Raised Inter Cranial Pressure Flashcards
The inter-cranial volume is not fixed and fluctuates. T/F
False
The inter crania volume in constant.
What happens if the inter cranial volume increases and why?
The inter-cranial pressure increases as the cranial cavity is a enclosed space with no elasticity.
List some causes of an increased inter-cranial pressure?
Tumour
Hydrocephaly
Meningitis
What is a main presenting complaint of someone with a raised inter-cranial pressure?
Visual problems
What are the three layers of the meninges?
Dura - lies inferior to the skull
Arachnoid
Pia - adjacent to the brain
Why is the optic nerve technically a CNS tract?
As it is completely covered in meninges.
Where is CSF located within the meninges?
Located in the sub arachnoid space, between the arachnoid and Pia.
Why then if the optic tract is coated in meninges does a raised ICP lead to visual defects?
The raised ICP is transmitted along the optic tract compressing the optic nerve artery and vein.
What is papilloedema?
Swollen optic disc
What are some symptoms of papilloedema?
Transient visual obscurations and flickering
Blurring of the vision
Decreased colour perception
What is CNIII susceptible to when exposed to an increased ICP?
The oculomotor nerve is at risk o compression and cerebellar herniation.
Obstruction on CN III leads to?
Paralysis off somatic motor innervation - 4 extra ocular muscles and the eyelid.
Paralysis off parasympathetic innervation of the sphincter papillae.
What muscles are not paralysed by damage to CN III?
Superior oblique and lateral rectus
What extra ocular muscles are paralysed by damage to CN III?
Medial rectus
Superior rectus
Inferior Rectus
Inferior Oblique
What are some clinical signs of someone with a CN III pathology?
Dilated eye - slow pupillary light reflex
Eye turned inferolaterally
Drooping eyelid
What muscle within the eyelid would still be functioning in a CN III pathology and why?
Mullers muscle - sympathetic control
What is the muscle within the eyelid that will be paralysed in a CN III pathology?
Levator Palpebrae Superioris
What create the septa within the cranial cavity?
Folds of dura matter
What are the two main septa within the cranial cavity?
Falx Cerebric - lies inferior to the sagittal suture
Tentorium cerebelli - lies superior to the cerebellum
What is a common cause of compression of CN III in raised ICP?
Medial temporal lobe herniates through the tentoral notch into the cerebellum.
What is CN IV?
Trochlear nerve
What is the only function of the trochlear nerve?
Innervates the Superior Oblique
- think the SO passes through a trochlear
What is special about the trochlear nerve?
Its the longest inter-cranial nerve
What is CN IV susceptible to if there is a raised ICP?
Stretching and compression
What is are the clinical signs of someone with a CN IV pathology?
Eye is unable to move inferiolaterally
if you gaze to the right the left eye will look up
If you gaze to the left the right eye will look up
Diplopia when you look down
What is diplopia?
Double vision
What is CN VI ?
Abducens
What is special about CN VI?
The abducens has the longest intradural course
What is CN VI susceptible to if expose to a raised ICP?
Stretching
What intracranial muscle will become paralysed in a CN VI pathology?
Lateral Rectus
What is the clinical picture of someone with a CN VI pathology?
Medial deviation of the eye
Eye is unable to move laterally within the horizontal plane.
