occurs in immediate peri-anesthetic period (hypercarbia, muscule rigidity, fever, tachycardia)