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
What are the clinical signs indicating visual deficits caused by post-chiasmatic/cortical blindness?
absent menace
intact plr
able to navigate room but may show abnormal compulsive behaviour and other forebrain signs
What are the clinical signs indicating visual deficits caused by pre-chiasmatic blindness?
absent menace
absent plr
may have partial mydriasis of affected eye
difficulty navigating room especially unfamiliar areas or low light
What is the most common degenerative forebrain disease?
cognitive dysfunction
What is the most common metabolic forebrain disease?
hepatic encephalopathy
What are the 2 most common neoplastic forebrain disease?
meningioma
glioma
What is the most common inflammatory forebrain disease?
meningoencephalitis of unknown aetiology MUA
What is the most common idiopathic forebrain disease?
idiopathic epilepsy
What is the most common vascular forebrain disease?
ischaemic stroke
