Principles of Nerve Conduction Studies (NCS) ; Lecture Flashcards
What is the principal goal of nerve conduction studies (NCS)?
To localize the problem, define the nature of the pathology, assess its severity, and, in some cases, infer the aetiology.
NCS serves as an extension of the _________, helping narrow the _________ diagnosis.
clinical examination; differential.
True/False: NCS alone can always confirm the exact cause of neuropathy.
False (it often needs correlation with clinical findings).
What are the three connective tissue layers of a peripheral nerve?
Endoneurium.
Perineurium.
Epineurium.
Peripheral nerves are formed from plexuses or directly from _________ projections of the spinal cord.
ventral.
True/False: Myelinated axons conduct signals faster than unmyelinated axons.
True.
What is the resting membrane potential of a nerve fiber?
-90mV.
During depolarization, sodium channels open, allowing _________ ions to enter, making the inside of the membrane _________ charged
sodium; positively.
True/False: Action potentials are an “all-or-none” phenomenon.
True.
How does myelin affect nerve conduction?
Myelin acts as an insulator, forcing current to travel longitudinally down the axon to the nodes of Ranvier, allowing saltatory conduction and increased speed.
How does temperature affect nerve conduction studies?
Cooling slows conduction velocity.
Increases amplitude and duration of responses.
Myelination is completed by age _________, and nerve conduction velocity declines progressively after age _________.
4-5; 60.
True/False: Taller individuals tend to have slower conduction velocities due to nerve tapering distally.
True.
Match the nerve injury type with its characteristics:
Neuropraxia.
Axonotmesis.
Neurotmesis.
Neuropraxia: Conduction block, preserved axonal continuity, good prognosis.
Axonotmesis: Axonal disruption with intact epineurium, Wallerian degeneration, variable prognosis.
Neurotmesis: Complete nerve disruption, no response, poor prognosis.
_________ is the failure of nerve conduction without axonal damage, often referred to as conduction block.
Neuropraxia.
True/False: Wallerian degeneration occurs in both axonotmesis and neurotmesis.
True.
What are the two main types of NCS?
Sensory nerve conduction studies.
Motor nerve conduction studies.
Slow responses in NCS suggest _________ loss, while low-amplitude responses indicate _________ loss.
myelin; axonal.
True/False: F-waves allow assessment of proximal portions of the nerve.
true.
What is the purpose of F-waves in NCS?
To evaluate the entire nerve, including the proximal segments.
Detect proximal demyelination or conduction delays.
What are the key types of generalized neuropathies?
Axonal (e.g., diabetes, alcohol).
Demyelinating (e.g., GBS, CIDP).
Hereditary (e.g., HMSN, HNPP).
Guillain-Barré Syndrome (GBS) has _________ onset and reaches its nadir within _________ weeks.
acute; 4.
True/False: Diabetes is associated with multiple patterns of neuropathy, including autonomic and small-fiber neuropathy.
True.
A diabetic patient complains of burning feet at night and dizziness. What types of neuropathy should be suspected?
Small-fiber neuropathy and autonomic neuropathy.
What are common examples of focal compressive neuropathies?
Carpal tunnel syndrome (CTS).
Ulnar neuropathy at the elbow (UNE).
Peroneal neuropathy at the fibular neck.
Wrist drop is caused by _________ neuropathy at the _________
radial; spiral groove.
True/False: Mononeuritis multiplex involves multiple nerves affected at atypical entrapment sites.
true
What conditions commonly cause mononeuritis multiplex?
Vasculitis, diabetes.
What are the patterns of diabetic neuropathy?
Generalized sensorimotor axonal neuropathy.
Diabetic amyotrophy (proximal neuropathy).
Autonomic neuropathy.
Small-fiber neuropathy.
Mononeuritis multiplex.
Proximal diabetic neuropathy often occurs during a switch to _________ due to poor glycemic control and is associated with _________ loss and pain.
insulin; weight.
