Cranial Positioning in Neurosurgery

[Music]

good morning from miami beach dr john bennett for neurosurgical tv we have the pleasure of hosting uh the uh neurosurgical neurosurgical webcast

hosted by kate drummond we'll let her run the show okay kate hi uh good morning to uh good morning to you but good evening to me and somewhere

in the middle for uh for the rest of our participants uh welcome to neurosurgical boot camp uh coming from the residents of the national neuroscience institute in

singapore um i'm kate drummond i'm a neurosurgeon in melbourne uh so we're going to have three wonderful presentations tonight there

will be a a short presentation basically on topics of interest to junior residents and anyone interested in joining neurosurgery training

um and that each of the the singaporean residents who are presenting also have a mentor to help out if they get any tricky questions uh now john are we putting the questions

in the q a or in the chat where where are the questions going i think the chat would probably be the best spot okay great so we if you do have any questions then uh

then then put them in the chat um but otherwise i will introduce our first speaker uh who's felicia choir and felicia is uh speaking about principles of

neurosurgical positioning hi everyone okay let me just

uh can you hear me yes okay okay uh is the presentation shared on the screen correct yep that's good yes okay

hi everyone i think i'll just dive straight into it i'm felicia one of the neurosurgical residents at nni singapore and i'll be talking about cranial positioning in neurosurgery basics that every neurosurgical resident

needs to know and my mentor is dr carlos ramez so going straight into it on the overview of what i'll be discussing today is essentially principles of ideal positioning

procedure and fixation methods of the surgery and also i'll be discussing the common positions that we use in our everyday practice the supine straight supine head rotation

lateral prone straight and three quarters also known as park bench approach so in terms of principles of ideal positioning we would want to essentially aim of

surgical resection really is to use the most direct approach possible to uh resect the lesion and firstly by doing that we will need to get the lesion at or as close to the surface as

possible and one of the ways is to do it is really to identify surface palpable landmarks that we can identify position a patient appropriately and intraoperatively also

to identify craniometric or osteometric landmarks to help guide a lesion or resection the second point is of of course we want to minimize brain retraction

and with that we would want to use the help of gravity to pull away or shift dependent lobes away from our operative field on a third note which is a more practical note

is really to consider the ergonomics of the surgeon and the assistant during the actual surgery so whether this operation is done sitting or standing the microscope that you use is it face

to face or left to right all these are considerations that you have to think about before actually putting a patient on table and fourthly is to provide a clear operative feel what i mean by that is really to prevent

unnecessary bleeding in terms of venous buildup venous pulling i'll elaborate more on this in my presentation

so the first point about uh landmarks when we talk about landmarks really one there are many many surface landmarks that we can identify on the skull obviously uh one of the main ones i want

to zone in on is the taylor hotner lines and the main one being that of the nasion indian line so this imaginary arc or line is what we mark out anteriorly from the

nasion which is a depression found between the eyes is the most interior point of your frontal nasal suture and you join it at the midsection cut really forming up to the posterior

point of the indian and that's the tip of the external occipital protuberance uh what this line gives out for gifts for you is essentially avenues or rather method to eventually

measure your silver fissure as well as your central sulcus do you have some other people in your room yeah yes is there a lot of insurance

there's a lot of back background noise yeah i'm sorry i clear it up i think okay is it better now anyone else yeah okay sorry just a shout

out if you can't hear me i'll try i think it might be you shuffling your paper even weak in here all right keep going okay

so uh back to the nasion indian line basically is divided into four parts and the silver fissure really is a line drawn from three-quarters point posterior

of the ni line down to the lateral canthus and that forms your silver fissure the second point that we want to draw that i want to focus on is really to identify the

central sulcus and this is a 0.2 cm behind the midline or the midpoint of this ni line and is drawn to imaginary 0.5 cm above your external auditory

meatus so that marks out the central sulcus which really points to the the differentiation between uh how you identify your motor strip and your sensory strip

and that's important especially when you want to identify lesions during the surgery other things you want to think about is coronal suture so about four to five cm behind this line also is a point that you can identify the

motor strip as well the other the other landmark

found inferior to the lambdoid and this really demarcates where your occipital pole is um it's also good for identifying points so all these are just a guide to

help you in your surface landmarks to really localize a lesion when you're trying to do an operation you will need to identify it and then pair it with your neural navigation to

see how accurate you are because firstly not everywhere has never neural navigation and secondly if it fails intra-op you still need to be able to identify the lesion regardless

other landmarks that are also important this is just really purely for general when they are feeling the patient on table is to find out if you have a lesion centered at the anterior fossa such as the cribiform

basementing joma where you want to find the floor or the skull base of the anterior fossa that would be at the roof of the orbits uh the middle fossa would be your zygoma that you can identify

in front entoro would be a life on a zygomat backwards to the indian i'll elaborate more about this later in my prone approach how it's useful for for example for a vestibular

genome identifying the transverse sinus and the sigmoid sinus and limits of the foramen magnum as well it's useful to know the indian posteriorly and the anterior border which is the bayesian

okay so moving on to clear operative field uh really this is to make sure when you're positioning a patient you have at the back of your mind that you don't over flex and over rotate um a patient to prevent kinking

of the internal jugular vein as this will cause a build up in venous pressures and also reduce cerebral perfusion pressure so there's a lot of bio mechanics and mathematics models

that have been discuss in literature but i won't go into the details of it but the graph at that site shows you the different positions and the different icp and perfusion pressures

that come with it um another consideration to note is also in terms of cervical manipulation you need to know whether the patient underlying has unstable cervical spine or cervical

myelopathy so you need to be careful in handling such patients and also during intubation if you need to you may need to ask the anesthetist to do a inline intubation

or a weak fiber optic intubation okay so talking about equipment i just want to have a brief run-through of it because as a junior resident you might not be

aware of all the instruments that are available to you these are really the basics of what you need to know um as a junior resident really so i'll be talking about frame

and the adjuncts i'll discuss more in the positions later so in terms of frame we have the making and dora frame which uh it is used very commonly

in a three-point fixation device system so it's one of the more commonly used skull clamps today and it's really a fixation device that allows us to

clamp a patient's head in operating theater make sure it doesn't move from operating also allow us to do a neural navigation accurately um so the three point system is made out

of really two components the silver rocker arm which is this uh two pin 360 degree rotation locking mechanism um as well as a contralateral single pin

and a quick release lock at the bottom and the idea of it really is to fix the point you have the two pins in front and one pin at the back and in my drawing there you essentially

want to let the single contralateral pin be equidistant to the two pins such that the center of gravity or rather where it's centered is equal to each other and the second point to note of course

is when you're positioning a patient the pins should be below the equator so that there's no slippage when you fix the patient in position there's the additional body halo retractor system

which may not be available to all or not everyone uses it but it is an option to add on so you can have the c-clam adapter as shown there and the halo and support

rods as an add-on this provides the system for you to have retracted arms and blades such that you may not need an assistant when you are retracting so moving on to the sujita frame this is another device

that we commonly use as you can see here there are many parts and attachments but the point is the same the difference between this and the three pin uh skull clamp is that this one actually has more

options in a sense there are actually six pin sights that you can use and you would use four out of the six at any one point of time and you would position them um rather you would pin

two pins at a time opposite and equidistant to each other and again the aim is really to center the lesion in the middle you also have to attach the construct

together with the basal frame and the retractor system that we use okay in terms of pitfalls of pinning i think this is important to note there

are areas of vulnerable bone when you are pinning and it's important to take note of the frontal sinus specifically as well as the squamous temporal bone

which is especially thin so if you fracture through it you really need to um or rather you really need to take note of the landmarks before you actually pin

start pinning a patient and all craniotomy sites definitely you need to you know based on your ct that you have done before and based on palpation really avoid the

lines where it has had a you know b1 go through it before because you can plunge straight into the brain of course you have to make sure there are no additional devices such as

shunt tubings or even the valve pump itself and and really for safe fixation you need at least one pin below the equator to hit okay

a horseshoe frame is something you can also use it's slightly easier to maneuver it has a vertical and natural adjustment and really it's quite uh easy to use but definitely not

as fixed as a skull clam or a sugita frame okay so now moving on to positions itself like i mentioned before i'll be talking about supine straight supine head rotated natural prone

straight and a three quarter or park bench approach so i decided to make it a more practical approach so for the supine position really this is something that junior

residents would have to be very familiar with because you would use this for positions for evd or icp monitor insertions it's really in a neutral position when a

patient is supine on a doughnut and you shave the head to identifying the midline and thereafter you draw out the caucus point and this is the tan tree

um 10 cm from the nasion and 3cm from the midline to correspond with the mid capillary line really and then you try check you you aim your ebd in the trajectory

and yes another example of supine neutral or supine straight that we can do is really for bicoronal craniotomies

and this can be done electively so for example if you have acrylic form uh meningioma you would want a bi-frontal approach or even for biofrontal cream to me as in the ct

below the main point to note i think for this elective clamping procedure is usually the pins come very near to the incision side so you really do need to mark out your

hairline your incision site the coronal suture and make sure when you pin you avoid the incision line and give enough space for your draping to come on after

the supine hit rotated position this is another common one for junior residents essentially for chronic subdurals where you just need a bit of head tilt really to make the

parietal eminence or irion more prominent um from there you can do your two bow holes the frontal and the parietal bojo which is in the photo here or if you need to do a small

mini craniotomy that's possible as well the supine head rotated which requires a lot more head rotation would be for example for decompressive craniactomy

it may not be as commonly done but it is something that you will need to take no note off so for these positions because there's so much hit till involved you would need a much larger shoulder roll

such that the such that when you are rotating the head you don't over kink the the neck and king the iga vessels and horse worsening of venous congestion and

bleeding but really the head tilt is required so that you can make a large reverse question mark incision and have adequate exposure of your parietal eminence but also able to see your midline really

okay so uh one of the most common procedures that we use in the workhorse in neurosurgery is the therional approach this is something that we use for almost i mean we use for our aneurysm cases as

well as a lot of our tumors essentially this can go anywhere from a 30 degree 45 degree to a 60 degree heat tilt and all this depends on

what kind of excision you're hoping to achieve so for the important thing to note for this um i guess is you want to avoid over rotation of

the head as this causes the temporal lobe to lie over the silver fissure so if you are trying to dissect through uh identify a civilization and dissection you would not want too much of a head rotation as you would

for another procedure that you are trying to access more temporal lobe for for example and also need to take note that over extension of the hit may also uh result in obstruction of

view by the orbital rim so these are just some considerations to take note of okay a natural approach so this is uh where the head is mostly in a neutral position

may be selected for more middle cranial fossa skull based approaches and the use of a lateral approach really just lessens the blood pooling in the surgical field

because you have a relief of pressure and from the abdomen and this decreases the compression of the vena cover reduces the intra-abdominal pressure and also by gravity really just allows

better drainage problem position uh this is uh something that we commonly use for unilateral uh bilateral sub-orcipital craniotomies uh as well as for

cerebellar for ventricular pathologies of the pulse fossa some examples uh put up the scan there of a bleed and a tumor but essentially for this the positioning

would be a military type position where you extend the neck and flex it and you would need to do it adequately to expose the c1 up if not if your

patient is not flexed enough you will not be able to visualize it when you're doing the surgery but to take note of that you also cannot do it too excessively in case you kink

the ett ett2 or or king the ij so usually we would say two fingers breath between the chin and the sternum okay so the park bench approach

um this one would be the three quarter prone approach you can use this really for exposure of posterior parietal or septal lateral sub-occipital

cranial cervical junction at some points and really this approach is quite widely used for uh vestibular trauma mvd for example

so one of the important landmarks that i just want to highlight when doing this procedure is really to be able to identify the transverse sinus and the transverse

sinus sigmoid junction the way we draw out the transverse sinus really is from the zygomatic root to the ineon and for the sorry

and for the sigmoid sinus it's a digestive point so this is the superior aspect of the mastoid notch and in the bony landmark wise the esterion is marks out the transverse sigmoid

junction so usually you use that as one of the bull holes when you are approaching this okay i guess the pitfalls for this

position again number one is the hip flexion the kinking of the ijett but on top of that because for this these kind of surgeries usually they're slightly

longer and as you can tell the position is not in a neutral position there's a lot of issues with pressure source a lot of padding chest padding shoulder

padding even pillows under the feet under the legs and between legs have to be provided so there are a lot of pressure points and pressure point pressure sores that we would need

to avoid the second thing is really for nerve pulses as well the axilla radial ulna breaker plexus also so all these uh need to be padded with foam or you

will need to put gel paddings on to avoid these as well um [Music] okay so i think i've come to my conclusion of uh what a summary of positioning

uh that a junior resident would really need to know uh for the neurosurgical training so just a recap you need to think about principles of ideal positioning the procedure and

fixation methods and for that you need to be familiar with the equipment you have the various positions the ones that i've gone through really are the standard positions that we use in everyday

practice and something that you would really need to be very familiar with and with that i come to the end

thank you felicia that was fantastic so um i do if anyone's got any questions please put them in the chat i've got one question from dr deepak jar

who sorry you might see my dog in the background here she's deciding to have a chat with me um dr deepak jar who's asking why not use why only use three pins in the

sagitta frame instead of four three pins don't give sufficient stability although i must admit i always use three pins um i haven't had any problems yet but

have you had any experience with four pins and um maybe your your your mentor or dr kirilos might also want to help answer there um okay for the sujita frame

actually we usually have the practice of using four i think the three pins uh i did mention it was more for the skull clamp but maybe mr ramez can comment about the

three pins if he's yeah the the gita has six slots which we use for at the time to opposite each other diagonally

which you tighten diagonally at the same time so you can always four will make it stable you can use three and the the beauty of

eliminating one because you have some patients who have multiple craniotomies and there is a bone gaps and sometimes it is not correct do you want to really to

avoid and even with your six choices you cannot avoid certain gap in your previous craniotomy holes in cases of revisions so you have the option but usually we

use the four and the sagitta rather than the three but for the mayfield and the doro three will be enough provided as felicia said that

you put don't put the whole pins superior to the equator otherwise the head will slip down i've got two very relevant questions

here for the junior residents felicia the youngest age limit for a patient to be pinned

malaysia oh sorry okay uh the youngest age limit really uh we cannot pin less than three that's my understanding

three i'd go probably go a bit older any advance on three

sorry dr kirilos would you would you uh pin a three-year-old or maybe wait a little while i i

i i couldn't hear the question right okay so below below five you have

to be careful and of course neonates you will not do it but before below five year you have to be careful but some positions you know if you are doing a vascular procedure that you need fixed really

fixed uh procedures there is especially you you use the special pediatric pins because these are not designed even for neonates or young people so the

pediatric pins have a shoulder on it rather than it's completely like a conical in shape so that they do not penetrate the inner table they have like a safety stop on it

okay so we've got somewhere between three and five but with great care below five and felicia one more question here um i'm gonna i'm gonna drop it stop it at

this one after this one and move on to the next what position would you use um if the patient had bilateral subdural hematomas uh we would standardly use a

neutral supine yeah yeah yeah that's that that's what that's what we'd use as well neutral supine okay felicia thank you very much for

your presentation that was that was fantastic you guys you've got great you've got great residents there in singapore all of the presentations i've seen so far have been excellent