Spaces of middle ear and their surgical importanceDr Soumya Singh
one of the imp topics in ENT that should be understood very thoroughly if u want to pursue as an otologist.I tried to simplify the topic with simple diagrams and models for better understanding .
I have tried my level best to complete this one. Basics & subjective details as much possible, are included here with understandable diagrams, CT-scans & charts. Clinical associations with possible anatomical structures are also touched . Frequent questions based on the topic discussed, will be there at the middle & end of presentation.
If you find it helpful then please like it & if any query regarding this ppt or upcoming ppts then mail me
drsuraj1997@gmail.com
Development of the middle ear is not covered in this presentation. If you are interested then please mail me. I will try to upload it as a separate one.
Spaces of middle ear and their surgical importanceDr Soumya Singh
one of the imp topics in ENT that should be understood very thoroughly if u want to pursue as an otologist.I tried to simplify the topic with simple diagrams and models for better understanding .
I have tried my level best to complete this one. Basics & subjective details as much possible, are included here with understandable diagrams, CT-scans & charts. Clinical associations with possible anatomical structures are also touched . Frequent questions based on the topic discussed, will be there at the middle & end of presentation.
If you find it helpful then please like it & if any query regarding this ppt or upcoming ppts then mail me
drsuraj1997@gmail.com
Development of the middle ear is not covered in this presentation. If you are interested then please mail me. I will try to upload it as a separate one.
Lateral skull base anatomy and applied science by Dr, bomkar bamBomkar Bam
the lateral skull base is complex anatomy that is usually students finds difficult to understand. here concise literature is made to understand the skull base more easily.
Surgical approach for tumors in the lateral and third ventricleSherif Watidy
Professor Sherif Elwatidy explains in this lecture the approach to the lateral and third ventricle with emphasis on the anatomy of the region and through the trajectory.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Introduction:
RNA interference (RNAi) or Post-Transcriptional Gene Silencing (PTGS) is an important biological process for modulating eukaryotic gene expression.
It is highly conserved process of posttranscriptional gene silencing by which double stranded RNA (dsRNA) causes sequence-specific degradation of mRNA sequences.
dsRNA-induced gene silencing (RNAi) is reported in a wide range of eukaryotes ranging from worms, insects, mammals and plants.
This process mediates resistance to both endogenous parasitic and exogenous pathogenic nucleic acids, and regulates the expression of protein-coding genes.
What are small ncRNAs?
micro RNA (miRNA)
short interfering RNA (siRNA)
Properties of small non-coding RNA:
Involved in silencing mRNA transcripts.
Called “small” because they are usually only about 21-24 nucleotides long.
Synthesized by first cutting up longer precursor sequences (like the 61nt one that Lee discovered).
Silence an mRNA by base pairing with some sequence on the mRNA.
Discovery of siRNA?
The first small RNA:
In 1993 Rosalind Lee (Victor Ambros lab) was studying a non- coding gene in C. elegans, lin-4, that was involved in silencing of another gene, lin-14, at the appropriate time in the
development of the worm C. elegans.
Two small transcripts of lin-4 (22nt and 61nt) were found to be complementary to a sequence in the 3' UTR of lin-14.
Because lin-4 encoded no protein, she deduced that it must be these transcripts that are causing the silencing by RNA-RNA interactions.
Types of RNAi ( non coding RNA)
MiRNA
Length (23-25 nt)
Trans acting
Binds with target MRNA in mismatch
Translation inhibition
Si RNA
Length 21 nt.
Cis acting
Bind with target Mrna in perfect complementary sequence
Piwi-RNA
Length ; 25 to 36 nt.
Expressed in Germ Cells
Regulates trnasposomes activity
MECHANISM OF RNAI:
First the double-stranded RNA teams up with a protein complex named Dicer, which cuts the long RNA into short pieces.
Then another protein complex called RISC (RNA-induced silencing complex) discards one of the two RNA strands.
The RISC-docked, single-stranded RNA then pairs with the homologous mRNA and destroys it.
THE RISC COMPLEX:
RISC is large(>500kD) RNA multi- protein Binding complex which triggers MRNA degradation in response to MRNA
Unwinding of double stranded Si RNA by ATP independent Helicase
Active component of RISC is Ago proteins( ENDONUCLEASE) which cleave target MRNA.
DICER: endonuclease (RNase Family III)
Argonaute: Central Component of the RNA-Induced Silencing Complex (RISC)
One strand of the dsRNA produced by Dicer is retained in the RISC complex in association with Argonaute
ARGONAUTE PROTEIN :
1.PAZ(PIWI/Argonaute/ Zwille)- Recognition of target MRNA
2.PIWI (p-element induced wimpy Testis)- breaks Phosphodiester bond of mRNA.)RNAse H activity.
MiRNA:
The Double-stranded RNAs are naturally produced in eukaryotic cells during development, and they have a key role in regulating gene expression .
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
A brief information about the SCOP protein database used in bioinformatics.
The Structural Classification of Proteins (SCOP) database is a comprehensive and authoritative resource for the structural and evolutionary relationships of proteins. It provides a detailed and curated classification of protein structures, grouping them into families, superfamilies, and folds based on their structural and sequence similarities.
Slide 1: Title Slide
Extrachromosomal Inheritance
Slide 2: Introduction to Extrachromosomal Inheritance
Definition: Extrachromosomal inheritance refers to the transmission of genetic material that is not found within the nucleus.
Key Components: Involves genes located in mitochondria, chloroplasts, and plasmids.
Slide 3: Mitochondrial Inheritance
Mitochondria: Organelles responsible for energy production.
Mitochondrial DNA (mtDNA): Circular DNA molecule found in mitochondria.
Inheritance Pattern: Maternally inherited, meaning it is passed from mothers to all their offspring.
Diseases: Examples include Leber’s hereditary optic neuropathy (LHON) and mitochondrial myopathy.
Slide 4: Chloroplast Inheritance
Chloroplasts: Organelles responsible for photosynthesis in plants.
Chloroplast DNA (cpDNA): Circular DNA molecule found in chloroplasts.
Inheritance Pattern: Often maternally inherited in most plants, but can vary in some species.
Examples: Variegation in plants, where leaf color patterns are determined by chloroplast DNA.
Slide 5: Plasmid Inheritance
Plasmids: Small, circular DNA molecules found in bacteria and some eukaryotes.
Features: Can carry antibiotic resistance genes and can be transferred between cells through processes like conjugation.
Significance: Important in biotechnology for gene cloning and genetic engineering.
Slide 6: Mechanisms of Extrachromosomal Inheritance
Non-Mendelian Patterns: Do not follow Mendel’s laws of inheritance.
Cytoplasmic Segregation: During cell division, organelles like mitochondria and chloroplasts are randomly distributed to daughter cells.
Heteroplasmy: Presence of more than one type of organellar genome within a cell, leading to variation in expression.
Slide 7: Examples of Extrachromosomal Inheritance
Four O’clock Plant (Mirabilis jalapa): Shows variegated leaves due to different cpDNA in leaf cells.
Petite Mutants in Yeast: Result from mutations in mitochondrial DNA affecting respiration.
Slide 8: Importance of Extrachromosomal Inheritance
Evolution: Provides insight into the evolution of eukaryotic cells.
Medicine: Understanding mitochondrial inheritance helps in diagnosing and treating mitochondrial diseases.
Agriculture: Chloroplast inheritance can be used in plant breeding and genetic modification.
Slide 9: Recent Research and Advances
Gene Editing: Techniques like CRISPR-Cas9 are being used to edit mitochondrial and chloroplast DNA.
Therapies: Development of mitochondrial replacement therapy (MRT) for preventing mitochondrial diseases.
Slide 10: Conclusion
Summary: Extrachromosomal inheritance involves the transmission of genetic material outside the nucleus and plays a crucial role in genetics, medicine, and biotechnology.
Future Directions: Continued research and technological advancements hold promise for new treatments and applications.
Slide 11: Questions and Discussion
Invite Audience: Open the floor for any questions or further discussion on the topic.
Richard's aventures in two entangled wonderlandsRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
Nutraceutical market, scope and growth: Herbal drug technologyLokesh Patil
As consumer awareness of health and wellness rises, the nutraceutical market—which includes goods like functional meals, drinks, and dietary supplements that provide health advantages beyond basic nutrition—is growing significantly. As healthcare expenses rise, the population ages, and people want natural and preventative health solutions more and more, this industry is increasing quickly. Further driving market expansion are product formulation innovations and the use of cutting-edge technology for customized nutrition. With its worldwide reach, the nutraceutical industry is expected to keep growing and provide significant chances for research and investment in a number of categories, including vitamins, minerals, probiotics, and herbal supplements.
Seminar of U.V. Spectroscopy by SAMIR PANDASAMIR PANDA
Spectroscopy is a branch of science dealing the study of interaction of electromagnetic radiation with matter.
Ultraviolet-visible spectroscopy refers to absorption spectroscopy or reflect spectroscopy in the UV-VIS spectral region.
Ultraviolet-visible spectroscopy is an analytical method that can measure the amount of light received by the analyte.
(May 29th, 2024) Advancements in Intravital Microscopy- Insights for Preclini...Scintica Instrumentation
Intravital microscopy (IVM) is a powerful tool utilized to study cellular behavior over time and space in vivo. Much of our understanding of cell biology has been accomplished using various in vitro and ex vivo methods; however, these studies do not necessarily reflect the natural dynamics of biological processes. Unlike traditional cell culture or fixed tissue imaging, IVM allows for the ultra-fast high-resolution imaging of cellular processes over time and space and were studied in its natural environment. Real-time visualization of biological processes in the context of an intact organism helps maintain physiological relevance and provide insights into the progression of disease, response to treatments or developmental processes.
In this webinar we give an overview of advanced applications of the IVM system in preclinical research. IVIM technology is a provider of all-in-one intravital microscopy systems and solutions optimized for in vivo imaging of live animal models at sub-micron resolution. The system’s unique features and user-friendly software enables researchers to probe fast dynamic biological processes such as immune cell tracking, cell-cell interaction as well as vascularization and tumor metastasis with exceptional detail. This webinar will also give an overview of IVM being utilized in drug development, offering a view into the intricate interaction between drugs/nanoparticles and tissues in vivo and allows for the evaluation of therapeutic intervention in a variety of tissues and organs. This interdisciplinary collaboration continues to drive the advancements of novel therapeutic strategies.
2. INTRODUCTION
• Temporal bone is a composite structure
consisting of tympanic bone, mastoid process,
squama and petrosa.
• Styloid process eventhough is closely associated with temporal bone,
is not considered as a part of it.
• From lateral view……, tympanic, squamous and
mastoid portions are seen.
• All these parts are interfaced at their junctions
forming tympano-squamous suture, tympano-
mastoid suture and squamo-mastoid suture.
3. Tympanic bone
• Tympanic bone forms anterior, inferior and parts of posterior wall of
EAC.
• It constitutes posterior wall of glenoid fossa for TMJ.
• Tympano-mastoid suture is traversed by arnold’s nerve.
• Chorda tympani, anterior process of malleus and anterior tympanic
artery traverse the petro-tympanic fissure.
• Henle’s spine is a projection at
postero-superior aspect of
external auditory canal.
4. Tympanic bone cont….
• Inferiorly, the vaginal process, a projection of tympanic bone, forms
the sheath of the styloid bone.
• Laterally, tympanic bone borders the cartilaginous EAC and
medially it bears a circular groove called annular sulcus.
• Annular sulcus houses the annulus of TM except
superiorly, where it is deficient called as notch of
rivinus where tympanic membrane
attaches directly to the squama.
• Tympano-squamous and tympano-mastoid sutures are
landmarks for the vascular strip incisions used in
tympanomastoid surgery.
5. Squamous bone
Squamous portion of temporal bone
forms lateral wall of middle cranial fossa
and interfaces with parietal bone
superiorly, with zygomatic & sphenoid
anteriorly.
Medial surface is grooved by a
sulcus for middle meningeal
artery and lateral surface for
middle temporal artery.
6. Mastoid bone
• Mastoid portion of temporal bone is the inferiorly extending
projection seen on lateral surface.
• It is composed of squamous portion
laterally and petrous portion medially
separated by petrosquamous korner’s septum.
• Macewen’s triangle (fossa mastoidea) –
linea temporalis, posterosuperior margin of
EAC and a tangent to posterior margin of
EAC. It is a cribrose area having numerous,
perforating small blood vessels. It laterally
overlies the mastoid antrum.
7. Mastoid bone cont….
• Mastoid foramen, located posteriorly on the mastoid
process, is traversed by a mastoid emissary vein and
1 or 2 mastoid arteries.
• Inferiorly, sternocleidomastoid attaches to mastoid tip.
• Mastoid tip is easily palpable & is landmark for
positioning of postauricular incisions.
• Linea temporalis is an avascular plane due to which
it is an ideal location for the superior limb of ‘T’
musculoperiosteal incision used in the postauricular
approach to the tympanomastoid compartment.
8. Mastoid bone cont….
• Mastoid process in children is not fully developed, thus cannot be
palpated easily.
• Hence, postauricular incision in children should be given more
horizontally to prevent injury to the facial nerve.
9. Styloid process
• 2.5 cm in length.
• Slender, pointed piece of bone below
the ear.
• Projects down & forwards from inf
surface of temporal bone.
• Proximal tympanohyal part is ensheathed by vaginal process of
tympanic bone.
• Distal stylohyal part gives attachment to –
• Ligaments – stylohoid & stylomandibular
• Muscles – styloglossus, stylohyoid & stylopharyngeal
10. Styloid process cont….
• Stylomandibular ligament is a specialised band of
cervical fascia which extends from anterior surface
of apex of styloid process to the posterior surface
of the angle of mandible.
• This ligament separates parotid gland from submandibular gland &
medial pterygoid muscle.
• Eagle syndrome is characterised by recurrent
pain in the oropharynx and face due to
elongated styloid process or calcified
stylohyoid ligament which interferes with
adjacent anatomical structures giving rise to
pain.
11. Temporal bone cont….
• Petrosa can be seen in superior, medial and posterior views.
• From superior view, landmarks seen are –
• Arcuate eminence (corresponding to sup scc)
• Tegmen tympani
• Foramen spinosum (for middle meningeal art)
• Facial hiatus (marking GPN departure from GG)
• Petrous ridge (sup petrosal sinus resides on it)
• Lesser petrosal nerve + superior tympanic artery = occupies superior
tympanic canaliculus that lies lateral and parallel to the path of GPN to
petrous apex.
• Petrous apex points anteromedially and is marked by the transition of
the intrapetrous to the intracranial ICA, orifice of bony ET & ganglion
of trigeminal nerve in meckels cave anterolaterally.
12. Temporal bone cont….
Arcuate eminence –
• Key landmark in MCF surgeries where IAM can be identified. The bone
anteromedial to AA & GSPN is the meatal plane and lies above the IAC.
It is often marked by a shallow depression.
• In this region, dura is firmly attached on medial side & loosely
attached on lateral side
Meckel’s cave –
• In trigeminal neuralgia cases, glycerol injection is given in gasserion
ganglion located in this area.
13. Temporal bone cont….
• Medial view of temporal bone –
• Porus of IAC
• ICA exits at petrous apex through internal carotid foramen
• Deep sulcus posteriorly – sigmoid portion of lateral venous sinus
• Sulcus at posterior & middle fossa faces of temporal bone – superior petrosal
sinus runs in it.
• Cochlear aqueduct
• Vestibular aqueduct
• Mastoid process
• Styloid process
• Jugular fossa
14. Temporal bone cont….
Posterior view –
• Posterior face of petrosa dominates
• Lies between superior & inferior petrosal sinuses
• It forms ant border of post cranial fossa.
• Landmarks –
• Porus of IAC
• Operculum
• Endolymphatic fossette cradling endolymphatic sac
• Subarcuate fossa
15. Temporal bone cont….
• Sigmoid sulcus is an indentation at the
lateral aspect of post surface and
accommodates sigmoid sinus.
• Anterior to SS, lies the foveate fossa for intradural portion of
endolymphatic sac.
• Operculum, a ledge at the superior extent of the fossa covers
intraosseous portion of endolymphatic sac.
• Vestibular aqueduct runs anteriorly, medially & superiorly from
operculum to end at the medial wall of vestibule.
• Sup petrosal sulcus at the interface between MCF & PCF plates of
temporal bone carries SPS from SS.
16. Temporal bone cont….
Inferior surface –
• Interfaces with sphenoid & occipital
bones.
• Provides attachment for deep muscles of neck
• Jugular fossa – houses jugular bulb, separated from ICA by
jugulocarotid crest.
• Inferior tympanic artery & jacobson’s nerve passing through aperture
of inferior tympanic canaliculus, is seen in the jugulocarotid crest
• Cranial aperture of cochlear aqueduct – anteromedial to jugular fossa
• Groove for inferior petrosal sinus – near petrous apex
17. Temporal bone cont….
• Stylomastoid foramen – posterior to styloid process.
• Occipital artery – occipital groove
• Digastric muscle – mastoid incisure
• Jugular foramen Contents – IX, X, XI cranial nerves + Post meningeal art + Inf
petrosal & sigmoid sinuses.
Medial aspect
of the tip
IJV & JB are removed
18. Temporal bone cont….
• Classically, jugular foramen has been
divided into anteromedial pars nervosa
consisting IX, X, XI CN and posterolateral
pars venosa containing the jugular vein.
• Styloid process lies lateral to jugular
foramen.
• Glomus jugulare tumours are rare, slow-
growing, hypervascular tumors that arise
within the jugular bulb.
• Phelp’s sign – loss of crest of bone as seen
in CT between carotid canal & jugular
canal in glomus jugulare.
19. Temporal bone cont….
• In jugular fossa
• IX CN lies more ant & lat
• X, XI CN are located post & med to IX CN
• CN XI is generally identified as it crosses over IJV in the
neck & lat pr of atlas. Sometimes, it can pass medial to IJV.
• When approached intracranially, IX CN is found in the a
anteromed compartment & X, XI CN are posterolateral.
• Hence it is suggested to consider jugular fossa as a canal rather than
an opening so that the IX CN courses from anteromedial to
anterolateral as it passes out of the skull making X & XI CN lying
posterolateral initially and then posteromedially.
20. Temporal bone cont….
• Hypoglossal canal –
• Located in the anterior portion of occipital
condyle & anteroinferior to the jugular foramen.
• Carries XII cranial nerve that courses medial to
cranial nerve X and inferior to jugular foramen.
Inferior petrosal sinus –
Drains into anterior aspect of jugular bulb.
Runs inferior & medial to IX cranial nerve
Runs superior & lateral to X, XI cranial nerves
21. Temporal bone cont….
Cochlear aqueduct –
• Runs from medial aspect of scala tympani of basal cochlear turn to
terminate anteromedial to the jugular bulb lying parallel & inf to IAC.
• In translabyrinthine CPA tumor surgery, drilling
medial to jugular bulb opens it and CSF flows into
mastoid decompressing CSF pressure.
• IX nerve, inf petrosal sinus are found immediately
inferior to the lateral terminus of it (X & XI also in
some cases).
• Therefore, it can be used as a guide to the lower limits of
IAC dissection in translabyrinthine approach as it allows full
exposure of IAC without risking the lower cranial nerves.
22. Temporal bone cont….
INNER EAR –
• Bony labyrinth houses sensory organs & soft tissue structures of the
inner ear and consists of cochlea, 3 scc & vestibule.
• Bone has 3 layers – inner endosteal, outer periosteal & middle layer
consisting of endochondral and intrachondrial bone.
• Cochlea spirals 2.5 turns about its central axis,
the modiolus and height of it is 5mm.
• Base of cochlea abuts
the fundus of IAC & is
perforated by cochlear
nerve fibres.
23. Temporal bone cont….
• Apex lies medial to tensor tympani muscle.
• Osseous spiral lamina winds around the modiolus and along with
basilar membrane separates scala media from scala tympani.
• Interscalar septum separates adjacent turns of cochlea.
• 3 scc – superior, posterior & lateral are orthogonally
related to one another and arc over a span of 240 degrees.
• Each canal has an ampullated (2mm) & a nonampullated (1mm) end.
• Ampulla is cribrose for passage of nerve fibres.
• Nonampullated ends of posterior & superior
scc fuse to form crus commune.
24. Temporal bone cont….
• All ends open into the vestibule.
• Solid angle – angle formed by the 3 scc
• Trautmanns triangle – bony labyrinth, sigmoid
sinus & superior petrosal sinus are the boundaries.
• Thinning or frank dehiscence of the bone of superior
scc may cause sound or pressure induced vertigo.
• Vestibule is the central chamber of
labyrinth & is 4mm in diameter.
• Medial wall of vestibule – spherical recess for saccule &
elliptical recess for utricle and a cochlear recess for
cochlear duct.
25. Temporal bone cont….
• Mike’s dot – (macula cribrosa superior) :-
passageway for superior vestibular nerve
fibres to the cristae ampullares of lateral and superior scc. It is an
important landmark in translabyrinthine surgery as it corresponds to
the extreme lateral aspect of IAC.
• Fissures in bony labyrinth – 3 in number.
• Fissula ante fenestrum - evagination of the perilymphatic space anterosuperior
to oval window, filled with fibrous tissue & cartilage in adult
• Fossula post fenestrum – perilymphatic evagination posterior to oval window.
• Hyrtle’s fissure (tympanomeningeal hiatus) – embryologic remnant.
26. Temporal bone cont….
• Microfissures – 2 in number.
• 1) between round window niche & ampulla of
posterior scc
• 2) superior & inferior to oval window.
• Microfissures are breaks in the endosteal and enchondral layers of
temporal bone, and filled with fibrous tissue & acellular matrix.
• Hyrtle’s fissure if persistent is a route of CSF leakage into ME.
• Other fissures are hypothesised to be the routes of perilymph leakage.
27. Temporal bone cont….
• Membranous labyrinth consists of cochlear duct,
3 scd & their cristae ampullares, otolithic organs like utricle & saccule,
endolymphatic duct & sac.
• Space between bony & membranous labyrinths are filled with
connective tissue, blood vessels, perilymph + s.tympani, s.vestibuli,
perilymphatic cistern of vestibule, perilymphatic duct, perilymph
spaces surrounding the scd.
• Endolymphatic duct originates in med wall of vestibule.
• It first parallels crus commune & then posterior scc as
it heads to endolymphatic sac, anterior & medial to
sigmoid sinus.
28. Temporal bone cont….
• Endolymphatic sac lies 10mm inferior & lateral to porus of IAC. It has
an intraosseous portion covered by operculum and a more distal
intradural portion.
• Donaldson’s line – a surgical landmark in endolymphatic sac surgery, is
derived by extending the plane of the lateral scc so that it bisects the
posterior scc and contacts the posterior fossa dura. Endolymphatic sac
lies inferior to this line.
30. Temporal bone cont….
• The nerves rotate as we progress medially, with
fusion of the cochlear & vestibular nerves.
• Facial nerve comes to lie anterior to
vestibulocochlear bundle
• Cochlear nerve moves to lie inferior to the
vestibular nerve.
• Bill’s bar – important landmark in translabyrinthine
surgery of CPA tumor as it separates SVN from
anteriorly located facial nerve.
31. NEUROANATOMY
TRIGEMINAL NERVE –
• Gasserian ganglion of trigeminal
nerve occupies meckel’s cave on
middle cranial fossa face of the
temporal bone, anterolateral to the petrous apex.
SUP VIEW
SAGITTAL VIEW
32. NEUROANATOMY cont….
ABDUCENS NERVE –
• Abducens nerve runs in dorello’s canal beneath
posterior petroclinoid (gruber’s) ligament.
• Petrous apicitis can manifest with purulent
otorrhea, retro-orbital pain and VI nerve palsy.
33. NEUROANATOMY cont….
FACIAL NERVE –
• Innervates structures derived
from Reichert’s cartilage.
• 3 nuclei give rise to its fibres –
• Motor nucleus in caudal pons
• Superior salivatory nucleus dorsal to motor
nucleus
• Nucleus tractus solitarius in medulla
oblongata
• Superior aspect of the motor nucleus that
innervates frontalis and orbicularis oculi,
receives input from both sides but
inferior portion receives only ipsilateral
input.
34. NEUROANATOMY cont….
• 5 fibre types make up the
trunk of the facial nerve.
• SVE – facial expression,
stapedius, stylohyoid, digastric
post belly
• GVE – lacrimal, nasal cavity
seromucinous, submaxillary,
sublingual
• Taste ( sensory ) fibres from
ant 2/3rd tongue, tonsillar
fossae, posterior palate
• Somatic sensory from EAC &
concha
• Visceral afferent from mucosa
of nose, pharynx, palate.
35. NEUROANATOMY cont….
Course of the facial nerve is divided into 5 segments.
• Intracranial segment – 24mm from pons to the porus of IAC
• Intracanalicular segment – traverses IAC, occupies anterosuperior
quadrant at fundus where it is joined by nervus intermedius.
• Intralabyrinthine segment – shortest, 4mm, from beginning of
fallopian canal to the geniculate ganglion.
• Tympanic segment – 13mm long, courses in the medial wall of
the tympanic cavity, superior to the cochleariform process & oval
window.
• Mastoid segment – 20mm, from 2nd genu (at lat scc) to
stylomastoid foramen.
37. NEUROANATOMY cont….
Anomalous courses –
• Tympanic segment may be anterior and inferior to oval window.
• Mastoid segment may bulge more posteriorly & laterally than usual.
• Vertical segment may be bi or tripartite.
Fallopian canal dehiscences –
• Most likely site is tympanic segment over oval window.
Subarachnoid space –
• extends till junction of labyrinthine & tympanic segments.
• Occasionally it extends into GG or rarely into tympanic segment.
38. NEUROANATOMY cont….
• CSF otorrhea may occur in such cases as proposed by
Gacek.
Branches of facial nerve –
• Intratemporal –
• Greater petrosal nerve – arises from anterior
aspect of GG & emerges onto floor of MCF via
the facial hiatus.
• Nerve to stapedius – arise from mastoid
segment near pyramid.
• Chorda tympani – 6mm proximal to
stylomastoid foramen.
39. NEUROANATOMY cont….
Facial recess –
• Triangular area inferior to the incudal fossa.
• Lateral to facial nerve vertical segment.
• Medial to chorda tympani nerve.
• Used in intact canal wall mastoidectomy to gain access to ME.
Nervus intermedius (nerve of wrisberg) –
• Carries taste, secretory & sensory fibres of facial nerve.
• Runs separate in IAC
• Occupies dorsal aspect in tympanic segment & posterolateral aspect in
mastoid segment.
40. NEUROANATOMY cont….
Cochlear nerve –
• Arise from spiral ganglion neurons.
• At the fundus, it is in anteroinferior compartment.
• Rotates as it heads towards porus
• Enters brainstem a few mm caudal to root entry
zone of V nerve.
Vestibular nerves –
• SVN & IVN occupy posterior half of IAC.
• SVN innervates superior & lateral scc, utricular
macula, superior saccular macula.
• IVN innervates inferior saccular macula
• Posterior ampullary br of IVN, separates a few mm
away from porus, traverses singular canal to
posterior canal ampulla and supplies post scc.
41. NEUROANATOMY cont….
Sensory nerves of tympanomastoid compartment –
• Jacobson’s nerve (tympanic br of IX nerve) -
• Arises from petrosal ganglion located in petrosal fossa of jugulocarotid crest
• Through inferior tympanic canaliculus, enters ME along with inf tymp art
• Then it climbs the promontory to meet caroticotympanic plexus.
• Lesser petrosal nerve is formed here by joining of pregaanglionic
parasympathetic jacobson fibres with postganglionic sympathetic
caroticotympanic plexus.
• LPN heads to floor of MCF within or parallel to semicanal of tensor tympani.
• Jacobson’s nerve mediates otalgia from pharynx.
42. NEUROANATOMY cont….
• Arnold’s nerve (auricular br of X nerve)-
• It has fibres from VII, IX & X nerves.
• Originates in jugular foramen
• Passes over dome of jugular bulb (via mastoid canaliculus)
• Enters fallopian canal
• It has been implicated in herpetic involvement of the EAC in herpes zoster
oticus and the cough reflex elicited by manipulation of EAC.
43. VASCULAR ANATOMY
Temporal bone arteries –
• ICA :-
• Enters temporal bone through external
carotid foramen located anteromedial to
styloid process.
• Course in intrapetrous segment –
• 1st passes anterior to tympanic cavity &
cochlea
• Then bends (it’s knee) to run medial to ET &
inferomedial to semicanal of TT muscle
• Then it climbs to exit the temporal bone at
internal carotid foramen.
• Venous & sympathetic plexus accompanies it
throughout intrapetrous course.
• Bony shell covering it is very thin (<0.5mm)
and dehiscent in 6% cases.
• In ME surgeries, medial wall of ET gently
dissected not to injure ICA.
44. VASCULAR ANATOMY cont….
• Anterior Inferior Cerebellar Artery –
• AICA often extends a loop into the IAC.
• This may cause symptoms like vertigo & tinnitus.
• Disruption of AICA causes haemorrhage in and infarction of the labyrinth &
brainstem.
Temporal bone veins –
• 3 dominant sinuses are sigmoid, superior
petrosal & inferior petrosal.
• Sigmoid is a portion of lat venous sinus.
45. VASCULAR ANATOMY cont….
• Sup sagittal & straight sinuses
merge at the internal occipital
protuberance.
• Right and left transverse sinuses
extend beyond this junction & lie
inferior to the tentorium.
• Anteriorly, sup petrosal sinus joins
the transverse sinus and this
junction marks the beginning of
sigmoid sinus.
46. VASCULAR ANATOMY cont….
• Lateral venous sinus
• occupies an S-shaped sulcus in posterior mastoid extending from transverse
sinus to internal jugular vein.
• Angle of citelli – angle between sigmoid sinus/
PCF dura and the MCF dura.
• Superior petrosal sinus
• drains cavernous into lateral venous.
• Runs in sup petrosal sulcus at junction of
PCF & MCF dural plates.
• Inferior petrosal sinus
• Courses in petro-occipital suture line.
• Drains cavernous into jugular bulb.
47. VASCULAR ANATOMY cont….
• Emissary veins are drainage routes of the dural venous sinuses
through the skull that communicate with the superficial veins of the
scalp.
• A fairly constant emissary vein, the mastoid emissary vein, can be
found at the junction of the temporal and occipital bones and usually
communicates with the occipital or postauricular vein.
Greisinger’s sign –
• Tenderness and edema over the mastoid are
pathognomonic for suppurative thrombo-
phlebitis of the sigmoid sinus and reflect
thrombosis of mastoid emissary vein.
49. VASCULAR ANATOMY cont….
• Arachnoid granulations (pacchionian bodies) –
• projections of pia-arachnoid into the venous sinuses & venous lacunae
• are extensions of subarachnoid space.
• also extend from arachnoid of MCF & PCF into adjacent mastoid air cells.
• Gacek linked adult onset spontaneous CSF leak to these granulations.
• Jugular bulb –
• Between sigmoid sinus & internal jugular vein
• Has a thin wall that does not contract with bipolar & is prone to rupture
• High-riding (extending above the level of inferior tympanic annulus) jugular
bulbs have a very thin wall (0.1-0.3mm). It encroaches <2mm inferior to IAC. It
may mimic ME vascular mass like glomus tympanicum
50. VASCULAR ANATOMY cont….
Middle ear blood vessels –
• Inferior tympanic artery
• Br of ascending pharyngeal (br of ECA)
• Traverses inferior tympanic canaliculus with jacobson nerve.
• Feeder of tympanic paragangliomas
• Anastomotic network of tympanum –
• Formed by br of ECA like ant tympanic, deep auricular, mastoid, stylomastoid,
superficial petrosal & tubal……
51. VASCULAR ANATOMY cont….
Labyrinthine vessels –
• Labyrinthine artery
• Br of AICA
• Subarcuate artery
• Br of labyrinthine or AICA or both
• Passes within arch of sup scc.
52. VASCULAR ANATOMY cont….
Facial nerve vessels –
• Intrinsic system
• Runs within the nerve
• Poorly developed in labyrinthine segment
• Well developed in tympanic & mastoid segments
• Extrinsic system
• AICA supplies intracranial segment
• Superficial petrosal supplies GG & superior mastoid segment
• Stylomastoid artery supplies inferior mastoid segment