IPS 360°24-4-2016

1.47am

Great teachers – All this is their work . I am just the reader of their books .

Prof. Paolo castelnuovo

Prof. Aldo Stamm Prof. Mario Sanna

Prof. Magnan

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IPS & HVP hypoglossalvenous plexus

Cadaveric dissection image showing the hypoglossal nerve exiting the hypoglossal foramen with its corresponding vein thatcommunicates the internal jugular vein with the basilar plexus

JT = jugular tubercle separates the hypoglossal canal from Jugular foramen

The petrous portion of the temporal bone or pyramid is pyramidal

the anterior petrosectomy with preoperative embolization of the inferior petrosal sinus is a time-conserving approach giving one of the best routes to reach the ventral brainstem while working in front of the cranial nerves and

preserving hearing.http://www.worldneurosurgery.org/article/S0090-3019(00)00271-8/fulltext

The Petro-occipital Fissure- contains IPS

The Petro-occipital Fissure- contains IPS

Exocranial & Endocranial views of Jugular Foramen : Within the JF

area 2 venous compartement can be identified: a large postero-lateral_SIGMOID_venous channel and a small antero-medial_PETROSAL_venous

channel which can receive the drainage of the inferior petrosal sinus (IPS). An intermediary neural compartment is located between the venous ones and houses

lower cranial nerves (IX, X, XI).

CC carotid canal, CR carotid ridge, ESF endolymphatic sac fossa, FS foramen spinosum, IAM internal acoustic meatus, JT jugular tubercle, OC occipital condyle, PCF petroclival fi ssure, SAF subarcuate fossa, SP styloidprocess, SSG sigmoid sinus groove, TB tympanic bone, VPTB vaginal process of the tympanic bone, white

arrow intrajugular process of the temporal bone, red arrow external ori fi ce of the hypoglossal canal, violet arrow petroclival fi ssure, blue-sky arrow tubal isthmus, black arrow endocranial orifice of the hypoglossal canal, orange arrow trigeminal impression, green arrow pyramidal fossa, black asterisks intrajugular ridge,

black circle intrajugularprocess of the occipital bone

Usually inferior petrosal sinus opens into jugular bulb

Sometimes along with jugular bulb opening , it opens into internal jugular vein also [ lower single arrow in below photo ]

Inferior petrosal sinus

a. IPS inferior to nerve IX and superior to nerves X and XII.

b. IPS inferior and medial to all four nerves.

c. IPS superior and lateral to all four nerves

d. A second IPS joining the internal jugular vein passing medial to IX and lateral to X, XI, and XII

An anatomical classification according to the level of the inferior petrosal sinus–internal jugular vein junction has been developed

1. Junction at the level of the jugular bulb

2. Junction at the level of the anterior condylar vein junction (extracranialopening of the hypoglossal canal)

3. Junction at the level of the lower extracranial jugular vein

• CoC - level of the condylarcanal

• IJV- internal jugular vein

• JF- level of the jugular foramen

• SS- sigmoid sinus

• VVP- vertebral venous plexus

4. Multiple junctions: upper junction at the level of the jugular bulb and lower junction at the level of the anterior condylar vein

a )Multiple upper junctions at the level of the jugular bulb (JB).

b )Multiple junctions: upper junctions at the level of the jugular bulb and lower junction at the level of the anterior condylar vein.

c) No connection between the internal petrosal sinus and the internal jugular vein. The sinus drains in the vertebral venous plexus.

In Transcochlear approach

In infratemporal fossa [=intact cochlear approach –Dr.Morwani ] type B approach

See IPS in Kawase approach

Inferior petrosal sinus is superior to jugular tubercle & hypoglossal canal is inferior to jugular tubercle

Infratemporal fossa [=intact cochlear approach – Dr.Morwani ] type B approach

See IPS & SPS in below photo A dissection from the superior aspect of the temporal bone. The horizontal portion of the

internal carotid artery (ICA) is identified and its anterior medial part is covered by the gasserianganglion (GsG). The greater superficial petrosal (gspn) nerve runs on the superolateral aspect of

the artery.

Right sided anterior petrosectomy on a cadaver dissection: intradural exposureand operative field. PCA Petrous carotid artery; DPA drilled petrous apex; IPS

inferior petrosal sinus; BA basilar artery; VI 6th cranial nerve; AICA anterior inferiorcerebellar artery; P pons; V 5th cranial nerve

NOTE Inferior petrosal sinus at CLIVUS ICAc cavernous portion of the internal carotid artery, IPS inferior petrosal sinus, PAp petrous

apex, SPCG sphenopetroclival gulf, cVIcn cisternal segment of the abducens nerve, gVIcn gulfarsegment of the abducens nerve, pVIcn petrosal segment of the abducens nerve, white asterisks

dura of the posterior cranial fossa

In infrapetrous approach there are chances of injury to 6th nerve [ in dorello’scanal medial to paraclival carotid ] & 12th nerve

In middle cranial fossa approach

In middle cranial fossa approach

ITFA with TranscondylarTranstubercular approach

Here Transcondylar is through Occipital Condyle ;

Transtubercular is through Jugular tubercle

* occipital condyle , IJV internal jugular vein , IPS inferior petrosal sinus , JB jugular vein , PCV posterior condylar vein , SS sigmoid sinus

Note the relationship among the sigmoid sinus, jugular bulb, posterior condylar vein, vertebral artery, and lower cranial nerves. C1 atlas , C2N C2 nerve , JB jugular bulb , PCV posterior

condylar vein SS sigmoid sinus , TP transverse process of C1 , VA vertebral artery , X vagus nerve , XI spinal accessory nerve

The posterior condylar vein crossing the occipital condyle is noted.ICA internal carotid artery , JB jugular bulb , PCV posterior condylar vein

IX glossopharyngeal nerve , XI spinal accessory nerve

After removal of the posterior condylar vein and further removal of the occipital condyle (OC), the hypoglossal nerve (XII) is noted. , ICA internal carotid artery , JB jugular bulb

JT jugular tubercle , OC occipital condyle , VA vertebral artery , XI spinal accessory nerve , XII hypoglossal nerve

The lower cranial nerves have an intimate relationship with the jugular tubercle (three black arrows). When the occipital bone and jugular tubercle are being drilled, careful attention should be paid to avoiding damage to the lower cranial nerves. , Cbl cerebellum , ICA internal carotid artery , OC occipital condyle , TP transverse process of the C1 vertebra , VA vertebral artery , VIII cochleovestibular nerve , IX

glossopharyngeal nerve , XI spinal accessory nerve

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