21 Temmuz 2014 Pazartesi

Transcallosal +/- Transforaminal +/- Transchoroidal Approach

Transcallosal +/- Transforaminal +/-  Transchoroidal Approach (Right) 

Picture
Positioning
  • Supine, slight tilt to left   
        [Head tilt lateral for gravity to help w/ retraction]
Incision
  • Midline: 4 cm to right
  • Coronal suture: 2 cm anterior, 3 cm posterior 
  • Anterior: [________] 
  • Posterior: behind sensory cortex [prefer L side b/c R side -> neglect]
  • Scalp flap to right
Picture
Craniotomy
  • 4 burr holes: around superior sagittal sinus
  • Dura reflected to left, sutured
  • Retract interhemispheric fissure
  • Microscope in

Expose bridging veins
  • Bridging veins b/w R frontal cortex and superior sagittal sinus
  • No bridging veins near coronal suture
  • Leave >3 cm anterior - posterior distance b/w bridging veins to allow for retraction

Interhemispheric dissection to corpus callosum
  • Dissect / retract arachnoid adhesions
  • Through cingulate gyri
  • To corpus callosum (appears pearly white), expose <3 cm (to avoid disconnection syndrome)
Picture
Dissect through corpus callosum
  • Avoid pericallosal arteries
  • Incision: electrocautery, sharp dissection, aspiration until reach ependyma (appears gray)

Open ependyma
  • Sharp opening
  • CSF drains - relaxing brain, increasing exposure

Dissect to foramen of monro
  • 3 structures lead to foramen of monro: choroid plexus, thalamostriate vein, fornix (at base of septum pellucidum)

Picture
Transforaminal approach
  • for tumors small and evident (eg, colloid cysts)

Transchoroidal approach
  • to expand exposure for larger tumors
Dissect tenia fornicis
  • Start posterior edge of foramen of monro
  • Dissect 1 cm posterior, medial to choroid plexus and lateral to fornix
  • For better exposure: coagulate choroid plexus, retract septum
Dissect b/w internal cerebral veins
  • Start foramen of monro -> stay medial to thalamostriate vein -> internal cerebral veins
  • [If junction b/w internal cerebral veins is close to foramen of monro, may need to sacrifice anterior septal vein for exposure]
  • OK to take down small vessels from choroidal arteries and branching internal cerebral veins
  • [Avoid dissecting lateral to choroid plexus along tenia thalami b/c thalamostriate veins, choroidal arteries]

Remove tumor
  • Penetrate tumor, scoop out, remove smaller shell
  • [Germ cell tumors - vascular. Colloid cysts OK]
Closure
  • Hemostasis to avoid IVH -> HCP, +/- EVD
  • Irrigate to avoid pneumocephalus

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