Dorsal column vs spinothalamic tract: where each pathway crosses
Both sensory pathways start in the same ganglion and end in the same cortex, but one crosses in the medulla and the other in the cord. That one fact predicts the pattern of sensory loss.
Chapters (12)
Trace the dorsal column–medial lemniscus and spinothalamic pathways, including where each crosses the midline, and predict the sensory loss from a lesion of the cord or brainstem.
The short version
- Both pathways use three neurons: a dorsal root ganglion neuron, a second neuron that crosses and climbs to the thalamus, and a third neuron to the postcentral gyrus.
- The dorsal column carries fine touch, vibration and position sense, and crosses in the medulla.
- The spinothalamic tract carries pain, temperature and crude touch, and crosses in the cord.
- A cord lesion takes dorsal column loss on the same side and spinothalamic loss on the opposite side.
- In the brainstem, above the medullary crossing, both pathways have already crossed, so whichever one a lesion damages, the loss is on the opposite side of the body.
Dorsal column vs spinothalamic tract: one plan, two routes
The dorsal column vs spinothalamic tract comparison starts from what they share. Both pathways use three neurons.[1]
- The first neuron has its cell body in a dorsal root ganglion, and its axon enters the cord through the dorsal root.[1]
- The second neuron crosses the midline somewhere and climbs to the thalamus.[1]
- The third neuron runs from the thalamus to the postcentral gyrus, where the sensation becomes conscious.[1]
What differs is the route, and above all where the second neuron crosses.
The route is where the exam question hides. A lesion changes which side loses sensation depending on whether it falls before or after a pathway's crossing, so the first job is to know where each crossing sits: the medulla for the dorsal column, the cord for the spinothalamic tract.[1][2]
| Dorsal column pathway | Spinothalamic pathway | |
|---|---|---|
| Carries | Fine touch, vibration, position sense | Pain, temperature, crude touch |
| First axon | Does not synapse in the cord; climbs the dorsal column on the same side | Synapses at once, in the dorsal horn |
| Where it crosses | In the lower medulla | In the cord, through the anterior white commissure |
| Position in the cord | Dorsal column, uncrossed | Anterolateral cord, on the opposite side |
The dorsal column pathway: uncrossed in the cord
The dorsal column pathway carries fine touch, vibration and position sense.[1][2] Its first axon does not synapse in the cord. It climbs the dorsal column on the same side.[1][3]
- Leg fibres run in the medial gracile fasciculus.[1][3]
- Arm fibres run in the lateral cuneate fasciculus.[1][3]
- Each ends in its own nucleus in the lower medulla: gracile fibres in the nucleus gracilis, cuneate fibres in the nucleus cuneatus.[1][3]
There the second neuron crosses the midline, forming the medial lemniscus, which climbs to the thalamus.[1][3]
So the dorsal column is uncrossed in the cord, and crosses only in the medulla.[2]
Because the fibres stay on the same side until the medulla, anything that damages one dorsal column in the cord affects vibration and position sense on that same side, below the lesion.[2]
The spinothalamic tract: crossed by the time it climbs
The spinothalamic pathway carries pain, temperature and crude touch.[1][2][3] Its first axon synapses at once, in the dorsal horn of the cord.[1][3]
The second neuron crosses through the anterior white commissure, within a segment or two of where the fibre entered, and ascends in the anterolateral cord on the opposite side.[1][2][3]
So the spinothalamic tract has already crossed by the time it climbs the cord.
Compare this with the dorsal column. The dorsal column carries its first axon up the cord without a synapse and crosses high, in the medulla. The spinothalamic tract synapses at the first opportunity and crosses low, in the cord.[1][3]
Sensory loss from a lesion in the cord
Put the two crossing rules together and each pathway gives its own pattern.[2][5]
| Lesion | Modalities lost | Side | Where |
|---|---|---|---|
| Dorsal column | Vibration and position sense | Same side as the lesion | Below the lesion |
| Spinothalamic tract | Pain and temperature | Opposite side | Starting about two levels below the lesion |
The lag exists because the fibres climb a segment or two before crossing.[5]
In practice, name the modality that is lost, then the side. Vibration and position lost on the same side as the lesion point to the dorsal column. Pain and temperature lost on the opposite side, starting a little below, point to the spinothalamic tract.[2][5]
A brainstem lesion: both pathways already crossed
A lesion in the brainstem, above the medullary crossing, is different. Both pathways have already crossed, so whichever pathway the lesion damages, the loss (pain and temperature, or vibration and position, or both) is on the opposite side of the body.[4][10]
The two rules explain it. The dorsal column crosses in the medulla and the spinothalamic tract has crossed in the cord, so above the medullary crossing both second neurons are on the opposite side.[1][4][10]
Testing each pathway at the bedside
At the bedside, each pathway is tested separately.[2]
| Pathway | Test |
|---|---|
| Dorsal column | Vibration with a tuning fork; joint position by moving a toe; balance with eyes closed (the Romberg test)[2][6] |
| Spinothalamic tract | A pin for pain and a cold object for temperature[2] |
Testing the two pathways separately is what lets the examiner see a dissociation: one modality intact on a side where the other is lost.[2]
The opening patient, solved
In the opening case, the fork was lost on the left foot and the pin was dull on the right foot. Two modalities cross at two different places, so one small lesion can explain both.
- Left dorsal columnThe dorsal column is uncrossed in the cord, so a lesion in the left half of the cord takes vibration from the left foot.
- Left spinothalamic tractThe left spinothalamic tract carries pain from the right side, because those fibres crossed in the cord, near where they entered. The same lesion takes pain from the right foot.
- ResultA small lesion in the left half of the cord: two modalities, two crossings, two sides.
Practice question
Original · USMLE styleA 28-year-old woman has burned her fingers several times without feeling the pain. On examination, she has lost pain and temperature sensation over both shoulders and both arms in a cape-like distribution. Vibration and joint position sense are normal throughout, and strength is normal. MRI shows a fluid-filled cavity in the central part of the cervical spinal cord.
Common questions
Where does the dorsal column pathway cross?
In the lower medulla. The first axon climbs the cord on the same side and synapses in the gracile and cuneate nuclei, and the second neuron crosses there to form the medial lemniscus.
Where does the spinothalamic tract cross?
In the cord. The first axon synapses in the dorsal horn, and the second neuron crosses through the anterior white commissure within a segment or two of where the fibre entered.
Which side is lost with a spinothalamic tract lesion in the cord?
The opposite side, starting about two levels below the lesion. The lag exists because the fibres climb a segment or two before crossing.
Which side is lost with a brainstem lesion above the medullary crossing?
The opposite side of the body, for whichever pathway is damaged, because both pathways have already crossed. A lesion that hits both loses pain, temperature, vibration and position on the opposite side.
What is the Romberg test used for in this context?
It tests dorsal column position sense. The patient stands with feet together and closes the eyes; swaying or falling once the eyes close suggests lost position sense, because vision can no longer make up for it. Vibration (tuning fork) and joint position (moving a toe) test the same pathway directly.
Transcript
Read the full narration, by chapter712 words
0:00A fork and a pin: two losses on opposite sides
A neurologist touches a buzzing tuning fork to a patient's left foot, and she feels nothing. A pin pricks the same foot, and she feels it sharply. On her right foot it is the other way round: the fork buzzes, the pin is dull. Same cord, same spinal level. Why do two kinds of touch fail on opposite sides? Today: trace both pathways,
0:23Today: trace both pathways
find where each crosses, and predict what a lesion takes away.
0:29Three neurons, two routes
Both pathways use three neurons. The first has its cell body in a dorsal root ganglion, and its axon enters the cord through the dorsal root. A second neuron crosses the midline somewhere, and climbs to the thalamus. A third neuron runs from the thalamus to the postcentral gyrus, where the sensation becomes conscious. What differs is the route, and above all where the second neuron crosses.
0:55Dorsal column pathway: uncrossed in the cord, crosses in the medulla
The dorsal column pathway carries fine touch, vibration and position sense. Its first axon does not synapse in the cord. It climbs the dorsal column on the same side: leg fibres in the medial gracile fasciculus, arm fibres in the lateral cuneate fasciculus. They end in the gracile and cuneate nuclei of the lower medulla. There the second neuron crosses the midline, forming the medial lemniscus, which climbs to the thalamus. So the dorsal column is uncrossed in the cord, and crosses only in the medulla. The spinothalamic pathway carries pain and
1:31Spinothalamic pathway: crosses in the cord
temperature, and crude touch. Its first axon synapses at once, in the dorsal horn of the cord. The second neuron crosses through the anterior white commissure, within a segment or two of where the fibre entered, and ascends in the anterolateral cord on the opposite side. So the spinothalamic tract has already crossed by the time it climbs the cord. Put the two rules together.
1:58Put the rules together: a lesion in the cord
A lesion of the dorsal column takes away vibration and position sense on the same side, below the lesion. A lesion of the spinothalamic tract takes away pain and temperature on the opposite side, starting about two levels below the lesion. The lag exists because the fibres climb a segment or two before crossing.
2:20A brainstem lesion: both pathways already crossed
A lesion in the brainstem, above the medullary crossing, is different: both pathways have crossed, so pain, temperature, vibration and position are lost on the opposite side of the body.
2:32Bedside tests for each pathway
At the bedside, you test each pathway separately. Vibration with a tuning fork, joint position by moving a toe, and balance with eyes closed, the Romberg test, probe the dorsal columns. A pin and a cold object probe the spinothalamic tract. Now our patient.
2:50Our patient, solved: a left hemicord lesion
A small lesion in the left half of the cord cuts the left dorsal column, so vibration is lost in the left foot, and the left spinothalamic tract, which carries pain from the right, so pain is lost in the right foot. Two modalities, two crossings, two sides.
3:09Practice question
Your turn. A 28-year-old woman has burned her fingers without feeling it. She has lost pain and temperature over both shoulders and both arms, like a cape. Vibration and joint position are normal everywhere. Strength is normal. MRI shows a fluid-filled cavity in the central cervical cord. Damage to which of the following best explains the sensory loss? A, the dorsal columns of the cord. B, the crossing spinothalamic fibres. C, the lateral spinothalamic tracts. D, the dorsal root ganglion neurons. E, the medial lemnisci in the medulla. Pause here and decide.
3:56Answer and explanation
A is out: damaged dorsal columns would take away vibration and position sense, and hers are normal. C is out: damage to the lateral tracts would cause loss below the lesion, not a cape over the arms. D is out: ganglion neurons feed both pathways, so vibration would be lost too. E is out: the medial lemniscus carries the dorsal column modalities, which are normal. So the answer is B. A central cavity cuts the second neurons as they cross in the anterior white commissure, and the dorsal columns are spared.
4:32Recap and next lesson
Three things to keep. One: the dorsal column carries touch, vibration and position, and crosses in the medulla. Two: the spinothalamic tract carries pain and temperature, and crosses in the cord. Three: a cord lesion takes dorsal column loss on the same side and spinothalamic loss on the opposite side. Next, spinal cord syndromes compared.
Sources
Numbers in the text, e.g. [1], point here- OpenStax. Anatomy and Physiology 2e, 14.2 Central Processing. openstax.org/books/anatomy-and-physiology-2e/pages/14-2-central-processing
- OpenStax. Anatomy and Physiology 2e, 16.4 The Sensory and Motor Exams. openstax.org/books/anatomy-and-physiology-2e/pages/16-4-the-sensory-and-motor-exams
- Dorsal column-medial lemniscus pathway; Spinothalamic tract (Wikipedia, used for cross-checking). en.wikipedia.org/wiki/Dorsal_column%E2%80%93medial_lemniscus_pathway · en.wikipedia.org/wiki/Spinothalamic_tract
- Brainstem dysfunction in critically ill patients. Crit Care 2020. europepmc.org/article/PMC/PMC6945639
- Management of Acute Traumatic Spinal Cord Injury. Front Surg 2021 (Europe PMC PMC8710452). europepmc.org/article/PMC/PMC8710452
- Dorsal Column Bedside Examination Test. Malays J Med Sci 2023 (Europe PMC PMC10125238). europepmc.org/article/PMC/PMC10125238
- Chiari I-associated syringomyelia, case report. Eur J Case Rep Intern Med 2026 (Europe PMC PMC13666566). europepmc.org/article/PMC/PMC13666566
- Syringomyelia (Wikipedia, used for cross-checking). en.wikipedia.org/wiki/Syringomyelia
- Brown-Sequard syndrome (Wikipedia, used for cross-checking). en.wikipedia.org/wiki/Brown-S%C3%A9quard_syndrome
- Additional cross-checks (brainstem lesions, syringomyelia): Europe PMC PMC7710193 · PMC10741770 · PMC12072671 · PMC4322850. europepmc.org/article/PMC/PMC7710193 · europepmc.org/article/PMC/PMC10741770 · europepmc.org/article/PMC/PMC12072671 · europepmc.org/article/PMC/PMC4322850
The cord, the pathways, the crossings, the lesion marks and all handwriting are schematic drawings made in code. The hook patient and the cape distribution are illustrative. A spinothalamic loss starting about two segments below the lesion is the usual teaching figure.
The practice question is original and its patient is synthetic. Every fact is checked against the sources above in independent accuracy reviews. Always follow your local guidelines and your own laboratory’s ranges.
Image credits. Illustrations: Servier Medical Art (smart.servier.com), CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/), adapted (cropped, recoloured, outlined, mirrored): foot; dermatome figure. Gray's Anatomy (H. V. Carter), plates 691 (medulla) and 756 (cerebral cortex), public domain, via Wikimedia Commons (https://commons.wikimedia.org/wiki/File:Gray691.png · https://commons.wikimedia.org/wiki/File:Gray756.png), recoloured and outlined. Everything else (cord cross-sections, pathways, icons, notebook pages) is drawn in code (original).
Corrections. None so far. Spotted an error? Email info@medservatory.com with the lesson code MS-S1-NEURO-008.
For exam study only, not medical advice. Read the medical disclaimer.
In this series
Playlist on YouTube- EP 01Upper vs lower motor neuron lesions: signs and localisation5:08
- EP 02Dorsal column vs spinothalamic tract: where each pathway crosses5:01
- EP 03Spinal cord syndromes compared: rebuild each from three tracts5:06
- EP 04Cranial nerve nuclei: a brainstem map by level and position5:10
- EP 05Brainstem crossed findings: the localisation rule4:50
- EP 06Medial vs lateral medullary syndrome: artery, structures and signs5:30
- EP 07Facial nerve palsy: why the forehead tells you the lesion4:59
- EP 08Stroke syndromes by artery: ACA, MCA and PCA4:41
- EP 09Lacunar stroke syndromes: pure motor, pure sensory and more4:54
- EP 10Visual pathway lesions and field defects4:42
- EP 11Basal ganglia direct and indirect pathways: D1, D2 and movement5:19
- EP 12Cerebellar lesion localisation: vermis vs hemisphere4:42
- EP 13Brain herniation syndromes: what is squeezed, and where4:56
- EP 14CSF flow and hydrocephalus: where the flow fails5:12
- EP 15Corticospinal tract: from cortex to anterior horn4:59
- EP 16Hypothalamic nuclei and their functions5:24