Principles of forebrain disease Flashcards
What are the components of the forebrain?
cerebrum: 2 hemispheres, cortical grey matter and cerebral white matter
thalamic region: hypothalamus, subthalamus, thalmencephalon
What are the cerebral functions?
conscious perception and interpretation of sensory information
cognition and behaviour
learning and memory
+/- voluntary motor activity/planning
What are the 5 cerebral lobes and their function?
olfactory/piriform: smell
temporal: hearing/balance
occipital: vision
frontal: motor
parietal: sensory
What are clinical signs of forbrain disease?
obtunded, behavioural changes
head turn, +/- body turn
wide/compulsive circling (usually normal gait)
reduced/absent postural reactions in limbs contralateral to lesion
contralateral menace deficit (intact plr), contralateral reduced facial sensation
reduced sensation contralateral to lesion, cervical hyperaesthesia
seizures (generalised), hemi-inattention, head pressing
What is the hemi-neglect syndrome?
ignore 1/2 of the world
indicates a forebrain lesion contralateral to side “ignored”
What are the thalamic functions?
acts as relay station for integration sensory and motor pathways: gateway to forebrain
role in maintaining consciousness
autonomic and homeostatic functions
regulation of sleep/wake
seasonal reproductive cycles
What is the main consequence of lesions in ARAS?
marked reduction in mentation: stupour/coma
What mentation/behavioural changes indicate forebrain lesion?
change in personality
behaviour change
loss of learned habits
mild to moderate obtundation
What mentation/behaviour changes indicate brainstem lesion?
significant changes in level of mentation possible
obtunded to commatose
What are some clinical signs of thalamic dysfunction?
stupor/coma
endocrine abnormalities (ex: PU/PD)
altered thermoregulation
chnages in sleep/wake cycle
altered appetite
vestibular signs
seizures NOT associated with thalamic disease
How do forebrain diseases affect vision?
optic nerve is an extension of the diencephalon/thalamus
surrounded by glial cell, meninges, CSF
disease affecting CNS can also affect oftic nerve
Does forebrain disease affect menace response?
not a reflex! learned response which is sensed by the occipital lobe and motor sent out through facial nerve
pathway goes through forebrain = yes
Does forebrain disease affect PLR?
PLR is sub-cortical reflex: no relay through the forebrain = no
How does lesion of the retina and optic nerve/chiasm present?
causes ipsilateral blindness
absent menace and PLR
affected eye has a partially dilated pupil?
How does a lesion of the optic tract/visual cortex (forebrain) present?
contralateral “central” blindness
absent menace with intact PLR
no change to pupil size
