4 th ventricle- Anatomical and surgical perspective
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4th ventricle connects the entire ventricular system of brain. Its connection with cisterns magna and cerebella pontine cistern via foramen of magenta and Luschka. CSF absorbs into the arachnoid granulation.
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4 th ventricle- Anatomical and surgical perspective
- 1. cka SURESH BISHOKARMA, MS MCH RESIDENT, NEUROSURGERY NINAS FOURTH VENTRICLE ANATOMY AND SURGICAL PERSPECTIVE
- 2. The fourth ventricle is a broad, tent- shaped midline cavity located between cerebellum and brainstem. It is lined by a membrane consisting of ependyma and a double fold of pia mater which constitutes the tela choroidea of the fourth ventricle.
- 4. It has a roof, a floor and two lateral recesses
- 5. *The roof : superior and inferior medullary velum and cerebellar vermis. *Apex: tented into cerebellum *The upper part of the roof :superior cerebellar peduncles and the superior medullary velum (thin sheet of white matter). *The inferior part of the roof : Inferior medullary velum (non- nervous tissue): Medulloblastoma origin.(Youman) ROOF
- 6. FLOOR OF FOURTH VENTRICLE Each inferolateral margin of the floor is marked by a narrow white ridge called taenia. The right and left taeniae meet at the inferior apex of the floor to form a small fold called the obex.
- 7. *The lateral recesses : pouches : below the cerebellar peduncles: Luschka CPA. *The ventral wall of each lateral recess is formed by the junctional part of the floor and the rhomboid lip. *The rostral wall of each lateral recess : Caudal margin of the cerebellar peduncles. *The peduncle of the flocculus, which interconnects the inferior medullary velum and the flocculus, crosses in the dorsal margin of the lateral recess. LATERAL RECESS
- 9. *The caudal wall is formed by the tela choroidea, which stretches from the taenia and attaches to the edge of the peduncle of the flocculus. *The rootlets of the glossopharyngeal and vagus nerves arise ventral, and the facial nerve rostral, to the choroid plexus, which extends through the lateral recess and the foramen of Luschka into the CPA. *The fibers of the vestibulocochlear nerve cross the floor of the recess. LATERAL RECESS
- 10. LATERAL RECESS
- 11. *The cavity or fossa of the fourth ventricle communicates with the third ventricle superiorly as a continuation of the cerebral aqueduct. *Inferiorly it extends as the central canal of the brainstem, which in turn runs through the vertebral column. *The cavity also communicates with the subarachnoid space through the three apertures. CAVITY
- 12. Foramina of the fourth ventricle
- 13. *First described during the 19th century. *François Magendie :French physiologist Magendie (1783-1855): Pioneer of experimental physiology. *Hubert von Luschka : German anatomist (1820-1875). *Rhoton provided detailed descriptions of the neurosurgical anatomy of the fourth ventricle and its foramina. FORAMINA OF 4TH VENTRICLE
- 14. *The choroid plexus of the fourth ventricle consists of several segments. *Its lateral segments extend laterally through the foramina of Luschka (protruding into the cerebellopontine angle below the flocculus and behind the glossopharyngeal, vagus and accessory nerves) and *Its medial segments extend longitudinally through the foramen of Magendie. *The tonsillar parts of the choroid plexus are located anterior to the tonsils and extend inferiorly through the foramen of Magendie. CHOROID PLEXUS OF 4TH VENTRICLE
- 15. *The PICA is intimately related to the inferior half of the roof. *The PICA segment coursing in the cleft between the tonsil on one side and the tela and velum on the opposite side is referred to as the “telovelotonsillar segment”3. *This PICA loop, which forms a convex rostral curve in its course around the rostral pole of the tonsil, is also referred to as either the “cranial” or “supratonsillar loop.” VASCULAR RELATIONS
- 16. PICA
- 17. *The main trunks of the anterior inferior cerebellar artery course near the foramen of Luschka, where they extend small choroidal branches to the tela and choroid plexus in the lateral recess.
- 18. *The largest vein of the cerebellomedullary fissure Originate: nodule and uvula, courses laterally near the junction of the inferior medullary velum and tela choroidea, Courses: dorsal or ventral to the flocculus CPA Superior petrosal sinus. Venous system
- 19. *Ikezaki and co-workers, classified posterior fossa ependymomas into three groups based on location: (1)The lateral type presenting in the CPA characterized by a poor prognosis secondary to involvement of cranial nerves and brainstem; (2) Ependymomas localized to the floor of the fourth ventricle with an intermediate prognosis; and (3) Those localized to the roof of the fourth ventricle with the most favorable outcome. *Leptomeningeal dissemination *Medulloblastoma: 33%. *Ependymoma: 8% to 12%. Spread and dissemination route
- 20. *Hydrocephalus is one of the conditions that can result from blockage of the median and lateral apertures. *In Arnold Chiari malformation (Type II Chiari malformation), the medulla and the tonsils of the cerebellum come to lie in the vertebral canal by descending through the foramen magnum. *The median and lateral apertures are blocked by this condition leading to obstruction of CSF flow. *This causes internal hydrocephalus. *Chiari II can also present with syringomyelia due to the development of CSF-filled cyst or syrinx. CLINICAL IMPORTANCE OF 4TH VENTRICLE
- 21. PICA
- 22. *Medulloblastoma is the most common malignant brain tumour in children, which arises in the cerebellum and can therefore impinge on the roof of the fourth ventricle. *The area postrema of the caudal region of the fourth ventricle is also of clinical significance because of its role in the control of vomiting.
- 23. *In adults, the occlusion is rather acquired than congenital, linked to infection, head trauma, intraventricular haemorrhage, tumours or Arnold-Chiari malformation. *Despite its rare occurrence, congenital imperforation or membranous obstruction of the foramen of Magendie must be considered as a possible etiology of chronic hydrocephalus in adult.
- 24. Main pathological conditions affecting the foramina of the fourth ventricle 1 Occlusion (Infection, head trauma, intraventricular haemorrhage, space- occupying lesions, congenital anomalies) 2 Membrane obstruction 3 Congenital imperforation (agenesis) 4 Idiopathic stenosis 5 Arachnoid adhesions 6 Cystic dilation
- 25. Tumors of the ventricular system account for less than 1% of intracranial lesions, most of which are benign and slow growing. 14% of all ventricular tumor occurs within the fourth ventricle. Tumor originating in 4th Ventricle 1. Medulloblastoma: most common: childhood. 2. Ependyoma: most common : adults 3. Hemangioblastoma 4. Epidermoid cyst Tumor expanding inside the 4th Ventricle. 1. Astrocytoma 2. Oligodendroglioma 3. Exophytic cavernous malformation Tumor of 4th venticle
- 26. Medulloblastoma Usually originates from inferior medullary velum from germinative cells originating in the neuroepithelial roof of the fourth ventricle and grow anteriorly into the fourth ventricle .
- 27. Hemangioblastoma
- 30. • Midline pathology of the fourth ventricle that arises from the cerebellar vermis or brainstem •Tumors: Medulloblastoma, ependymoma-subependymoma, as- trocytoma, choroid plexus papilloma, hemangioblastoma, dermoid- epidermoid cysts, brainstem glioma, and metastatic lesions . • Vascular lesions: Arteriovenous and cavernous malformations • Inflammatory and infectious conditions: Cerebellar and brainstem abscesses • Traumatic or spontaneous hematomas INDICATION
- 31. *CSF diversion : endoscopic ventriculostomy, external ventricular drain or permanent ventriculoperitoneal shunt. *followed by microsurgical resection of the underlying ventricular tumor. *Emergency: Acute obstructive hydrocephalus or intratumoral hemorrhage. INDICATIONS
- 32. *In the past, operative access to the fourth ventricle was obtained by splitting the cerebellar vermis or by removing part of a cerebellar hemisphere.
- 33. *Dandy: Median suboccipital craniectomy and splitting the vermis TRANSVERMIAN APPROACH
- 34. *Transvermian approach provided slightly better visualization of the medial part of the superior half of the fourth ventricular roof. *(Disadv: Lateral recess) *In cases where a tumor is located around the fastigium or originates from the vermis. ADVANTAGES
- 35. It avoids complications related to injuries of the posterior inferior cerebellar artery (PICA) branches to the brainstem and the inferior and middle cerebellar peduncles.
- 36. TELOVELAR (TRANSCEREBELLO-MEDULLARY FISSURE) APPROACH 1980:Rhoton AL Jr This approach is identical to traditional midline approaches . Preserve the cerebellar tissue : Anatomic plane through the tela choroidea and velum interpositum.
- 37. *Opening the CMF : safe retraction of the cerebellar hemisphere *Good visualization of lateral recess. *The cerebellar mutism syndrome: Avoids vermian split *Early vascular control. ADVANTAGES OF TELOVELAR APPROACH
- 38. STEPS OF TELOVELAR APPROACH
- 39. POSITIONING
- 40. INCISION
- 41. *The craniotomy includes opening of the foramen magnum dorsally and is larger in the superior portion than in the inferior. CRANIOTOMY
- 42. Dural opening is usually performed in a Y-shaped fashion. Bleeding from the occipital sinus can be controlled with silver dural clips or bipolar coaguation or running silk suture DURAL OPENING
- 44. Opening techniques for the telovelar approach depending on different targets Matsushima T et al.
- 45. *Small arachnoid trabeculae around the tonsil is sharply cut and cerebellar tonsil is gently elevated off its inferior fixation. *The superior portion of the tonsils is separated from the cerebellar vermis on both sides to gain access to the tela choroidea. *Careful inspection of the tela reveals small branches of the PICA that supply the choroid plexus.
- 46. *In similar fashion, the caudal loop of the PICA is freed from the neuraxis by incising small arachnoid trabeculae while slightly retracting the tonsils laterally
- 47. *The uvula of the cerebellar vermis is elevated gently with a self-retaining retractor, and the arachnoid between the uvula and the tonsil is gradually incised to expose the course of the PICA.
- 49. *The telovelar junction is visualized *The superior medullary velum may be further divided to allow for more rostral exposure of the fourth ventricle.
- 50. *When the roof of the fourth ventricle is adequately opened to allow for exposure of the tumor, the interface of the tumor and the brainstem is inspected. Cottonoid strip along floor and cervicomedullary junction
- 51. *Superior and lateral edges : adherence to the cerebellum. *Larger tumors: debulk the tumor : lateral margins. *A point of origin of the tumor : more adherant part TUMOR INSPECTION
- 52. *Hemostasis: cerebellum: bipolar cautery or tamponade *Inspect aqueduct : blood clot. *Saline irrigation until clear Finishing touch
- 53. Closure
- 54. *Retraction injury to cerebellar tonsils, vermis, and cerebellar peduncles *Injury or occlusion of posterior inferior cerebellar arteries from retraction. *Injury to the floor of the fourth ventricle (brainstem) *Tracking of blood into third and lateral ventricles that may produce hydrocephalus. *Injury to the transverse sinus during the craniotomy. *Significant blood loss or air emboli from occipital sinus or midline occipital bone . *Tumor dissemination along foramina and obex Avoidances/Hazards/ Risks
- 55. 1. Postoperative hematoma 2. CSF leak 3. Infection 4. Cranial nerve deficits or other brainstem deficits 5. Hydrocephalus 6. Cerebellar deficits 7. Supratentorial epidural hematoma 8. Tumor residual or recurrence 9. Posterior inferior cerebellar artery or vertebral artery infarction 10.Cerebellar edema Complications
- 56. *Medulloblastoma (13), ependymoma (10), and then choroid plexus papilloma (2). *GTR:8 cases (32%), near total (˃80% of tumor volume) in 14 cases (56%), and subtotal excision (˂80% of tumor volume) in 3 cases (12%). *Cerebellar mutism in 2 cases (8%), facial palsy: 2 cases(8%), postoperative bulbar affection: 3 cases (12%) *Mortality: 2 *Conclusion: Telovelar approach: access : Low incidence of CM Retrospective study 25 cases with midline posterior fossa tumors 2012-2014 Neurosurgery Department, Cairo University, Egypt Refaat MI, Elrefaee EA, Elhalaby WE (2016) Telovelar Approach for Midline Posterior Fossa Tumors in Paediatrics: 25 Cases Experience. J Neurol Disord 4:315. doi: 10.4172/2329-6895.1000315
- 57. Thank you 1. Mussi AC, Rhoton AL. Telovelar approach to the fourth ventricle: microsurgical anatomy. JNS. 2000;92(5):812-23. 2. Schmidek and Sweet operative technique; 6th Edn 3. Refaat MI, Elrefaee EA, Elhalaby WE.Telovelar Approach for Midline Posterior Fossa Tumors in Paediatrics: 25 Cases Experience. J Neurol Disord. 2016;4:315 References
Editor's Notes
- Sylvius : Third ventricle Obex : Spinal canal Magendie : Vallecula cerebelli (cleft between the cerebellar tonsils) and cisterna magna. This is through which the entire ventricular system communicates. Luschka : cerebellopontine angles below the junction of the facial and vestibulocochlear nerves.
- The roof of the fourth ventricle is mainly formed by the superior and inferior medullary vela and cerebellar vermis. The fourth ventricle is a tent-shaped midline cavity: the superiorand inferior halves of the roof are connected at its apex, the fastigium. The superior half comprises the superior medullary velum and superior vermis, including the lingula, central lobule, and culmen. The lingula is often adherent strongly to the superior medullary velum. The inferior half comprises the inferior medullary velum and tela choroidea laterally and the nodulus medially. The tonsils are situated on the inferior medullary velum and tela choroidea, and the uvula and pyramis are situated above the nodulus. The tela choroidea extends laterally to form the roof of the lateral recess. The choroid plexus, adherent to the tela choroidea, protrudes through the foramen of Magendie and foramina of Luschka. The lateral walls of the fourth ventricle are formed by the three cerebellar peduncles. The taeniae, which are lateral attachments of the tela choroidea, form the inferolateral margins of the fourth ventricle.
- Removal of the tela choroidea reveals the floor of the fourth ventricle The floor of the fourth ventricle : Rhomboid fossa because of its shape. It is divisible into a right and left half by the median sulcus and a superior and inferior triangle by the striae medullares. The upper triangular part is formed by the posterior surface of the pons. The upper part of the posterior surface of the medulla and an intermediate part at the junction of the medulla and pons make up the lower triangular part. The intermediate part is prolonged laterally over the inferior cerebellar peduncle as the floor of the lateral recess. Its surface is marked by the presence of delicate bundles of transversely running fibres that constitute the striae medullares. Striae medullares, or white strands, run transversely across the boundary between the pons and medulla. The lowest part of the floor of the fourth ventricle is referred to as the calamus scriptorius. Each inferolateral margin of the floor is marked by a narrow white ridge called taenia. The right and left taeniae meet at the inferior apex of the floor to form a small fold called the obex Each facial colliculus comprises nuclei of the CN VI and intramedullary fibers and the genu of the CN VII. The floor is divided into three parts: 1) a superior or pontine part; 2) an intermediate or junctional part; and 3) an inferior or medullary part. The superior part has a tri- angular shape: its apex is located at the cerebral aqueduct; its base is represented by an imaginary line connecting the lower margin of the cerebellar peduncles; and its lateral limits are formed by the ventricular surface of the cerebral peduncles. The intermediate part is the strip between the lower margin of the cerebellar peduncles and the site of attachment of the tela choroidea to the taeniae just below the lateral recess. The intermediate part extends into the lateral recesses. The inferior part has a triangular shape and is limited laterally by the taeniae that mark the infe- rolateral margin of the floor. Its caudal tip, the obex, is an- terior to the foramen of Magendie
- The ventral wall of each lateral recess is formed by the junctional part of the floor and the rhomboid lip, which is a sheetlike layer of neural tissue that extends laterally from the floor and unites with the tela choroidea to form a pouch at the outer extremity of the lateral recess. The lateral recesses are narrow curved pouches, formed by the union of the fourth ventricle roof and floor The roof of the lateral recess comprises the inferior medullary velum and tela choroidea.
- B: The cerebellar tonsils have been gently retracted to expose the uvula, which is located behind and hides the nodule of the vermis. The uvula hangs downward between the cerebellar tonsils, thus mimicking the situation in the oropharynx. The tela choroidea, in which the choroid plexus arises, encloses the lower portion of the roof of the fourth ventricle and has an opening, the foramen of Magendie, located at the caudal end of the fourth ventricle. C: Enlarged view. Both cerebellar tonsils have been removed to expose the inferior medullary velum and the tela choroidea, which form the lower half of the roof of the fourth ventricle. The velum arises on the surface of the nodule, which is located deep with respect to the uvula. The telovelar junction is the line of
- The location of the foramina of the fourth ventricle (human brain, right hemisphere, fourth ventricle area). 1: arbour vitae, 2: posterior commissure, 3: cerebellar tonsil, 4: lingula, 5: midbrain, 6: superior medullary velum, 7: quadrigeminal cistern (of the great cerebral vein), 8: roof of the fourth ventricle, 9: cerebral aqueduct (of Sylvius), 10: pons, 11: fourth ventricle, 12: cerebellar hemisphere, L: right foramen of Luschka, M: foramen of Magendie (line: intercommissural line)
- The medial segments stretch from the level of the nodule, anterior to the cerebellar tonsils, to the level of the foramen of Magendie. It has recently become clear that the choroid plexus is a major determinant of neuroplasticity and the production of new neurons in both the ventricular sub ventricular zone (V-SVZ zone) and the sub granular zone of the hippocampus. These are the two large areas already known to make substantial amounts of neurons each day for learning and memory.
- The telovelotonsillar segment courses in the cerebellomedullary fissure, which forms the lower half of the roof of the fourth ventricle, The PICA passes around the medulla, between the fila of the glossopharyngeal, vagus, and accessory nerves, and across the posterior aspect of the medulla near the caudal one half of the tonsil, where it turns upward along the medial surface of the tonsil, at first passing in the cleft between the tonsil and tela choroidea and, later, between the tonsil and inferior medullary velum.
- The largest vein crossing the inferior portion of the fourth ventricle, the vein of the cerebellomedullary fissure, originates on the lateral edge of the nodule and uvula, courses laterally near the junction of the inferior medullary velum and tela choroidea, and passes caudal to the cerebellar peduncles and dorsal or ventral to the flocculus to reach the CPA where it drains into the veins emptying into the superior petrosal sinus.
- Approximately 14% of medulloblastomas may show foraminal extension.
- Angiography showed the presence of feeding arteries originating from the posterior inferior cerebellar artery bilaterally and draining veins associated with a heavy blush of the tumor (
- Cauliflower like 4th ventricular mass. The pathologic diagnosis was choroid plexus papilloma .
- Lesions of the fourth ventricle have posed a special challenge to neurosurgeons because of severe deficits that may occur after injury to cranial nerve nuclei and pathways in the floor and because of disturbances fo llowing injury to the cerebellar peduncles and dentate nuclei in the ventricle roof.
- Removal of ventricular tumor and to prevent further deterioration, Total removal of the ventricular lesion is usually attempted and may be performed as first-line therapy.
- Dandy who stated that this approach can be performed without causing a disturbance of function, provided that the dentate nuclei are carefully avoided.
- In cases where a tumor is located around the fastigium or originates from the vermis, it may be necessary to switch from the trans-CMF approach to the transvermian approach.
- Ailure to visualise lateral recess through the transvermian approach is a cause of recurrence of 4th ventricular tumor as transvermian approach was insufficient and thenceforth started to dissect the CMF almost entirely to expose the entire fourth ventricle, particularly the lateral recess.
- While studying the fourth ventricle in cadaveric specimens in the early 1980s, Rhoton AL Jr and I observed a large fissure between the cerebellum and medulla, which we named the CMF. After 1990s CMF approach started to be valued. it has become established that opening the CMF during fourth ventricular surgery yields a wide operative field and decreases the incidence of vermal split syndrome (cerebellar mutism syndrome) and residual tumors in the lateral recess Tumors of the fourth ventricle are often hidden by the vermis, the cerebellar tonsils, or part of the cerebellar hemispheres. Their close contact with the brainstem, which can be displaced, invaded, or even be their origin, makes them a formidable surgical chal- lenge. In many instances, the tumor extends through the foramen of Luschka into the cerebellomedullary, premedullary, prepon- tine, and anterior spinal cisterns and has relationships with the cranial nerves and the vertebral and basilar arteries, along with their major branches and perforators. To remove lesions of the fourth ventricle, all these structures have to be kept in mind. Only profound knowledge of the microsurgical anatomy and judicious planning of the surgical approach in conjunction with meticulous microsurgical technique lead to complete tumor removal with low surgery-related morbidity.
- Opening the CMF makes retraction of the cerebellar hemisphere (tonsil and/or biventral lobule) safe and pronounced and facilitates Good visualization of the lateral portion of the fourth ventricle, including the lateral recess The cerebellar mutism syndrome, a common complication caused by splitting the inferior vermis, is avoided in this approach Early control: feeding arteries of a tumor : reducing bleeding This approach enables coagulation of the feeding arteries of a tumor at the early stages of surgery, thereby reducing bleeding from the tumor
- The patient should be placed in the sitting position with the head flexed and firmly fixed in the Mayfield holder. Concorde position The surgeon stands on the left side of the patient and obtains almost the same view as with the patient placed in the sitting position.
- The skin incision extends from above the occipital protuberance down to the level of the C2 spinous process Exposure of the dorsal suboccipital area is obtained with this midline skin incision and by detaching the muscles from the posterior squama of the occipital bone and atlantal arch. Depend- ing on the size of the underlying lesion, the C1 arch, and sometimes the C2 arch, must be exposed as well. It is advisable to extend the craniotomy superiorly up to the level of the transverse sinus or, if the telovelar approach is combined with a supracerebellar approach, above this level.
- In tumors confined to the fourth ventricle, the first step is opening the arachnoid to release CSF from the cisterna magna.
- Black arrows indicate the direction of approach for each type; black circles denote the spaces for dissection of the CMF; green oval areas indicate the target for each type; dotted lines indicate incisional lines of the taenia or tela choroidea. Extensive (aqueductal) type. All the uvulotonsillar and medullotonsillar spaces should be dissected bilaterally. Cutting of the taenia must extend laterally to the lateral recess on both sides. Lateral wall type. Both the uvulotonsillar and medullotonsillar spaces should be completely dissected on the lesion side. Cutting of the unilateral taenia should extend slightly superiorly and/or laterally to the lateral recess. Lateral recess type. Both the tonsil and the biventral lobule on the lesion side should be separated from the medulla oblongata. Incision of the unilateral taenia and lateral recess is sufficient to obtain an operative field.
- When the choroid plexus is situated superior to the tumor, it may indicate that the tumor originates from the floor of the fourth ventricle. On the other hand, when the choroid plexus is located inferiorly, it probably originates from the ventricular roof, i.e., the cerebellum.
- Telovelar junction is the junction between the inferior medullary velum and tela choroidea.
- A cottonoid strip is placed as far distally as possible along the floor of the fourth ventricle. A cotton strip may also be placed at the cervicomedullary junction to prevent seeding of tumor cells into the spinal canal
- larger tumors, it is usually necessary to debulk the tumor to visualize the lateral margins. A point of origin of the tumor is often identified where it is more adherent to the cerebellum.
- Hemostasis: cerebellum: bipolar cautery, and tamponade with absorbable gelatin sponge (Gelfoam).
- pathological nature of the lesion and vital neural tissue infiltration are limiting factors for total tumour removal Total removal of tumours focally attached to critical areas in the fourth ventricle should not be attempted at the expense of patient's morbidity and mortality. To achieve optimum outcome, near total excision is acceptable in cases where complete removal may endanger function or life.
- pathological nature of the lesion and vital neural tissue infiltration are limiting factors for total tumour removal Total removal of tumours focally attached to critical areas in the fourth ventricle should not be attempted at the expense of patient's morbidity and mortality. To achieve optimum outcome, near total excision is acceptable in cases where complete removal may endanger function or life.