Cochlear implant - line diagrams

Cochlear implant - Line
diagrams
22-06-2017
2.32 pm

Dr. N. Murali Chand MS (ENT ) DLO, FHM
Fellowship in HIV medicine
Websites = www.skullbase360.in & www.integratedmedicine.co.in
Youtube =
https://www.youtube.com/channel/UC3vRSTN8Rx46MQwq06XRJIA/playlists
CELL = +919949677605

Updated further time to time –
check www.skullbase360.in
Dr. N. Murali Chand MS (ENT ) DLO, FHM
Fellowship in HIV medicine
Websites = www.skullbase360.in & www.integratedmedicine.co.in
Youtube =
https://www.youtube.com/channel/UC3vRSTN8Rx46MQwq06XRJIA/pl
aylists
CELL = +919949677605

The lecture of this PPT present in youtube video ( Cochlear
implant surgery concepts )
https://www.youtube.com/watch?v=aRnKkjiJHn4&t=203
0s
abnormal cochleas lecture videos present in
https://www.youtube.com/playlist?list=PLZquE6mn0cym
Eae9sQZK2N_1AVIFNjttd

OW = oval window ; RW = round window ; H = Helicotrema
OW & RW & H forms 90 degree
triangle
Centre of OW roughtly
corresponds to groove for tensor
tympani

Below RW devided into 4 quadrants

In difficult conditions where finding RW is difficult try
to identify FUSTIS , it leads to RW

In “ RW insertion ” technique , RW membrane is incised [ red
mark ] at anterior inferior quadrant of RW membrane after
drilling RW operculum – which leads to scala tympani

MC = Margin Cochleostomy ;
Cf = Crista fenestrae ; OSL =
Osseus spiral laminae ; OW =
Owter wall of basal turn
MARGIN
COCHLEOSTOMY – in
some patients Crista
Fenestrae has to be
drilled to expand
round window to
access scala tympani

ANTERO- INFERIOR COCHLEOSTOMY . When we devide round
window into 4 quadrants , at anterior & inferior quadrant area if
we make cochleostomy it becomes anterior-inferior
cochleostomy

The round inferior to Antero-inferior cochleostomy is
INFERIOR COCHLEOSTOMY , which is direct trajectory
to scala tympani

cochleostomy made anterior to anterior & superior quadrant
of RW is called SUPERIOR COCHLEOSTOMY – Which you are
NOT supposed to do in CI surgery

If we drill between OW & RW it is
SCALA VESTIBULAR COCHLEOSTOMY

If we drill 2 mm anterior to OW it is MIDDLE TURN COCHLEOSTOMY- Don’t
drill more than 2 mm anteior to OW because there are chances of injuring
the labyrinthine part of facial nerve in DANGEROUS TRIANGLE or PARISIER’S
TRIANGLE .

Relation of middle
turn cochleostomy
in relation to
dangerous triangle
– explained
further indetail

Osseus spiral laminae is seen through SUPERIOR COCHLEOSTOMY . The space
above osseus spiral laminae is SCALA VESTIBULI & space below osseus spiral
laminae is SCALA TYMPANI

SV insertion of CI electrode in basal turn stimulates SG of middle
turn instead of SG of basal turn

Osseus spiral laminae is seen through SCALA VESTIBULAR
COCHLEOSTOMY with angulation of microscope

hole at root of GSPN is SUPERIOR
TURN COCHLEOSTOMY

1. In middle cranial fossa approach – hole at root of GSPN leads to SUPERIOR TURN
COCHLEOSTOMY
2. In middle ear appraoch - In the groove of Tensor Tympani also leads to SUPERIOR TURN
COCHLEOSTOMY
BOTH HOLES lie exactly at same level

AIC = antero-inferior cochleosomy IC = inferior cochleostomy SC
= superior cochleosomy SVC = scala vestibular cochleosomy
MTC = middle turn cochleostomy STC = superior turn
cochleostomy FN = facial nerve IAC = internal auditory canal

SV ( Scala Vestibular ) Drilling has to be done in the same arch of ST ( Scala
Tympani ) drilling & Middle turn drilling has to be done in the same arch of SV
drilling – while drillouts we should not injure the OSL ( Osseus spiral laminae )
because neurons will damage

Intratemporal Carotid & facial nerve – same parts – both have
vertical & horizontal parts
Vertical part of facial nerve
bisects jugular bulb
GSPN bisects V3 & petrous
carotid

Infratemporal fossa anatomy
line diagram in both anterior
& lateral skull base (
Infratemporal fossa approach
A, B, C , D )

PARS ( = PARTS ) of Cochlea & Duodenum
1= pars inferior 2= pars ascendens 3 = pars superior 4 = pars
inferior

1. Supeior cochleostomy at root of
GSPN from middle cranial fossa
side & Superior cochleostomy in
the groove for tensor tympani
from middle ear – both reaches to
almost superior turn
2. Pars ascendens associated with
vertical part of intratemporal
carotid where as Pars superior
corresponds with labyrinthine
part of facial nerve .
3. In literature it is not mentioned
about where exactly the middle
turn starts & basal turn ends –
What I am understanding is if we
draw a line from midpoint of
stapes foot plate to groove for
tensor tympani ( Green line ) , the
turn above is ending of basal turn
, the turn below is starting of
middle turn .

Junction of pars superior & pars
inferior is labyrinthine part of facial
nerve

Pars ascendens associated with Pre-cochlear carotid [ vertical
part of intra-temporal carotid ]
Pars = Part

Just outside the outer wall of basal turn vertical part of intratemporal carotid present OR in
other wards scala tympani is adjacent to vertical part of intratemporal carotid - so when
carotid canal is dehiscent OR maltracked cochleostomy , there are chances of entering the CI
electrode array into carotid canal . ST= Scala tympani ; SV = Scala vestibuli ; OSL = osseus spiral
laminae ; OW = outer wall of basal turn

Middle cranial
fossa drilling of
cochlear turns
Pars superior is seen
through middle cranial
fossa
1. Angle between
SSC & GSPN is IAC
1. Angle between
labyrinthine part
of facial nerve &
GSPN is COCHLEA (
Pars superior of
basal turn )

In ST (scala tympani) drill outs we have to be very careful -
vertical part of intratemporal carotid is just outside the outerwall
of basal turn or scala tympani

Schematic presentation of Grade I (IA)
ossification: only the area of the round
window is affected.
Grade I (IB) ossification: up to half of the
scala tympani of the basal turn is affected.

Grade II: more than half up to whole of the
scala tympani of the basal turn is affected.
Grade II: the scala tympani of the basal
turn is completely ossified; the scala
vestibuli is less than half ossified, also
grade II.

Grade III: both the scala tympani and scala vestibuli of the basal
turn are ossified, while the middle and apical turns are patent. This can occur
with the ascending part of the basal turn being accessible (IIIA) or inaccessible
(IIIB)

Grade IV: totally ossified cochlea.

PARISIER'S TRIANGLE
(DANGEROUS TRIANGLE)
Perisier's triangle is very important triangle in cochlear implant surgery
1) Superior limb is formed by inferior part of HFN
2) The apex is formed by the geniculate ganglion
3) The base is formed by the anterior commissure (end) of oval window
4) Inferior limb is formed by tunning point of jocobson's nerve to the the
geniculate ganglion.

Perisier's triangle is very important triangle in cochlear impalnt surgery
1) Superior limb is formed by inferior part of HFN
2) The apex is formed by the geniculate ganglion
3) The base is formed by the anterior commissure (end) of oval window
4) Inferior limb is formed by tunning point of jocobson's nerve to the the geniculate
ganglion.

Wall of Parisier’s triangle is by “ wall of middle turn cochlea ” & cavity
is by “ cavity of middle turn ” - & labyrinthine part of facial nerve stays
above the middle turn cochlea which may be stimulated by CI
electrode array causing facial twichings .

Relation of middle turn
cochleostomy in relation
to dangerous triangle

Diagrammatic representation of
the intracochlear electrode
array (red) and the division of the
cochlea into five segments.
The beginning of
segment 1 corresponded
to the RW membrane,
while that of segments 2
and 4 indicated the
surface where the
modiolus was no longer
visualized. In the latter
two segments, the
electrode could be
visualized in the
transverse orientation.

So it is the 3rd part of the electrode/cochlea which is causing facial twistings . So in
Programming we have to stop that electrode . Facial twistings commonly affects in
pathological & abnormal cochleas like Otosclerosis & common cavity respectively . How it
effects AVT [ Audio-verbal therapy ] I will explain in next slides .

• The surgical implications are
1) This triangle contains labyrinthine part of FN.
2) During transotic or transcochlear approaches surgeon should respect this triangle and drill carefully
to avoid injury to FN.
3) Clinically labyrinthine part consists of two segments a meatal segment of nerve, labyrinthine part of
nerve. total length of this nerve is 3 to 5 mm. Anteriorly we can see these parts clearly through this
triangle.
4) 1st part of FN passes close to lower border of precochlear HFN towards anterior end of oval window
in this triangle.
5) Irregular drilling of cochlea in this triangle damages FN That is why it is called DANGERS TRIANGLE.
6) During trans meatal endoscopic dissection of IAC, this triangle important for identification of nerves
7) Translabyrinthine approach visualises posterior surface of 1st part of FN, in transcochlear approaches
the anterior surface of the nerve is exposed. In transottic approaches 270 to 320 degrees of 1 st part of
FN is exposed.
8)Observe closely the labyrinthine part of FN there is a constriction of labyrinthine segment and meatal
segment.
Facial nerve key points
1) Facial nerve changes direction 5 times during its course from brain stem to styloid foramen.
2) No other nerve in body covers such a long distance in bony canal
3) facial nerve contains 10000 axons that are responsible for the innervation of the face musculature
and also for the communications with other nerves human body
4) work with injured facial nerve requires lot of patience.

Perisier's triangle ( dangerous triangle ) which denotes labyrinthine
part of facial nerve …… Corresponds exactly to middle turn drillout

Perisier's triangle ( dangerous triangle ) which denotes labyrinthine part of
facial nerve…….. Corresponds exactly to middle turn drillout

RW = Round Window - Is the
Human Round Window Really
Round?
Answer = NO

Different shapes of the human round
window (medial views).

Prof. Proctor – variations of RW
• • Fossula fenestrae rotundae lata
• • Fossula fenestrae rotundae alta
• • Fossula fenestrae rotundae ovalis
• • Fossula fenestrae rotundae lateritia
• • Fossula fenestrae rotundae quadrata
• • Fossula fenestrae rotundae trapezoides
• • Fossula fenestrae rotundae rhomboidea
• • Fossula fenestrae rotundae semilunaris
• • Fossula fenestrae rotunda rotundae
• • Fossula fenestrae rotundae triangularis
• • Fossula fenestrae rotundae semicircularis
• • Fossula fenestrae rotundae dentata
• • Fossula fenestrae rotundae spinosa
• • Fossula fenestrae rotundae trabecularis

Fossula fenestrae rotundae lata

ROUND WINDOW
REGION – studied/
discussed accordingly
1. Structures out
side the Round
window niche
2. Round window
niche Variations &
Grading
3. Peri – RW niche
area
4. Round window
membrane
5. HOOK region

Microscopic / ENDOSCOPIC anatomy of Operculum
aio: anteroinferior overhang; po: postero-superior overhang; cf:
crista fenestrae.
Microscopic anatomy Endoscopic anatomy

Upper OW & lower RW
t= tegmen - tegmen & anterior
pillar & posterior pillar all together
called as “ operculum ” by
some CI surgeons .
ap= Anterior pillar
pp= Posteriror pillar
Su=Subiculum
f= Finicullus
Fu= Fustis
Scc= Sub cochlear canal leads to
petrous apex
CM = Comcomerata medialis
CL = Comcomerata lateralis
Anterior pillar continues as
finicullus ; posterior pillar
continues as Subiculum
SCC [ Subcochlear canal ] present
between two “F” words i.e., Fustis
& Finicullus - CI surgeons
mistakenly pass CI electrode array
into this SCC .

RW niche [ = opening ] types - below is NORMAL
t = tegmen [ = roof ] , pa = postis [ = door ] anterior , pp = postis
[ = door ] posterior , f = fundus [ = floor ]

1. Structures outside the niche
which hide its entrance

Exostosis = The most frequent
variation is exostosis near the entrance
of the niche

jugular dome = A less frequent but clinically very
important variation, the jugular dome can partially or even fully
hide the round window niche

The thin bone separating the roof of the JF from the RW (<1 mm in 8%) highlights a
potential risk of injury to the JB during cochleostomy placement.

trabeculae niche is protected by
trabecules of varying sizes

2. Round window niche
Variations & Grading

Narrow Niche = When all the walls are thick, the niche
becomes very narrow.
Its surroundings show without exception a ‘cellfree’, compact bony surface
without a fustis

Descending tegmen = The tegmen of the niche
may stretch to varying degrees which results in a V-
shaped transformation of the niche’s form

Anterior septum = The most frequent variation of the round
window entrance is the lamellar growth of the postis anterior which covers the
majority of the opening of the round window. The shape of the postis anterior
shows a wide variability from a continuous plate to the trabecular form

Bony membrance = In the rarest
variation the pseudomembrane is partially or completely ossified
in the round window’s entrance and forms a thin bony plate

Open fudus = Lack of ossification lateral to the fustis
results in the absence of bony tissue between the fustis and the
anterior wall which occurs when the inferior wall remains
incomplete

Round Window Grades - FOUR grades
- through Facial recess approach

3. Peri - RW area
a. Fustis
b. SCC = Subcochlear Canal

ENDOSCOPIC anatomy of Operculum
aio: anteroinferior overhang; po: postero-superior overhang;
cf: crista fenestrae.

Type A fustis. f fustis, sp styloid
proeminence, st scala tympani, rw round
window

Type B fustis. f fustis, sp styloid
proeminence, st scala tympani, rw round
window

FUSTIS
•
it is fustis a solid bony column connecting the retrotympanum to round
window niche. So far this structure is neglected Microscopically it may
not be clearly visible, but endoscopically it is seen clearly The surgical
implications of this structure are
1) its origin is pylogenically different from other parts of that area
hence it behaves differently
2) It contains enzymes which are resistant to cholesteatoma
destruction
3) it prevents sinus cholesteatoma extending downwards..
4) This structure is directed towards round window, in narrow round
window niche by following its upper border, we can identify the round
window membrane
5) It divides upper part of subtympanic sinus, concomerata into
medialis and lateralis. C medialis is site for posterior ampullary nerve
section.
6) Fustis regulates smooth out flow of sound waves from round
window membrane.

• 7) It helps in creation of pressure difference between round and oval windows
encourages acoustic coupling.
8) It gives support round window niche because both postis anticus and postis
posticus contains cochlea and subcochlear portion that are hollow structures.
9) This structure modulates according to round window niche i. e, "V" shaped,
square shaped, triangular gothic shaped, like that, to have a relation with RW
10) In absent sibiculum, the fustis gives support.
11) Fustis narrows the round window niche there by protects the round window
membrane (rupture)normally.
12) embryologically fustis develops between periosteal layer of the labyrinthine
capsule and the thin smooth plate of Pavementum Pyramidalis and it is
ontogenically important structure.
So surgeons, fustis is very important structure at outflow gate of sound in middle
ear.
In 1968 Bruce Proctor mentioned, Recently prof Presutti, Prof Marchioni and Prof
Joao F Nogueira described this part.
so surgeons please look this important but poor part while performing surgeries
because it is present in all middle ears..

Right ear. Endoscopic view of fustis type B. ow oval
window, st scala tympani, fu fustis, pe pyramidal
eminence, rw round window

Right ear. The tool shows the scala tympani. ow oval
window, st scala tympani, fu fustis, rw round window

Sometimes you may not appreciate fustis by Sinus tympani
approach but for Veria technique fustis is very important.

between fustis & finiculus SCC (
subcochlear canal ) present

FUSTIS VARIATIONS – Prof.
Proctor

SCC = Subcochlear Canal
CI surgeons mistakenly pass CI electrode array
into this SCC . Previously they used to call
this SCC as “ Hypotympanic cell ” in older
literature . Now with the advant of
Endoscopy SCC is clearly defined which leads
to petrous apex

(Right ears) a–d in these subjects a deep (Type A) “subcochlear canaliculus” is
found between the fustis bone and the finiculus and has different dimensions
pp posterior pillar, ap anterior pillar, pr promontory, rw round window, t
tunnel of subcochlear canaliculus, ac area concamerata, f finiculus, su
subiculum, fu fustis, su subiculum, sty styloid complex

(Right ears) Three types of conformations of the round window chamber related to the relationship
between the fustis, area concamerata and the finiculus bone.
Type A between the fustis and the finiculus a deep hole/tunnel is present with deep extension to the
petrous apex cells lying below the cochlea; in these cases a CT scan in a sagittal view shows the
presence of a well pneumatized temporal bone at the most inferior and medial portion of the petrous
apex below the internal auditory canal.
pp posterior pillar, ap anterior pillar, rw round window, red arrow tunnel of subcochlear canaliculus, ac
area concamerata, f finiculus, su subiculum, fu fustis, su subiculum, sty stylod complex

Type B between the fustis and the finiculus a small hole is present, the connection
between this hole and the apex is not recognizable endoscopically because of the
dimensions of this area; in these cases a CT scan in a sagittal view shows the presence of
a limited pneumatized bone below the cochlea.
pp posterior pillar, ap anterior pillar, rw round window, red arrow tunnel of subcochlear
canaliculus, ac area concamerata, f finiculus, su subiculum, fu fustis, su subiculum, sty
stylod complex

Type C the fustis and area concamerata are fused with the finiculus and anterior pillar
without any connection between the round window chamber and the petrous apex, in
these cases no air cells are present at the most inferior and medial portion of the petrous
apex on the CT scan in a sagittal view
pp posterior pillar, ap anterior pillar, rw round window, red arrow tunnel of subcochlear
canaliculus, ac area concamerata, f finiculus, su subiculum, fu fustis, su subiculum, sty stylod
complex

(Right ear) Infracochlear approach in pediatric subjects affected by tympanic cavity cholesteatoma with
involvement of the petrous apex through the tunnel of the subcochlear canaliculus. a a cholesteatoma
matrix is endoscopically visible extending into the tunnel of the subcochlear canaliculus. b extension of the
cholesteatoma into the depth of the subcochlear canaliculus, medially with respect to the internal carotid
artery. c endoscopic infracochlear approach after cholesteatoma removal from the petrous apex conserving
the cochlea. d endoscopic magnification of the petrous apex below the cochlea after cholesteatoma removal
ch cholesteatoma, rw round window, t tunnel of subcochlear canaliculus, ca carotid artery, pr promontory,
ow oval window, white arrow deep extension of the subcochlear canaliculus
medially with respect to the internal carotid artery into the petrous apex

A. Original round window. B. Basilar membrane. C. Osseous spiral lamina. D.
Reflection of perilymphatic fluid. E. Darker area of first curve of the basal turn
of the scala tympani. F. Blood vessels. G. Modiolus. H. Removed bone of
round window overhang.

When you don’t have any landmark especially RW drill infra-cochlear
cells & try to identify the outer wall of cochlea & make cochleostomy –
Dr. Satish jain

Inside chitradurga fort – cochlea ,
RW , SCC , FUSTIS

Obavva story https://www.youtube.com/watch?v=tdNjRgW3hBk
Inside red circle ( round window ) - Scala tympani
yellow circle – Subcochlear tunnel

Yellow ring = subcochlear canal [ SCC ]

Inside Subcochlear tunnel - leads to petrous
apex

RIGHT EAR PERI-RW AREA
Inside red circle ( round window ) -
Scala tympani
yellow circle – Subcochlear tunnel

4. RWM = Rouond Window
Membrane

1 Round window membrane 2 Crista semilunaris 3 Fustis
4 Horizontal bar 5 cavum posterior 6 Cavum anterior 7 vertical bar 8 Antero-inferior
RWM 9 Postero-superiro RWM PS RWM = postero-superior round window membrane OR
Horizontal part of RWM AI RWM = antero-inferior round window membrane OR Vertical
part of RWM

8 Antero-inferior RWM
9 Postero-superior RWM
8) Antero-inferior RWM
always for sound vibration
RWM vibration is evident
at 1500 to 3000 hzs and at
higher frequencies it
vibrates irrigularly
9) Postero-superior RWM
is always tor
micromolecules diffusion
in to inner ear ant it
contains more
melanocytes so for
gentamycin instillation it is
better to place fluid . In
posterior part of RWM for
better diffusion

. The posterosuperior overhang impedes visibility of the posterior portion of the round
window membrane, aio: anteroinferior
overhang; po: postero-superior overhang; cf: crista fenestrae.
Both Operculum & RWM has postero-superior &
antero-inferior parts.

Right RWM [ Round Window Membrane ] - the junction of PS RWM & AI
RWM is anchored to Crista semilunaris
PS RWM = postero-superior round window membrane OR Horizontal part of
RWM
AI RWM = antero-inferior round window membrane OR Vertical part of RWM

Area of vertical part of RWM [ AI RWM ] is more than horizontal
RWM [ PS RWM ] - the ratio of the area of the horizontal part of the
RW to the area of the vertical part is about 3 : 4

Sagittalsection of the right human cochlea. The anterior and posterior portions of the round window
membrane form a right angle to each other. The posterior portion, hidden by the postero-superior
overhang, lies very close to the osseous spiral lamina. The distance between the window membrane and the
osseous spiral lamina is only 0.1 mm. at the posterior periphery of the round window, cf: crista fenestrae;
set: scala tympani; pspl: primary spiral lamina; sspl: secondary spiral lamina; Rm: Reissner's
membrane; hrwm: horizontal portion of window membrane; vrwm: vertical portion of window membrane;
po: postero-superior overhang; * blind end of scala tympani.

Various distances between PS RWM & OSL ( actually secondary
OSL ) – this various distances is Sinus tympani
PS RWM = Postero-superior RWM ; OSL = Osseus spiral laminae

hrwm = PS RWM ; vrwm = AI RWM
ST = = Scala tympani
Coronal section Saggital section

After removing the
RWM ( Round
window
membrane ) you
can appreciate at
posterior superior
area Modiolus &
OSL+BM + SL
complex.
& at antero-iferior
area ST ( scala
tympani )

4 quadrants vital areas
of right ear RW area
Antero- Superior
quadrant = OSL + BM +
SL complex
Postero-superior
quadrant = Modiolus
Antero-inferior quadrant
= Scala tympani
Postero – inferior
quadrant = Scala tympani

Vital structures in
each quadrant of
Right ( Rt ) ear Round
window
1. ASQ = Antero-superior
quadrant - OSL+BM+SL
complex
2. AIQ = Antero-inferior quadrant
– Scala tympani ( ST )
3. PSQ = Postero-superior
quadrant – Modiolus ( M )
4. PIQ = Postero-inferior
quadrant – Scala tympani ( ST )
+ Crista semilunaris ( CS )
5. RED/BLUE PLUS is imaginary
mental plus
OSL = Osseus spiral laminae
BM = Basillar membrane
SL = Spiral ligament

1. < 1mm gap present between postero-superior
RWM & OSL+ BM + SL complex
2. Prof. Clark & Dr. Prahlad sir says we should not
drill the postero-superior part of the operculum as
it injures the OSL+BM+SL complex , we have to drill
the only the antero-inferior part of the operculum
& do the RWM insertion .

This plaster tape is my RW [ = round window ]

This paper strip
is OSL ( inner ) +
BM + SL ( outer )
OSL = osseus spiral
laminae
BM = basillar
membrane
SL = spiral ligament

Now this is OSL + BM + SL & round
window unit

Now let me keep in anatomical position ; This is right ear ……. Now observe ,
superiorly & anteriorly OSL + BM + SL strip present in relation to RW

So conclusion is we
should not drill
superiorly &
anteriorly , we may
damage this OSL + BM
+ SL complex --- in
hearing preservation
technique even more
important
&
in routine surgeries
also endolymph &
perilymph shouldn't
mix

BOTH PHOTOS RIGHT ROUND WINDOW MEMBRANES - The right round window in a human temporal bone
as seen from an endaural approach demonstrating the close relationship between the osseous spiral lamina
and the posterior portion of the round window membrane. For better demonstration the postero-superior
and the antero-inferior overhang have been removed, bm: basiliar membrane; spl: spiral lamina; set: scala
tympani; rwm: found window membrane, cf: crista fenestrae

A microdissected left human temporal bone. The lower basal turn has been opened
showing the position of the OSL [ Osseus spiral laminae ] . The SL [ Spiral ligament ]
and its topographic relationship with the RW rim are depicted. A cochleostomy drilled
anterior or superior to the RW rim may affect the SL [ Spiral ligament ] anatomy of the
human round window (left ear-medial view). A, The RW is fan shaped and and even
the OSL in this specimen. A, lateral view; B, surgical view.

Plaster tape is right ear ; below photo
is left ear – compare both

Crista fenestera is intracochlear inferior border of
RW and Crista Semilunaris is inferior bony
attatchment of RW which is removed before
insertion .

HOOK region – the narrowest point of
Crista fenestrae & Crista Semilunaris
& Initial turn of OSL is called HOOK
region

View of the round window from a posterior tympanotomy in a right human
temporal bone. The posterosuperior overhang impedes visibility of the
posterior portion of the round window membrane, aio: anteroinferior
overhang; po: postero-superior overhang; cf: crista fenestrae.

a & b are width & height of Crista
fenestrae ( Cf )
a = width = 1.6 ± 0.20mmSD
b = height = 2.0 ± 0.28mmSD

Facial recess view – View of same OSL ( Osseus spiral laminae ) ,
modiolus , crista fenestrae , crista semilunaris & outer wall of basal
turn

A tangential insertion along the outer wall of the basal turn is possible
after removal of the crista fenestrae. cf: crista fenestrae; spl: spiral lamina; ow: outer wall of
basal turn.

Amount of drilling is somuch in INFERIOR cochleostomy to some extent in ANTERO-
INFEIROR cochleostomy – due to crista fenestrae drilling
Cf = Crista fenestrae ; OSL = Osseus spiral laminae ; OWC = Owter wall of basal turn ;
IC = inferior cochleostomy ; AIC = antero-inferior cochleostomy

Amount of drilling is somuch in INFERIOR cochleostomy
– due to crista fenestrae drilling

• The crista fenestrae forms the anteroinferior sharp bony margin of
the round window. This margin of the round window lies closer to the
modiolus and the osseous spiral lamina than the outer wall of the scala
tympani in the basal turn of the cochlea. When the crista fenestrae is left
in place only the medial portion of the scala tympani gives room for the
electrode insertion. The narrow space between the crista fenestrae and
the modiolus can cause friction, and the electrode cannot be led
tangentially along the outer wall of the basal turn right from the start . A
good view along the basal turn of the cochlea is achieved when the
antero-inferior overhang and the crista fenestrae are removed. Only after
the removal of the crista fenestrae can the whole width of the scala
tympani in the basal turn be seen and this gives enough space for the
electrode insertion. It is important to preserve the osseous spiral lamina
anatomically and thus prevent a reduction of the nerve fibre population.
When attention is paid to the above particular features of the round
window at surgery, damage to the osseous spiral lamina should not occur,
and a deep electrode insertion will be possible.

A post-mortem view of the hook region of the osseous spiral lamina (osl) in a cat cochlea as
seen through the round window. For the purposes of this figure, the round window membrane
and all the perilymph has been removed. The basilar membrane is visible as the medium gray
crescent (black arrows) below the margin of the round window. The extreme basal end of the
cochlear spiral is toward the right. The scala tympani spirals counterclockwise and away into the
basal turn at the bottom left of the round window. The modiolus (large asterisk) is toward the
bottom. The white arrow indicates a 1-mm spiral ganglion lesion. The lesion is visible due to
extravasated blood in Rosenthal's canal, which can be seen as a light gray crescent (small
asterisk) in the osseous spiral lamina.

Relation of OSL [ = Osseus spiral
laminae ] & RW niche [ = opening ]

OSL= Osseus spiral laminae ;
SV = Scala vestibuli ; ST =
Scala tympani ; F = Fustis
Cochleostomy
drilled anterior or
superior [ SC =
SUPERIOR
COCHLEOSTOMY ]
to the RW rim
may affect the
OSL anatomy .

Dissected temporal bone specimen. The view is through the facial recess to the RW area of the
promontory. The promontory inferior and anterior to the RW has been drilled down to show the close
relation of the osseous spiral lamina and basilar membrane to the anterior RW membrane. ST/scala
tympani; SV/scala vestibuli; OSL/osseous spiral lamina; RWM/RW membrane; LSCC/lateral semicircular
canal.

The right round window in a human temporal bone as seen from an endaural
approach demonstrating the close relationship between the osseous spiral
lamina and the posterior portion of the round window membrane. For better
demonstration the postero-superior and the antero-inferior overhang have
been removed, bm: basiliar membrane; spl: spiral lamina; set: scala tympani;
rwm: found window membrane, cf: crista fenestrae.

Human temporal bone specimen drilled to simulate the typical trans-
mastoid, trans-facial recess approach to the inner ear. The buttress has
been taken down and the incus removed. The view shows the authors’
preferred cochleostomy site, just inferior to and extending into the RW.
This allows visual control of the basal turn prior to implantation.

FUSTIS continues as ( points to ) CRISTA
SEMILUNARIS
white arrow = Crista Semilunaris ; f = Fustis ; t = tegmen ; pa = Postis anterior ; pp = Postis
posterior ; OSL= Osseus spiral laminae ; SV = Scala vestibuli ; ST = Scala tympani ; F = Fustis

Coronal diagrams of the RW region of a right cochlea. Note the change in orientation of the
osseous spiral lamina from (a) vertical to (b, c) a more oblique position deeper within the
basal turn. At the same time, the scala tympani gains cross-sectional depth.
st = scala tympani ; sv = scala vestibuli ; osl = osseous spiral lamina ; M = modiolus ; SL= spiral
ligament ; V =vestibule ; S = Subiculum ; OC = otic capsule ; PS RWM = Postero-superior Round
window membrane

Compare Subiculum in
both diagrams
t= tegmen - tegmen & anterior
pillar & posterior pillar all
together called as “
operculum ” by some CI
surgeons .
ap= Anterior pillar
pp= Posteriror pillar
Su=Subiculum
f= Finicullus
Fu= Fustis
Scc= Sub cochlear canal leads to
petrous apex
CM = Comcomerata medialis
CL = Comcomerata lateralis
Anterior pillar continues as
finicullus ; posterior pillar
continues as Subiculum

total paper can be get at -
http://sci-
hub.cc/10.1016/j.aanat.2005.09.0
06
Development of the bony round
window niche from the 16th fetal
week (A) to newborn (F). The first
ossification centers of the otic capsule
appear around the round window, but
the inferior wall of the niche does not
begin to ossify until the 17th fetal
week (B). The first sign of the crest of
round window can be seen in the 18th
week (C) and it develops rapidly up to
the 23rd week (D). The walls of the
niche show intensive growth during
the entire prenatal period but its
typical appearance is not complete
until the eighth fetal month (E). f –
fustis, pa – postis anterior, pp – postis
posterior, t – tegmen of the round
window, arrow – crest of the round
window.

Left ear - medial view [ Looking from inside of scala tympani to RW ] from paper
http://sci-hub.cc/10.1097/MAO.0000000000000332
CA = Cochlear aqueduct is immedialy behind the Crista Semilunaris [ Here we are
looking from inside of scala tympani ]
t = tegmen [ = roof ] , pa = postis [ = door ] anterior , pp = postis [ = door ] posterior , f
= fundus [ = floor ]

CA = Cochlear aqueduct is immedialy behind the Crista Semilunaris
RED RING = Crista semilunaris

Anatomy of the human round window (left ear-medial view). A, The RW
is fan shaped and conical and opens into the RW niche (*). CA, cochlear
aqueduct; ST, scala tympani. B, A CI electrode array has been inserted
through the RW. The electrode rides on the crista fenestrae. – from
paper title “Is the Human Round Window Really Round? An Anatomic
Study With Surgical Implications”

INTRACOCHLEAR TRAUMA
CLASSIFICATION = VERY
IMPORTANT --- Eshraghi et al.
OSL = Osseus spiral lamine ; BM =
Basillar Membrane ; SL = Spiral laminae
grade 0, no trauma;
grade 1, elevationof the basilar
membrane;
grade 2, rupture of the
basilarmembrane;
grade 3, dislocation of the
electrode array to thescala
vestibuli; and
grade 4, severe trauma such as
fracture ofthe osseous spiral
lamina, modiolus, or stria
vascularis.

grade 0, no trauma; grade 1, elevationof the basilar membrane;
grade 2, rupture of the basilarmembrane;
grade 3, dislocation of the electrode array to thescala vestibuli; and
grade 4, severe trauma such as fracture ofthe osseous spiral lamina, modiolus, or stria vascularis.

Indetail HRCT temporal bone videos
– click YouTube link
https://www.youtube.com/playlist
?list=PLZquE6mn0cynJF47j2PZjEBKv
q1GqU446

Comprehensive HRCT temporal bone – click YouTube weblink
https://www.youtube.com/watch?v=iJp9ZLNMad0&index=9&list
=PLZquE6mn0cynJF47j2PZjEBKvq1GqU446&t=226s

PARS [ = Parts ] of cochlea & HRCT
temporal bone – histological study

So it is the 3rd part ( pars superior ) of the electrode/cochlea which is causing facial twistings
. So in Programming we have to stop that electrode . Facial twistings commonly affects in
pathological & abnormal cochleas like Otosclerosis & common cavity respectively . How it
effects AVT [ Audio-verbal therapy ] I will explain in next slides .

(a) Identification of segments 1 and 4. The modiolus is
located deeper than the bone surface..

(b) Identification of segments 1, 3, and 5. The
modiolus is now visible on the surface of the bone.
This defines the beginning of segments 3 and 5.

(c) Visualization of segments 1 and 3 and the
modiolus.

(d) Visualization of the beginning of segment 2. The
modiolus can no longer be visualized.

In the lap of basal turn middle turn present & in lap of middle turn superior turn present .
So in both cranial most & caudal most axial cuts of HRCT Temporal bone you will see basal turn
only .
Don't confuse that in cranial most axial of HRCT you will see superior turn

Samples of corrosion casts from the temporal bone collection in Uppsala showing variations in
the anatomy of the human cochlea. The collection contains 324 human inner-ear molds. Both
methacrylate and silicon were used as material for casting. --- from paper http://sci-
hub.cc/10.1179/146701011X13001035752174

Letter W in axial HRCT temporal bone

Click this video link to get lecture of
facial nerve variations
https://www.youtube.com/watch?
v=7s1dGND7W7A

Variations of vertical part of
facial nerve
Variations of horizontal part of
facial nerve

Trajectory of cochlear implant
electrode array

Trajectory of electrode
array – I will explain in
future PPTs - Prof.
House says multichannel
electrodes hits the spiral
ligament at 7mm . So he
made short electrode of
6 mm
AIC = Antero-inferior
cochleostomy ;
IC = Inferior
cochleostomy ; OW =
outer wall of basal turn ;
OSL = Osseus spiral
laminae ; RW = round
window

Figure 3–4. Cochlear dissection showing veins associated with
the modiolus. The osseous lamina and basilar membrane have been removed to view the floor of
scala tympani (ST) and modiolar wall (MW). The white arrow indicates a vein coursing down the
modiolar wall to join the posterior spiral vein (black arrows). These superficially positioned
vessels are vulnerable to injury by perimodiolar electrode arrays. Reproduced with permission
from Roland PS,Wright CG. Surgical aspects of cochlear implantation: mechanisms of insertional
trauma. Adv Otorhinolaryngol. 2006;64:11–30. --- from book Cochlear Implants and
Other Implantable Hearing Devices

Figure 3–2. A. Cochlear cross-section showing
the lower portion of
the spiral ligament (SL) facing scala tympani (ST).
The curved arrow indicates a venule coursing
through the spiral ligament toward the floor of
scala tympani. The straight arrow indicates the
portion of the spiral ligament seen in B. The
ligament and its vasculature are vulnerable to
trauma by electrode arrays positioned against
the lateral wall of scala tympani. Scale bar = 100
microns.
B. Scanning electron micrograph
of the surface of the spiral ligament in the area
immediately below the attachment of the basilar
membrane. The site of attachment of the
basilar membrane to the lateral wall tissues is
indicated by the dotted line. Note the highly
porous, meshlike structure of the spiral ligament
surface, which is susceptible to electrode array
penetration and injury. Scale bar = 20 microns.
Reproduced with permission from Roland PS,
Wright CG. Surgical aspects of cochlear
implantation: mechanisms of insertional trauma.
Adv Otorhinolaryngol. 2006;64:11–30.

A modiolar cross section showing a vein (arrow) located on the side of the modiolus
and covered only by a thin layer of bone. This blood vessel is quite similar to one
illustrated in the dissected specimen shown in figure 11. SG Spiral ganglion. --
http://sci-hub.cc/10.1159/000094642

Prof.House single channel electrode
paper

For Video click YouTube link
https://www.youtube.com/watch?
v=6NFaxi8IOn8&t=382s

“Uncoiled” electrode array has to be used as the cochlear neurons
present at outer wall of common cavity
my fingers = cochlear nerve fibres ; hand = cochlear nerve

“Uncoiled” electrode
array has to be used as
the cochlear neurons
present at outer wall of
common cavity
my fingers = cochlear
nerve fibres ; hand =
cochlear nerve

right IAC when we are seeing from inside the cranium to IAC
CN & IVN diverges ; FN & SVN converges – all the 4 cranial
nerves must be confirmed in saggital MRI

I will explain in further PPTs

Cochlear implant - line diagrams

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Cochlear implant - line diagrams