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Operative approaches to lateral and third ventricular tumors Presented By : Nilesh S. Kurwale 6/20/2009 1 Velum interpositum • Located in the roof of third ventricle • Formed by two membranous layers • Contains two paired internal cerebral veins and its tributaries 6/20/2009 2 Lateral ventricular tumors • Confined to ventricles – Neurocytoma – Colloid cyst – Choroid plexus papilloma • Extending into the parenchyma – Astrocytoma – Ependymoma – ODG 6/20/2009 3 Key features • Craniotomy flap placed so as to minimize brain retraction. • Self retaining rather than handheld retractor • Minimum Neural incision 6/20/2009 4 • Internal debulking of tumor before separation. • Preservation of arteries • Minimal sacrifice of veins • CSF diversion 6/20/2009 5 Frontal horn tumors • Interhemispheric transcallosal approach • Transcortical approach 6/20/2009 6 Transcallosal approach • Indications: – Frontal horn tumors located mainly in the ventricle. – Minimal hydrocephalus – Tumor extending to both frontal horns and to third ventricle 6/20/2009 7 Positioning and craniotomy • Supine position • Lateral position – Ipsilateral approach – Contralateral approach • Craniotomy – Cross midline – 2/3rd anterior and 1/3rd posterior to coronal suture 6/20/2009 8 Surgical technique • Reflect dura based on sinus • Identify bridging veins and preserve • Identify corpus callosum and ACAs • Callosotomy 6/20/2009 9 Intraventricular orientation • Choroid plexus and thalamostriate veins • Foramen of monro • Tumor identification • Resection of tumor as internal debulking followed by dissection. 6/20/2009 10 Complications • Vascular injury – – – • Arachanoid granulations Bridging veins ACAs Corpus callosal syndrome – – 6/20/2009 Reduced spontaneity of speech to frank mutism. Interhemispheric transfer syndromes 11 Advantages • Less chances of Neural injury • Access to both ventricles • Less chances of epilepsy (?) • Entry to third ventricle easy if required 6/20/2009 12 Disadvantages • More chances of Vascular injury • Theoretical risks of callosotomy • Superiorly located tumors are generally can not be tackled. 6/20/2009 13 Transcortical approach • Indication: – Tumor growing outside the ventricle – Tumor located mainly in anterio‐superiorly in frontal horn – Non‐dominant hemisphere – Surgeons preference 6/20/2009 14 Positioning and craniotomy • Principles followed are same • Corticectomy in middle frontal gyrus • Entry in ventricle • Tumor debulking and dissection 6/20/2009 15 Complications • Epilepsy – Direct cortical incision and damage • Memory loss – Retraction of caudate nucleus. • Hemiplegia – Retraction of centralis semiovalis 6/20/2009 16 Disadvantages • More chances of epilepsy and porencephalic cysts • Limited entry to opposite ventricles • Small ventricles‐ chances of missing 6/20/2009 17 Tumors involving the body • Transcallosal approach is better • Combined transcallosal and transcortical approach is needed for large tumors involving both ventricles 6/20/2009 18 Atrial tumors • Transcortical approach is favored. • Lateral decubitus position with face turned towards the floor • Superior lobule is identified • 1‐2 cm corticectomy 6/20/2009 19 Why transcortical approach preferred? • Ventricles diverge posteriorly • Splenium sacrifice has physiological risks • PCA injury is more common 6/20/2009 20 Complications • Speech problems – Acalculia, apraxia • Visual field deficits – Homonymous hemianopia – Visual spatial processing • Splenium syndrome – Interhemisphere disconnection syndrome 6/20/2009 21 Additional approaches • Approach through occipital pole incision • Occipital lobectomy – Cortical incision placed in sup. occipital gyrus – Invariably lead to visual field deficits 6/20/2009 22 Temporal horn tumors • Supine with head turned almost laterally. • Small temporal craniotomy • Dura opened based on base 6/20/2009 23 Entry corridors to ventricle • Middle gyrus approach • Temporal tip resection • Occipitotemporal gyrus resection • Temporo‐parietal junction 6/20/2009 24 Complications – Visual field deficits • Superior quadrantonopia – Language deficits – Others • Dyslexia • Agraphia • Acalculia 6/20/2009 25 Third ventricular tumors – Tumors growing inside out – Tumors growing outside in 6/20/2009 26 diagram 6/20/2009 27 Approach to Ant. TV tumors • Subfrontal • Frontotemporal • Anterior transcallosal • Anterior transcortical • Transsphenoidal 6/20/2009 28 Subfrontal approach • Supine position with head extension • Coronal flap incision • Quadrangular craniotomy flush with • orbital margins • Frontal sinus exteriorized and packed • Olfactory nerve divided if necessary 6/20/2009 29 Corridors • Interoptic • Opticocarotid • Lamina terminalis • Transfrontal‐ transsphenoidal • Lamina terminalis‐rostrum of callosum approach 6/20/2009 30 Frontotemporal or subtemporal approach • Frontotemporal craniotomy • Dura reflected on sphenoid ridge • Tumor approached through corridor between third nerve and carotid. • Temporal pole can be elevated or resected. 6/20/2009 31 Anterior transcallosal approach • Advantages – Short trajectory to third ventricle – Can access posterior and basal TV – Bilateral exposure of foramina of monro – No requirement of ventriculomegaly 6/20/2009 32 Maneuvers for TV entry • transforaminal • Transchoroidal • Transfornicial 6/20/2009 33 Transforaminal • Gives access to anterior TV • Foramen of monro identified • Initial dilatation can be tried • Incision is made through one column of fornix at anteriosuperior edge. 6/20/2009 34 Transchoroidal • Entry into the middle of TV • Opening through the velum interpositum • Two approaches: – Suprachoroidal • Incision in tinea fornicia – Subchoroidal • Incision in teniea choroidea 6/20/2009 35 Transfornicial • Identify the septum pellucidum • Develop a plane between septa. • Incision is given in the body of fornix not exceeding 2 cm behind the FM. 6/20/2009 36 • In both the approaches velum interpositum is opened. • The interval between two internal cerebral veins is separated and entered. • Minor veins can be sacrificed. 6/20/2009 37 • Tumors can be decompressed as stated earlier • Complete hemostasis is mandatory • Post operative cavity drain can be kept 6/20/2009 38 Complications • Fornicial injury – Recent memory disturbances • Vascular compromise – Basal ganglia infarcts – Thalamic infarcts – Limbic system ischemia • Hippocampal syndrome 6/20/2009 39 Approaches to the post TV tumors • Transventricular • Interhemispheric transcallosal • Occipital transtentorial • Infratentorial supracerebellar 6/20/2009 40 Indications • Transventricular (Wegen’s) – Tumors arising in corpus callosum and extending to third ventricle • Transcallosal (Dandy’s) – Tumor extending to splenium 6/20/2009 41 • Occipital‐ transtentorial ( Popen’s) – Tumor extending to medial wall of ventricle and in occipital lobe • Supracerebellar infratentorial (krause’s) – Pineal region tumors 6/20/2009 42 Endoscopy • Treatement of choice for malignant third ventricular tumors • Biopsy of lesion • Post operative radiotherapy 6/20/2009 43 Technique • Selection of burr hole point • Advancement of scope • Biopsy using endoscopic instrument 6/20/2009 44 Disadvantages • Two dimensional vision • Less freedom of movements 6/20/2009 45 Complications • Inadequacy of hemostasis • Conversion of procedure to open 6/20/2009 46 Image guidance • Recent development • Useful for biopsy • Anatomical orientation 6/20/2009 47 6/20/2009 48