Principles of Neurosurgery

• brain 1400ml
• blood 150ml
• CSF 150ml

extracellular edema

increased capillary permeability

intracellular edema

cellular swelling (neuronal, glial, endothelial)

Increased brain water due to impairment of absorption of cerebrospinal fluid

mainly white matter

grey and white matter

• transpendymal flow of CSF
• periventricular white matter in hydrocephalus

plasma filtrate containing plasma proteins

• incresed intracellular water and sodium
• due to failure of membrane transport

cerebrospinal fluid

increased

decreased

increased

• primary or metastatic tumor
• abscess
• late stages of infarction
• trauma

• early stages of infarction (hypoxia)
• water intoxication

obstructive or communicating hydrocephalus

• effective
• effective

• not effective
• effective

• not effective
• questionable

Cerebral Profusion Pressure

• blood pressure gradient across brain
• MAP - ICP

• systemic blood pressure
• CO2 and H+ concentration in arterial blood
• O2 concentratino

diastolic pressure + 1/3 pulse pressure

ablility to maintain blood flow to brain at a wide range of MAPs, 50 to 160 mmHg

cerebral arteriole dilation --> greater flow at decreased pressure

arteriole constriction

cerebrovascular dilation

cerebrovascular dilation

decreases CO2, decreases dilation

• 10 to 15 mm Hg
• 136 to 204 mm H2O

• falx cerebri - sickle shaped in midline
• tentorium cerebelli - tent shaped

• Localized masses
• Obstruction of CSF pathways
• Obstruction of major venous sinuses
• Diffuse brain edema or swelling
• Idiopathic

• Hematomas
• Neoplasms
• Abscesses
• Focal edema due to trauma

Obstructive and communicating HCP

• depressed skull fractures damaging sinus
• thromboembolic desease from contraception

• Encephalitis, meningitis
• diffuse head injury
• SAH
• Reye's syndrome
• Lead enxephalopathy
• Water intoxication, fluid overload, near drowning

pseudotumor cerebri

no specific clinical signs or symptoms

• due to supratentorial mass
• herniation of cingulate gyrus across falx cerebri
• usual displacement of ventricular system
• ACA may be compromissed

• impaired consciousness - compressed RAS
• dilated ipsilateral pupil - compressed CNIII
• contralateral hemiplegia - compressed cerebral peduncles

• most common
• due to middle cranial fossa mass
• inferomedial temporal lobe herniation between rostoral edge and tentorial edge into posterior fossa

• due to masses far from tentorial hiatus such as frontal, perietal, or occipital
• downward displacement of diencephalon and midbrain throu tentorial incisura

• not easily recognizable
• bilaterally small reactive pupils
• Cheyne stoke respirations
• obtunded
• loss of vertical gaze

• due to acute expansion of posterior fossa lesions or (LP with increase ICP)
• herniation of cerebellum tonsils through foramen magnum in to spinal canal, compressing medulla

• Cardiorespiratory impairment
• Hypertension
• High pulse pressue
• Cheyne Stoke respirations
• Neurogenic hyperventilation
• Impaired consciousness
• Stiff neck or in opisthotonic position
• Decorticate or decerebrate posturing

• HA with generalized location
• HA worse at night and in recumbant position
• Vomiting without nausea
• Vomiting with neuro sign points to lesion
• Papilledema

• closed head injury
• SAH

• intraventricular catheter connected to manometer and drainage system
• fiberoptic transducer tipped catheter system placed within the ventricle, parenchyma, or subdural space.

• zero point does not require recalibration with differences in head position
• not susceptable to blockage

• higher cost
• inability to tunnel - thus higher rate of infx
• baseline drift - less reliable over time
• possible inaccuracies

• percussion wave
• tidal wave
• dicrotic notch
• dicrotic wave

tidal waves or dicrotic waves of greater amplitude

• due to abrupt elevation in ICP for 5 to 20 minutes
• appear as plateau
• may be marked by decread conciousness, restlessness, increased tone, tonic clonic movements

• frequency of .5-2/min
• related to rhythmic variations in breathing

• rhythmic variations related to Traub-Meyer Hering waves of systemic blood pressure
• frequency of 6/min

have questionable clinicle significance.

• removal of blood or mass cause
• ventricular drainage
• mannitol
• hyperventilation
• loop diuretics
• steroids
• barbituate coma

cerebral edema

• osmotic agent for tx of cerebral edema
• by increasing serum osmolality it cause fluid in brain to be drawn from the parenchyma into the vascular space.

275 to 290 mOsm/kg

10 mOsm/kg

• usually small boluses rather then continuous drip
• 0.25g/kg at Q4 or 6

• decrease in CSF production
• increases in cerebral blood flow
• increases cerebral oxygen consumption
• decreases blood viscosity
• (increases profusion)

48 to 72 hours then begins to leak from vesels

• reduces ICP by reducing intracerebral blood flow and volume through vasoconstriction
• used for acute management only

the brain is often under perfused and hyperventilation will decrease profusion further

pCO2 28 to 32 mm Hg

• used in conjuction with manitol has synergistic effect on ICP
• may reduce CSF production

dexamethasone is used for treating chronic issues with ICP - for example vasogenic edema from neoplasm

vasogenic edema from infarct or trauma

• stabilizing the cell membrane by inhibiting lysosomal activity
• suppressing polyunsaturated fatty acid production
• decreasing free radical production

• dexamethasone
• loading dose of 10mg IV followed by 4mg Q6H.
• after goal then taper over 3 to 4 days

last resort in increased ICP managment

• scavenging free radicals from mitochondrial respiration
• inhibiting cerebral metabolism and reducing cerebral blood flow

• thiopental
• loading dose 3 to 10 mg/kg over 10min
• maintenance dose of 1-2mg/kg/h
• serum level mantained to 3-4mg/L

intensive monitoring of hemodynamic function, ICP, and blood gasses

• ICP normalizes
• there is good intracranial compliance

vasopressors