Third ventricle surgical anatomy and approaches

Third ventricle surgical anatomy and approaches

1. ANATOMY OF THIRD VENTRICLE AND SURGICAL APPROACHES DR PRAVEEN K TRIPATHI

2. HISTORICAL REVIEW HEROPHILUS(335-280 B.C):First to describe ventricles GALEN(129-200A.D):Described ventricles in detail,studied the symtoms and signs of hydrocehalus LEONARDO DA VINCI(1452-1519):First wax casting of ventricles WALTER DANDY(1886-1946):First pneumoencephalography

3. HISTORICAL REVIEW First successful endoscopic third ventriculostomy (ETV) was performed in 1923 by william J. Mixter . In 1947, mcnickle described a modified technique of performing a percutaneous third ventriculostomy utilizing a 19-gauge needle to puncture the floor of the third ventricle. In 1952, Nulsen and Spitz first reported creation of a shunt diverting cerebrospinal fluid ( csf ) from the ventricular system to the jugular vein. 1990 Jones Etal reported successful ETV in 24 pt.

4. Third ventricle is a narrow slit-like cavity whose lateral walls are formed by the thalamus and hypothalamus on either side. At the rostral margin of the midbrain, the cerebral aqueduct opens into the third ventricle. 4

5. Third Ventricle - ventriculus tertius The third ventricle is a narrow, funnel-shaped, unilocular midline cavity. Slit-like space, lying in the sagittal plane It communicates at its anterosuperior margin with each lateral ventricle through the foramen of monro and posteriorly with the fourth ventricle through the aqueduct of sylvius .

6. Neural tube

7. Third Ventricle Comprises of: Anterior wall Two side walls Floor Roof

8. Third Ventricle Anterior wall: lamina terminalis anterior commissure Two side walls: Thalamus Interthalamic adhesion (60% of brains) Hypothalamus Supraoptic nucleus – ADH Paraventricular nucleus – Vasopressin/ Oxytocin Subthalamus Subthalamic nucleus

9. The lamina terminalis has been opened. The chiasmatic recess is located between the lower part of the lamina terminalis and the posterior part of the optic chiasm. Anterior wall of the third ventricle

10. The anterior communicating artery commonly passes in front of the lamina terminalis . Perforating arteries arise from a precallosal branch of the anterior communicating artery and penetrate the anterior wall of the third ventricle to reach the columns of the fornix. Anterior wall of the third ventricle

11. The roof The roof extends from the foramen of Monro anteriorly to the suprapineal recess posteriorly constituted superiorly to inferiorly by five layers the fornix the superior membrane of the tela choroidea vascular layer located in a space between the superior and inferior membranes of the tela choroidea called the velum interpositum the inferior membrane of the tela choroidea the choroidal plexus of the third ventricle

12. Roof of the third ventricle through a transchoroidal approach. 1 , Head of the caudate nucleus and anterior caudate vein; 2, rostrum of the corpus callosum; 3, column of the fornix; 4, anterior septal vein; 5, foramen of Monro ; 6, body of the fornix; 7, thalamostriate vein; 8, inferior membrane of the tela choroidea and choroid plexus of the third ventricle (the superior membrane of the tela has been removed); 9, body of the caudate nucleus and thalamostriate vein; 10, dorsal surface of the thalamus; 11, internal cerebral vein and medial posterior choroidal artery; 12, splenium of the corpus callosum.

13. The roof of the ventricle is formed by pia-ependyma , which spans between the two striae medullaris thalami, situated along the dorsomedial border of the thalamus. 15

14. In the rostral part of the third ventricle lies an aperture, the interventricular foramen or foramen of Monro , which is located between the column of the fornix and the anterior pole of the thalamus. 16

15. Cont..

16. The floor The floor extends from the Anteriorly -optic chiasm Posteriorly- to the orifice of the aqueduct of Sylvius From anterior to posterior The optic and infundibular recesses, The tuber cinereum , The mamillary bodies, The posterior perforated substance, The midbrain, and the aqueduct

17. THIRD VENTRICLE

18. CHOROIDAL FISSURE AND CHOROID PLEXUS The choroidal fissure is the narrow C shaped cleft between the fornix and the thalamus along which the choroid plexus is attached The fissure extends from the foramen of Monro to the choroidal point along the surface of thalamus Choroid plexus continues as two parallel strands of plexus in the roof of third ventricle

19. Cont.. Choroidal arteries arise from internal carotid and posterior cerebral arteries and enter the ventricles through the choroidal fissure Choroid plexus is divided into body,atrial and temporal parts

20. LESIONS WITHIN THIRD VENTRICLE Anterior third ventricle 1. colloid cyst 2. sellar mass 3. sarcoidosis 4. aneurysm 5. hypothalamic glioma 6. histiocytosis 7. meningioma 8. optic glioma Posterior third ventricle 1. pinealoma ( dysgerminoma ) 2. meningioma 3. arachnoid cyst 4. vein of Galen aneurysm

21. (A, foramen of Monro ; B, anterior third ventricle; C, posterior third ventricle) and relevant vascular anatomy of the third ventricle. Schematic representation highlighting common tumor locations

22. THIRD VENTICLE-APPROACHES

23. THIRD VENTRICLE -APPROACHES

24. THIRD VENTRICLE -APPROACHES

25. COMBINED TRANSLAMINAR TRANSCORTICAL

26. Indications Transventricular ( Wegen’s )–Tumors arising in corpus callosum and extending to third ventricle Transcallosal (Dandy’s)–Tumor extending to splenium Occipital‐ transtentorial ( Popen’s ) –Tumor extending to medial wall of ventricle and in occipital lobe Supracerebellar infratentorial ( krause’s ) –Pineal region tumors

27. Approach to Ant. TV tumors Subfrontal Frontotemporal Anterior transcallosal Anterior transcortical Transsphenoidal

28. Corridors Interoptic Opticocarotid Lamina terminalis Transfrontal‐transsphenoidal Lamina terminalis ‐rostrum of callosum approach

29. THIRD VENTRICLE -APPROACHES

30. Corridors For Transcallosal Approach

31. THIRD VENTRICLE -APPROACHES

32. Transcortical approach to the lateral and third ventricles. A , the scalp incision (solid line ) and bone flap (dotted line) are centered over the middle frontal gyrus . B , The cortical opening exposes the right lateral ventricle. C , the third ventricle has been exposed by opening the choroidal fissure along the site of the attachment of the choroid plexus to the fornix. This exposes the internal cerebral veins and medial posterior choroidal arteries in the roof of the third ventricle.

33. TRANSCORTICAL VS TRANSCALLOSAL PROS

34. TRANSCORTICAL VS TRANSCALLOSAL CONS

35. 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

36. 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 .

37. 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

38. Maneuvers for TV entry transforaminal Transchoroidal Transfornicial

39. 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.

40. Transchoroidal Entry into the middle of TV Opening through the velum interpositum Two approaches: Suprachoroidal •Incision in tinea fornicia Subchoroidal •Incision in teniea choroidea

41. Roof of the third ventricle through a transchoroidal approach. 1 , Head of the caudate nucleus and anterior caudate vein; 2, rostrum of the corpus callosum; 3, column of the fornix; 4, anterior septal vein; 5, foramen of Monro ; 6, body of the fornix; 7, thalamostriate vein; 8, inferior membrane of the tela choroidea and choroid plexus of the third ventricle (the superior membrane of the tela has been removed); 9, body of the caudate nucleus and thalamostriate vein; 10, dorsal surface of the thalamus; 11, internal cerebral vein and medial posterior choroidal artery; 12, splenium of the corpus callosum.

42. 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.

43. Complications Fornicial injury–Recent memory disturbances Vascular compromise–Basal ganglia infarcts Thalamic infarcts–Limbic system ischemia Hippocampal syndrome

44. Approaches to the post TV tumors Transventricular Interhemispheric transcallosal Occipital transtentorial Infratentorial supracerebellar

45. Endoscopy Treatement of choice for malignant third ventricular tumors Biopsy of lesion Post operative radiotherapy Treatment of hydrocephalus

46. CHOICE OF ENDOSCOPIC ENTRY POINT

47. Indications -ETV

48. FAVOURABLE FACTORS-ETV

49. A, Oblique view showing the endoscope passing through the lateral ventricle and foramen of Monro and into the third ventricle. B, Sagittal view depicting the perforation of the floor of the third ventricle. It is important to understand the close relationship of the floor of the third ventricle to the anterior structures (optic chiasm, infundibulum , and clivus ) and posterior structures (basilar artery and brainstem) to avoid undesired complications. Schematics demonstrating the surgical trajectory for ETV using a rigid endoscope

50. LOCATION OF ETV The location of the opening is chosen: A. in the midline B. in the region of the tuber cinereum (prominence of the base of the hypothalamus, extending ventrally into the infundibulum and pituitary stalk) C. posterior to the infundibular recess D. anterior to the mammillary bodies E. anterior to the tip of the basilar artery

51. . A, View of foramen of Monro from right lateral ventricle. The choroid plexus (center), anterior septal vein (medial), and thalamostriate vein (lateral) are seen. Care must be taken not to damage these structures when entering the foramen of Monro in order to prevent hemorrhage or venous infarcts. B, View of the floor of the third ventricle. From anterior to posterior, the optic chiasm, infundibulum , tuber cinereum , paired mammillary bodies are clearly seen. The basilar artery can also be seen between the mammillary arteries and must be avoided upon perforation of the third ventricular floor. Intraoperative views and corresponding schematic representations

52. showing the thin area in front of the mamillary bodies (yellow arrow) through which a third ventriculostomy is completed . FLOOR OF THIRD VENTRICLE

53. ETV

54. COMPLICATIONS

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