Clinical Anatomy Of The Fourth Ventricle Foramina

Page 1 of 5Clinical AnatomyCritical reviewClinical anatomy of the fourth ventricle foraminaAbstractIntroductionThe three foramina of the fourthventricle of the human brain werefirst described during the 19th century.The primary purpose of this articlewas to review the anatomy of theforamina of the human fourthventricle, as well as the main clinicalconditions related to pathology oftheseneurosurgicallyimportantstructures. The existing literatureregarding the gross and neurosurgicalanatomy of the foramina of the humanfourth ventricle was reviewed withemphasis on the clinical disorderscaused by several pathologicalconditions of these structures.Neuroanatomical comments on thelocation of these foramina are alsoprovided.DiscussionThe fourth ventricle is connectedthrough the foramen of Magendie withvallecula cerebelli and cisterna magna,and laterally through the foramina ofLuschka with the cerebellopontineangles. The foramen of Magendie isprobably the main path for theoutflow of the cerebrospinal fluidfrom the ventricle. The Luschkaforamina are found (at or) above thepontomedullary junction. The rightLuschka foramen seems to be locatedslightly more superior and moreposterior as compared to the left.Neuroendoscopy offers a detailedvisualisation, particularly of thestructures located in the inferiortriangle of the fourth ventricle. Themain pathological conditions affectingthe foramina of the fourth ponsibleforclinical manifestations) and includeocclusion, membrane obstruction,congenital imperforation, idiopathic*Corresponding authorEmail: pap-van@otenet.gr1Department of Neurology, ‘K.A.T.-N.R.C.’General Hospital of Attica, Athens, Greecestenosis, arachnoid adhesions andcystic dilation.ConclusionThe foramina of the fourth ventricle,anatomicallydelicateandneurosurgically crucial apertures,have close relations with severalimportant structures of the brainstemand cerebellum. Slight differencesseem to exist between the two sidesregarding the location of the Luschkaforamen. Pathological conditionsaffecting the foramina of the fourthventricle usually produce clinicalmanifestations due to obstruction ofthe cerebrospinal fluid normal flow.Microsurgical treatment of such rarebut challenging lesions is nowadaysfeasible.IntroductionThe three foramina of the fourthventricle of the human brain werefirst described during the 19thcentury1,2. The foramen of Magendie isnamed after the French physiologistFrançois Magendie (1783-1855) heforamina of Luschka are named afterthe German anatomist Hubert vonLuschka (1820-1875) who lent hisname to several structures2.In 1931, Rogers and West3 describedthe anatomy and relations of theforamen of Magendie, presenting it asa complete defect in the lower part ofthe ventricular roof through which thefourthventricleisinfreecommunication with the cisternamagna3. In 1948, Barr4 reportedobservations on the foramen ofMagendie in a series of human brains4.Half century later, Rhoton5 provideddetaileddescriptionsoftheneurosurgical anatomy of the fourthventricle and its foramina5.The primary purpose of this articlewas to review the anatomy of theforamina of the human fourthventricle, as well as the main clinicalconditions related to pathology of theseneurosurgically important structures.The existing literature regarding thegross and neurosurgical anatomy of theforamina of the human fourth ventriclewas reviewed with emphasis on theclinical disorders caused by severalpathological conditions affecting thesestructures. Neuroanatomical commentson the location of these foramina arealso provided.DiscussionThe author has referenced one of hisown studies in this review. Thisreferenced study has been conducted inaccordance with the Declaration ofHelsinki (1964) and the protocols ofthis study have been approved by therelevant ethics committees related tothe institution in which it wasperformed.Anatomy and morphometryThe fourth ventricle is a broad, tentshaped midline cavity located betweencerebellum and brainstem. It isconnected rostrally through thecerebral aqueduct (of Sylvius) with thethird ventricle, caudally with the spinalcanal and through the foramen ofMagendie with vallecula cerebelli (acleft between the cerebellar tonsils)and cisterna magna, and laterallythrough the foramina of Luschka withthe cerebellopontine angles. It has aroof, a floor and two lateral recesses5.The roof expands laterally andposteriorly from its narrow rostral endjust below the aqueduct to the level ofthe fastigium and lateral recess, the siteof its greatest height and width, andfrom there it tapers to a narrow caudalapex at the level of the foramen ofMagendie5. The floor has a rhomboidshape. Its cranial apex is at the level ofthe cerebral aqueduct; its caudal tip, theobex, is located at the rostral end of theremnant of the spinal canal, anterior tothe foramen of Magendie; and its lateralangles open through the lateralLicensee OAPL (UK) 2014. Creative Commons Attribution License (CC-BY)FOR CITATION PURPOSES: Mavridis IN. Clinical anatomy of the fourth ventricle foramina. OA Anatomy 2014 Apr09;2(1):9.Competing interests: None declared. Conflict of interests: None declared.All authors contributed to conception and design, manuscript preparation, read and approved the final manuscript.All authors abide by the Association for Medical Ethics (AME) ethical rules of disclosure.IN Mavridis1*

Page 2 of 5Critical reviewThe choroid plexus of the fourthventricle consists of several segments.Its lateral segments extend laterallythrough the foramina of Luschka(protruding into the cerebellopontineangle below the flocculus and behindthe glossopharyngeal, vagus andaccessory nerves) and its medialsegmentsextendlongitudinallythrough the foramen of Magendie. Themedial segments stretch from thelevel of the nodule, anterior to thecerebellar tonsils, to the level of theforamen of Magendie. The tonsillarparts of the choroid plexus are locatedanterior to the tonsils and extendinferiorly through the foramen ofMagendie5.Ciołkowski et al.6 described themedian aperture (foramen) ofMagendie as the largest of the threeopenings of the fourth ventricle andthus forming the main path for theoutflow of the cerebrospinal fluid(CSF) from the ventricle. TheMagendie foramen makes a naturalcorridor for neurosurgical approachand inspection of the fourth ventricleand its floor6. According to the sameauthors6, this foramen is limited bythe following structures: obex andgracile tubercles inferiorly and telachoroidea with choroid plexussuperolaterally.Obextuberclesusually have the form of a piece ofneural tissue bridging two halves ofthe brainstem above the entrance tothe central canal. Gracile tuberclestogether are 8.15 mm wide and themaximal width of the foramen is 6.53mm. Tela choroidea attaches laterallyat both sides to the inferior medullaryvelum. In most cases the right and leftchoroid plexuses are connected toeach other with a triangularmembrane of tela choroidea, whichprotrudes through the medianforamen and attaches to the vermis ata highly variable level6.Sharifi et al.7 studied 40 humancerebella and distinguished twocompartments of the foramen ofLuschka, namely the choroidal andpatent part. Interestingly, 7.5% of theforamina were closed. The meandistance between the foramen ofLuschka and the anterior inferiorcerebellar artery was 3.9 mm. Thedistance from the posterior inferiorcerebellar artery was 7.08 and 5.81mm to the left and right foramina ofLuschka, respectively. In ten cases,tortuousvertebralarterywasoccupying the left cerebellopontineangle space and the foramen ofLuschka7.The Magendie foramen is, to theauthor’s gross anatomical experience,located 12 mm (9-15 mm) inferior tothe pontomedullary junction, whilethe Luschka foramen is located 1.4mm (0-11 mm) superior to thisjunction. The fourth ventricle extends 9 mm inferior and the Luschkaforamina are located superior to thisjunction (37% placed exactly at thislevel). The Magendie foramen islocated 0.3 mm (0-2 mm) posterior tothe fourth ventricle floor, while theLuschka foramen is located 1.3 mm(0-4 mm) posterior to this floor (16%of the Luschka and 83% of theMagendie foramina were found at thelevel of this floor). Interestingly, theright Luschka foramen seems to belocated 1.5 mm more superior fromthe pontomedullary junction and 0.7mm more posterior from the fourthventricle floor as compared to the left.Longatti et al.8 examined the access tothe fourth ventricle achieved by theendoscopic transaqueductal approach,to enumerate and describe theanatomically identifiable landmarksand to compare them with thosedescribedduringmicrosurgery.Twenty anatomical structures couldconsistently be identified by exploringthe fourth ventricle with a fiberscope,including the foramina of Luschka andMagendie. Neuroendoscopy offers aquite different outlook on the anatomyof the fourth ventricle, and comparedwith the microsurgical descriptions itseems to provide a superior anddetailed visualisation, particularly ofthe structures located in the inferiortriangle8.Clinical conditionsThereareseveralpathologicalconditions of the fourth ventricleforamina, congenital or acquired, whichusuallycausehydrocephalus(principally responsible for clinicalmanifestations),mainlyduetoobstruction of the normal CSF flow.Occlusion of the foramen of Magendie(e.g. by a plexus ependymal cyst) cancause hydrocephalus9. In children,occlusion of the foramen of Magendie isusually the consequence of DandyWalker cysts10 or Arnold-Chiari type Imalformation11. In adults, the occlusionis rather acquired than congenital,linked to infection, head trauma,intraventricular haemorrhage, tumoursor Arnold-Chiari malformation. In rarecases, in children as well as in adults,obstructive hydrocephalus has beenreported due to the occlusion of theforamen of Magendie by a membrane,likely to be an extension of the inferiormedullary velum and the telachoroidea. Until now, the diagnosis wassuggested on indirect data, confirmedby invasive procedures such asventriculography or direct surgicalexploration10.Cystic malformations in the posteriorcranial fossa result from developmentalfailure in the paleocerebellum andmeninges12. Takami et al.12 reported acase of an infant with hydrocephalusassociated with cystic dilation of theforamina of Magendie and Luschka.This 7-month-old female infantpresented with sudden onset of tonicclonic seizures. Computed tomography(CT) scan revealed quadri-ventricularhydrocephalus. Magnetic resonanceimaging (MRI) demonstrated a cystcommunicating with the fourthLicensee OAPL (UK) 2014. Creative Commons Attribution License (CC-BY)FOR CITATION PURPOSES: Mavridis IN. Clinical anatomy of the fourth ventricle foramina. OA Anatomy 2014 Apr09;2(1):9.Competing interests: None declared. Conflict of interests: None declared.All authors contributed to conception and design, manuscript preparation, read and approved the final manuscript.All authors abide by the Association for Medical Ethics (AME) ethical rules of disclosure.recesses and foramina of Luschka5.The foramen of Luschka opens intothe cerebellopontine angle below thejunctionofthefacialandvestibulocochlear nerves with thelateral end of the pontomedullarysulcus5. The lateral recesses arenarrow, curved pouches formed bythe union of the roof and the floor.They extend laterally below thecerebellar peduncles. The anteriorinferior cerebellar artery is intimatelyrelated to the lateral recess and theforamen of Luschka5.