EDAIC Regional Anesthesia and Pain Management 5 — Questions and Answers
Question 1: Which spinal cord tract is primarily responsible for transmission of nociceptive and temperature signals?
- Dorsal columns (posterior funiculus)
- Spinothalamic tract (anterolateral system) (Correct answer)
- Corticospinal tract
- Spinocerebellar tract
Correct answer: Spinothalamic tract (anterolateral system)
The spinothalamic tract crosses at the level of entry within 1-2 spinal segments and ascends contralaterally in the anterolateral funiculus to transmit pain, temperature, and crude touch to the thalamus.
Question 2: During epidural anesthesia, the 'loss of resistance' technique identifies needle entry into which space?
- Subdural space
- Subarachnoid space
- Epidural space (Correct answer)
- Paravertebral space
Correct answer: Epidural space
The epidural space is a negative-pressure potential space containing fat and venous plexuses; resistance to injection through ligamentum flavum gives way to easy injection upon entering this space.
Question 3: Gabapentin and pregabalin produce analgesia in neuropathic pain primarily by binding to which receptor subunit?
- GABA-A receptor beta subunit
- Alpha-2-delta subunit of voltage-gated calcium channels (Correct answer)
- Mu-opioid receptor
- NMDA receptor NR2B subunit
Correct answer: Alpha-2-delta subunit of voltage-gated calcium channels
Gabapentinoids bind to the alpha-2-delta-1 subunit of voltage-gated calcium channels on presynaptic neurons, reducing calcium influx and decreasing release of excitatory neurotransmitters like glutamate and substance P.
Question 4: A 45-year-old presents with lancinating pain along the T5 dermatome following herpes zoster infection 6 months ago. What is the most accurate diagnosis?
- Acute herpetic neuralgia
- Post-herpetic neuralgia (PHN) (Correct answer)
- Intercostal neuralgia
- Complex regional pain syndrome type II
Correct answer: Post-herpetic neuralgia (PHN)
Post-herpetic neuralgia is defined as pain persisting in the distribution of herpes zoster beyond 90 days after acute infection onset, characterized by lancinating, burning, or allodynic pain.
Question 5: Which landmark defines the level of the conus medullaris in adults and guides safe intrathecal injection?
- T12-L1 interspace
- L1-L2 interspace (Correct answer)
- L2-L3 interspace
- L4-L5 interspace
Correct answer: L1-L2 interspace
In adults, the conus medullaris typically ends at L1-L2; spinal anesthesia is most safely performed at L3-L4 or L4-L5 to avoid direct cord trauma.
Question 6: What is the mechanism by which neuraxial opioids cause delayed respiratory depression?
- Rapid systemic absorption producing peak plasma concentration
- Rostral migration in cerebrospinal fluid reaching brainstem respiratory centers (Correct answer)
- Direct cervical spinal cord depression
- Histamine release causing bronchospasm
Correct answer: Rostral migration in cerebrospinal fluid reaching brainstem respiratory centers
Hydrophilic opioids like morphine injected intrathecally or epidurally undergo rostral CSF migration to reach mu-receptors in the brainstem (pre-Bötzinger complex), causing delayed respiratory depression 6-12 hours post-injection.
Question 7: Which parameter best guides adequacy of sympathetic blockade during spinal anesthesia?
- Loss of cold sensation (temperature discrimination) (Correct answer)
- Loss of sharp/dull discrimination (pinprick)
- Loss of proprioception
- Absence of motor movement
Correct answer: Loss of cold sensation (temperature discrimination)
Sympathetic block extends approximately 2 dermatomes higher than sensory block; temperature discrimination (cold testing) detects the highest level of blockade because A-delta cold fibers are blocked first.
EDAIC Regional Anesthesia and Pain Management 5
Which spinal cord tract is primarily responsible for transmission of nociceptive and temperature signals?