Principles of Forebrain Disease Flashcards
What is the forebrain known as embryonically?
Prosencephalon
The forebrain consists of two main structures-
the cerebrum (not cerebellum!!) & the thalamic region
What is the role of the Cerebrum?
Conscious perception, behaviour/ personality, learning and memory
[also in humans responsible for gait]
What lobes are there in the Cerebrum and what is their role?
POTOF
Olfactory- smell
Temporal- hearing/ balance
Occipital- vision
Frontal- motor
Parietal- sensory
In animals, what is responsible for the gait?
works as an upper motor neuron extra pyramidal system) so responsible are the basal nuclei in the brainstem
Is the forebrain an ipsilateral or contralateral system?
Contralateral so sensory & motor info is interpretated by opposite sides (crosses over in the brainstem)
What are some clinical signs you might find in a Neuro exam of a patient associated with a forebrain lesion?
circling towards the side of the lesion (WIDE CIRCLES)
normal gait
postural reactions are absent in limbs contralateral to the lesion
contralateral menace deficits with intact PLR
What is Hemi neglect syndrome?
reduced awareness of stimuli on one side of space, even though there may be no sensory loss- indicates a forebrain lesion contralateral to the side ignored
What is the role of the thalamus?
Maintains consciousness- regulation of sleep/ wake cycles
How does the thalamic region control consciousness in the brain?
the thalamic region is the most rostral part of the ARAS (ascending reticular activation system) which is a network of neurons- decreased activity in these neurons= SLEEP
What are some clinical signs of thalamic dysfunction?
Coma
Endocrine abnormalities
Changes in sleep/ wake cycle
Altered appetite
[SEIZURES NOT ASSOCIATED AT ALL]
What do we mean when we say the Optic Nerve is a misnomer and how does this relate to forebrain pathology?
Means it is an extension of the diencephalon/ thalamus- this means diseases that affect the CNS also effect the optic nerve contralaterally
Why do forebrain lesions affect the menace response but not the PLR?
The PLR is a sub cortical reflex so doesn’t pass through the forebrain- for the menace, the pathway diverges caudal to the optic chiasm
