pathofizz
This structural component of the NMJ is responsible for rapidly hydrolyzing acetylcholine, thereby terminating the synaptic signal and preventing tetany
What is acetylcholinesterase (AChE)?
This depolarizing NMBA can cause life-threatening hyperkalemia, particularly in patients with massive denervation, large burns, or crush injuries, due to the upregulation of extrajunctional receptors.
What is succinylcholine?
Clinical signs of this type of motor neuron lesion include spasticity, hyperreflexia, and a positive Babinski sign.
What is an Upper Motor Neuron (UMN) lesion?
22-year-old male is taken for emergency surgery for a ruptured appendix. He is given succinylcholine for rapid sequence intubation. Following administration, he has diffuse muscle fasciculations, and then becomes flaccid, allowing intubation. The surgery lasts 60 minutes. At the end of the case, the patient remains completely apneic and flaccid. A nerve stimulator shows no response. The anesthesia team suspects a prolonged block and administers neostigmine, which unexpectedly makes the paralysis worse.
1. What is the patient's most likely underlying pharmacogenetic condition, and what enzyme is deficient?
2.Explain the pathophysiology of a Phase I block, which is the normal (but in this case, prolonged) mechanism of action of succinylcholine.
3.Why did the administration of neostigmine (an AChE inhibitor) at the 60-minute mark worsen the paralysis instead of reversing it?
1. The patient has pseudocholinesterase (or butyrylcholinesterase) deficiency.
2. Succinylcholine is a depolarizing neuromuscular blocker. It is an agonist that mimics acetylcholine. It binds to the nicotinic ACh receptors at the motor endplate and opens them, causing a single, massive depolarization of the muscle membrane (seen clinically as fasciculations). Unlike ACh, it is not broken down by AChE in the cleft, so it binds persistently. This persistent depolarization "locks" the voltage-gated sodium channels around the endplate in their inactivated state, preventing the membrane from repolarizing and firing any subsequent action potentials. This results in a flaccid paralysis.
3. Neostigmine is only effective at reversing a non-depolarizing (competitive) block, where more ACh is needed to "win" the competition for the receptor. Adding more ACh increases the amount of ACTH in the cleft as neostigmine is a AChE inhibitor.
olfactory
1
These glial cells cap the NMJ and are critical for maintaining synaptic integrity, modulating neurotransmission, and guiding reinnervation after injury.
What are perisynaptic Schwann cells?
This drug treats Myasthenia Gravis by reversibly inhibiting acetylcholinesterase, increasing the amount of acetylcholine in the synaptic cleft.
What is pyridostigmine?
DAILY DOUBLE
NAME ME THE CRANIAL NERVE NUMBERS ASSOCIATED WITH THE FOLLOWING:
1. MIDBRAIN
2. PONS
3. MEDULLA
NOW....WHAT ARE THE 12 CRANIAL NERVES >:)
1. 3-4
2. 5-8
3. 9-12
4. olfactory, optic, oculomotor, trochlear, trigeminal, abducens, facial, vestibulocochlear, glossopharyngeal, vagus, accessory, hypoglossal
OCULOMOTOR
3
On NCV studies, this pattern of non-uniform slowing, conduction block, and varying latencies strongly suggests an acquired, rather than hereditary, demyelinating process.
What is temporal dispersion?
This non-depolarizing neuromuscular blocker acts as a competitive antagonist at nicotinic acetylcholine receptors.
What is rocuronium?
After prolonged exposure to succinylcholine, the motor endplate repolarizes, but the block strangely converts to one that resembles a non-depolarizing block and can be partially reversed by AChE inhibitors
What is a Phase II block?
What cranial nerve is 8?
vestibulocular
DAILY DOUBLE
This delayed-onset (24-96 hours) syndrome of proximal limb and respiratory weakness can occur after an acute organophosphate cholinergic crisis has resolved.
What is the "intermediate syndrome"?
This novel reversal agent directly encapsulates steroidal non-depolarizing NMBAs like rocuronium, forming an inert complex and rapidly pulling the drug from the neuromuscular junction.
What is sugammadex?
This is the antidote for organophosphate poisoning that only addresses the life-threatening muscarinic effects (e.g., bronchospasm, bronchorrhea, bradycardia) but does not reverse the skeletal muscle paralysis
What is atropine?
what is cranial nerve 10?
vagus
Unlike in MG (postsynaptic) or LEMS (presynaptic calcium channel), the pathophysiology of botulism involves the toxin's cleavage of these specific presynaptic proteins.
What are SNARE proteins (e.g., SNAP-25, synaptobrevin)?
This specific class of antibiotics is relatively contraindicated in Myasthenia Gravis patients because it can precipitate a myasthenic crisis by inhibiting the presynaptic release of acetylcholine.
What are aminoglycosides?
DAILY DOUBLE
The AMAN (Acute Motor Axonal Neuropathy) variant of Guillain-Barré syndrome is strongly associated with antibodies against these molecules in the axolemma, often after a Campylobacter jejuni infection.
What are gangliosides (specifically GM1 or GD1a)
what is cranial nerve 6?
abducen