NMH; Lecture 12, 13 and 14 - Neurology of visual system, A scientific and clinical approach to acute vertigo, Organisation of the cerebral cortex Flashcards
(103 cards)
1
Q
What is vertigo?
A
Illusion of movement -> usually rotation or true vertigo
2
Q
What is unsteadiness?
A
Off-balance
3
Q
What are two disorders of balance?
A
Peripheral vestibular disorders and Central vestibular disorders
4
Q
What part of the NS is involved in peripheral vestibular disorders?
A
Labyrinth and VIII nerve
5
Q
What part of the NS is involved in central vestibular disorders?
A
CNS -> brainstem/cerebellum
6
Q
What are examples of peripheral vestibular disorders?
A
Vestibular neuritis, bppv, Meniere’s disease
7
Q
What are examples of central vestibular disorders?
A
Stroke, MS, tumours
8
Q
What is an example of an acute vestibular disorder?
A
Vestibular neuritis (labyrinthitis), Labyrinthine concussion -> inflammation of nerve on one side with sudden onset, continuing
9
Q
What is an example of an intermittent vestibular disorder?
A
Benign paroxysmal positional vertigo - comes and goes
10
Q
What is an example of a recurrent vestibular disorder?
A
Meniere’s disease (rare) and migraine (common)
11
Q
What is an example of a progressive vestibular disorder?
A
Acoustic neuroma (8th nerve) - uilateral hearing loss even if tinnitus needs an MRI to check for tumour hitting CN8
12
Q
What is the physiology of the vestibulo-ocular reflex?
A
Angular acceleration - 3 SCCs; linear acceleration: 2 otolith organs; ocular, spinal, autonomic and cortical connections
13
Q
What is the symptom caused by damaged vestibulo-ocular projection?
A
Nystagmus
14
Q
What is the symptom caused by damaged vestibulo-spinal projection?
A
Unsteadiness not ataxia
15
Q
What is the symptom caused by damaged vestibulo-autonomic projection?
A
Nausea and vomiting
16
Q
What is the symptom caused by damaged vestibulo-cortical projection?
A
Vertigo
17
Q
What is vestibular neuritis?
A
Sudden, unilateral vestibular loss - hearing spared; viral flavour after URTI, mini-epidemics; days to weeks
18
Q
What are the symptoms of vestibular neuritis?
A
Vertigo, nausea, unsteadiness, nystagmus
19
Q
What is Meniere’s disease?
A
Build up of endolymphatic pressure (hydrops)
20
Q
What are the symptoms of Meniere’s disease?
A
Hearing impaired, Vertigo, tinnitus and deafness are Meniere’s triad
21
Q
How do you know it’s migraine?
A
History of migraine, migraine symptoms during vertigo attack, hearing usually spared and response to treatment
22
Q
What is acute unilateral vestibular lesion?
A
Not known cause and there are many known ethiologies - can cause nystagmus, unsteadiness, nausea, vertigo depending on which vestibular projection is affected
23
Q
How do you test the vestibulo-ocular reflex?
A
Moves eyes with the sharp turn of the head -> the side that doesn’t have the catch up saccade, (eyes cannot follow the movement) is the healthy side
24
Q
What is the different between vestibular and central nystagmus?
A
Vestibular always stays in the same direction, central can change direction as the brain works by compensating
25
What are some physiological symptoms of a damaged vestibular ocular reflex?
Vestibular tone is changed, lesion induced asymmetry, visual suppression of nystagmus (VOR suppression), vestibular compensation
26
How can you check for BPPV?
Hallpike manoevure -\> if nystagmus comes on immediately then it is not BPPV - needs 4-6 seconds of latency
27
What is chronic vestibular disorder?
Many aetiologies, dizzy patient; anxiety is a confounding factor -. chronicity is due to lack of full vestibular compensation, inadequate testing, idiosyncratic reactions
28
What is an example of an acute brainstem/cerebellar lesion causing central vestibular disorder?
MS/Vascular cause for lesion -\> diplopia, facial numbness, speech affected
29
What causes chronic/progressive central vestibular disorders?
Cerebellar degeneration
30
What are the other (non-vestibular) causes of 'dizziness'?
Heart disorders, presyncopal episodes, orthostatic hypotension, anaemia, hypoglycaemia, psychological, gait disorders
31
What are the major parts of the brain?
Cerebrum, cerebellum and brainstem
32
What is grey matter?
Most superficial layer of the cerebrum (30% visible, 70% hidden in sulci), containing neuronal cell bodies, dendrites, synaptic connections and glial cells; 50 billion neurones and x10 glial cells
33
What is white matter?
Myelinated neuronal axons forming white matter tracts
34
What are the cortical layers of the grey matter and what is present in each layer?
Molecular, External granular, external pyramidal, internal granular, internal pyramidal, multiform
35
How does information move through grey matter?
Layer 4 receives input from thalamus and moved to all layers until cortex is satisfied and layer 1-3 send information outside to the cortical areas, and if extra analysis is needed then it is sent to other parts of cortex for further analysis;
layer 5-6 send information to sub-cortical areas, such as thalamus (layer 6 and then amygdala), layer 5 which contains large pyramidal cells and sends movement to different parts of the brain
36
What are the different Broadmann's areas?
x
37
What are the different lobes of the cortex?
x
38
What are the different fibres that make up the cerebral white matter?
Association fibres, commissural fibres, projection fibres
39
What is the function of the association fibres?
Connect areas within the same hemisphere
40
What are the 2 types of association fibres?
Short (U-fibres) and long fibres (Sup. longitudinal fasciculus (connects frontal and occipital lobes), arcuate fasciculus (connects temporal and occipital lobes), inferior longitudinal fasciculus (connects temporal and occipital lobes), uncinate fasciculus (connects ant frontal and temporal lobe))
41
What is the function of commissural fibres?
Connect left hemisphere to right hemisphere
42
What is the function of projection fibres?
Connect cortex with lower brain structures
43
What is the function of the frontal lobe?
Production of voluntary skeletal muscle movements -\> Primary motor cortex BA4 (precentral gyrus -\> carries out movement) and Premotor cortex BA6 (motor association area -\> plans movement); Prefrontal association area (coordinates information from other association areas)
44
What is the motor homunculus?
Physical representation of the contralateral parts of the human body organised in the characteristic and very precise somatotopic fashion -\> size is based on the complexity of movements that can be carried out by each part of the body
45
What is the function of the parietal lobe?
Sensory association area -\> primary somatosensory cortex (post central gyrus), recognition and interpretation of sensory information of sensory information from skin, muscles, taste buds
46
What is the function of the occipital lobe?
Visual association area (detailed information), primary visual cortex -\> vision
47
What is the function of the temporal lobe?
Auditory association area, primary auditory cortex -\> hearing
48
How do you test the function of the primary motor cortex?
Lesions -\> Paralysis (full or partial loss of fine voluntary movements in the contralateral side), paresis (muscular weakness)
49
How do you test the function of the motor association area?
Apraxia -\> difficulty with motor planning to perform voluntary movements and tasks
50
How do you test the function of the prefrontal association area?
Personality, self-control, attention, planning, emotions, motivation, decision making, reasoning all affected -\> Broca's motor aphasia (impaired speech production but preserved comprehension)
51
How do you test the function of the primary somatosensory cortex?
Sensory deficits -\> in perception of basic sensory information
52
How do you test the function of the sensory association area?
Sensory deficits -\> In interpretation of sensory information; spatial neglect
53
What is the sensory association area involved in?
Tactile recognition, flavour recognition, spatial orientation, ability to read maps, read (alexia), writing (agraphia), calculations (acalculia)
54
How do you test function of primary visual cortex?
Blindness in the corresponding part of visual field (deficit in perception of basic visual information)
55
How do you test the visual association area?
Visual deficits (in interpretation of visual information) -\> prosopagnosia
56
How do you test the primary auditory cortex?
Deafness (deficit in perception of basic auditory information) -\> unilateral lesions cause partial deafness in both ears
57
How do you test the auditory association area?
Visual deficits -\> in interpretation of auditory information; e.g. Wernicke's (receptive) aphasia -\> impaired comprehension but preserved speech production
58
How do you test the function of the temporal lobe?
Memory and semantics -\> lesion causes anterogradeamnesia
59
How does the function of grey matter in primary cortices differ from association cortices?
Primary cortices: Function predictable, organised topographically, left-right symmetry; association cortices: function less predictable, not organised topographically and left-right symmetry is absent/weak
60
What is transcranial magnetic stimulation?
Measures effects of interference with normal information processing due to electromagnetic stimulation of neurones -\> If brain region is involved in function and brain is stimulated then it should interrupt function (lower accuracy)
61
What is PET and what does it test in the brain?
Positron emission tomography -\> Measures changes in amount of blood flow directly to a brain region
62
What is fMRI and what does it test in the brain?
Functional MRI -\> measures changes in amount of blood oxygen in a brain region
63
What is EEG and what does it test in the brain?
Electroencepphalograpy -\> measures electric signal generated by the brain
64
What is MEG and what does it test in the brain?
Magnetoencephalography -\> measures magnetic field generated by the electric currents in the brain
65
How is each hemisphere specialised?
x
66
How have we found out about hemisphere specialisation?
x
67
What is the visual pathway anatomy?
Signals from eye to visual cortex: Eye -\> optic nerve-ganglion nerve fibres -\> optic chiasm (1/2 fibres cross here) -\> optic tract -\> Lat geniculate nucleus -\> optic radiation -\> primary visual cortex or stirate cortes within occipital lobe -\> extrastriate cortex
68
What are the cells in the retina for the visual pathway?
x
69
What is a photoreceptor?
A small circular space surrounding the photoreceptor
70
What is a retinal ganglion cell?
Joining of the input from neighbouring photoreceptors -\> convergence
71
How does convergence vary between rods and cones?
x
72
What are on-centre and off-centre ganglion cells?
x
73
What happens if there are lesions in the optic chiasm (ant and posterior) and what is the optic chiasm?
x
74
What are the causes of bitemporal and homonymous hemianopia?
x
75
What are the different visual pathway disorders and where is affected in each?
x
76
What is bitemporal hemianopia?
Bitemporal Hemianopia Typically caused by enlargement of Pituitary Gland Tumour Pituitary Gland sits under Optic Chiasma. Homonymous Hemianopia Stroke (CVA)
77
What is the primary visual cortex and where is it located?
x
78
How is the primary visual cortex organised?
Organized as columns with unique sensitivity to visual stimulus of a particular orientation. Right eye and left dominant columns intersperse each other
79
What is macular sparing homonymous hemianopia caused by?
x
80
What is the extrastriate cortex and what are the pathways that exist?
x
81
What happens in light and in dark to the pupil?
x
82
What is the pupillary reflex pathway?
Rods and cones -\> retinal ganglion cells -\> lat geniculate nucelus -\> pretectal nucleus -\> Edinger-Westphal nuclei -\> oculomotor nerve efferent -\> Ciliary ganglion -\> short posterior ciliary nerve -\> pupillary sphincter
83
What is the difference between direct and consensual reflex?
x
84
What happens if there is a defect in the afferent vs efferent pathways in pupillary reflex?
x
85
What is the swinging torch test?
x
86
What is duction?
Eye movement in one eye
87
What is version?
Simultaneous eye movement in both eyes in the same direction
88
What is vergence?
Simultaneous movement of both eyes in the opposite direction
89
What is convergence?
Simultaneous adduction movement in both eyes when viewing a near object
90
What is a saccade?
short fast burst, up to 900deg/sec Reflexive saccade to external stimuli Scanning saccade Predictive saccade to track objects Memory-guided saccade
91
What is smooth pursuit movement in the eye?
sustain slow movement Slow movement – up to 60°/s Driven by motion of a moving target across the retina.
92
What are the extraocular muscles?
Sup, inf, lat, medial rectus and sup, inf oblique
93
Where are the attachments of the sup/inf rectus and what do they do to the eye?
x
94
What are the attachments and movement of the lateral rectus?
x
95
What are the attachments and movement of the medial rectus?
Attached on the nasal side of the eye Moves the eye toward the middle of the head (toward the nose)
96
What are the attachments and movement of the superior oblique?
x
97
What are the attachments and movement of the inferior oblique?
Attached low on the nasal side of the eye. Passes over the Inferior Rectus. Moves the eye in a diagonal pattern -- up and out.
98
What is the innervation of the extraocular muscles?
x
99
How do you test each eye movement by muscle?
x
100
What is the terminology for directions of eye movement?
x
101
What is third nerve palsy?
Affected eye down and out Droopy eyelid Unopposed superior oblique innervated by fourth nerve (down) Unopposed lateral rectus action innervated by sixth nerve (out)
102
What is sixth nerve palsy?
Affected eye unable to abduct and deviates inwards Double vision worsen on gazing to the side of the affected eye
103
What is the optokinetic nystagmus reflex?
x
