Jugular foramen anatomy and approaches

neurosurgical

1. JUGULAR FORAMEN ANATOMY AND APPROACHES Dr Dikpal

2. Anatomy located at the posterolateral skull base long axis obliquely directed in the posterolateral to anteromedial formed by the petrous temporal bone anterolaterally and by the jugular process of the condylar part of the occipital bone posteromedially

3. The jugular foramen is traditionally divided into a large posterolateral compartment (pars venosa ) and a smaller anteromedial compartment (pars nervosa) three compartments: two venous compartments and one neural intrajugular compartment in between

4. The venous compartments include a large posterolateral sigmoid part and a small anteromedial petrosal part. At the junction : two bony prominences ( intrajugular processes ), arising from the temporal and occipital bones: intrajugular septum

5. The dura over the intrajugular septum has two characteristic perforations : ( 1) The glossopharyngeal meatus for the IX nerve and ( 2) A larger vagal meatus for X and XI nerves

6. The inferior petrosal sinus (IPS) joins the jugular bulb in 90%, passing between the IX nerve superolaterally and the X and XI nerves inferomedially In 10% it drains directly into the internal jugular vein

7. Condylar emissary vein The occipital condyle (OC) contains a condylar emissary vein in 70 % of cases . This posterior condylar vein enters the jugular foramen at its posteromedial part and serves as a landmark to the foramen for the posterior approaches The hypoglossal canal contains a venous plexus, called anterior condylar vein in addition to the XII nerve

8. Relations at skull base

9. Classification of JF lesions Fisch’s and Glasscock and Jacobson’s classification for glomus jugular tumours Keye’s and Franklin’s classification for schwannoma . The one proposed by Bertalanffy and Ulrich is applicable to any type of lesion

10. Bertalanffy and Ulrich classification

11. difficulties in exposing its deep location the carotid artery anteriorly, the facial nerve laterally, the hypoglossal nerve medially, The vertebral artery inferiorly,

12. Surgical approaches Posterior Lateral Anterior

13. Posterior approach Sub occipital (SO) retrosigmoid SO transcondylar SO supracondylar

14. SO retrosigmoid One component of more extensive exposure Main indication ( intradural ) type A schwannoma , acoustic schwannoma epidermoid cyst Intracranial part of JF exposed by dissecting arachnoid around 9,10,11 Disadv : extradural and intrajugular

15. Suboccipital Transcondylar More extended lateral and inferior exposure Bony resection includes Post and medial occipital condyle Jugular tubercle to expose hypoglossal canal Jugular foramen dorsally and inferiorly (post emissary vein landmark) Risk : Injury (VA, CN)

16. Supracondylar app Small lesion limited to hypoglossal canal and medial rim of JF SOC extended down to supracondylar fossa OC and FM preserved Jugular tubercle drilled extradurally Disadv : radical resection not possible

17. Anterolateral Approach Postauricular transtemporal Preauricular subtemporal – infratemporal approach The skin incision: pre- or retroauricular , and starts above the level of the pinna extends in a curvilinear fashion inferiorly into the neck superficial to the SCM

18. Postauricular transtemporal Key component : mastoidectomy and neck dissection Mastoidectomy : involve the intralabyrinthine region with exposure of the sigmoid sinus, jugular bulb, and mastoid portion of the facial nerve Facial nerve mobilsed Rectus capitis lateralis ms detached Hearing does not sacrificed

19. Preauricular subtemporal – infratemporal approach Preauricular incision across zygoma FT craniotomy Mobilisation of TM joint Middle cranial fossa removed , until carotid canal is reached eustachian tube and tensor tympani muscle sacrificed   removal styloid process allows anterior mobilization of the internal carotid artery and access to the clivus . Drilling of Kawase's triangle gains access to the posterior cranial fossa.

20. Fisch description Type A allows access to the temporal bone in its infralabyrinthine and apical compartments Postauricular incision EAC transected Neck dissection : identification of CN , vessels Radical mastoidectomy and subtotal petrosectomy Facial N anterior transposition

21. Both middle and posterior cranial fossa dura in front ( Trautmann's triangle) and behind of the sigmoid sinus are exposed. The petrous internal carotid artery is identified and the eustachian tube is obliterated at its bony isthmus. The mandibular condyle is resected, and the temporal root of the zygoma and lateral orbital rim are removed for additional exposure

22. Lateral approaches Juxtacondylar Lateral skull base

23. Juxtacondylar app Extradural, confined to jugular F Incision : superior nuchal line to medial border of SCM below mastoid Transverse process of atlas removed and VA transposed PL aspect of OA and AA joint exposed Post belly of digastric resected and occipital artery ligated

24. Partial mastoidectomy done distal SS exposed Post inf wall of jugular bulb drilled to expose JF Adv : wide exposure of post inf JF without petrous drilling : preserves hearing Extradural : no csf leak Risk : VA injury , venous bleed

25. Lateral Skull base Conserving Otic capsule infratemporal fossa type A Petro Occipital Trans Sigmoid (POTS) Sacrificing Otic Capsule Translabyrinthine transcochlear

26. I nfratemporal fossa type A Incision : post auricular extending superiorly to temporal region Inferiorly along ant border of SCM

27. EAC closed VII CN exposed by neck dissection Lower CN , ICA, ECA, IJV exposed SCM and Digastric divided ECA ligated beyond Lingual br TM , malleus incus removed Radical mastoidectomy done

28. VII CN freed from geniculate ganglion to stylomastoid foramen and transposed anteriorly Mandibular condyle is resected SS is packed or ligated Lateral wall of SS is opened to bulb and IPS and entry of condylar vein packed ADV : wide exposure of anterior of JF till petrous apex

29. Petro Occipital Trans Sigmoid Infralabyrinthine lateral skull base Indicated for : lower cranial nerve schwannomas with intracranial extensions meningioma of the jugular bulb small petroclival meningiomas lying anterio to the internal auditory canal (IAC) with preserved hearing .

30. Technique: c shaped post auricular incision U shaped musculoperiosteal flap raised SCM retracted post IJV ant to lateral process of atlas identified & ligated Radical mastoidectomy VII CN and JB identified

31. Bone over SS and JB and posterior fossa dura in front of the SS are removed suboccipital craniotomy The infralabyrinthine petrous bone is drilled away taking care not to injure the posterior semicircular canal or VII nerve . The occipital condyle is partially drilled up to the hypoglossal canal

32. SS is then opened and packed distally and proximally A horizontal dural incision is made starting posterior to the SS, coursing anteriorly traversing the medial wall of the SS The removal of the lateral wall of the JB and, if necessary, its medial wall, fully exposes the intracranial part of IX−XI nerves . The dura over the drilled part of the OC is excised exposing the hypoglossal canal

33. ADV: hearing preserved Disadv : limited control over ICA , so involovemet of ICA is contraindication