1. The Dorsal Column-Medial Lemniscal System
Learning Module
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2. Used with permission of the Academy of Neurologic Physical Therapy of the APTA Do not duplicate without acknowledging Learning Activity author Michael McKeough, PT, EdD

3. Contents Overview Introduction Learning Objectives Instructions Legend
Read these Instructions!
Dorsal Column-Medical Lemniscal System
Fasciculus gracilis
Fasciculus cuneatus
Lesion lessons
Fasciculus gracilis lesion
Fasciculus cuneatus lesion
Dorsal column lesion
Medial lemniscus lesion
Internal capsule lesion
Patient Cases
Case 1
Case 2
Case 3
Contents DCML Lesions Patient Cases Exit

4. Overview Introduction Learning Objectives Instructions Legend
Contents DCML Lesions Patient Cases Exit

5. Introduction
This module reviews the Dorsal Column-Medial Lemniscal System (DCML).
Module organization consists of three components. Overview consists of this Introduction and the Learning Objectives. Contents consists of Navigation Instructions, a Legend, Review of the normal structure and function of the DCML, and 5 interactive lesion lessons. Cases consists of Instructions and 3 interactive patient cases with feedback.
At the bottom of each page a navigation bar contains options to move throughout the module.
Material is presented at both the behavioral level and the neuroanatomical level.
The behavioral level is presented first and depicts a patient’s clinical presentation.
The neuroanatomical level depicts the detailed anatomy of first-order, second-order and third-order neurons.
The neuroanatomical level accounts for the patient’s behavioral presentation on examination under normal and lesioned conditions.
Contents DCML Lesions Patient Cases Exit

6. Learning Objectives
After completing this module you should be able to:
describe, in detail, the structure and function of the dorsal column-medial lemniscal system (fasciculus gracilis and fasciculus cuneatus).
given a lesion, identify the signs and symptoms that would be expected.
given a patient case (examination results and chief complaint), identify the location of the lesion causing the signs and symptoms .
correlate neurology information between the behavioral and neuroanatomical levels.
Contents DCML Lesions Patient Cases Exit

7. Instructions
This module contains 5 interactive lesion lessons with animation.
Lesson lessons begin with a question about the symptoms produced by that particular lesion.
Clicking the answer button will reveal the answer to the question.
Clicking the explanation button will lead to both behavioral and neuroanatomical explanations of the lesion.
Each presentation is launched by clicking the animation button. The same button serves to replay the animation if desired.
Any of the 5 lessons may be accessed by simply clicking on the lesion title on the Contents page.
Please refer to the legend that defines the symbols used throughout the module.
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8. Legend Mechanism of injury First-order neuron Lesion
Second-order neuron
Sensory stimulus
Third-order neuron
Light touch stimulus
Sensory impairment
Function intact
Function lost
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9. Medial Lemniscal System
Primary sensory cortex
The Dorsal Column-
Medial Lemniscal System
Thalamus
Nucleus Gracilis
Nucleus Cuneatus
Discriminative touch, vibration, and position information from the body is conveyed by the dorsal column-medial lemniscal system (DCML). The DCML is a crossed system. It originates from mechano-receptors (sensory receptors sensitive to mechanical deformation) located in the body wall and projects to the contralateral cerebral hemisphere via a three neuron projection system. The DCML is comprised of the fasciculus gracilis and fasciculus cuneatus.
Fasciculus Cuneatus
Fasciculus Gracilis
Fasciculus gracilis
Fasciculus cuneatus
First-order neuron
Second-order neuron
Third-order neuron
Stimulus
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10. Fasciculus Gracilis: Behavioral Description
Primary sensory cortex
Fasciculus Gracilis: Behavioral Description
Thalamus
Nucleus Gracilis
Fasciculus gracilis
Fasciculus gracilis: light touch, vibration, and position sense from the contralateral leg and lower trunk
Consists of a 3-neuron projection system extending from receptors in the periphery to the primary somatosensory cortex (Click neuroanatomical explanation)
Fasciculus Gracilis
Click to animate
Neuroanatomical Explanation
First-order neuron
Second-order neuron
Third-order neuron
Stimulus
Fasciculus cuneatus
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11. Behavioral Explanation
Fasciculus Gracilis: Neuroanatomical Description
First-order neurons
Cell body: dorsal root ganglion (DRG)
Distal axon: innervates mechanoreceptors in leg and lower trunk via peripheral nerves
Proximal axon: enter dorsal column (fasciculus gracilis), ascend ipsilaterally and terminate in the nucleus gracilis
Second-order neurons
Cell body: nucleus gracilis
Axon: decussates in the medulla and projects to the contralateral thalamus (ventral posterior lateral nucleus, VPL) via the medial lemniscus
Third-order neurons
Cell body: VPL of thalamus
Axon: ascends via the posterior limb of the internal capsule and terminates in the primary somatosensory cortex
Click to animate
Behavioral Explanation
DRG
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Fasciculus cuneatus

12. Fasciculus Cuneatus: Behavioral Description
Primary sensory cortex
Fasciculus Cuneatus: Behavioral Description
Thalamus
Nucleus Cuneatus
Fasciculus Cuneatus
Fasciculus cuneatus:
Fasciculus cuneatus: light touch, vibration, and position sense from the contralateral arm and upper trunk
Consists of a 3-neuron projection system extending from receptors in the periphery to the primary somatosensory cortex (Click neuroanatomical explanation)
Click to animate
Neuroanatomical Explanation
First-order neuron
Second-order neuron
Third-order neuron
Stimulus
Contents DCML Lesions Patient Cases Exit

13. Behavioral Explanation
Fasciculus Cuneatus: Neuroanatomical Description
First-order neurons
Cell body: dorsal root ganglion (DRG)
Distal axon: innervates mechanoreceptors in arm and upper trunk via peripheral nerves
Proximal axon: enter dorsal column (fasciculus cuneatus), ascend ipsilaterally and terminate in the nucleus cuneatus
Second-order neurons
Cell body: nucleus cuneatus
Axon: decussates in the medulla and projects to the contralateral thalamus (ventral posterior lateral nucleus, VPL) via the medial lemniscus
Third-order neurons
Cell body: VPL of thalamus
Axon: ascends via the posterior limb of the internal capsule and terminates in the primary somatosensory cortex
Click to animate
DRG
Behavioral Explanation
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14. Lesion Lessons Fasciculus gracilis lesion Fasciculus cuneatus lesion
Dorsal column lesion
Medial lemniscus lesion
Internal capsule lesion
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15. Lesion of the left fasciculus gracilis at T8 produces what impairment?
Click for answer
Damage to the left fasciculus gracilis at T8 causes the absence of light touch, vibration, and position sensation in the left leg and lower left trunk. Only the fasciculus gracilis exists below T6.
Click for explanation
Contents DCML Lesions Patient Cases Exit

16. Lesion of the fasciculus gracilis on the left: Behavioral Explanation
Primary sensory cortex
Lesion of the fasciculus gracilis on the left: Behavioral Explanation
Thalamus
Nucleus Gracilis
Nucleus Cuneatus
Fasciculus Cuneatus
Fasciculus Gracilis
Sensory impairment:
absence of light touch, vibration, and position sensation in the left leg and lower left trunk.
Sensory impairment:
left leg and lower left trunk.
Click to animate
Neuroanatomical Explanation
Lesion
Lost function
Impairment
Contents DCML Lesions Patient Cases Exit

17. Lesion of the fasciculus gracilis
on the left: Neuroanatomical Explanation
Because the tract has not yet decussated, impairment is ipsilateral to the lesion. Lesion of first-order neurons interrupts ascending information so light touch, vibration, and position sensation is impaired in the left leg and lower left trunk. Receptors and reflex connections below the lesion level remain intact.
Click to animate
Behavioral Explanation
Contents DCML Lesions Patient Cases Exit

18. Lesion of the left fasciculus cuneatus at C3 produces what impairment?
Click for answer
Damage to the left fasciculus cuneatus at C3 causes the absence of light touch, vibration, and position sensation in the left arm and upper left trunk.
Click for explanation
Contents DCML Lesions Patient Cases Exit

19. Lesion of the fasciculus cuneatus on the left: Behavioral Explanation
Primary sensory cortex
Thalamus
Lesion of the fasciculus cuneatus on the left: Behavioral Explanation
Nucleus Gracilis
Nucleus Cuneatus
Fasciculus Cuneatus
Fasciculus Gracilis
Sensory impairment:
absence of light touch, vibration, and position sensation in the left arm and upper left trunk.
Sensory impairment:
left arm and upper left trunk.
Click to animate
Neuroanatomical Explanation
Lesion
Lost function
Impairment
Contents DCML Lesions Patient Cases Exit

20. Behavioral Explanation
Lesion of the fasciculus cuneatus on the left: Neuroanatomical Explanation
Because the tract has not yet decussated, impairment is ipsilateral to the lesion. Lesion of first-order neurons interrupts ascending information so light touch, vibration, and position sensation is impaired in the left arm and upper left trunk. Receptors and reflex connections below the lesion level remain intact.
Behavioral Explanation
Click to animate
Contents DCML Lesions Patient Cases Exit

21. Lesion of the left dorsal columns at T2 produces what impairment?
Click for answer
Damage to the left dorsal columns at T2 causes the absence of light touch, vibration, and position sensation in the left side of the body below the lesion level (trunk, arm, and leg).
Click for explanation
Contents DCML Lesions Patient Cases Exit

22. Lesion of the dorsal columns on the left: Behavioral Explanation
Primary sensory cortex
Lesion of the dorsal columns on the left: Behavioral Explanation
Thalamus
Nucleus Gracilis
Nucleus Cuneatus
Fasciculus Cuneatus
Sensory impairment:
absence of light touch, vibration, and position sensation in the left side of the body below the lesion level (trunk, arm, and leg).
Fasciculus Gracilis
Sensory impairment:
left side of the body, below the lesion level.
Click to animate
Neuroanatomical Explanation
Lesion
Lost function
Impairment
Contents DCML Lesions Patient Cases Exit

23. Lesion of the dorsal columns on the left: Neuroanatomical Explanation
Because the lesion involves first-order neurons that have not yet decussated, impairment is ipsilateral to the lesion. Because both gracilis and cuneatus are damaged, light touch, vibration, and position sensation is impaired in the left trunk, leg and arm below the lesion level. Receptors and reflex connections below the lesion level remain intact.
Behavioral Explanation
Click to animate
Contents DCML Lesions Patient Cases Exit

24. Lesion of the right medial lemniscus produces what impairment?
Click for answer
Damage to the right medial lemniscus causes the absence of light touch, vibration, and position sensation in the entire left side of the body from the neck down.
Click for explanation
Contents DCML Lesions Patient Cases Exit

25. Lesion of the medial lemniscus on the right: Behavioral Explanation
Primary sensory cortex
Thalamus
Nucleus Gracilis
Lesion of the medial lemniscus on the right: Behavioral Explanation
Nucleus Cuneatus
Fasciculus Cuneatus
Sensory impairment:
absence of light touch, vibration, and position sensation in the entire left side of the body from the neck down.
Fasciculus Gracilis
Sensory impairment:
the entire left body, from the neck down.
Click to animate
Neuroanatomical Explanation
Lesion
Lost function
Impairment
Contents DCML Lesions Patient Cases Exit

26. Behavioral Explanation
Lesion of the medial lemniscus on the right: Neuroanatomical Explanation
Because the lesion involves second-order neurons that have already decussated, impairment is contralateral to the lesion. The medial lemniscus conveys light touch, vibration, and position sensation from the entire left trunk, leg and arm below the neck. Sensation from the face is unaffected because it is conveyed via cranial nerves.
Behavioral Explanation
Click to animate
Contents DCML Lesions Patient Cases Exit

27. Lesion of the right internal capsule or primary somatosensory cortex produces what impairment?
Click for answer
Damage to the right internal capsule or primary somatosensory cortex causes the absence of light touch, vibration, and position sensation in the entire left side of the body including the face.
Click for explanation
Contents DCML Lesions Patient Cases Exit

28. Primary sensory cortex
Thalamus
Lesion of the internal capsule or primary somatosensory cortex on the right: Behavioral Explanation
Nucleus Gracilis
Nucleus Cuneatus
Fasciculus Cuneatus
Fasciculus Gracilis
Sensory impairment: absence of light touch, vibration, and position sensation in the entire left side of the body including the face.
Sensory impairment:
the entire left body, including the face.
Click to animate
Neuroanatomical Explanation
Lesion
Lost function
Impairment
Contents DCML Lesions Patient Cases Exit

29. Behavioral Explanation
Lesion of the internal capsule or primary somatosensory cortex on the right: Neuroanatomical Explanation
Because the lesion involves third-order neurons that have decussated, impairment is contralateral to the lesion. The internal capsule conveys light touch, vibration, and position sensation from the entire left side of the body, trunk, leg, arm and face.
Behavioral Explanation
Click to animate
Contents DCML Lesions Patient Cases Exit

30. Patient Cases Read these instructions! Patient Case 1 Patient Case 2
Contents DCML Lesions Patient Cases Exit

31. Case Instructions
These patient cases are intended to facilitate the integration and clinical application of information about the DCML by coupling the findings on examination and patient interview with their neuroanatomical correlates.
Each case begins with the patient’s chief complaint and significant examination findings. Then, the question is asked, Damage to what system(s) is causing this patient’s problems? Clicking the Answer button will reveal the answer and clicking the Show lesion button will reveal the neuroanatomic lesion along with the patient’s behavioral impairments.
Cases are presented from two perspectives. What lesion would account for a given set of examination results and patient history? For a given lesion, what signs and symptoms would be expected on examination?
Click on a Case number to begin the exercise.
Contents DCML Lesions Patient Cases Exit

32. Case 1 Clumsiness and difficulty grasping with the left hand
A left handed patient complains of “clumsiness” of her left arm and hand due to uncertainty of the limb’s position in space. She frequently fails to grasp or drops object with her left hand. Strength and AROM are WNL in all four extremities. Light touch, two-point discrimination, proprioception, and vibration sense are intact in the right upper extremity but absent in all dermatomes below the C3 dermatome in the left upper extremity. She is able to distinguish sharp from dull WNL in all four extremities and trunk, bilaterally.
Damage to what system(s) is causing this patient’s problems?
Answer
Lesion of the left fasciculus cuneatus at approximately C3.
Lateral corticospinal tracts are intact, bilaterally: strength and AROM are WNL in all four extremities.
Lateral spinothalamic tracts are intact, bilaterally: sharp/ dull is WNL.
Fasciculus gracilis is intact, bilaterally: light touch, two-point discrimination, proprioception, and vibration are WNL in bilateral lower extremities.
Fasciculus cuneatus is absent on the left: light touch, two-point discrimination, proprioception (limb position in space), and vibration are absent in all dermatomes below C3 on the left but intact on the right upper extremity.
Contents DCML Lesions Patient Cases Exit
Show lesion

33. Lesion of the fasciculus cuneatus on the left: Behavioral Explanation
Primary sensory cortex
Thalamus
Lesion of the fasciculus cuneatus on the left: Behavioral Explanation
Nucleus Gracilis
Nucleus Cuneatus
Fasciculus Cuneatus
Fasciculus Gracilis
Sensory impairment:
absence of light touch, vibration, and position sensation in the left arm and upper left trunk.
Sensory impairment:
left arm and upper left trunk.
Click to animate
Neuroanatomical Explanation
Lesion
Lost function
Impairment
Contents DCML Lesions Patient Cases Exit

34. Behavioral Explanation
Lesion of the fasciculus cuneatus on the left: Neuroanatomical Explanation
Because the tract has not yet decussated, impairment is ipsilateral to the lesion. Lesion of first-order neurons interrupts ascending information so light touch, vibration, and position sensation is impaired in the left arm and upper left trunk. Receptors and reflex connections below the lesion level remain intact.
Behavioral Explanation
Click to animate
Contents DCML Lesions Patient Cases Exit

35. Case 2: Numbness and tingling on the left side of the body
Following a brainstem stroke, the patient complains of numbness and tingling on the left side of the body. Sharp/dull and temperature sensation is unimpaired, throughout. 2 point discrimination on the fingertips are: 5 mm on the right and 15 mm on the left. In the absence of vision, the patient is able to identify common objects in the right hand but not the left and able to reproduce limb positions with the right lower extremity but not the left. Light touch and vibration sensation are WNL on the right but absent on the left side of the body. Pain and temperature as well as light touch, vibration and position sense are intact on both sides of the face. Strength and AROM are WNL in all four extremities.
Damage to what system(s) is causing this patient’s problems?
Lesion of the medial lemniscus on the right.
Lateral corticospinal tracts are intact, bilaterally: strength and AROM are WNL in all four extremities.
Lateral spinothalamic tracts are intact, bilaterally: sharp/ dull is WNL.
Fasciculus gracilis is intact, bilaterally: light touch, two-point discrimination, proprioception, and vibration are WNL in bilateral lower extremities.
Fasciculus cuneatus is absent on the left: light touch, two-point discrimination, proprioception (limb position in space), and vibration are absent in all dermatomes below C3 on the left but intact on the right upper extremity.
Answer
Contents DCML Lesions Patient Cases Exit
Show lesion

36. Lesion of the medial lemniscus on the right: Behavioral Explanation
Primary sensory cortex
Thalamus
Nucleus Gracilis
Lesion of the medial lemniscus on the right: Behavioral Explanation
Nucleus Cuneatus
Fasciculus Cuneatus
Sensory impairment:
absence of light touch, vibration, and position sensation in the entire left side of the body from the neck down.
Fasciculus Gracilis
Sensory impairment:
the entire left body, from the neck down.
Click to animate
Neuroanatomical Explanation
Lesion
Lost function
Impairment
Contents DCML Lesions Patient Cases Exit

37. Behavioral Explanation
Lesion of the medial lemniscus on the right: Neuroanatomical Explanation
Because the lesion involves second-order neurons that have already decussated, impairment is contralateral to the lesion. The medial lemniscus conveys light touch, vibration, and position sensation from the entire left trunk, leg and arm below the neck. Sensation from the face is unaffected because it is conveyed via cranial nerves.
Behavioral Explanation
Click to animate
Contents DCML Lesions Patient Cases Exit

38. Case 3: Multiple Sclerosis
A 34 year-old Caucasian female with a six year history of Multiple Sclerosis (exacerbating-remitting) has reported to the emergency room complaining of severe symptoms. A magnetic resonance image (MRI) of her spine shows a visible plaque, not seen in previous images, at the level of T10. The plaque involves the entire dorsal column on the left.
What signs and symptoms would be expected from this lesion?
Answer
Lesion of the left dorsal column at T10 would impair (in the case of a large lesion possibly obliterate) light touch, vibration, and position sensation in the left leg and lower left trunk. Only the fasciculus gracilis exists below T6.
Because she has the exacerbating-remitting type of MS, her previous symptoms will remain. If the DCML is the only system affected by this most recent exacerbation, the functions controlled by the corticospinal tract (voluntary movement) and lateral spinothalamic tract (pain and temperature sensation) would remain as before.
Contents DCML Lesions Patient Cases Exit
Show lesion

39. Lesion of the fasciculus gracilis on the left: Behavioral Explanation
Primary sensory cortex
Lesion of the fasciculus gracilis on the left: Behavioral Explanation
Thalamus
Nucleus Gracilis
Nucleus Cuneatus
Fasciculus Cuneatus
Fasciculus Gracilis
Sensory impairment:
absence of light touch, vibration, and position sensation in the left leg and lower left trunk.
Sensory impairment:
left leg and lower left trunk.
Click to animate
Neuroanatomical Explanation
Lesion
Lost function
Impairment
Contents DCML Lesions Patient Cases Exit

40. Lesion of the fasciculus gracilis
on the left: Neuroanatomical Explanation
Because the tract has not yet decussated, impairment is ipsilateral to the lesion. Lesion of first-order neurons interrupts ascending information so light touch, vibration, and position sensation is impaired in the left leg and lower left trunk. Receptors and reflex connections below the lesion level remain intact.
Click to animate
Behavioral Explanation
Contents DCML Lesions Patient Cases Exit

41. D. Michael McKeough, PT, EdD
The End
D. Michael McKeough, PT, EdD
 2015