Infratentorial Cavernous Malformations

32 Infratentorial Cavernous MalformationsMichael L. DiLuna and Murat Gunel

♦ Preoperative

Operative Planning

Review Imaging

  • Computed tomography (CT) scan: low yield with respect to operative planning, unless patient has had a previous craniotomy, then might be helpful with understanding bone anatomy
  • Magnetic resonance imaging (MRI)
    • Location
      • For brain stem cavernous malformation, T1 with thin slices to see if and where the lesion comes to the surface
    • Size and age of clot, if previous hemorrhage
    • Proximity to adjacent eloquent structures/nuclei and to the pial surface (in the case of brain stem cavernous malformation)
    • Presence of multiple lesions
    • Presence of venous angioma
    • Stereotactic sequences for use of frameless imaging guidance intraoperatively
  • Angiogram
    • Only useful if an associated venous malformation or arteriovenous malformation (AVM) is suspected
    • Will rule out other vascular pathology, indicated in patients presenting with spontaneous intracerebral hemorrhage; this could change operative planning (i.e., presence of true AVM could lead to surgical management with radiosurgery)

Neurophysiology

Special Equipment for Operating Room

  • As for acoustic neuroma

Operating Room Set-up

  • Operating microscope
  • Frameless stereotaxy

Anesthetic Issues

  • Hyperventilation; optimize pCO2 to 30 to 35 mm Hg
  • Intravenous (IV) steroids (dexamethasone 10 mg IV or methylprednisolone 150 mg IV)
  • Antibiotics (cefazolin 1 gm IV every 6 hours, oxacillin 2 gm every 6 hours, or vancomycin 1 gm every 12 hours); all antibiotics should be given at least 30 minutes prior to incision
  • Diuresis with mannitol (0.5 to 1 g/kg) or mannitol + furosemide at time of skin incision
  • Anticonvulsants continued if patient already on medications; not necessary in infratentorial lesions
  • Blood pressure as per routine with any intracranial surgery
  • If neurophysiology (SSEP, BAERs) is to be used, limitations to use of muscle relaxants and paralytics similar to acoustic neuroma

♦ Intraoperative

Preparation of Frameless Stereotaxy

  • Load images onto system
  • Perform patient coregistration
  • Check accuracy of instruments and probes

Positioning

  • Highly variable depending on location of lesion and approach used

Shave Patient

  • Clip hair with electric razor, do not shave
  • Approximately 3 cm width along length of incision

Sterile Scrub and Prep

Incision, Craniotomy, Dural Opening

  • Approaches
    • Suboccipital: midline cerebellar or cerebellar hemisphere lesions; transvermian modification for midline pontine lesions, consider velotelar approach
    • Infratentorial supracerebellar: collicular lesions
    • Occipital transtentorial
    • Retrosigmoid or presigmoid: lateral pontine lesions
    • Far lateral
    • Transtemporal
    • Frontotemporal/subtemporal transtentorial: lesions of the cerebral peduncle
    • Velotelar: fourth ventricle lesions
  • Pial Incision

Resection of Lesion

  • Dissection of glial plane
  • Empty caverns within lesion of clot to internally debulk (internal decompression) then roll lesion on itself to resect away from glial plane

♦ Postoperative

  • Intensive care unit monitoring for at least 24 to 48 hours, rule out postoperative hydrocephalus
  • Blood pressure: systolic control below 120 mm Hg (140 if patient with poorly controlled hypertension preoperative) for first 24 to 48 hours
  • Antibiotics continued for 24 hours, longer if ventriculostomy catheter in place
  • Steroids tapered slowly
  • CT scan in 12 to 18 hours
  • MRI eventually
  • Sutures removed in 7 to 10 days

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Jul 11, 2016 | Posted by in NEUROSURGERY | Comments Off on Infratentorial Cavernous Malformations

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