Tract anatomy and crossings · Neuroanatomy
Spinal Cord Pathways MCQ
Lateral corticospinal tract, dorsal columns, and spinothalamic tract, where each one decussates and what its lesions look like (Brown-Séquard, ASA infarct). 25 board-style MCQs plus 8 INBDE patient cases.
25 practice MCQsQuick-reference tableMnemonics + clinical pearlsFull distractor explanations
High-yield review
Concept summary and clinical relevance.
Quick-reference structure first, then detailed coverage. Mnemonics in amber, clinical pearls in blue.
Spinal cord pathway questions on the INBDE come down to three things per tract: what it carries, where it crosses, and what a lesion looks like ipsilateral vs contralateral to the level. Get those three facts straight for the corticospinal tract, dorsal columns, and spinothalamic tract, and the syndrome questions become straightforward.
The three core tracts at a glance
| Tract | Function | Crossing point | Lesion below crossing |
|---|---|---|---|
| Lateral corticospinal | Voluntary motor (limb) | Medullary pyramids (decussation of pyramids) | Ipsilateral weakness below lesion |
| Dorsal columns | Vibration, proprioception, fine touch, two-point discrimination | Medulla (gracile/cuneate nuclei → medial lemniscus) | Ipsilateral loss below lesion |
| Spinothalamic (anterolateral) | Pain, temperature, crude touch | Within 1–2 levels of entry, via anterior white commissure | Contralateral loss starting 1–2 levels below |
Classic spinal cord syndromes
| Syndrome | Pattern | Cause |
|---|---|---|
| Brown-Séquard (hemicord) | Ipsilateral motor + vibration loss; contralateral pain/temp loss | Penetrating trauma, tumor, MS plaque |
| Anterior spinal artery (ASA) infarct | Bilateral motor + pain/temp loss; vibration/proprioception SPARED | Aortic surgery, severe hypotension |
| Posterior spinal artery (PSA) infarct | Bilateral vibration/proprioception loss only | Rare; isolated dorsal column deficit |
| Central cord syndrome | Bilateral pain/temp loss; motor + vibration spared | Syringomyelia, hyperextension injury |
Clinical pearl, The decussation rule for localization
If you have a brain lesion, deficits are contralateral (motor and sensation already crossed). If you have a spinal cord lesion, motor and dorsal column findings are ipsilateral, but pain/temp findings are contralateral (because spinothalamic crossed within 1–2 segments of entry). This is the single most-tested concept in spinal cord neuroanatomy.
Clinical pearl, Why dental students need this
Patients with spinal cord injury, MS, or stroke may have profound proprioception or motor deficits without obvious external signs. Transferring patients to the chair, positioning safely, and recognizing autonomic dysreflexia in high cord injuries can all matter clinically: even if the neuro exam itself rarely happens in the operatory.
Mnemonic, Brown-Séquard triangle
“Ipsi motor + ipsi vibes, contra pain.” The ipsilateral findings are motor (LCST) and vibration/proprioception (dorsal columns); the contralateral finding is pain/temperature (spinothalamic).
Mnemonic, Vascular spinal cord syndromes
“ASA = All but Sensation of vibration.” Anterior spinal artery infarct spares vibration/proprioception; everything else is bilaterally lost. PSA = vibration/proprioception lost in isolation.
Lateral corticospinal tract (LCST): voluntary motor
- Origin: motor cortex → internal capsule → cerebral peduncle → medullary pyramids (decussation) → descends contralaterally → synapses on lower motor neurons in the anterior horn.
- Above the decussation (e.g., cortical or capsular stroke): contralateral weakness.
- Below the decussation (cord lesion): ipsilateral weakness below the level.
Dorsal columns: fine touch, vibration, proprioception
- Origin: peripheral receptor → dorsal root ganglion → ascends ipsilaterally in the dorsal columns.
- Decussation in the medulla: gracile nucleus (lower body, medial) and cuneate nucleus (upper body, lateral) → medial lemniscus → thalamus → cortex.
- Cord lesion → ipsilateral loss of vibration and proprioception below the level.
- Romberg test: positive (falls when eyes close) confirms a dorsal column deficit.
Spinothalamic tract: pain, temperature, crude touch
- Origin: nociceptor → dorsal root → synapses in the dorsal horn.
- Decussates within 1–2 levels via the anterior white commissure → ascends contralaterally.
- Cord lesion → contralateral pain/temperature loss starting 1–2 levels below the lesion (because the fibers ascend a couple of segments before crossing).
Vascular supply
- Anterior spinal artery: anterior two-thirds of the cord (motor + spinothalamic). Infarct → bilateral motor + pain/temperature loss; vibration spared.
- Posterior spinal arteries: posterior third (dorsal columns). Infarct → isolated vibration/proprioception loss.
Core Recall Check
25 board-style MCQs.
Active recall is the highest-yield study method. Pick an answer, check it, and read why every distractor is wrong.
0 of 25 answered · 0 correct
Keys: A-E or 1-5, Enter to check
- Question 1EasyWhich spinal cord tract carries voluntary motor commands for limb movement?
- Question 2EasyWhere do fibers of the corticospinal tract decussate?
- Question 3ModerateA lesion of the right lateral corticospinal tract at C6 produces weakness on which side?
- Question 4EasyWhich tract carries vibration and proprioception?
- Question 5ModerateWhere do dorsal column fibers cross to the opposite side?
- Question 6EasyThe spinothalamic tract primarily carries:
- Question 7ModerateWhere do spinothalamic tract fibers cross to the opposite side?
- Question 8HardBrown-Séquard syndrome (hemicord lesion) classically produces:
- Question 9EasyWhich artery supplies the anterior two-thirds of the spinal cord?
- Question 10ModerateAnterior spinal artery infarct typically spares which function?
- Question 11ModerateA patient with chronic alcoholism stumbles when his eyes are closed during a Romberg test. Which spinal pathway is most likely impaired?
- Question 12ModerateProprioceptive fibers from the leg synapse in which medullary nucleus?
- Question 13ModerateAfter dorsal column fibers decussate in the medulla, they ascend to the thalamus as the:
- Question 14ModerateSpinothalamic fibers cross the midline through which structure?
- Question 15HardCentral cord syndrome (e.g., syringomyelia) classically produces:
- Question 16HardA young patient has a cape-like loss of pain and temperature sensation across both shoulders and arms, with preserved light touch and strength. The most likely lesion is:
- Question 17ModerateA posterior spinal artery infarct produces:
- Question 18ModerateIn Brown-Séquard syndrome, the contralateral pain and temperature loss begins:
- Question 19ModerateThe lateral corticospinal tract synapses on its target neurons in the:
- Question 20ModerateThe first-order sensory neuron cell bodies for both the dorsal columns and the spinothalamic tract are located in the:
- Question 21EasyTwo-point discrimination and fine touch are carried by which pathway?
- Question 22HardA cortical stroke causes contralateral weakness, but a spinal cord hemisection causes ipsilateral weakness below the lesion. The reason is that the corticospinal tract:
- Question 23HardA patient with a C5 spinal cord injury develops a pounding headache, flushing above the lesion, and severe hypertension while a full bladder goes unnoticed during a long dental appointment. This is:
- Question 24HardVitamin B12 deficiency (subacute combined degeneration) damages which spinal cord tracts?
- Question 25HardA stab wound hemisects the right side of the cord at T10. Which deficit pattern results?
Clinical Reasoning Cases
INBDE patient cases.
8 ADA INBDE-format patient cases on spinal pathways. Each case is a shared patient box plus linked questions with full distractor explanations.
INBDE Patient Cases
Spinal Pathways INBDE Patient Cases →
8 patient cases · 40 linked questions
Open cases →
Author
Dr. Isaac Sun, DDS
Founder, KYT Dental Services. These MCQs are reviewed by a practicing clinician and offered as an educational reference for dental students.
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