Podcast
Questions and Answers
What type of weakness is caused by damage to the lateral corticospinal tract in Brown-Sequard syndrome?
What type of weakness is caused by damage to the lateral corticospinal tract in Brown-Sequard syndrome?
What symptom is seen due to the interruption of the posterior column in Brown-Sequard syndrome?
What symptom is seen due to the interruption of the posterior column in Brown-Sequard syndrome?
What causes contralateral loss of pain and temperature sensation in Brown-Sequard syndrome?
What causes contralateral loss of pain and temperature sensation in Brown-Sequard syndrome?
Which condition involves bilateral regions of suspended sensory loss to pain and temperature?
Which condition involves bilateral regions of suspended sensory loss to pain and temperature?
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What is the common cause of central cord syndrome?
What is the common cause of central cord syndrome?
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Which condition results in damage to the lateral corticospinal tract and upper motor neuron (UMN) signs?
Which condition results in damage to the lateral corticospinal tract and upper motor neuron (UMN) signs?
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What is a characteristic symptom of posterior cord syndrome?
What is a characteristic symptom of posterior cord syndrome?
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In anterior cord syndrome, what does damage to the anterolateral pathways cause?
In anterior cord syndrome, what does damage to the anterolateral pathways cause?
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What does a fluid-filled cyst within the spinal cord define?
What does a fluid-filled cyst within the spinal cord define?
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What can cause bilateral regions of suspended sensory loss to pain and temperature?
What can cause bilateral regions of suspended sensory loss to pain and temperature?
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Which trigeminal nucleus provides proprioception?
Which trigeminal nucleus provides proprioception?
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Where do primary sensory neurons for the trigeminal nuclei mainly lie?
Where do primary sensory neurons for the trigeminal nuclei mainly lie?
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Which structure is the main pathway to the thalamus for the trigeminal sensory system?
Which structure is the main pathway to the thalamus for the trigeminal sensory system?
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Where does the spinal trigeminal nucleus provide sensory input to?
Where does the spinal trigeminal nucleus provide sensory input to?
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What deficits might be more noticeable if there's a lesion in the thalamic ventral posterior lateral (VPL) nucleus?
What deficits might be more noticeable if there's a lesion in the thalamic ventral posterior lateral (VPL) nucleus?
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What type of symptoms can occur if there's a transverse cord lesion?
What type of symptoms can occur if there's a transverse cord lesion?
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What is a common cause of spinal cord syndromes according to the text?
What is a common cause of spinal cord syndromes according to the text?
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Where do secondary sensory neurons synapse after primary sensory neurons from trigeminal ganglion?
Where do secondary sensory neurons synapse after primary sensory neurons from trigeminal ganglion?
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What is the main pathway from the spinal trigeminal nucleus to the thalamus?
What is the main pathway from the spinal trigeminal nucleus to the thalamus?
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What type of deficit may be more noticeable if there is a lesion at the thalamic ventral posterior medial (VPM) nucleus according to the text?
What type of deficit may be more noticeable if there is a lesion at the thalamic ventral posterior medial (VPM) nucleus according to the text?
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Study Notes
Hemicoord Lesion: Brown Sequard Syndrome
- Lateral corticospinal tract damage causes ipsilateral UPN-type weakness
- Posterior column interruption causes ipsilateral loss of vibration and joint position sense
- Contralateral loss of pain and temperature sensation in the anterolateral system, 2-3 segments below the lesion, as they cross the ventral (anterior) commissure
- Ipsilateral sensory loss and pain caused by damage to posterior horn cells at the spinal cord level before axons cross over
Common Causes of Hemicoord Lesion
- Penetrating injuries
- Multiple sclerosis (MS)
- Lateral compression from tumors
Central Cord Syndrome (Small Lesions)
- Damage to spinothalamic fibers crossing in the ventral commissure causes bilateral regions of suspended sensory loss to pain and temperature
- Causes: syringomyelia (fluid-filled cavity in spinal cord), tumors, and MS
Syringomyelia
- A fluid-filled cyst (syrinx) that forms within the spinal cord
- The syrinx can grow large enough to damage the spinal cord and compress and injure nerve fibers that carry information to and from the brain to the body
Posterior Cord Syndrome
- Loss of vibration and position sense below the level of the lesion
- Larger lesions can cause encroachment on the lateral corticospinal tract, resulting in UPN weakness
- Common causes: trauma, tumors, MS, vitamin B12 deficiency, and tabes dorsalis
Anterior Cord Syndrome
- Damage to the anterolateral pathways causes loss of pain and temperature sensation below the level of the lesion
- Damage to anterior horn cells produces LMN weakness at the level of the lesion
- Larger lesions can cause damage to the lateral corticospinal tract, resulting in UPN signs
- Common causes: trauma, tumors, MS, and infarct
Trigeminal Nerve (CN V)
- Provides sensory information for the face and head
- Analogous to the posterior and anterolateral systems
- Mesencephalic trigeminal nucleus provides proprioception
- Chief trigeminal sensory nucleus provides fine touch and dental pressure
- Main pathway to the thalamus is the trigeminal lemniscus
- Main thalamic nucleus: VPM (ventral posterior medial nucleus)
Trigeminal Somatic Sensory Functions
- Trigeminal nuclei receive general somatic sensory inputs from CN V and other cranial nerves
- Trigeminal nuclear complex runs from the midbrain to the upper cervical spinal cord and contains 3 nuclei (Mesencephalic, Chief, and spinal)
- Primary sensory neurons for these trigeminal nuclei lie mainly in the trigeminal ganglion
- They synapse on secondary order sensory nuclei on the ipsilateral side
Trigeminal Pathway
- Secondary sensory neurons travel in the trigeminal lemniscus, which crosses to the opposite side of the brainstem to ascend with the medial lemniscus towards the thalamus
- Second-order neurons cross midline and travel to the thalamus
- Trigeminal lemniscus travels to VPM
- Third-order neurons from thalamus to facial region of somatosensory cortex
Primary Somatosensory Cortex/Thalamic Lesion
- Thalamic ventral posterior lateral (VPL) and ventral posterior medial (VPM) nuclei or thalamic somatosensory radiations are affected
- Deficit may be more noticeable in the face, hand (lips and finger tips), and foot than trunk/proximal extremities
- Sensory loss in the left face corresponds to sensory loss at the opposite side of the body (afferent bodies)
Spinal Cord Syndromes
- Can include motor, sensory loss, or both (depending on areas affected by injury)
- Transverse cord lesion: all sensory/motor pathways are either partially or completely interrupted
- Often, the sensory level diminishes sensation in all dermatomes below the level of the lesion
- Positive LMN symptoms at the level of the lesion, and UPN if the corticospinal tract is affected
- Common causes: trauma, tumors, MS, and transverse myelitis
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Description
Test your knowledge on the sensory pathways of the trigeminal nerve, including the mesencephalic trigeminal nucleus, chief trigeminal sensory nucleus, and spinal trigeminal nucleus. Learn about the main pathway to the thalamus and the VPM nucleus.
