different approaches Flashcards
what does a complete subfrontal approach give access to?
- The anterior cranial fossa
- MIddle and posterior fossa between the petrous and cavernous ICA
- Foramen Magnum
- The anterior portion of the third ventricle
Describe a subfrontal approach short with + and -
- Bifrontal craniotomy
+ extended – removal of the supraorbital rim
+ removal of the anterior aspect of the orbital roof - frontal craniotomy by the naso-frontal sutur through the frontal sinus.
What is a postfixed chiasm?
Its a term for when the optic chiasm is pushed so far back (posteriorly displaced) that it is situated superior to the dorsum sellae.
(this might make it difficult to access lamina terminalis in suprasellar tumor resections.)
what is lamina terminalis?
Its grey matter and pia mater that attaches to the upper surface of the optic chiasm and stretches upward to fill the interval between the optic chiasm and the rostrum of the corpus callosum. It composites most of the anterior wall of the third ventricle. This area is including the preoptic nucleus and 2 circumventricular organs (CVOs) - the subfornical organ and organum vasculosum of the lamina terminalis.
What is the name of the “membrane”/area over the optic chiasm that gives access to the third ventricle from a subfrontal approach?
the lamina terminalis (forming part of the anterior wall of the 3rd ventricle)
Where to enlarge foramen Monro safely?
between the choroid plexus and the fornix
Describe the situation of foramen of Monro
Each of the foramen are situated between the roof and the anterior wall of the third ventricle. Its behind the fornix and anterior to thalamus
what passes through each of the foramen of Monro?
- Choroid plexus
- distal (end) branches of the medial posterior choroidal arteries.
*superior thalamostriate vein, superior choroid veins and septal veins.
The greatest risk of ligating the posterior 2/3 of the SSS
venous infarction
what are the skin insicions for the 3 differentapproaches by the mastoid notch to:
- 7th and 8th nerve
- 5th nerve (microdecompression)
- 9th nerve (glossopharyngeus)
- 5-5-5
- 5-6-4
- 5-4-6
-mm medial off, - cm superior off and cm inferior off the mastoid notch
outer identification mark of the inferior margin of the transverse sinus?
2 fingerwith (straight) above the mastoid notch.
What is the Liliequist membrane and what structures does it protect?
Its an arachnoid membrane separating the chiasmatic cistern, the interpeduncular cistern and the prepontine cistern from diaphragma sellae and ?
Protects: BA, PCA and perforators from the posterior circulation.
What approaches are there to the middle fossa?
- the middle fossa approach
- the anterior petrosal approach
- the subtemporal approach
what is situated between the choroid plexus and the fornix?
foramen monroi - enlarged in hcph and a sfe place to go through for VCS
Koshers point lays over what gyri?
The frontal middle gyri.
What is the greatest risk with the interhemispheric approach to the 3rd ventricle?
Bilateral cingulate gyri injury with risk of transient mutism
What vein serves as indicator for right/left ventricle orientation in a VCS together with the choroid plexus?
The Striatothalamic vein. If its on the right side of the choroid plexus, its the right ventricle. If it is on the left side of the choroid plexus its the left side.
Between what structures does the transcallosal approach to the third ventricle have to go?
Between the paired pericallosal arteries.
What is the greatest risk with anterior transcallosal approach (to the 3rd ventricle)?
Bilateral fornices injury with risk of injuring the short term memory and to the ability of new learning.
Structures found in the middle fossa approach?
*Petrosal part of ICA behind/above the
* V1, V2, V3 and together ganglion gasseri
and thereunder
* the cavernosal part of ICA above it:
* Trochlearis
* Occulomotorius
* opticus nerve
“to the left” (egentligen under, men i bilden till vänster) are:
SCA and PCA
Etiliogies of severe swelling of brain out of the craniotomy during surgery
- extra or intraparenchymal bleeding
- venous outflow obstruction
- vasodilation induced by hypercarbia
- severe diffuse cerebral edema following stroke or TBI
Acute measures in a situation of swelling, herniating brain during op
- hyperventilation down to CO2 3.2 - control the tube so that no hypercarbia is present as areason for the swelling first.
- position so that venous outflow is available.
- position so brain “fall down”
- 200-300cc Mannitol (1g/kg IV bolus)
- More anesthetics - pentho is not acute measure but can be started. (down to burst suppression)
- drainage of CSF
- ultrasound to find source (fast det verkar ju inte supersnabbt)
- sponge and pressure brain in. - om det inte är aktuellt med
- Widen the craniotomy (at least palm size)
What are the postoperative risks with craninotomy?
- type of hemorrhage?
- risk of death?
The risk is 0.8 - 1.1%
-ca 50% intraparenchymal
-ca 30% epidural
-ca 6% subdural
-ca 5% intracellar
-ca 8% mixed
-ca ?ca 11% superficial wounds
If recieving a postoperative hemorrhage, the risk of death is 32%
Position options for posterior fossa approach (6st)
- sitting
- lateral oblique - 3/4 almost prone
- semisitting
- supine w shoulder roll - head almost horizontal.
- prone
- concorde - prone, thorax elevated, neck flexed and tilted away from surgeon.
