ABEM Evoked Potentials & Late Response Studies

Question 1

The H-reflex is most commonly elicited from which nerve-muscle combination?

Accepted Answer

Tibial nerve - soleus

Answer

The H-reflex is most reliably elicited by stimulating the tibial nerve and recording from the soleus, representing the S1 monosynaptic reflex arc.

Question 2

Which of the following best describes the physiological basis of F-waves?

Accepted Answer

Late motor responses due to antidromic activation of motor neurons followed by orthodromic discharge

Answer

F-waves result from antidromic activation of alpha motor neurons, causing a small percentage to 'backfire' orthodromically and produce a late muscle response.

Question 3

What does prolonged F-wave latency most commonly indicate in electrodiagnostic studies?

Accepted Answer

Proximal motor nerve demyelination or radiculopathy

Answer

Prolonged F-wave latency indicates slowing in the proximal segment of the motor nerve, suggesting proximal demyelination, polyradiculopathy, or Guillain-Barré syndrome.

Question 4

H-reflex latency in adults is most significantly influenced by which factor?

Accepted Answer

Limb length and patient height

Answer

H-reflex latency is primarily determined by limb length (and patient height), since longer limbs require greater conduction distance for the same reflex arc.

Question 5

Bilateral absent H-reflexes at rest in an adult most strongly suggests which diagnosis?

Accepted Answer

Diffuse peripheral neuropathy

Answer

Bilateral absent H-reflexes suggest diffuse peripheral neuropathy affecting the S1 arc bilaterally, whereas radiculopathy typically causes unilateral H-reflex changes.

(ABEM) American Board of Electrodiagnostic Medicine Practice Test

(ABEM) American Board of Electrodiagnostic Medicine Practice Test

ABEM Evoked Potentials & Late Response Studies