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NSx Neuroanatomy > Brainstem > Flashcards

Brainstem Flashcards

1
Q

Midbrain=

A

Mesencephalon

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2
Q

Pons=

A

Metencephalon (along with cerebellum)

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3
Q

Medulla=

A

Myelencephalon

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4
Q

CN nuclei in midbrain?

A

3 and 4

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5
Q

CN nuclei in pons

A

5, 6, 7, 8

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6
Q

CN nuclei in medulla

A

9, 10, 11, 12

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7
Q

Level of CN3 exiting midbrain

A

Ventral midbrain at the level of the superior colliculus in the interpeduncular sulcus

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8
Q

Superior colliculus associated with?

A

Visual system

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9
Q

Inferior colliculus associated with?

A

Hearing

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10
Q

Which is the only cranial nerve to exit from the dorsal brainstem and at what level?

A

Trochlear.

Inferior colliculus

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11
Q

Why does the trochlear nerve exits from the posterior brainstem?

A

Pineal gland is the embryological rudimentary eye.

Trochlear nerve was likely associated with that.

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12
Q

Where does the trigmeinal emerge from the pons?

A

Mid-pontine level.

Anterolateral region.

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13
Q
A
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14
Q

What level do the 6, 7 ,8th cranial nerves emerge?

A

Ponto-medually junction

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15
Q

In what order from medial to lateral do the 6th, 7th and 8th CN emerge?

A

6 medial, 7 then 8 most laterally.

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16
Q

6th 7th nerve palsy.

Location of lesion?

A

?medial ponto-medullary sulcus/junction.

As more medial structures and internal genu of facial nerve intimately related to CN6 nuclei

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17
Q

7th 8th nerve palsy

A

Lateral pontomedullary problem/IAM

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18
Q

Etymology of vagus

A

Wanderer

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19
Q

Location of hypoglossal nerve

A

Emerges from the ventral medulla at the sulcus between pyramid and olive.

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20
Q

3 divisions from ventral to dorsal of brainstem

A

Basis

Tegmentum

Tectum

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21
Q

Tegmentum etymology

A

Covering

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22
Q

Tectum etymology

A

Roof

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23
Q

Descending tracts found in which portion of brainstem?

A

Basis

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24
Q

Ascending tracts found in which portion of brainstem?

A

Tegmentum

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25
Relation between motor and sensory nuclei in braistem
Motor medial, sensory lateral.
26
Supplementary motor grey matter in medulla
Superior and inferior olivary nuclei
27
Location of supplementary grey matter in the brainstem
Ventral tegmentum
28
Supplementary grey matter in pons
Pontine nuclei
29
Supplementary grey matter nuclei in midbrain
SN and red nuclei
30
Cranial nerve nuclei arrangement
Dorsal tegmentum
31
Location of special grey matter in brainstem
Tegmentum lateral to motor nuclei
32
In simple terms what is the reticular formation
As grey matter and white matter ascends in the brainstem and decussates the grey matter is broken up into the indiviudal nuclei but also fragments of grey matter interspersed with white matter in the ventral tegmentum which is the reticular formation
33
Neurones in the anterior horn are?
Motor
34
Draw the general arrangement of structures in the medulla.
35
Dorsal sensory neurones develop embryologically from the?
Alar plate
36
Ventral motor neurones develop embryologically from the?
Basal plate
37
Lateral grey horn neurones are involved in?
Visceral function
38
Arrangement of efferent neurones from medial to lateral in SC
General somatic efferents General visceral efferents
39
Arrangement of afferent fibres from lateral to medial in SC
General somatic afferents General visceral afferents
40
Location of hypoglossal nuclear tract
Tegmentum of medulla medially adjacent to fourth ventricle (GSE)
41
Location of vagus nuclear tract
Dorsal nucleus is lateral to hypoglossal nuclei (GVE) in tegementum of medulla.
42
From what embryological structure do the special muscles in head and neck derive?
Branchial pouch
43
Where are the SVE nuclei found in the medulla
Anterolateral to the GVE tract as the nucleus ambiguus
44
Where are the CN nuclei for 3 and 4 found?
Just lateral to midline in midbrain
45
What is the remaining GSE nuclei and where is it found?
Midline in the pons (GSE column)
46
Where are the nuclei involved in lacrimation and salivation
Latearl to GSE tract as the superior and inferior salivary nuclei in the pons. (Superior portion of the superior salivary gland contributes to lacrimation)
47
Structures supplied by nucleus ambiguus?
Muscles of the larynx and pharynx
48
Location of facial nerve nuclei
In the SVE column at the pontomedullary junction.
49
Location of the motor nucleus of trigeminal
Midpons in the SVE column.
50
CNs receiving fibres from the nucleus ambiguus
9, 10 and cranial portion of 11
51
Location of GVA tract
Lateral to GVE
52
Location of SVE in brainstem
Lateral to the GVA
53
Components of nucleus solitarius?
Medially- GVA Laterally- SVA
54
SVA in medulla
Taste
55
What carries taste fibres from the vallecula of the tongue?
X
56
Which nerves carry taste sensation and to what do they connect?
7, 9, 10 Nucleus solitarius
57
Location of special somatic afferent in brainstem
Medial to general somatic
58
What recieves auditory stimuli?
Ventral and dorsal cochlear nucleus, ventral and dorsal to inferior cerebellar peduncle
59
Fine touch trigeminal sensation goes to?
Principle nucleus
60
Pain and temperature sensation in trigeminal goes to which nucleus?
Spinal
61
Proprioceptive information goes to which trigeminal nucleus?
Mesencephalic
62
Rhombencephalon=
Pons, medulla and cerebellum
63
What is the inferior border of the medulla?
Pyramidal decussation
64
With which nuclei of the thalamus do reticular formation systems connect?
Intralaminar nuclei of thalamus Which then connect with all parts of cortex.
65
Most important function of ascending reticular formation
Consciousness
66
What are the functions of the medullary reticular formation?
Cardiac centre Vasomotor centre Respiratory centre- Inspiratory centre Gastrointestinal centre
67
Location of area postrema?
Adjacent to fourth ventricle Next to chemoreceptor trigger zone Near GIT connecting nervous system.
68
What is significant about the area postrema
Portion of the medulla in which there is a break in BBB to allow chemical substances to influence neurones in area postrema.
69
Ascending pathways of medulla
Dorsal column- Fasciculus gracilis + cuneatus Nucleus cuneatus and gracilis Internal arcuate fibres Medial leminisci Spinothalamic- Anterior and lateral tracts. Spinotectal tract
70
Dorsal column sensations
Fine touch Proprioception Vibration Two-point discrimination
71
What happens to dorsal column tracts on reaching medulla?
Synapse with nucleus gracilis and nucleus cuneatus which is located in the posteroinferior portion of the medulla. Second order neurones originate there and decussate
72
Where do second-order dorsal column fibres synapse?
VPL nucleus of thalamus
73
What is the name of the decusssating dorsal column fibres in the inferior medulla?
Internal arcuate fibres
74
How do the second order fibres of dorsal column ascend?
Medial lemniscus
75
Left medial lemniscus fibres carry what modality?
Dorsal column from right body.
76
Spinotectal tract involved in?
Spinovisual/ Spinoauditory reflexes
77
What forms in the medulla from the spinothalamic and spinotectal tracts?
Spinal lemniscus
78
Which tracts make up the spinal lemniscus?
Anterior and lateral spinothalamic tracts Spinotectal tract
79
Right spinal lemniscus injury
Left spinotectal and spinothalamic information
80
Descending pathways of the medulla
Corticospinal
81
What proportion of corticospinal fibres decussate at the level of the medulla?
90%
82
LMN to lower limb come from which corticospinal tract?
Lateral corticospinal tract
83
Axial musculature LMN come from which corticospinal tract?
Anterior (i.e. do not decsusate in medulla but cross at the level of crossing)
84
How is the medulla connected to the cerebellum?
Inferior cerebellar peduncle
85
What is the accessory cuneate nucleus?
Nucleus at dorsal portion of medulla near to cuneate nucleus. Receives fibres from upper limb which subsequently enter the cerebellum via the inferior cerebellar peduncle as the cuneocerebellar pathway
86
Cuneocerebellar fibres carry
Proprioceptive information from the upper limb via the accessory cuneate nucleus in the medulla to the cerebellum via the inferior cerebellar peduncle
87
Origin of dorsal spinocerebellar tract
Fibres from lower limb, travel ipsilaterally along with cuneocerebellar pathway into the cerebellum via inferior cerebellar peduncle (though not via accessory cuneate nucleus)
88
Origin of ventral spinocerebellar pathway
Lower limb, second order neurone decussates , pass through medulla, pons and then through superior cerebellar peduncle where they decussate again to return to their original side.
89
What is the difference between dorsal spinocerebellar tract and ventral cerebellar tract?
Dorsal ipsilateral and passes through inferior cerebellar peduncle. Ventral decussates ( in SC and then within the cerebellum) twice and passes through superior cerebellar peduncle.
90
Lower limb proprioception carried by?
Dorsal and ventral spinocerebellar tract
91
Upper limb proprioception carried by?
Cuneocerebellar tract (via accessory cuneate nucleus)
92
What are the posterior parthways of the medulla? 7
Cuneocerebellar tract Dorsal spinocerebellar tract (Ventral spinocerebellar tract) Olivocerebellar tract Arcuato-cerebellar tract Reticulo-cerebellar pathway Central tegmental pathway
93
Passage of olivocerebellar tract?
From olivary nucleus in medulla to contralateral cerebellum via inferior cerebellar peduncle
94
What area in the midbrain communicates with the inferior olivary nucleus?
Red nucleus via rubro-olivary fibres
95
Function of rubro-olivarycerebellar tract?
Important control of motor movements
96
Function of corticopontocerebellar tract
Allows cerebral cortex to influence cerebellar function
97
Components of corticopontocerebellar tract
Corticopontine tract-\> pontine nuclei-\> cerebellum via middle cerebellar peduncle
98
What are arcuate nuclei?
Inferiorly dispalced pontine nuclei found in the medulla
99
What fibres are present in the central tegmental pathway
Rubro-olivary Reticulothalamic fibres Central taste pathway (from nucelus solitarius to thalamus)
100
What nucleus of the thalamus receives taste information?
VPM nucleus
101
Which nerve emerges from the preolivary sulcus in the medulla?
12
102
Which nerves emerge from post-olivary sulcus?
9 10 11
103
Which cranial nerve fasciculus passess between the pyramid and olive of the medulla?
12
104
Where do the parasympathetic fibres of the vagus nerve originate?
Dorsal vagal nucleus
105
Where do general visceral afferent fibres of the vagus nerve terminate?
Medial portion of nucleus of tractus solitarius
106
Where do special visceral afferent fibres of the vagus nerve terminate?
Lateral portion of tractus solitarius
107
Where do special efferent (branchial motor) fibres of vagus nerve originate?
Nucleus ambiguus
108
Which branch of vagus carries touch pain and temperature from the external ear? To which nucleus is it connected?
Arnold's nerve (auricular branch of vagus) Trigeminal nuclear system
109
Which nuclei are associated with vagus nerve?
Dorsal vagal nuclei Nucleus of tractus solitarius Nucleus ambiguus Trigeminal nucleus
110
Where does touch pain and temperature sensation carried from the poserior 1/3rd of the tongue terminate?
Spinal trigeminal nucleus
111
Which thalamic nuclei does the trigeminal lemniscus terminate in
VPM
112
9th communicates with which nuclei?
Nucleus ambiguus Spinal nucleus of trigeminal system Nucleus solitarius
113
Origin of cranial part of 11th?
Nucleus ambiguus Travels with vagus to phayrynx
114
Where are the vestibular nuclei found?
Lower pons Upper medulla
115
Location of cochlear nuclei
Rostral medulla
116
Location of area postrema
Floor of 4th ventricle near the obex
117
Obex of fourth ventricle
Where the fourth ventricle narrows to become SC
118
What are the three major levels of medulla
Level of motor decussation Level of sensory decussation (internal arcuate fibres) Midolivary level
119
What level is the spinal part of accessory nerve seen?
Pyramidal decussation in caudal medulla
120
What causes the shallow longitudinal depression on the ventral surface of pons?
Basilar artery
121
What are the fibres that are bridging the two cerebellar hemispheres in the ventral pons?
Corticopontine fibres that travel to ipsilateral basal pontine nuclei and then to the contralateral cerebellar hemisphere
122
What is the posterior surface of the pons?
Upper half of the floor of the fourth ventricle
123
What is the longitudinal depression in the floor of the fourth ventricle?
Median sulcus
124
What are the fibres running transversely at the pontomedullary junction in the floor of 4th verntricle?
Stria medullaris
125
What are the longitudinal elevations adjacent to median sulcus in pontine floor of fourth ventricle?
Facial colliculus formed by internal genu of CN7 as it encircles CN6
126
What longitudinal sulcus is found lateral to the facial colliculus?
Sulcus limitans
127
What is the elevation found between median sulcus and sulcus limitans in pontine floor of fourth?
Median eminence
128
What is found lateral to sulcus limitans in floor of fourth?
Vestibular area
129
How many cochlear nuclei are there? Where are they found?
4, two ventral, two dorsal Laterally in caudal pons
130
How many vestibular nuclei are there?
4 Superior, inferior, medial, lateral
131
Which vestibular nuclei are found in caudal pons
Part of superior, medial and lateral nuclei. Not inferior.
132
What is found in the superior part of the sulcus limitans?
Substantia ferruginea
133
What is founf ventral to the substantia ferruginea in the pontine tegmentum?
Locus coeruleus (Nadr)
134
What demarcates the basal and tegmental pons?
Trapezoid body
135
What is the trapezoid body?
Decussating fibres from the ventral and dorsal cochlear nuclei which cross over and then ascend
136
What happens to ascending fibres from the trapezoid body?
End up at posterior midbrain at the nucleus of the inferior colliculus
137
Where do ascending fibres from the cochlear nuclei travel to after synapsing in nucleus of the inferior colliculus?
Medial geniculate body of the thalamus
138
What is the lateral leminisicus?
Ascending auditory fibres from the trapezoid body of cochlear nuclei
139
What structure connects nucleus of inferior colliculus with medial geniculate body of thalamus?
Inferior brahcium
140
How do fibres get from middle geniculate body to auditory cortex?
Via auditory radiations
141
In which pontine levels may the trapezoid body be seen?
In both upper and lower Though they arise in the lower section from cochlear nuceli, some pass obliquely upwards
142
What is found embedded within the trapezoid body?
Nuclei of trapezoid body
143
What nucleis is found within the lateral lemniscus?
Superior olivary nucleus
144
What are found in the basal pons?
Pontine nuclei
145
Function of pontine nuclei?
Receive corticopontine fibres from all parts of the cortex. Give off pontocerebellar fibres contributing to middle cerebellar peduncle
146
Through which portion of the pons do corticonuclear and corticospinal neurones pass?
Basal pons
147
Which ascending tracts pass through the pons?
Medial lemniscus (dorsal) Spinal lemniscus (spinothalamic + spinotectal) Lateral lemniscus Ventral spinocerebellar tract (which ascends to superior cerebllar peduncle)
148
The superior portion of which nucleus present in the caudal pons provides contributions to facial nerve and carries taste from anterior 2/3rds of tongue?
Nucleus of tractus solitarius
149
Where do the parasympsthetic fibres contributing to the facial nerve arise?
Superior salivatory nucleus
150
What is the somatic sensory component of the facial nerve?
From ear Travel in nervus intermedius to trigeminal sensory nucleus
151
Fine touch and two-point discrimination come to which trigeminal nucleus?
Principle pontine
152
Pain and temperature sensation from the face pass to which trigeminal nucleus?
Spinal trigeminal
153
What is the location of the MLF?
Medially in pontine tegmentum adjacent to floor of 4th ventricle
154
Wnat are the structures shaded green? Shaded black?
Cerebral peduncle Crus cerebri
155
def: tegmentum
covering
156
def: tectum
roof
157
What is the boudnary between crus cerebri and tegmentum of midbrain?
Substantia nigra
158
What is the boundary between the tegmentum and tectum of midbrain?
Cerebral aqueduct
159
Which brainstem area helps to mediate visuospinal reflexes?
Superior colliculus in tectum of midbrain
160
Which brainstem area helps to mediate audio spinal reflexes
Inferior colliculus of midbrain tectum
161
Tectospinal tract concerned with
Audio/visual spinal reflexes
162
What is the posterior part of the SN?
Pars compacta Anteriorly is the pars reticularis
163
What structures descendn in the crus cerebri of the midbrain
Corticopontine fibres (medially and laterally) Corticospinal fibres (midportion) Corticonuclear fibres (medially)
164
What grey matter is found in the inferior colliculus?
Nucleus of inferior colliculus
165
What grey matter is found around cerebral aqueduct?
Periaqueductal grey matter
166
What structures will be seen going to and from inferior colliculus at its level in the midbrain?
Lateral lemniscus Inferior brachium Commissure of inferior colliculus
167
What are the ascending fibres in the tegmentum of the midbrain at level of inferior colliculus?
Cerebellorubro fibres (from dentate nucleus to red nucleus) Medial lemniscus Spinal lemniscus Lateral lemniscus (not seen at level of superior colliculus)
168
Fibres from dentate nucleues of left cerebellum syanpse on which red nucleus?
From dentate nucleus of leftcerebellum decussate going to right red nucleus and then thalamus
169
Which cranial nerve nucleus is found at the level of inferior colliculus in periaqueductal grey matter?
Trochlear
170
What fascicle is found medially in periaquductal grey matter of midbrain?
MLF
171
What is located lateral to CN4 in periaqueductal grey matter of midbrain?
Mesencephalic nucleus of trigeminal
172
What other important nuclei found in periaqueductal grey matter at level of inferior colliculus in midbrain?
Locus coeruleus Central tegmental nucleus Nucleus raphe
173
What is the function of centrall tegmental nucleus and nucleus raphe of midbrain?
Have descending pathways carrying enkephalin like substances to dorsal horn to modulate spinothalamic tract
174
What is the function of the interpeduncular nucleus?
Recevies fibres from habenular system via fasciulus retroflux, involved in regulation of eating behaviours
175
What is the function of central tegmental tract? ROST
Connects reticular formation with thalamus (reticulothalamic) Connects red nucleus with olivary nucleus (rubro-olivary)
176
What is found in the tegmentum of the midbrain at the level of superior colliculus rather than the dentatorubral fibres?
Red nucleus
177
Which lemniscus is no longer seen in midbrain at level of superior colliculus?
Lateral lermniscus
178
What is found in the superior colliculus of midbrain?
Nucleus of superior colliculus
179
What is the function of the red nucleus of the midbrain?
Additional descending pathway (rubrospinal pathway), for flexor attitude- i.e. sitting down + involved in hand movements
180
Vestibuolospinal pathway is for which attitude
Extensor or standing up
181
Which to cranial nerve nuclei are found in the periaqueductal grey matter at the level of superior colliculus
Somatic nucleus of CN3 and EW nucleus
182
What are fibres travelling ton and from nucleus of superior colliculus
Superior brachium (connects with LG body) Tectospinal Commissure of superior colliculus
183
Where isn the pretectal nucleus
Tectun of midbrain ventral and rostral to nucleus of superior colliculus
184
Function of pretectal nucleus
Involved in pupillary reflex
185
What is the name of the connection between the pretectal nuclei?
Posterior commissure
186
187
188
189
190
191
192
193
194
195
4 major elements of the brainstem
Long ascending and descending tract CN nuclei and fascicles Cerebellar nuclei and their connections Reticular neurones and their processes
196
Corpora quadrigemina
Superior and inferior colliculi
197
First CN nuclei column
Immediately adjacent to the midline Nuclei to somatic muscles CN III, IV, VI, XII
198
Second CN nuclei column
Nerves to branchial arch muscles (i.e. muscles of mastication, facial expression, pharynx, larynx, SCM and trapezius) CN V (mandibular portion) - pons Facial motor nucelus- pons Nucleus ambiguus- IX and X, medulla Nucleus of spinal accessory nerve- cervicomedullary region
199
Third CN nuclei column
Preganglionic parasympathetic neurones that innervate smooth muscle and glands of head and neck Edinger Westphal - III Ciliary ganglion Superior salivatory nucleus- VII Submandibular and pterygopalatine ganglia Inferior salivatory nucleus- IX, otic ganglion Dorsal motor nucleus of vagal nerve
200
What are the three major sensory nuclei in brainstem?
Trigeminal Vestibular and cochlear nuclei Solitary nucleus
201
Organisaiton of trigeminal nucleus
Mesencephalic- proprioceptive Principle- light touch Spinal trigeminal- pain and temperature Receives afferents from V, VII, IX, X
202
Solitary nucleus
Located in medulla Receives general and special visceral afferents from VII, IX, X Mediates taste, general visceral sensations of organs. The cel bodies are located outside brainstem and they possess central connections with thalamus, reticular formation and limbic system
203
What are the four main tracts that traverse the brainstem?
Two ascending: Spinothalamic Medial lemniscus Two descending: Corticospinal Corticobulbar
204
Location of spinothalamic tract in brainstem
Lateral aspect of the tegmentum fo the brainstem adjacent to the descending tract. Consists of 2o neurones originating in the dorsal gray of the spinal cord, which crosses the midline as the anterior white commissure and project to the VPL of thalamus
205
As what do 2o spinothalamic tract neurones decussate?
As the anterior white commissure
206
Where do 3o spinothalamic neuroens originate?
VPL nucleus of the thalamus
207
Ipsilateral Horner's Contralateral hemisensory loss
Suggests lesion in lateral pons or medulla
208
Location of medial lemniscus in brainstem
Second-order neurones originating in the nucleus cuneatus and gracilis in caudal medulla. Decussate as the internal arcuate fibres and ascend as the medial lemniscus to the contralateral VPL. Situated in the medulla close to the midline between the MLF posteriorly and the corticospinal and corticopontine tract anteriorly In its rostral portion, it moves more laterally
209
Corticospinal tract in the brainstem
Transmits motor-related impulses from cortex to laminae IV through IX Traverse the corona radiata and posterior limb of the internal capsule and continue in the middle of the midbrain crura cerebri flanked either side by corticopontine fibres. In the pons, the corticospinal tract is broken into small bundles by transverse pontocerebellar fibres which traverse to the contralateral cerebellar hemisphere via the middle cerebellar peduncle. They come together again to form the medullary pyramids, decussating in the caudal medulla (15% continue as the anterior corticospinal tract which decussates at the anterior commissure in the cervicothoracic spine.
210
What other function does the corticospinal tract perform in the pons
It also sends numerous collateral branches to the pontine nuclei, including those of the reticular formation
211
Corticobulbar tract in the brainstem
Efferents from the motor cortex to motor cranial nerve nuclei Except for the part of the facial, cortical input to these nuclei is more or less symmetrically bilateral. This means that disruption to one of the corticobulbar tracts usually only results in mild paresis whereas bilateral lesions are usually significant.
212
Which nuclei have afferent cerebellar connections
Pontine nuclei Inferior olivary nucleus Vestibular nuclei Reticular formation
213
Afferent cerebellar connections: Pontine nuclei
Corticopontine fibres terminated in the pontine nuclei These nuclei projects crossed fibres that proceed through the middle cerebellar peduncles to reach the contralateral cerebellar hemisphere. These are concerned with the initiation and planning of movements They also relay information from LGN, superior colliculus and striate cortex regarding vision
214
Afferent cerebellar connections Inferior olivary nucleus
Nucleus located in the rostral medulla Receives input from SC\< brainstem, the cerebral cortex. INvolves multiple sensory and motor impulses that cross the midline through the inferior cerebellar peduncle to reach the contralateral cerebellar hemisphere
215
Afferent cerebellar connections Vestibular nuclei
Located in rostral medulla Traverse inferior cerebellar peduncle to terminate in ipsilateral cerebellar hemisphere providing information about eye movements, head movements and changes in position of head.
216
Afferent cerebellar connections Reticular formation
Reticulocerebellar fibres originating in medulla and pons project through inferior cerebellar peduncles to ipsilateral and contralateral cerebellar hemispheres. Integrate and relay information from SC and higher cortex
217
Which of the cerebellar afferents connections is uncrossed
Vestibulocerebellar fibres are ipsilateral
218
Which brainstem nuclei receive cerebellar efferents
Red nucleus Vestibular nuclei Reticular formation
219
Efferent cerebellar connections Red nucleus
Located in midbrain tegmentum dorsal to SN Receives cerebellar fibres from the contralateral hemisphere that cross the midline in the decussation of the superior cerebellar peduncles. Efferent fibres from red nucleus descend as the crossed rubrospinal tract- relays cerebellar impulses that influence ipsilateral flexor muscle tone
220
Cerebellar efferents from left hemisphere involved in rubrospinal tract effect which side of the body?
Left- decussate in the superior cerebellar peduncle Then decussate again to descend as the rubrospinal tract
221
Efferent cerebellar connections Vestibular nuclei
Recieve input from ipsialteral cerebellar hemisphere via inferior cerebellar peducnle Influence equilibrium and control of axial musculature (extensor muscle tone via uncrossed vestibulospinal tract) Coordination of eye movements via uncrossed MLF
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Efferent cerebellar connections Reticular formation
Cerebellloreticular fibres reach ipsilateral reticular formation in pons and medulla via inferior cerebellar peduncle Influences extensor muscle tone via uncrossed pontine and medullary reticulospinal tract
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Two main zones of the reticular formation
Magnocellular zone Parvocellular zone
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Magnocelular zone
Contains large cells that give rise to long ascending and descending pathways Located in the medial 2/3rds of the retiuclar formation
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Parvocellular zone
Contains predominantly small cells cells that send axons to the medial central nuclei More laterally located in retricular formation
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Which functional systems are influenced by reticular formation
Motor Cardiorespiratory Sensory Consciousness
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Reticular formation Motor control
Reticular neurones influence muscle tone via descending reticulospinal tracts to motor neurones. These tracts originate in the medial portion of the medulla and pons to exert both facilitatory and inhibitor effects on muscle tone. Receive both afferents and efferents from cortex and cerebellar zones so integrate a wide array of influences on motor control. The pontine reticular spinal tract is facilitating to extensor tone but its held in check by the medullary reticular spinal tract (hence extensor posturing in lesions below red nucleus but above medulla)
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Reticular formation Respiratory control
Respiratory related reticular neurones are spread throughout the brainstem Dorsal respiratory centre located in the dorsal medulla and controls inspiration and is the main respiratory centre Ventral respiratory centre located in ventrolateral medulla controls both inspiration and expiration but only during significant respiratory efforts Pneumotaxic centre controls rate and patter of breathing, found in rostral pons
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Dorsal respiratory centre
Dorsal medulla Main respiratory centre Controls inspiration
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Ventral respiratory centre
Ventrolateral medulla Controls both inspiration and expiration but only during significant respiratory efforts
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Pneumotaxic respiratory centre
Dorsal rostral pons Controls rate and pattern of breathing
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Reticular formation Cardiac control
Cardiovascular reticular neurones are involved in complex polysnaptic pathways, receiving afferents from many oruces and sending efferent impulses via reticulospinal tracts to end on sponal neurones
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Reticular formation RAS
Modulates wakefulness and arousal Receives collaterals from long ascending sensory pathways including medial meniscus and spinothalamic tracts Efferents are conduced via centromedian nucleus of thalaus to widespread ares of cerebral cortex
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Blood supply of rostralmost midbrain
From PComm
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Blood supply of dorsolateral pons
Rostrally by SCA Caudally by AICA
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How to localise brainstem lesions?
What cranial nerve nuclei involved= level of the lesion What long tracts are involved= medial or lateral
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Right sided impairment of facial pain and temperature Left sided impairment of body pain and temperature Right limb and gait ataxia Right Horner's Nausea vomiting/vertigo and nystagmus Dysphagia and dysarthria
Right lateral medullary syndrome Ipsilateral facial pain and temperature impairment due to the involvement of the spinal trigeminal nucleus and tract Contralateral facial pain and temperature impairment due to the involvement of spinothalamic tract Ataxia due to cerebellar connections Ipsilateral Horner's due to involvement of descending sympathetic tract Vertigo etc due to vestibular tract Dysphagia and dysarthria due to involvement of nucleus ambiguus
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Right-sided hemiparesis Right-sided loss of vibration and positional sense Tongue deviation to left
Left-sided medial medullary syndrome (Dejerine's) Contralateral hemiparesis due to involvement of corticospinal tract COntralateral loss of dorsal tract due to the medial lemniscus Left hypoglossal palsy due to involvement of hypoglossal nuclei. Sparing of spinothalamic tract
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Quadriplegia with facial sparing Complete paralysis of the tongue Complete loss of vibratory and position sensation below the head
Bilateral medial medullary lesion
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Right-sided impairment of facial pain and temperature Left-sided impairment of body pain and temperature sensation Ipsilateral Horners Nausea, vomiting, nystagmus Ipsilateral limb and gait ataxia Ipsilateral facial paralysis Paralysis of gaze to the side of the lesion Deafness and tinnitus
Right lateral pontine syndrome (Millard-Gubler) Either due to AICA or SCA occlusion Facial pain/temperature due to trigeminal Spinothalamic tract Sympathetic tract Vestibular nuclei and connections Impaired gaze to the side of the lesion due to PPRF involvement Ipsilateral facial paralysis due to involvement of facial nerve Deafness and tinnitus due to involvement of cochlear nerve or nucleus
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Right hemiparesis Right-sided loss of vibration or the positional sense Left-sided limb ataxia Impaired abduction of the left eye INO Paralysis of gaze to side of lesion
Left medial pontine syndrome Contralateral hemiparesis- corticospinal tract Contralateral dorsal column- medial lemniscus Ipsilateral cerebellar signs- cerebellar connections Ipsilateral impaired abduction- CN 6 INO- MLF Impaired conjugate gaze to ipsilateral side- PPRF
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Right sided hemiparesis Left CN3 palsy
Left Weber's syndrome Ventral midbrain
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Right CN3 palsy Left involuntary movements or tremor Left impaired dorsal column
Right Benedikt's syndrome Central midbrain Red nucleus Medial lemniscus
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Impaired upgaze Pupillary dilatation Lid retraction Convergence retraction nystagmus Light-near dissociation Sunsetting
Parinaud's
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Pontine reticulospinal tract
Arises from pontine tegmentum and descend ipsilaterally in medial anterior funiculus Predominantly excitatory
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Medullary reticulospinal tract
Arises from medial two-thirds of the medullary reticular formation Most arise from nucleus reticularis gigantocellularis Descends in lateral funiculi and projects bilaterally to multiple levels Predominantly inhibitory
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Tectospinal tract
Originates from cells in the superior colliculus Tract crosses dorsal tegmentum and descends in contralateral funiculus. In medulla, fibres become incorporated into the MLF Continues only cervical segments.
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Dorsal cochlear nucleus
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NSx Neuroanatomy (25 decks)

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