1
Q
3 Bases of the Brainstem
A
- Midbrain - Cerebral Peduncle
- Pons - Basis Pontis
- Medulla - Pyramid and Olive
2
Q
Anterior median fissure of the spinal cord continues on the
ventral medulla. On each side of this fissure are the __.
A
medullary pyramids
3
Q
In the lower part of the medulla, the Corticospinal tracts partly cross to form the __. (Pyramidal Decussation)
A
Lateral Corticospinal Tract
4
Q
- where rootlets of the hypoglossal nerve exit
- line between pyramid and olive
A
Lateral Sulcus
5
Q
- Uppermost layer
- Shortest part of the brainstem, which contains the cranial nerves that stimulates the muscle for eye movement, lens shape and pupil diameter.
A
Midbrain
6
Q
- Superior to the medulla and inferior to the midbrain in
location. Point of origin of nerves that transfer sensory information and motor impulses to and from the facial region and the brain. - Serves as a pathway for nerve fibers connecting the
cerebral cortex with the cerebellum
A
Pons
7
Q
- last portion of the brains before the spinal cord
- Contains the nerve tracts of the Corticospinal and
Spinothalamic pathways. - Contains the autonomic center for regulating heart
rate, vasomotion, and respiratory rhythm
A
Medulla
8
Q
Ventral Dorsal Organization (Brainstem)
A
- Tectum - roof; superior and inferior colliculus
- Tegmentum - floor; it forms the floor of the midbrain.
Nuclei of CN III and IV are located here - Basis- Base; 4th ventricle
9
Q
Internal Structure of Medulla (Cross section at three levels)
A
- Level of pyramidal decussation
- Level of lemniscal decussation
- Level of inferior olivary nuclei
10
Q
- is a column of cells dorsolateral or lateral to the hypoglossal nucleus and extending both rostrally and caudally a little beyond the hypoglossal nucleus.
- Axons in this column course ventrolaterally in the medulla, emerging from the lateral surface of the medulla between the inferior olive and inferior cerebellar peduncle.
- It also receives fibers from the vestibular nucleus thus excessive vestibular stimulation results in nausea, vomiting and change in heart rate.
A
dorsal motor nucleus of the vagus
11
Q
- motor function of the Vagus nerve
A
Dorsal motor nucleus of Vagus nerve
12
Q
- sensory nucleus for CN VII, IX, X
- clusters of nerve cell bodies forming a vertical column of grey matter embedded in the medulla oblongata.
- Lesion results in arterial blood pressure elevation.
A
Nucleus Tractus solitarius
13
Q
- motor nucleus for CN IX, X and XI
- is also known as the ventral motor nucleus of the vagus
- It is a column of cells situated halfway between the inferior olive and the nucleus of the spinal tract of the trigeminal nerve. In addition to the vagus nerve, it also contributed efferent fibers to the glossopharyngeal and accessory nerves.
A
Nucleus Ambiguus
14
Q
Pons (Landmarks and Cranial Nerves)
A
Landmarks: Basis pontis; 4th ventricle; Cerebellum and Middle Cerebellar Peduncle
Cranial nerves V, VI, VII, VIII
15
Q
Internal Structure of the Pons: Cross section at three levels
A
- Level of facial nucleus (CN VII) - lower
- Level of middle cerebellar peduncle - middle
- Level of locus ceruleus - upper
16
Q
Cranial Nerves of the Lower Pons
A
- CN VIII - pure sensory; lateral in location; for balance
- CN VI - abduction of the eye; longest and most vulnerable CN
- CN VII - muscles of the face; loop around CN VI
17
Q
- is the pontine center for lateral gaze, it is a physiologically defined neuronal pool that is rostral to the abducens nucleus.
- It is composed of caudal and rostral part.
A
PPRF (paramedian pontine reticular formation)
18
Q
Mid Pons
A
- Lateral lemniscus - associated with auditory pathway
- Medial lemniscus fibers - from dorsal column (position and vibration)
- Trigeminal tract - pain, temperature, touch from contralateral face
19
Q
- Primary source of noradrenergic innervation to the brain
- Neurons contain melanin
A
Locus ceruleus
20
Q
- Also release catecholamines
- Neurons also contain melanin
A
Parabrachial Nucleus
21
Q
- Some neurons release acetylcholine
- Other neurons release glutamate
- They assist in learning and voluntary motor control, e.g. locomotion, saccadic eye
A
Pediculopontine Nucleus
22
Q
Midbrain (Landmarks and Cranial Nerve)
A
Landmarks 1. Cerebral peduncles 2. Optic chiasm 3. Interpeduncular fossa (Superior colliculi) (Inferior colliculi) (Superior cerebellar peduncle)
Cranial Nerves III, IV
23
Q
External Structure of Midbrain
A
- Optic chiasm
- Interpeduncular fossa
- Oculomotor nerve (CN III)
- Trochlear nerve (CN IV)
- Pons
- Cerebral peduncles (crus cerebri)
24
Q
Cranial Nerves of the Midbrain (anterior and posterior exit)
A
Anterior exit; CN III, CN VI
Posterior exit - CN IV
25
- Melanin-containing cells that produce dopamine Project to the basal ganglia
Substantia nigra
26
– projects serotonergic fibers to basal ganglia and throughout cortex
Dorsal raphe nucleus
27
- analogous to dorsal root ganglion but within CNS
Mesencephalic nucleus of V
28
Upper Midbrain
Vision
Superior colliculus >> Lateral geniculate body
Hearing
Inferior colliculus >> Medial geniculate body
29
- relay from cortex and cerebellum to spinal cord, inferior olive, reticular formation, cerebellum
- Controls arm movement
Red nucleus
30
Lesion in the red nucleus the posturing will be __ because the rubrospinal tract takes over
decorticate
31
Lesion in the rubrospinal tract the posturing will be __ because the vestibulospinal tract rakes over
decerebrate
32
Blood supply to the midbrain
1. Posterior Cerebral Artery (superior and lateral)
| 2. Basilar artery (entire medial)
33
Blood supply to the Middle pons
1. Anterior inferior cerebellar artery (superolateral)
| 2. Basilar Artery (ventrolateral)
34
Blood supply to the Upper Medulla
1. Posterior inferior cerebellar artery (superolateral)
2. Vertebral Artery (dorsolateral portion)
3. Anterior Spinal Artery (medial ventral portion)
35
Blood supply to the Caudal Medulla
1. Posterior Spinal Artery (superior portion)
2. Posterior inferior cerebellar artery (small lateral portion)
3. Vertebral Artery (Tegmentum)
4. Anterior Spinal Artery (ventromedial portion)
36
(Midbrain Syndrome)
| - occlusion of paramedian branches of upper basilar and proximal posterior cerebral arteries
Medial midbrain syndrome
37
Medial midbrain syndrome (ON SIDE OF LESION)
1. Eye "down and out" secondary to unopposed action of fourth and sixth cranial nerves,
2. with dilated and unresponsive pupil: Third nerve fibers
38
Medial midbrain syndrome (ON OPPOSITE SIDE OF LESION)
Paralysis of face, arm, and leg: Corticobulbar and corticospinal tract descending in crus cerebri
39
(Midbrain Syndrome)
| - syndrome of small penetrating arteries arising from posterior cerebral artery
Lateral midbrain syndrome
40
Lateral midbrain syndrome (On side of lesion)
Eye "down and out" secondary to unopposed action of fourth and sixth cranial nerves, with dilated and unresponsive pupil: Third nerve fibers and/or third nerve nucleus
41
Lateral midbrain syndrome (On side opposite lesion)
Hemiataxia, hyperkinesias, tremor: Red nucleus, dentatorubrothalamic pathway
42
Site: Base of midbrain
Cranial Nerves Involved: III
Tracts Involved: Corticospinal tract
Signs: Oculomotor palsy with crossed hemiplegia
Weber Syndrome
43
Site: Tegmentum of midbrain
Cranial Nerves Involved: III
Tracts Involved: Red nucleus and brachium conjunctivum
Signs: Oculomotor palsy with contralateral cerebellar ataxia and tremor
Claude Syndrome
44
Site: Tegmentum of midbrain
Cranial Nerves Involved: III
Tracts Involved: Red nucleus, corticospinal tract, and brachium conjunctivum
Signs: Oculomotor palsy with contralateral cerebellar ataxia, tremor and corticospinal signs
Benedikt Syndrome
45
Site: Tectum of midbrain
Cranial Nerves Involved: Unilateral or Bilateral III
Tracts Involved: Superior cerebellar peduncles
Signs: Ocular palsies, paralysis of gaze and cerebellar ataxia
Nothnagel syndrom
46
Site: Dorsal midbrain
Tracts Involved: Supranuclear mechanism for upward gaze and other structures in periaqueductal gray matter
Signs: paralysis of upward gaze and accommodation; fixed pupils
Parinaud syndrome
47
occlusion of paramedian branch of basilar artery
Medial inferior pontine syndrome
48
Medial inferior pontine syndrome (On side of lesion)
1. Paralysis of conjugate gaze to side of lesion (preservation of convergence): Center for conjugate lateral gaze(PPRF)
2. Nystagmus: Vestibular nucleus
3. Ataxia of limbs and gait: Likely middle cerebellar peduncle
4. Diplopia on lateral gaze: Abducens nerve
49
Medial inferior pontine syndrome (On side opposite of the lesion)
1. Paralysis of face, arm, and leg: Corticobulbar and corticospinal tract in lower pons
2. Impaired tactile and proprioceptive sense over one-half of the body: Medial lemniscus
50
occlusion of anterior inferior cerebellar artery
Lateral inferior pontine syndrome
51
Lateral inferior pontine syndrome (On side of lesion)
1. Horizontal and vertical nystagmus, vertigo, nausea, vomiting, oscillopsia: Vestibular nerve or nucleus
2. Facial paralysis: Seventh nerve
3. Paralysis of conjugate gaze to side of lesion: Center for conjugate lateral gaze
4. Deafness, tinnitus: Auditory nerve or cochlear nucleus
5. Ataxia: Middle cerebellar peduncle and cerebellar hemisphere
6. Impaired sensation over face: Descending tract and nucleus fifth nerve
52
Lateral inferior pontine syndrome (On side opposite lesion)
Impaired pain and thermal sense over one-half the body (may include face): Spinothalamic tract
53
occlusion of paramedian branch of midbasilar artery
Medial midpontine syndrome
54
Medial midpontine syndrome (On side of lesion)
Ataxia of limbs and gait (more prominent in bilateral involvement): Pontine nuclei
55
Medial midpontine syndrome (On side opposite lesion)
1. Paralysis of face, arm, and leg: Corticobulbar and corticospinal tract
2. Variable impaired touch and proprioception when lesion extends posteriorly: Medial lemniscus
56
occlusion of the short circumferential artery
Lateral midpontine syndrome
57
Lateral midpontine syndrome (On side of lesion)
1. Ataxia of limbs: Middle cerebellar peduncle
2. Paralysis of muscles of mastication: Motor fibers or nucleus of fifth nerve
3. Impaired sensation over side of face: Sensory fibers or nucleus of fifth nerve
58
Lateral midpontine syndrome (On side opposite lesion)
Impaired pain and thermal sense on limbs and trunk: Spinothalamic tract
59
occlusion of the paramedian branches of upper basilar artery
Medial superior pontine syndrome
60
Medial superior pontine syndrome (On side of lesion)
1. Cerebellar ataxia (probably): Superior and/or middle cerebellar peduncle
2. Internuclear ophthalmoplegia: Medial longitudinal fasciculus
3. Myoclonic syndrome, of palate, pharynx, vocal cords, respiratory apparatus, face, oculomotor apparatus, etc.: —central tegmental bundle.
61
Medial superior pontine syndrome (On side opposite lesion)
1. Paralysis of face, arm, and leg: Corticobulbar and corticospinal tract
2. Rarely touch, vibration, and position are affected(arm>leg): Medial lemniscus
62
syndrome of superior cerebellar artery
Lateral superior pontine syndrome
63
Lateral superior pontine syndrome (On side of lesion)
1. Ataxia of limbs and gait, falling to side of lesion: Middle and superior cerebellar peduncles, superior surface of cerebellum, dentate nucleus
2. Dizziness, nausea, vomiting; horizontal nystagmus: Vestibular nucleus
3. Paresis of conjugate gaze (ipsilateral): Pontine contralateral gaze
4. Miosis, ptosis, decreased sweating over face (Horner's syndrome): Descending sympathetic fibers
64
Lateral superior pontine syndrome (On side opposite lesion)
1. Impaired pain and thermal sense on face, limbs, and trunk: Spinothalamic tract
2. Impaired touch, vibration, and position sense, more in leg than arm : Medial lemniscus (lateral portion)
65
- occlusion of vertebral artery or of branch of vertebral or lower basilar artery
Medial medullary syndrome
66
Medial medullary Syndrome (On side of lesion)
Paralysis with atrophy of one-half half the tongue: Ipsilateral twelfth nerve
67
Medial medullary Syndrome (On side opposite lesion)
Paralysis of arm and leg, sparing face; impaired tactile and proprioceptive sense over one-half the body: Contralateral pyramidal tract and medial lemniscus
68
occlusion of posterior inferior cerebellar artery
Lateral medullary syndrome
69
Lateral medullary syndrome (On side of lesion)
1. Pain, numbness, impaired sensation over one-half the face: Descending tract and nucleus fifth nerve
2. Ataxia of limbs, falling to side of lesion: Uncertain—restiform body, cerebellar hemisphere, cerebellar fibers, spinocerebellar tract (?)
3. Nystagmus, diplopia, oscillopsia, vertigo, nausea, vomiting: Vestibular nucleus
4. Horner's syndrome (miosis, ptosis, decreased sweating): Descending sympathetic tract
5. Dysphagia, hoarseness, paralysis of palate, paralysis of vocal cord, diminished gag reflex: Issuing fibers ninth and tenth nerves
6. Loss of taste: Nucleus and tractus solitarius
7. Numbness of ipsilateral arm, trunk, or leg: Cuneate and gracile nuclei
8. Weakness of lower face: Genuflected upper motor neuron fibers to ipsilateral facial nucleus
70
Lateral medullary syndrome (On side opposite lesion)
Impaired pain and thermal sense over half the body, sometimes face: Spinothalamic tract
71
The __ is such that there are long circumferential branches (the anterior inferior cerebellar artery ‘AICA’, the posterior inferior cerebellar artery ‘PICA’ and the superior cerebellar artery ‘SCA’) and paramedian branches.
blood supply of the brainstem
72
Involvement of the __ results in paramedian brainstem syndromes and involvement of the circumferential branches results in lateral brainstem syndromes.
paramedian branches
73
Occasionally, medial or lateral brainstem syndromes occur with __.
ipsilateral vertebral occlusion
74
There are 4 structures in the ‘midline’ (the paramedian aspect of the midbrain adjacent to the midline) beginning with M:
* Motor nucleus
* Median longitudinal fasciculus
* Medial lemniscus
* Motor pathway (corticospinal tract)
75
There are 4 structures to the side (lateral) beginning with S:
* Spinocerebellar pathway
* Spinothalamic pathway
* Sensory nucleus of the 5th cranial nerve
* Sympathetic pathway
76
4 cranial nerves in the medulla:
* 12th hypoglossal nerve
* 11th accessory nerve
* 10th vagus nerve
* 9th glossopharyngeal nerve
77
4 in the pons:
* 8th auditory and vestibular nerve
* 7th facial nerve
* 6th abducent nerve
* 5th trigeminal nerve
78
4 above the pons:
* 4th trochlear nerve
* 3rd oculomotor nerve
* These two nerves are in the midbrain, the 2nd or ocular nerve and the 1st olfactory nerve are outside the midbrain
79
Eyeball moves into 3 different Axes
1. Vertical Axes - superior to inferior movement of the eye
2. Horizontal Axes
3. Anterior-Posterior Axes
80
Medial rectus
Primary Action: Adduction
81
Lateral rectus
Primary Action: Abduction
82
Superior rectus
Primary Action: Elevation
Secondary Action: Intorsion
Tertiary Action: Abduction
83
Inferior rectus
Primary: Depression
Secondary: Extorsion
Tertiary: Abduction
84
Superior oblique
Primary: Intorsion
Secondary: Depression
Tertiary: Adduction
85
Inferior oblique
Primary: Extorsion
Secondary: Elevation
Tertiary: Adduction
86
- Nucleus found in the midbrain at the level of the superior colliculus
- has motor and autonomic functions
Cranial nerve III – Oculomotor Nerve
87
- subserves the parasympathetic function of the Cranial Nerve III
- found in the periaqueduct of gray
Edinger-Westphal Nucleus
88
- Nucleus found in the midbrain at the lower superior colliculus
- longest cranial nerve
- emeges in the brainstem from the back
Cranial nerve IV – Trochlear Nerve
89
- Nucleus found at the level of the pons
- transverses to the tegmentum of the pons
- innervates the lateral rectus muscle
Cranial nerve VI – Abducens Nerve
90
2 ways to differentiate eye movements
1. Conjugate eye movements
| 2. Disconjugate/dysjunctive
91
– refers to the symmetric and synchronous movements of the eyes; also referred to as versional
Conjugate eye movements
92
– or vergence
Disconjugate/ disjunctive
93
- Rapid voluntary conjugate eye movements
- Serves to quickly change ocular fixation to bring images of new objects of interest onto the foveas
- Peak velocity may reach 700 degrees per second
- Saccadic latency is approximately 200 ms.
Saccades
94
Classification of Saccades
1. Reflexive
2. Intentional
3. Antisaccades
4. Spontaneous
95
– externally triggered by the sudden appearance of a visual target on the peripheral part of the retina
Reflexive
96
– internally triggered with a goal; may be visually-guided, predictive or memory-guided
Intentional
97
– made in the direction opposite a suddenly appearing lateral visual target
Antisaccades
98
– internally triggered but without a goal and occur during another motor activity or at rest in darkness
Spontaneous
99
- Slower and smoother
- Largely involuntary
- Serves to stabilize the image of a moving object on the foveas as the object is tracked by the eyes; to maintain a continuous clear image of the object as it changes position in the environment.
Pursuit
100
Major stimulus of Pursuit is a __
moving target
101
- Occurs when a series of visual targets enters the visual field
- Repeated cycles of pursuit and refixation
Optokinetic Nystagmus
102
- A reflex which seeks to produce a movement of the eyes that is equal and opposite to movement of the head
Vestibulo-Ocular Reflex
103
- Part of the accommodation reflex (near response, near reflex, accommodation-convergence synkinesis)
Vergence
104
Components of Accommodation Reflex
1. Vergence
2. Myosis - constriction of pupil
3. Contraction of the Ciliary muscle
105
Signals for volitional horizontal saccades – __ of the contralateral frontal lobe
frontal eye field (Brodmann area 8)
106
Horizontal Gaze: Concepts
- Fibers from frontal eye fields traverse the internal capsule
- Terminates mainly in the PPRF
- PPRF projects to the abducens nucleus
- Abducens internuclear neurons project via the MLF to the contralateral oculomotor nucleus
107
Vertical Gaze: Concepts
- Vertical eye movements are under bilateral control of the cerebral cortex and upper brainstem
- The vertical gaze brainstem “centers:”
1. Rostral interstitial nucleus of the MLF (riMLF)
2. Interstitial nucleus of Cajal (INC)
3. Nucleus and fibers of the posterior commissure
108
projects ipsilaterally to the oculomotor and trochlear nuclei
Rostral interstitial nucleus of the MLF (riMLF)
109
- projects to the contralateral motor neurons of the elevator muscles by fibers that pass through the posterior commissure; project ipsilaterally to the motor neurons of the depressor muscles
Interstitial nucleus of Cajal (INC)
110
On distant vision
1. Ciliary muscles are relaxed
2. Suspensory ligaments are tensed
3. Lens are thin
111
On near vision
1. Ciliary muscle are contracted
2. Suspensory ligaments are slack
3. Lens are thin
112
Disorders of ocular movements
1. Central - Supranuclear or Internuclear
| 2. Peripheral - Infranuclear
113
Horizontal Gaze (Lesions)
1. Cerebral origin/ lesions - Usually causes impersistence or paresis of contralateral gaze
2. Brainstem origin/ lesions
114
Frontal Lobe lesion
- Causes conjugate gaze palsy contralateral to the lesion
| - Preferential gaze ipsilateral to the lesion
115
lesion of the lower pons in or near the 6th nerve nucleus
- A lesion of the lower pons in or near the 6th nerve nucleus causes an ipsilateral paralysis of the lateral rectus muscle and a failure of adduction of the opposite eye – i.e., a combined paralysis of the 6th nerve and a conjugate lateral gaze
- Explanation for “wrong way eyes” in a pontine lesion
116
- Eye ipsilateral to the lesion in the pons fails to adduct
| - Contralateral eye may exhibit nystagmus
Internuclear ophthalmoplegia
117
Lesion on the total half of the pons and portion of the middle pons
One-and-a-half syndome
118
- One eye lies fixed in the midline for all horizontal movements; the other eye only makes abducting movements and may be engaged in horizontal nystagmus in the direction of abduction
One-and-a-half syndome
119
(Central Disorders)
- Usually caused by midbrain lesions affecting the pretectum and the region of the posterior commissure
- Parinaud or dorsal midbrain syndrome
Vertical Gaze
120
- Impaired upgaze – core feature, may cause setting sun eyes if severe
- Mid-dilated pupils
- Poor, rarely absent light response of the pupils and much better near response
Parinaud syndrome
121
[Peripheral (Nuclear and Infranuclear) Disorders]
- Ptosis
- Drooping of the upper eyelid
- Inability to rotate the eye upward, downward or inward
- Pupil will be dilated
Cranial nerve III palsy
122
[Peripheral (Nuclear and Infranuclear) Disorders]
- Most common cause of isolated, symptomatic, vertical diplopia
Cranial nerve IV palsy
123
[Peripheral (Nuclear and Infranuclear) Disorders]
- Paralysis of the lateral rectus muscle, which causes the affected eye to deviate medially
Cranial nerve VI palsy
124
- a sympathetic disorder that causes ptosis, anhydrosis, myosis and enophthalmos
Horner Syndrome
125
Central Disorders of Ocular Motility (Etiology)
1. Vascular – strokes
2. Demyelinating – Multiple sclerosis
3. Neoplasms – tumors like pinealomas,
126
Peripheral Disorders of Ocular Motility
Orbital disease – orbital pseudotumor, lymphoma, rhabdomyosarcoma
Muscle disease – Thyroid ophthalmopathy
Neuromuscular junction disorders – Myasthenia gravis
Individual nerve palsies
127
Lateral rectus palsy as a FALSE localizing sign
Unilateral or bilateral abducens weakness may be a nonspecific sign of increased intracranial pressure from any source
Postulated to be due to downward force caused by increased pressure which may stretch (and injure) the nerve
“False localizing sign” – if a neurologic deficit reflect dysfunction distant or remote from the expected anatomical location of pathology
128
- For evaluating trochlear nerve palsy
- Diplopia worsens on tilting the head ipsilateral to the trochlear nerve palsy; improves on tilting to the contralateral side
Bielschowsky head tilt test
129
- check for vestibulo-cochlear reflex in an unconscious patient
Doll’s maneuver
130
- is a test that uses differences in temperature to diagnose damage to the acoustic nerve. This is the nerve that is involved in hearing and balance. The test also checks for damage to the brain stem.
Caloric Testing
131
Caloric Testing
COWS: Cold Opposite, Warm Same.
Cold water = FAST phase of nystagmus to the side Opposite from the cold water filled ear
Warm water = FAST phase of nystagmus to the Same side as the warm water filled ear
In other words: Contralateral when cold is applied and ipsilateral when warm is applied
132
- OKN drum or tape
- Can be used to test VA in infants (4-6mos); psychogenic visual loss
- Suggests parieto-occipital lesions (pursuit ipsilateral to direction of target, and contralateral saccades
Optokinetic Nystagmus
133
When studying for any sensory pathway always look first
for the RECEPTOR, it will then pass the information to the
THALAMUS and ends in the CORTEX. EXCEPT for the __ which directly goes to the cortex.
CN I (Olfactory)
134
• Outgrowth of the diencephalon
• Contains Photoreceptors: Rods (Mediates Light
perception; low visualk acuity; nocturnal vision) and
Cones (Color vision - C is color - high visual acuity)
Retina
135
- inability to name an object
Anomia
136
- inability to identify colors
Color Agnosia
137
- inability to identify faces
Prosopagnosia
138
• Axons of ganglion cells on the entire surface of the
retina WILL START CONVERGE here where they EXIT the eye
• Area of the eye without rods and cones
Optic Disc
139
• Continuous with the optic disk, but becomes MYELINATED
• Divides into NASAL and TEMPORAL fibers
• Axons from macula (sharpest visual acuity) enters the
TEMPORAL SIDE/FIBERS
• Optic nerve (Pony tails of the ganglion cells of the
retina)
• Only in this area where the deficit is in ONE EYE
Optic Nerve
140
• Ant. part of the sella turcica (sphenoid bone) where
the pituitary gland rest
• Partial decussation of fibers, ONLY NASAL FIBERS
(ibig sabihin kung may lesion after the optic chiasm,
contralateral ang manifestation)
Optic Chiasm
141
Pituitary gland - most common type of endocrine tumor. It
can compress the optic chiasm especially the Nasal fibers
and can cause Bitemporal Hemianopsia, but EARLY ON, it compresses the INFERIOR FIBERS FIRST (Meaning the deficit is the superior visual field) which can cause __
Bitemporal Superior Quadrantanopia
142
Craniopharyngioma - A tumor originated from the remnant of Rathke's pouch. Early on it compresses your optic chiasm SUPERIORLY FIRST (Suprasellar)→ __
Bitemporal Inferior Quadrantanopia
143
Rule in Visual Field
If you damage the temporal fiber, you will not see the nasal field on the same eye.
If you damage the Nasal fiber, you will not see the temporal field on the same eye.
144
- library of everything you have ever seen
| - area beside the visual cortex
Visual Association Cortex
145
- only one eye will be affected
| - the damage is on the optic nerve only
Monocular Vision loss
146
• Continuation of Fibers WITHOUT any interruption as
TWO diverging optic tracts
• Optic tracts will terminate in the LATERAL GENICULATE BODIES (LGB) and PRETECTAL AREA
• A lesion in this area can cause Left /Right Homonymous
Hemianopsia (Depending on which optic tract is
affected)
Optic Tract
147
- constriction of the other eye even when you are not shining on that eye
Consensual eye reflex
148
Cranial Nerve II Damage on the Right Eye
Shine light on:
Affected eye >> won't constrict (because the light can't go in
affected eye >> (unaffected eye) won't constrict
unaffected eye >> the affected eye will CONSTRICT because there is a light that will trigger the affected eye in Edinger-westphal nucleus
149
Cranial Neve III Damage
Shine light on:
affected eye >> affected eye: won't constict
affected eye >> unaffected eye: will constict (consensual reflex)
unaffected eye >> affected eye: won't constrict
150
- paradoxical dilation of the eye
- afferent defect of the Cranial Nerve II lesion
- if you shine a light on the unaffected eye, the affected eye will constrict but if you shine a light on the affected eye immediately it will dilate (go back to its unconstricted state)
Marcus-Gunn Pupil
151
- you have a vision but you have a lesion in visual cortex
| - if you test for pupillary light reflex, it will constrict
Cortical Blindness
152
- type of blindness that there is no pupillary light reflex
Optic Nerve Blindess
153
Papilledema
• Initially there is no blurring of vision
• Most often, papilledema results from transmission of
increased intracranial pressure into the eye via the subarachnoid space, which extends out along the optic nerve. Other causes include direct pressure on the optic nerve from retrobulbar lesions.
• But if not able to decompress → optic nerve ischemia
→Blurring of vision
154
Signs of Papilledema on Fundoscopy
* Engorge vessels
* Retinal hemorrhage (Seen in HPN)
* (+) exudates = cloudy (HPN or Diabetes)
* Hyperemic
* indistinct optic disc border
* physiologic cup absent
155
• Depletion of the optic axons and capillaries exposes
the full extent of the chalk-white lamina cribrosa, which
then appears as a flat white disc with a cookie-cutter sharp border against the retina
• Optic neuritis
• Seen in Multiple Sclerosis = Inflammation of the Myeline sheets
• There is Early Blindness
• Pale Optic Disc
Primary Optic Atrophy
156
Papilledema Vs Papillitis
• Papillitis = Early Blindness
• Papilledema = Indistinct borders of the Optic Disc with
exudates
157
VISUAL ACUITY
1. Snellen vs. Jaeger Chart
2. Pinhole Test - If vision improves = Error in refraction
3. Count Fingers - Do this if vision did not improved using the pinhole test
- check if they could see hand movement
4. Light Projection- Close one eye, check for Light Projection in each quadrant
5. Light Perception- To test if they could perceive with or without light; If still negative for this test, this is the time
you call the patient LEGALLY BLIND
Neuroscience
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Decks in class (8)
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