Neurosurgery Flashcards
Ventricular system
Paired lateral ventricles
Communicate by foramin of Munro with third ventricle
Third ventircle communicates via the aqueduct to the foruth ventricle
Outflow foramina: Luschka, and Magendie connect with basal and subarachnoid spaces
Large CSF cisterns around the base of the brain (e.g. cisterna magna, cerebellopontine cistern).
Anterior cerebral artery supplies
Frontal lobe and medial parts of parietal lobes
Middle cerebral artery supplies
Posterior frontal region and most of temporal and parietal regions
Posterior circulation supplies
Brain stem
Cerebellum
Occipital lobes
Inferior part of temporal lobes
End-arteries –> well defined stroke syndromes
Paired vertebral arteries –> basilar artery –> paired posterior cerebral arteries
Posterior cerebral arteries communicate with the anterior circulation through the posterior communicating arteries
In a normal supine adult, ICP is the same as the CSF pressure
Opening pressure of LP = ICP
Cerebral perfusion pressure (CPP)
= MAP - ICP
Why do you get a brady with raised ICP?
Rising ICP
Cerebral perfusion pressure = MAP - ICP
To achieve CPP, MAP increases as ICP increases
Increased MAP –> reflex bradycardia
Cerebral perfusion pressure (CPP)
= MAP - ICP
CPP of > 60 mmHg is generally required to sustain adequate cerebral perfusion
Sub-falcine herniation (cingulate gyral)
Caused by para-sagittal mass
Ipsilateral cingulate gyrus may herniate beneath the free edge of the falx
Anterior cerebral artery may be compressed leading to hemispheric infarction
Otherwise, reduced GCS is only clinical sign
Tentorial herniation
Large ipsilateral lesion
Medial part of temporal lobe is pushed down through tentorial notch –> becomes wedged between tentorial cerebelli edge and midbrain
Cerebral peduncle is pushed against sharp tenrotial edge
Midbrain and uncus become wedges at tentorium
Aqueduct is compressed , obstructing CSF flow
Obstruced venous flow –> midbrain haemorrhage
Uncul herniation:
-Falling GCS
-Motor component of GCS becomes asymmetrical
-Ipsilateral 3rd nerve palsy, dilated an ddixed pupil
-Hypertension and bradycardia
-Respiratory arrest
Tonsillar herniation
Caused by a lesion in the posterior fossa. lowest part of the cerebellum pushed down into the foramen magnum and compresses the medulla.
Uncal hernation
Uncul herniation:
-Falling GCS
-Motor component of GCS becomes asymmetrical
-Ipsilateral 3rd nerve palsy, dilated an ddixed pupil
-Hypertension and bradycardia
-Respiratory arrest
Berri aneurysms
85% in anterior circulation
Nimodipine
Medical management of SAH for vasospasm
Alonside maintaining CCP and haemodilution
Avoid hypotension and fever - associated with poorer outcome.
Amyloid angiopathy
Common cause of intracerebral bleed
Coma
Defined as GCS of 8 or less
Indications for haematoma evacuation
> 5mm midline shift
Significant impairment of GCS
Protracted headache or vomiting