Term
| What are the 4 major divisions of the brainstem and their CN nuclei? |
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Definition
1) Mesencephalon (between 3rd ventricle and Pons)
- Superior/inferior colliculi, "tegmentum", crus cerebri (cerebral peduncles), and CN 3 (eye out and slightly down) and 4 nuclei (when eye is looking in towards nose, it can't look down).
2) Pons (ponto-mes to ponto-medullary junction)
- 4th ventricle sits posterior to pons
- Pontine nuclei and CN 5, 6, 7, 8
3) Medulla (Open in front of 4th ventricle and then closes)
- CN nuclei 9 (ipsilateral pharynx), 10 (ipsilateral palate), 11 (ipsilateral trapezius), 12 (ipsilateral tongue)
4) Spinal chord (spino-medullary junction to L1) |
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Term
| What is the functional significance of the Cervical and Lumbar enlargements of the spinal chord? |
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Definition
1) Cervical is for upper extremities
2) Lumbar is for lower extremeties
** need more neurons!** |
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Term
| What are the primary differences between the organization of dorsal and ventral root axons in the spinal chord? |
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Definition
Sensory/Motor distribution of spinal chord arises from sulcus limitans splitting alar and basal plates embryonically!
1) Dorsal root ganglia cell bodes are OUTSIDE of spinal chord (sensory afferents)
2) Ventral root cell bodies are INSIDE the spinal cord in the ventral horn (motor efferents) |
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Term
| What are the 4 critical fiber tracts in the spinal chord? |
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Definition
1) Dorsal (IPSILATERAL light touch, vibration, proprioception)
2) Spinothalamic (CONTRALATERAL pain, temperature, crude touch)
3) Spinocerebellar (IPSILATERAL proprioception of muscles and joints)
4) Corticospinal (IPSILATERAL motor control of striated muscles) |
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Term
| What is the functional organization of dorsal spinal columns? |
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Definition
**Ipsilateral lower body in F. gracilis (medial) and Upper body in F. cuneatus (lateral).
1) Located posterior and medial to dorsal horns, and convey touch, pressure and vibration, as well as proprioception from ipsilateral side.
- Myelinated axons DON'T synapse in spinal cord, but enter dorsal columns and run rostrally up chord (1st order afferents)
2) Topographical organization
- Sacral, lumbar and below T6 are located medial as F. gracilis
- Upper thoracic and cervical levels are lateral as F. cuneatus. |
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Term
| What is the functional organization of the Spinothalamic columns? |
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Definition
Pain, temperature and crude touch from contralateral side
1) 1st order afferents enter dorsal horn and synapse on neurons there
2) 2nd order axons cross to opposite side of cord forming spinothalamic tract in anterolateral white matter. |
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Term
| What is the functional organization of Spinocerebellar tracts? |
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Definition
Proprioception from muscle and joint receptors (tension and position)
1) 1st order afferents enter dorsal horn and synapse in dorsal nucleus of Clarke (C8-L2/3 vs. ALL levels for Spinothalamic)
2) 2nd order neurons congregate dorsolaterally in white matter and convey information from ipsilateral lower half of body. |
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Term
| What is a major difference between the functional and anatomical distribution of the Spinothalamic and Spinocerebellar tracts? |
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Definition
1) Function
- Spinothalamic is contralateral pain, temperature and crude touch
- Spinocerebellar is ipsilateral muscle and tendon proprioception)
2) Anatomy
- Spinothalamic is at all cord levels
- Spinocerebellar is only at C8-L2/3 |
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Term
| What is the functional organization of Corticospinal tract? |
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Definition
Contralateral motor signals from cerebral cortex to lateral funiculus of spinal cord white matter.
1) At appropriate levels, axons leave tract and synapse on neurons in ventral horn of ray matter
2) 2nd neurons project out of ventral root to IPSILATERAL striated muscle. |
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Term
| Which of the 4 primary spinal tracts are ipsilateral vs. contralateral? |
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Definition
1) CONTRALATERAL
-Spinothalamic (pain, temperature and crude touch) is
2) IPSILATERAL
- Dorsal (light touch, vibration and proprioception)
- Corticospinal (motor to striated muscle)
- Spinocerebellar (Proprioception of lower body) are |
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Term
| How does "Brown-Sequard Syndrome" arise and manifest? |
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Definition
Hemisection of Spinal Cord
1) Touch, vibration and conscious position sense lost Ipsilaterally (dorsal column and spinocerebellar tracts)
2) Pain and temperature sense lost Contralaterally (spinothalamic tract)
3) Motor loss ipsilaterally (corticospinal tract) |
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Term
A patient presents with impaired pain and temperature sensation contralateral to the location of a spinal cord lesion.
Where is the lesion? |
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Definition
| Pain and Temperature are in the Spinothalamic tracts, which distribute contralaterally. |
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Term
A patient presents with impaired proprioception of his lower limbs ipsilaterally to the location of a spinal cord lesion.
Where is the lesion? |
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Definition
| Ipsilateral lower limb proprioception is the Spinocerebellar tract. |
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Term
| How can you distinguish different spinal chord levels? |
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Definition
White Matter, Ventral Horn Size and Lateral Horns
1) White Matter- less as you go down because only lower limb vs. upper and lower limb.
2) Ventral horns (grey) are largest in cervical and lumbosacral levels, where motor neurons innervate muscles of extremities (smaller in thoracic)
3) Look for lateral horns (going to sympathetic ganglia) in thorax between T1-L3 |
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Term
| How do the Dorsal Column tracts of the spinal chord continue into the brainstem (called "Medial Lemniscus system")? |
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Definition
Supplied by anterior spinal artery off of vertebral artery (infarction causes contralateral deficit in tactile sensation as part of Medial Medullary Syndrome). Also supplied by pontine arteries and can be altered in paramedian pontine syndrome.
1) Axons from F gracilus (lower) and F. cuneatus (higher) enter caudal medulla and synapse in the nucleus gracilus and nucleus cuneatus, respectively.
2) 2nd order axons course ventrally as "internal acuate fibers" and cross, collecting as medial lemniscus bundle.
3) ML courses rostrally through upper medulla, pons and mesencephalon terminating in the thalamus. |
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Term
| How do the Spinolthalamic tracts of the spinal chord continue into the brainstem? |
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Definition
1) Travels up brainstem as anterolateral bundle
2) Eventually converges with medial lemniscus system and run around pons together |
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Term
| How do the Spinocerebellar columns of the spinal chord continue into the brainstem? |
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Definition
These were ipsilateral, lower proprioception in spinal chord (Proprioception is entirely IPSILATERAL!).
1) Maintains lateral position up through lower medulla, where it meets external cuneate nucleus, which receives upper extremity proprioceptive feedback from dorsal column.
2) Axons from both tracts travel rostrally together and enter cerebellum to provide sensory signals for coordinated movements. |
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Term
| How do the Corticospinal tracts of the spinal chord continue into the brainstem? |
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Definition
Supplied by anterior spinal artery off of vertebral artery (infarction causes hemiparesis as part of Medial Medullary Syndrome). Also supplied by pontine arteries of basilar artery and issues are seen in paramedian pontine syndrome.
1) Passes from cerebral cortex (pre-central gyrus) though internal capsule (caudate and thalamus) and mesencephalon, forming a tight bundle near ventral pons/medulla
2) Crosses to opposite side of brainstem at spinomedullary junction (pyramidal decussation) and takes up a position in lateral funiculus of spinal cord. |
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Term
| What basic principles define cranial nerves? |
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Definition
1) Nerve may be sensory (I, II, XIII) motor (III, IV, VI, XI, XII) or both (V, VII, IX, X)
Some Say Money Matters, But My Brother Says Big Boobs Matter Most.
2) Nucleus is only sensory or motor (spinal V is sensory and N. ambuguus is motor)
3) Nucleus may be associated with >1 CN (spinal is 5, 7, 9, 10 and solitary is 7,9,10)
4) Some nerves share similar targets/functions (V and VII, and IX and X)
5) Motor CN nuclei have contralateral and bilateral inputs (VII and V motor are bilateral) |
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Term
| Explain the blood supply of the Internal capsule, which is important for voluntary motor control? |
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Definition
Tract goes from M1 to internal capsule to crus cerebri to pyramidal tract of medulla.
1) Lenticulostriate arteries of MCA supply superior portions of anterior and posterior limbs
2) Recurrent artery of Heubner off of ACA supplies inferior anterior limb.
3) Anterior choroidal artery off of MCA or internal carotid supplies inferior posterior limb. |
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Term
| What are the four cranial nerve nuclei associated with CN V? |
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Definition
Main Sensory, Spinal, Mesencephalic, Motor
1) Main Sensory- fine touch from ipsilateral face and touch from cornea and conjunctiva (project axons across midline of Pons to ascend to contralateral thalamus via medial lemniscus)
2) Spinal- pain and temperature information from ipsilateral face and head (V) and receives input from 7,9,10 (projects to contralateral thalamus).
3) Mesencephalic trigeminal nucleus- relays proprioceptive information from muscles and joints of ipsilateral face and jaw (project to motoneurons in motor nucleus and provide sensory input to reflexively control bite strength and to the ipsilateral cerebellum (muscle coordination)
4) Motor nucleus- neurons that control muscles of mastication ipsilaterally (tensor tympani) |
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Term
| Which CN nuclei receive input from CN 7, 9 and 10? |
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Definition
1) The Spinal Nucleus of V, which conveys temperature and pain information from ipsilateral face and head.
Remember, temperature and pain is carried by the spinothalamic tract in the spinal chord and brain stem.
2) The solitary nucleus receives taste (7,9, 10) and vascular information (9, 10). |
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Term
| Which CN nuclei is involved in sensory-motor integration to control the strength biting, as well as muscle coordination? |
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Definition
The mesencephalic nuclei of V, which relays proprioceptive information from muscles and joints of ipsi. face and jaw to motoneurons of CN V
1) Provides sensory input to reflexively control tensor tympani
2) Provides sensory input to ipsilateral cerebellum |
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Term
| Which CN nucleus relays information abut discriminative touch on the ipsilateral face and from the cornea and conjunctiva of the eye? |
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Definition
| Main sensory nucleus of CN V , which sends axons across midline of ponds to ascend to contralateral thalamus via medial lemniscus. |
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Term
| What are the 4 major components of the Fascial Nerve (VII)? |
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Definition
VII (2 Sensory and 2 Motor)= muscles of facial expression and sensory for anterior 2/3 of tongue and pain/temperature.
Sensory
1) Visceral afferents for taste on anterior 2/3 of tongue, terminating in solitary tract/nucleus (taste), which project to thalamus.
2) Somatic Afferants (via intermediate nerve) convey pain, temp and some cutaneous sensation from tympanic membrane, ext. auditory meatus and skin behind ear, terminating in Spinal Trigeminal nucleus
Motor
1) Facial nucleus- 2 nuclei (upper and lower face) that recieve bilateral input from cortex via corticospinal tract, and from spinal trigeminal nucleus. Also innervate stapedius muscle (hyperacusis in Bell's Palsy)
2) Superior Salivatory nucleus- input from solitary nucleus and hypothalamus (taste and hunger) and send efferents to lacrimal gland and submandibular/sublingual salivary glands. |
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Term
| Which CN nuclei causes complete ispilateral Bell's Palsy when lesioned as well as hyperacusis? |
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Definition
Facial Nucleus of CN VII
- 2 nuclei (upper face reviews bilateral input and lower face receives only contralateral input)
- Innervates stapedius- hyperacusis |
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Term
| How can you distinguish between 1) Upper Motor Neuron vs. 2) Lower Motor Neuron Lesions causing Facial Weakness? |
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Definition
Remember, there are 2 divisions of the facial nucleus, Upper (bilateral motor cortex innervation) and Lower (contralateral only)
1) If there is a unilateral lesion in the telencephalic projections from the right-hand motor cortex, you will see contralateral, lower facial weakness
2) If there is a lesion of the facial nucleus or facial nerve on the left, you will see ipsilateral complete facial weakness, because both the upper and lower divisions will be affected. |
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Term
| Which CN fibers terminate in the solitary nucleus/tract? |
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Definition
The solitary nucleus/tract is involved in taste as well as vascular information (goes to dorsal motor of vagus), and continues to project to the thalamus and on to the cortex.
**Sends information to superior salivatory nucleus to increase salivation
1) Visceral sensory afferents from CN VII communicate taste from anterior 2/3 of tongue
2) Visceral sensory afferents from CN IX for posterior 1/3 of tongue |
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Term
| Which 2 CN nuclei receive input from both the solitary nucleus and the hypothalamus? |
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Definition
1) Superior Salivatory Nucleus of CN VII receives taste (solitary nucleus) and hunger (hypothalamus) information in order to produce appropriate amounts of secretion from lacrimal gland, as well as submandibular and sublingual salivary glands.
2) Inferior salivatory nucleus of IX sends to parotid. |
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Term
| What are the 4 major sensory/motor components of CN IX? |
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Definition
GSA, GVA, inf. Salivatory nucleus, Nucleus Ambiguus.
Sensory
1) GSA for touch/pain/temperature from posterior 1/3 of tongue, pharynx, ext. auditory meatus, tympanic membrane and nearby skin of ear. (Project on to spinal trigeminal nucleus of main sensory nucleus of V)
2) GVA for taste of posterior 1/3 of tongue and chemo- and baroreceptor information from carotid body and project to solitary nucleus/tract.
Motor
1) Inferior salivatory nucleus- gets input from solitary nucleus and hypothalamus and projects to parotid to produce saliva
2) Nucleus ambiguus- Midpoint at imaginary line connecting spinal trigeminal nucleus with dorsomedial part of inferior olivary nucleus
- Input from solitary nucleus and other sources and innervates muscles of larynx and pharynx (vocalization and swallowing) |
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Term
| What is the course of the CN fibers that convey pain/touch/temperature from the posterior 1/3 of the tongue |
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Definition
These are Somatic Afferents from CN IX
- Like somatosensory afferents of CN X, these fibers terminate in the spinal trigeminal nucleus or main sensory nucleus of CN V.
- Cells in the nuclei of CN V give rise to axons that cross the midline to travel with the contralateral medial lemniscus and spinothalamic tracts to the thalamus. |
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Term
| What information is processed by the visceral afferents of CN IX? |
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Definition
1) Taste from posterior 1/3 of tongue to solitary tract/nucleus, then on to the thalamus and cortex.
2) Chemo- and barorecpetor information from carotid body fed to the brainstem circuits (dorsal motor nucleus of CN X) that modulate heart rate, blood pressure and respiration. |
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Term
| Which CN nucleus is critical for swallowing and vocalization? |
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Definition
| The Nucleus ambiguus of CN IX (motor) and CN X (motor) receives input from the solitary nucleus as well as others, and innervates muscles of the larynx and pharynx and soft pallate. |
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Term
| What are the 4 major sensory/motor components of CN X? |
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Definition
SA, VA, Nucleus ambiguus, Dorsal motor nucleus
Sensory
1) SA pain/temp/touch similar to IX and terminate in spinal trigeminal nucleus or main sensory nucleus of V, and on to thalamus
2) VA convey taste from epiglottis and pharynx to solitary nucleus and chemo- and baroreceptor information from aortic arch to dorsal motor nucleus
Motor
1) Nucleus ambiguus innervates soft palate muscles, larynx and pharynx and is important for vocalization and swallowing.
2) Dorsal motor nucleus receives input for IX and X afferents via solitary nucleus, and innervates cardiac muscle (Ach slow rate), lungs (constriction), esophagus (increased peristalsis) and stomach (gastric secretion) |
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Term
| Which CN nuclei integrates information from aortic arch and carotid body, via the solitary nucleus? |
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Definition
Dorsal motor nucleus of vagus receives information from aortic arch (CN X) and carotid body (CN IX) and delivers it vis the solitary nucleus to
1) Heart (Ach slows rate)
2) Lungs (constriction)
3) Esophagus (peristalsis)
4) Stomach (gastric secretion) |
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Term
| Somatic afferents of which 2 cranial nerves send pain/temp/touch information to the spinal trigeminal nucleus and the main sensory nucleus of V? |
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Definition
| CN IX and X send somatic afferents, which then project on to the thalamus. |
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Term
| Which CN fibers convey taste information from the epiglottis and pharynx via the solitary nucleus? |
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Definition
| Visceral afferents from CN X |
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Term
| What are the classic clinical symptoms and their anatomical correlates associated with Lateral Medullary syndrome? |
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Definition
LMS is associated with PICA infarction
1) Nucleus ambiguus (IX, X)- Hoarseness and Dsyphagia (swallowing)
2) Spinal V tract/nucleus (SA from IX and X)- Pain and temperature loss on ipsi face
3) Inferior cerebellar peduncle- Ataxia ipsilaterally
4) Vestibular nucleus- Vertigo
5) Spinothalamic tract- Pain and temp. on contralateral body decreased.
6) Nucleus solitarius (VII, IX, X)- Taste decreased ipsilaterally
7) Descending sympathetics- Horner's (ptosis, myosis, anhydrosis) |
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Term
| What is the anatomical basis for the development of Horner's syndrome when descending sympathetics are lost because of PICA infarction? |
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Definition
1) Hypothalamus sends descending signals to pre-ganglioic sympathetic neurons in intermediolateral cell column of thoracic spinal cord (at around T1)
2) Spinal neurons poject to post-ganglinic sympathetic neurons (in chain ganglia outside of chord), which innervate smooth muscle of upper eyeslid (ptosis), pupillary dilator muscle of eye (myosis) and sweat glands of head and neck (anhydrosis). |
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Term
| What is the "Rule of 4" for remembering brainstem anatomy? |
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Definition
1) There are 4 structures in the ‘midline’ beginning with
M
- Motor pathway (contra corticospinal)
- Medial Lemniscus (contra vibration and proprioception)
- Medial longitudinal fasciculus (MLF)- CN III/XI integration with eye movement and turning of head
- Motor nucleus (3, 4, 6, 12)
2) There are 4 structures to the side beginning with S
- Spinothalamic
- Spinal Trigeminal
- Sensory nucleus of V
- Sympathetic pathway
3) There are 4 cranial nerves in the medulla, 4 in the
pons and 4 above the pons (2 in the midbrain).
4) The 4 motor nuclei that are in the midline are those
that divide equally into 12 except for 1 and 2, that is 3,
4, 6 and 12 (5, 7, 9 and 11 are in the lateral brainstem). |
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Term
| What 4 structures on the lateral brainstem start with "S" and what is each associated pathology? |
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Definition
1) Spinothalamic tract (pain and temp on contralateral arm, leg and sometimes the trunk).
2) Spinal V nucleus and Sensory nucleus (pain, temp and sensation on ipsilateral face from 5, 7, 9, 10)
3) Spinocerebellar (ipsilateral ataxia of arm and leg)
4) Sympathetic chain (Horner's) |
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Term
| What 4 structures on the medial brainstem start with "M" and what is each associated pathology? |
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Definition
1) Motor pathway (contralateral weakness of arm and leg)
2) Medial Lemniscus (vibration and proprioception contralateral arm and leg)
3) Medial longitudinal fasciculus (MLF)- CN III/XI integration with eye movement and turning of head
4) Motor nuclei (3, 4, 6, 12)- eye movements and tongue |
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Term
| What are the motor cranial nerve "parallels of latitude"? |
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Definition
1) Medulla (12th)- ipsilateral tongue weakness?
2) Pons (6th)- ipsilateral eye in and down?
3) Midbrain (3rd)- ipsilateral eye out and down? |
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Term
| How would a Lacunar infarction present clinically? |
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Definition
MLF would be affected at midline of brainstem.
- ipsilateral internuclear ophthalmoplegia, with failure of adduction (movement towards the nose) of the ipsilateral eye and leading eye nystagmus on looking laterally to the opposite side of the lesion in the contra lateral eye. If the |
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Term
| What pathology is most likely if you encounter for medial and lateral brainstem syndromes? |
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Definition
| Occlusion of basilar artery |
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