NMH; Lecture 12, 13 and 14 - Neurology of visual system, A scientific and clinical approach to acute vertigo, Organisation of the cerebral cortex Flashcards
What is vertigo?
Illusion of movement -> usually rotation or true vertigo
What is unsteadiness?
Off-balance
What are two disorders of balance?
Peripheral vestibular disorders and Central vestibular disorders
What part of the NS is involved in peripheral vestibular disorders?
Labyrinth and VIII nerve
What part of the NS is involved in central vestibular disorders?
CNS -> brainstem/cerebellum
What are examples of peripheral vestibular disorders?
Vestibular neuritis, bppv, Meniere’s disease
What are examples of central vestibular disorders?
Stroke, MS, tumours
What is an example of an acute vestibular disorder?
Vestibular neuritis (labyrinthitis), Labyrinthine concussion -> inflammation of nerve on one side with sudden onset, continuing
What is an example of an intermittent vestibular disorder?
Benign paroxysmal positional vertigo - comes and goes
What is an example of a recurrent vestibular disorder?
Meniere’s disease (rare) and migraine (common)
What is an example of a progressive vestibular disorder?
Acoustic neuroma (8th nerve) - uilateral hearing loss even if tinnitus needs an MRI to check for tumour hitting CN8
What is the physiology of the vestibulo-ocular reflex?
Angular acceleration - 3 SCCs; linear acceleration: 2 otolith organs; ocular, spinal, autonomic and cortical connections
What is the symptom caused by damaged vestibulo-ocular projection?
Nystagmus
What is the symptom caused by damaged vestibulo-spinal projection?
Unsteadiness not ataxia
What is the symptom caused by damaged vestibulo-autonomic projection?
Nausea and vomiting
What is the symptom caused by damaged vestibulo-cortical projection?
Vertigo
What is vestibular neuritis?
Sudden, unilateral vestibular loss - hearing spared; viral flavour after URTI, mini-epidemics; days to weeks
What are the symptoms of vestibular neuritis?
Vertigo, nausea, unsteadiness, nystagmus
What is Meniere’s disease?
Build up of endolymphatic pressure (hydrops)
What are the symptoms of Meniere’s disease?
Hearing impaired, Vertigo, tinnitus and deafness are Meniere’s triad
How do you know it’s migraine?
History of migraine, migraine symptoms during vertigo attack, hearing usually spared and response to treatment
What is acute unilateral vestibular lesion?
Not known cause and there are many known ethiologies - can cause nystagmus, unsteadiness, nausea, vertigo depending on which vestibular projection is affected
How do you test the vestibulo-ocular reflex?
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
What is the different between vestibular and central nystagmus?
Vestibular always stays in the same direction, central can change direction as the brain works by compensating
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
How can you check for BPPV?
Hallpike manoevure -> if nystagmus comes on immediately then it is not BPPV - needs 4-6 seconds of latency
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
What is an example of an acute brainstem/cerebellar lesion causing central vestibular disorder?
MS/Vascular cause for lesion -> diplopia, facial numbness, speech affected
What causes chronic/progressive central vestibular disorders?
Cerebellar degeneration
What are the other (non-vestibular) causes of ‘dizziness’?
Heart disorders, presyncopal episodes, orthostatic hypotension, anaemia, hypoglycaemia, psychological, gait disorders
What are the major parts of the brain?
Cerebrum, cerebellum and brainstem
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
What is white matter?
Myelinated neuronal axons forming white matter tracts
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
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
What are the different Broadmann’s areas?
x
What are the different lobes of the cortex?
x
What are the different fibres that make up the cerebral white matter?
Association fibres, commissural fibres, projection fibres
What is the function of the association fibres?
Connect areas within the same hemisphere
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))
What is the function of commissural fibres?
Connect left hemisphere to right hemisphere