Functional Neurosurgery

[kRakat0wa]

Hi,

I was wondering wether anyone could explain to me what type of surgery a Functional Neurosurgeon actually performs. What I mean is that Deep Brain Stimulation is very different to dissecting an acoustic neuroma. I ask this because if, well I think when, we have auditory, visual, sematosensory neural implants, and possibly cognitive, memory implants; collectively called neural prostethics - who will perform the surgeries to implant and fix problems. Will it a be functional neurosurgeons - because from my knowledge (not that it has any detail) functional neurosurgery isn't a speciality that involves complex surgery relevant to implants. So would it be a new specialist - who would "man" this new speciality. A combination of all neurosurgeons or is one particular more similar to implanting biomechanics devices. Cheers for replies.

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[RogueBanana]

Hi,

I was wondering wether anyone could explain to me what type of surgery a Functional Neurosurgeon actually performs. What I mean is that Deep Brain Stimulation is very different to dissecting an acoustic neuroma. I ask this because if, well I think when, we have auditory, visual, sematosensory neural implants, and possibly cognitive, memory implants; collectively called neural prostethics - who will perform the surgeries to implant and fix problems. Will it a be functional neurosurgeons - because from my knowledge (not that it has any detail) functional neurosurgery isn't a speciality that involves complex surgery relevant to implants. So would it be a new specialist - who would "man" this new speciality. A combination of all neurosurgeons or is one particular more similar to implanting biomechanics devices. Cheers for replies.

I'm sure a new specialty would evolve from general neurosurgery as neurological prosthetics evolves into a major portion of the field. If anything, I think the stereotactic guys handle a lot of the "implantation" aspect of neuro initially. They already handle a lot of the implantation cases I believe.

Functional Neurosurgeons handle cases where neurological disorders impede movement and basic functionality (parkinsons, MS, epilepsy, tremor etc...)
They don't handle implantation so much.....

if anyone knows better please correct me...

 

[kRakat0wa]

I'm sure a new specialty would evolve from general neurosurgery as neurological prosthetics evolves into a major portion of the field. If anything, I think the stereotactic guys handle a lot of the "implantation" aspect of neuro initially. They already handle a lot of the implantation cases I believe.

Functional Neurosurgeons handle cases where neurological disorders impede movement and basic functionality (parkinsons, MS, epilepsy, tremor etc...)
They don't handle implantation so much.....

if anyone knows better please correct me...

So what exactly is Sterotactic Neuorusgery, because I've heard of it, but thought it was inextricably linked to functional; like endovascualr and interventional neuroradiology. Cheers for any information.

 

[BurghStudent]

When doing a neurosurgery residency, you get exposure to functional and stereotactic neurosurgery. In fact, the fellowship program you complete after residency covers both aspects.

Functional neurosurgeons perform surgery to treat conditions like epilepsy. They plan and implement the placement of electrodes for deep brain stimulation. All of this is highly technical and still requires dexterity.

If anyone in surgery is going to oversee neural prostheses, it's functional neurosurgeons. If a prosthetic is intradural, a neurosurgeon will be involved. Moreover, functional neurosurgeons are much more informed and skilled in the area of implants, BCI than other neurosurgeons. As for the non-surgical side, there is a strong role for neurologists specializing in movement disorders, and physiatrists with respect to mobility and spine rehabilitation.

Check out BrainGate at Brown/MGH (Eskandar is Functional NSG)
http://www.braingate.org/

And the Motorlab at Pitt
http://motorlab.neurobio.pitt.edu/press.php

 

[kRakat0wa]

When doing a neurosurgery residency, you get exposure to functional and stereotactic neurosurgery. In fact, the fellowship program you complete after residency covers both aspects.

Functional neurosurgeons perform surgery to treat conditions like epilepsy. They plan and implement the placement of electrodes for deep brain stimulation. All of this is highly technical and still requires dexterity.

If anyone in surgery is going to oversee neural prostheses, it's functional neurosurgeons. If a prosthetic is intradural, a neurosurgeon will be involved. Moreover, functional neurosurgeons are much more informed and skilled in the area of implants, BCI than other neurosurgeons. As for the non-surgical side, there is a strong role for neurologists specializing in movement disorders, and physiatrists with respect to mobility and spine rehabilitation.

Check out BrainGate at Brown/MGH
http://www.braingate.org/

And the Motorlab at Pitt
http://motorlab.neurobio.pitt.edu/press.php

As of today, are there any current devices that are implanted into the brain by surgeons. If so, what are the devices and who implants them.

 

[BurghStudent]

As of today, are there any current devices that are implanted into the brain by surgeons. If so, what are the devices and who implants them.

Many technologies are in development right now.

Deep brain stimulation is being used for Parkinson's, and Essential Tremor, but is also being trialed for Alzheimer's, depression and even refractory obesity.

There are many spine stimulators in use right now to assist with pain management. These are typically placed by neurosurgeons, and sometimes if they're superficial enough, anesthesiologists.

Although not in the brain, vagus nerve stimulators are currently in use to treat refractory epilepsy. The one's I've seen have been placed by neurosurgeons.

 

[kRakat0wa]

Many technologies are in development right now.

Deep brain stimulation is being used for Parkinson's, and Essential Tremor, but is also being trialed for Alzheimer's, depression and even refractory obesity.

There are many spine stimulators in use right now to assist with pain management. These are typically placed by neurosurgeons, and sometimes if they're superficial enough, anesthesiologists.

Although not in the brain, vagus nerve stimulators are currently in use to treat refractory epilepsy. The one's I've seen have been placed by neurosurgeons.

I understand that they're all procedures completed by functional neurosurgeons. I think i have a misconception about the difficulty of deep brain stimulation. I always thought of skull base and open cerebro as the most difficult. Personally i was thinking of skull base and paediatric, but ever since childhood, implanting devices into the brain was always something I wanted to do. I can't see myself doing DBS, does it require technical skill, dexterity, because I thought there was a lot of computer guidance involved.

 

[BurghStudent]

I understand that they're all procedures completed by functional neurosurgeons. I think i have a misconception about the difficulty of deep brain stimulation. I always thought of skull base and open cerebro as the most difficult. Personally i was thinking of skull base and paediatric, but ever since childhood, implanting devices into the brain was always something I wanted to do. I can't see myself doing DBS, does it require technical skill, dexterity, because I thought there was a lot of computer guidance involved.

I see. I think @neusu could add to this conversation.

 

[kRakat0wa]

I see. I think @neusu could add to this conversation.

Im new to SDN. Should I DM neusu directly, or will the @ alert him to the convo?

 

[JustAPhD]

Im new to SDN. Should I DM neusu directly, or will the @ alert him to the convo?

It alerts him.

 

[Lawpy]

I see. I think @neusu could add to this conversation.

As could @mmmcdowe and @WedgeDawg

 

[WedgeDawg]

The closest thing to neural implants we have right now are cochlear implants which are generally put in and managed by ENTs. Functional neurosurgeons treat things like movement disorders and epilepsy with various methods of electrical stimulation (deep or superficial).

 

[kRakat0wa]

The closest thing to neural implants we have right now are cochlear implants which are generally put in and managed by ENTs. Functional neurosurgeons treat things like movement disorders and epilepsy with various methods of electrical stimulation (deep or superficial).

So if in the future we saw more advanced neural prostethics, from visual to cognitive, who do you think would be implanting the devices. Obviously cognitive implants are far from a reality, but as a surgical procedure would functional neurosurgeons or a new subspecialty perform the implants?

 

[kRakat0wa]

@WedgeDawg I have looked at the people involved in the BrainGate Research Consortium, one of the leading neural prostethics "labs" - what do you call a research group spread across numerous institutions?. The only PI neurosurgeon is Jamie Henderson, a Functional & Sterotactic Surgeon, who leads the clinical trials for the project at Stanford. There are only 2 or 3 other neurosurgeons - all functional neurosurgeons.

I think I have the wrong idea of DBS implants. I thought they were mostly positioned by robotic arms guided by computers, what does the surgeon actually do. With a more "detailed" implant wouldn't they have to wire up the device to various nerves? What does a DBS surgeon do during the procedure except supervise the robot?

 

[Go4Doc]

@WedgeDawg I have looked at the people involved in the BrainGate Research Consortium, one of the leading neural prostethics "labs" - what do you call a research group spread across numerous institutions?. The only PI neurosurgeon is Jamie Henderson, a Functional & Sterotactic Surgeon, who leads the clinical trials for the project at Stanford. There are only 2 or 3 other neurosurgeons - all functional neurosurgeons.

I think I have the wrong idea of DBS implants. I thought they were mostly positioned by robotic arms guided by computers, what does the surgeon actually do. With a more "detailed" implant wouldn't they have to wire up the device to various nerves? What does a DBS surgeon do during the procedure except supervise the robot?

It's funny you mention Jamie because I actually work with him. I'm a research assistant in the lab of the neurologist he collaborates with. I work exclusively with patients with Parkinson's Disease who are receiving DBS therapy and I'm helping test the first generation of sensing neurostimulators. I've sat in on several DBS surgeries and I can guarantee you there are no robots involved. We're not that futuristic yet! That being said, Jamie helped pioneer Medtronic's frameless-stereotactic system known as "Nexframe". Google it if you're curious as to how it works.

As I'm sure you know, stereotactic neurosurgery is also about precise localization and targeting of neural structures in 3D space. This most commonly makes use of a coordinate system based around the AC-PC, an imaginary line that connects the anterior and posterior commisures. Stereotactic planning is actually fairly straight forward and I used to do it for monkey DBS surgeries. You co-register MRI and CT scans, match what you see to a 3D brain atlas, identify the AC-PC and then use a computer program to digitally "place the electrodes". This gives you the coordinates you'll target in real life. The day of the surgery he drills burr holes that are relatively aligned with the tract in which he wants to place the leads (in DBS for PD we target the subthalamic nucleus). He then slowly advances a microelectrode hooked up to headphones that he and the neurologist are wearing. Once he gets to the approximate depth of the STN, he begins "mapping" the STN by flexing and extending the patients limbs. He's listening for bursts of static which is indicative of activity by nearby neurons. He can also stimulate through the microelectrode to test for side effects, improvement in symptoms, and twitches. If he's satistified we're in the motor area of the STN, he will retract the microelectrode and place the chronically implanted leads. He usually gets it on the first try. If there are weird side effects or if we're in non-motor areas, he retracts the microelectrode and tries again along a different tract.

I hope that helps in your understanding. Let me know if I can be of any further help!

 

[kRakat0wa]

It's funny you mention Jamie because I actually work with him. I'm a research assistant in the lab of the neurologist he collaborates with. I work exclusively with patients with Parkinson's Disease who are receiving DBS therapy and I'm helping test the first generation of sensing neurostimulators. I've sat in on several DBS surgeries and I can guarantee you there are no robots involved. We're not that futuristic yet! That being said, Jamie helped pioneer Medtronic's frameless-stereotactic system known as "Nexframe". Google it if you're curious as to how it works.

As I'm sure you know, stereotactic neurosurgery is also about precise localization and targeting of neural structures in 3D space. This most commonly makes use of a coordinate system based around the AC-PC, an imaginary line that connects the anterior and posterior commisures. Stereotactic planning is actually fairly straight forward and I used to do it for monkey DBS surgeries. You co-register MRI and CT scans, match what you see to a 3D brain atlas, identify the AC-PC and then use a computer program to digitally "place the electrodes". This gives you the coordinates you'll target in real life. The day of the surgery he drills burr holes that are relatively aligned with the tract in which he wants to place the leads (in DBS for PD we target the subthalamic nucleus). He then slowly advances a microelectrode hooked up to headphones that he and the neurologist are wearing. Once he gets to the approximate depth of the STN, he begins "mapping" the STN by flexing and extending the patients limbs. He's listening for bursts of static which is indicative of activity by nearby neurons. He can also stimulate through the microelectrode to test for side effects, improvement in symptoms, and twitches. If he's satistified we're in the motor area of the STN, he will retract the microelectrode and place the chronically implanted leads. He usually gets it on the first try. If there are weird side effects or if we're in non-motor areas, he retracts the microelectrode and tries again along a different tract.

I hope that helps in your understanding. Let me know if I can be of any further help!

The electrodes puncture the brain tissue, yes? How does this not impact the brain tissue. Does it not destroy neurones? It may sound stupid for an MD PhD to ask this sort of question, but im actually a maths undergrad, i can't figure out how to change my profile. So do the needles not destroy entire sections of neural tissue.

 

[Go4Doc]

Hey, never be afraid to ask what you don't know. I'm happy to help.

Regarding your question, they do indeed puncture the brain tissue hence "deep brain" stimulation. And you're right, this can and will have an impact on neural tissue. It's actually really neat, after we implant the leads and before we even begin stimulation, many patients experience significant but temporary (a week or so) relief of their symptoms. This is called the "microlesion" effect and it actually kinda makes sense. If you weren't aware, before there was DBS there was an alternative treatment for PD: a pallidotomoy. In the days before we realized we could stimulate rather than ablate, they essentially lesioned the internal capsule of the globus pallidus to produce the same effect. Therefore, the initial implantation of the electrodes has essentially the same effect as a lesion but it's temporary and the brain adjusts to the intrusion. This is why you need chronic stimulation. The great thing about DBS is that compared to a lesion, it's relatively reversible.

 

[Go4Doc]

One way to think about the effect of the actual stimulation is as an "informational lesion". Same effect as an actual lesion but it's reversible. Kinda like a much smaller, more precise, and more invasive version of TMS.

 

[kRakat0wa]

One way to think about the effect of the actual stimulation is as an "informational lesion". Same effect as an actual lesion but it's reversible. Kinda like a much smaller, more precise, and more invasive version of TMS.

Ah. So the lesion isn't necessarily damaging per say. Will it completely heal? Because CNS neural tissue doesn't have any natural regenerative ability does it? A question related to Parkinsons, are there any possible future surgical procedures for Alzheimers. It may be a bit far fetched, but is it even possible for surgical implantation of neural tissue to "treat" neurodegenerative diseases. Cheers for the detail on DBS.

 

[Go4Doc]

Ah. So the lesion isn't necessarily damaging per say. Will it completely heal? Because CNS neural tissue doesn't have any natural regenerative ability does it? A question related to Parkinsons, are there any possible future surgical procedures for Alzheimers. It may be a bit far fetched, but is it even possible for surgical implantation of neural tissue to "treat" neurodegenerative diseases. Cheers for the detail on DBS.

Exactly. There's bound to be a couple dozen or even 100+ neurons to get destroyed during this procedure but in the grand scheme of things that's completely negligible. Also remember that neurons are exceedingly small so rather than getting punctured, they usually get pushed out of the way. Furthermore, once you pass through the cortex, you're pretty much pushing through white matter (i.e. myelinated axons) until you reach the nuclei of the midbrain so those are even easier to be pushed out of the way. Long story short, there's unlikely to be any lasting damaging impact from the implantation and the benefits of the surgery far outweigh the relatively few neurons lost.

Regarding surgical procedures for Alzheimer's, I'd say the current outlook is relatively bleak. Pharmaceutics shows the most immediate promise. Unlike PD, Alzheimer's affects a much more diffuse number of structures and the degree of neurodegeneration experienced by those with Alzheimer's is significantly more pronounced as compared to Parkinson's. Therefore, the inherently focal nature of DBS is unlikely to get you anywhere. We think it works with PD because it helps to "pace" abnormal rhythms in the brain. AD on the other hand, is not a pacing issue.

The one possible future surgical procedure that might one day be used to treat AD would be the injection of genetically modified neural stem cells that are in some way resistant to "infection" by tau or death caused by amyloid beta plaques. This is more in the realm of regenerative medicine and it's also important to note that this would not restore memories. Once those are gone they're gone. Rather, it would increase capacity, allowing those with AD to relearn things again. It also may improve certain things like problem solving ability. Again though, this would simply replenish capacity and there would likely be a significant relearning curve in patients receiving this hypothetical treatment.

 

[kRakat0wa]

Exactly. There's bound to be a couple dozen or even 100+ neurons to get destroyed during this procedure but in the grand scheme of things that's completely negligible. Also remember that neurons are exceedingly small so rather than getting punctured, they usually get pushed out of the way. Furthermore, once you pass through the cortex, you're pretty much pushing through white matter (i.e. myelinated axons) until you reach the nuclei of the midbrain so those are even easier to be pushed out of the way. Long story short, there's unlikely to be any lasting damaging impact from the implantation and the benefits of the surgery far outweigh the relatively few neurons lost.

Regarding surgical procedures for Alzheimer's, I'd say the current outlook is relatively bleak. Pharmaceutics shows the most immediate promise. Unlike PD, Alzheimer's affects a much more diffuse number of structures and the degree of neurodegeneration experienced by those with Alzheimer's is significantly more pronounced as compared to Parkinson's. Therefore, the inherently focal nature of DBS is unlikely to get you anywhere. We think it works with PD because it helps to "pace" abnormal rhythms in the brain. AD on the other hand, is not a pacing issue.

The one possible future surgical procedure that might one day be used to treat AD would be the injection of genetically modified neural stem cells that are in some way resistant to "infection" by tau or death caused by amyloid beta plaques. This is more in the realm of regenerative medicine and it's also important to note that this would not restore memories. Once those are gone they're gone. Rather, it would increase capacity, allowing those with AD to relearn things again. It also may improve certain things like problem solving ability. Again though, this would simply replenish capacity and there would likely be a significant relearning curve in patients receiving this hypothetical treatment.

Again thanks for that explanation. I always pictures DBS as pushing through jelly, which is odd because I dont normally think of the brain like that. What other sort of procedures do functional neurosurgeons work with? I know of vagus nerve and spinal, but they are purely for pain relief, are there any other significant procedures functional neurosurgeons do both involving and not involving stimulation. One last thing, your status says pre-med, are you thinking about ginog into ns or neurology or another field completely.

 

[Go4Doc]

Haha yeah definitely not jelly but it is pretty squishy hence its ability to accommodate the electrodes. As for other functional neurosurgical procedures, I'm afraid I can't be of much help there. At the moment I'm fairly specialized in Parkinson's disease with some exposure to adult neurogenesis and stem cell biology.

And yes, I am pre-med. I'll actually be applying this cycle for MSTPs and yes, Neurology is probably the field I'm most interested in pursuing. I am interested in neurosurgery but don't know if I'd pursue a residency that insane after the extra years I'm putting in for the PhD.

 

[kRakat0wa]

Haha yeah definitely not jelly but it is pretty squishy hence its ability to accommodate the electrodes. As for other functional neurosurgical procedures, I'm afraid I can't be of much help there. At the moment I'm fairly specialized in Parkinson's disease with some exposure to adult neurogenesis and stem cell biology.

And yes, I am pre-med. I'll actually be applying this cycle for MSTPs and yes, Neurology is probably the field I'm most interested in pursuing. I am interested in neurosurgery but don't know if I'd pursue a residency that insane after the extra years I'm putting in for the PhD.

Cheers. Worth a shot. You've been a great help explaining DBS. You dont often get good responses from neurosurgeons on forums like these. Maybe they just dont have the time

 

[Go4Doc]

Cheers. Worth a shot. You've been a great help explaining DBS. You dont often get good responses from neurosurgeons on forums like these. Maybe they just dont have the time

Haha happy to help. And yea, I can imagine they get pretty busy so I figured I'd step in and offer what knowledge I had.

 

[neusu]

Sorry, I'm a little late to the party and a little busy to read all of the replies at the moment. I'll take a look later and try to comment as indicated.

If you guys have any specific questions I'd be happy to address.

For the most part, the subsection is named Stereotactic and Functional Neurosurgery. This includes as mentioned deep brain stimulators as well as spinal cord and peripheral nerve stimulators, epilepsy surgery, and intrathecal pumps. Before stimulators existed, functional neurosurgery involved lesioning. Stereotactic neurosurgery is the practice of using a frame that screws in to the skull (like a halo ring or Mayfield clamp), on which a fiducialized array is placed and an image obtained. From these source images, a target can be calculated and the associated needle guide set such that the needle can be placed anywhere within the skull with finite precision. This was exceptionally useful before the advent of computerized navigation. It is still commonly used for cases where the level of error built in to the other navigation systems is too great. We use these systems for electrode placement, lesioning, and biopsy.

At the moment, there are not the advanced neuroprosthetics that we dream of. The technology to interface between the brain and machines, as well as our understanding of how neurons communicate, is too rudimentary. The brain-gate team is doing some excellent work, and there are specific labs within the consortium around the country.

To answer your question, for the most part, functional neurosurgery is often not terribly technically challenging from a mechanical point of view. Even so, the technical challenge is in understanding the anatomy, physiology, and pathology associated with the diseases we treat, selecting the appropriate treatment modality, and performing that surgery the best we can.

Finally, epilepsy surgery is one of my favorite sub-specialty surgeries. Classically, for treatment of medically refractory epilepsy, we become involved. On imaging there may be signs of a region of concern for the seizures, and we may do invasive studies such as subdural grids and strips for a period of prolonged monitoring in the epilepsy monitoring unit. Following this, a lesionectomy, lobectomy, hemispherectomy or tractectomy (callosotomy etc) may be performed to remove the focus causing the seizures, the region from where the seizures appear to derive, or to disconnect the brain from itself so the seizures can no longer propagate.