Bionics 5
Kevin Warwick
Deep Brain Stimulation
• It is a surgical treatment involving the
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implantation of electrodes, which send electrical
impulses to the specific parts of the brain in
which they have been positioned by the surgeon.
First ‘official’ treatments like this were
commenced in 1997.
Most common use is to arrest the tremor
associated with Parkinson’s Disease – we will deal
with this in a separate lecture.
Also found to be useful for depression.
Can be side effects!!
Deep Brain Stimulation
• Definitely this is “Bionic”, as ultimately the
person’s brain is operating partly due to its
biological function and partly in response
to electronic stimulation.
• We will look here at what DBS is.
• We will look at the sort of cases that DBS
is presently employed to tackle.
Operation
• Only dealing with
serious/long term
cases here – where
all else has failed.
• Surgery can last for
10+ hours
• Test signals input
during operation
Components
• The system consists of three elements:
• The implanted pulse generator (IPG): is a battery
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powered neurostimulator encased in a titanium housing,
which sends electrical pulses to the brain to modify the
neural activity at the target site.
The electrode lead: is a wire insulated in polyurethane
with four/six platinum iridium electrodes at its tip and is
usually placed in one of three areas of the brain.
An extension wire: connects the lead to the IPG. It is an
insulated wire that runs from the head, down the side of
the neck, behind the ear to the IPG, which is placed
subcutaneously.
The IPG is adjusted and calibrated by a
neurologist/surgeon to optimize symptom suppression
and control side effects.
Surgery
• The procedure begins with preoperative
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identification of the neurosurgical target using
Computed Tomography (CT) or MRI.
During surgery, the patient is given local
anaesthesia and remains awake. A craniotomy is
performed and a DBS lead is placed either
unilaterally or bilaterally, depending on the
patient's symptoms.
Microelectrode recording may be used to more
precisely locate the desired target within the
brain.
The IPG and extension are subsequently
implanted and connected to each lead.
Uses of DBS
• Main use is for PD
• Potential use with Epilepsy??
• Clinical Depression
• Tourette Syndrome
• Obsessive-Compulsive Disorder
• Severe Persistent Pain – such as Phantom
Limb pain
Clinical Depression
• It is a state of intense sadness or despair that is
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disruptive to a person’s social functioning and life.
Term ‘depression’ is used widely to describe (in everyday
terms) a low mood – doesn’t affect main functioning.
Clinical depression is a clinical diagnosis, i.e. someone
else (a doctor) agrees with you that you are depressed.
Clinically depressed - feeling sad for no reason or having
no motivation to do anything.
Person may feel tired, sad, irritable, lazy, unmotivated,
and apathetic.
It leads to constant negative thinking and sometimes
abuse (alcohol/drugs) or self-harm. Extreme depression
can culminate in its sufferers attempting or committing
suicide.
Clinical Depression
• Treatment by Electric Shock?
• Electroconvulsive therapy (ECT) uses short bursts of a controlled
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electric current (typically 0.9 Amps) passed into the brain to induce
a brief seizure while the patient is under anaesthesia.
Typically a patient receives three treatments per week over three or
four weeks. Repeat sessions may be needed. Memory loss,
disorientation, and headache are very common side effects.
ECT offers the benefit of a very fast response; however, this
response has been shown not to last unless maintenance electric
shock or maintenance medication is used.
Antidepressants usually take around a month to take effect,
whereas the results of ECT have been shown to be much faster. It is
the treatment of choice in emergencies (e.g., when the patient has
ceased oral intake of fluid or nutrients).
There remains much controversy over electric shock treatment!
Clinical Depression
• DBS is still an experimental method of dealing with
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clinical depression.
Tested only in extreme cases thus far – where drugs,
ECT etc have failed
Electrode target – Brain Area 25 – frontal cortex.
When electrodes are switched on, patients describe a
‘black cloud lifting’ – immediately more interested in life.
When electrodes are switched off – depression returns.
Alternative area for stimulation – nucleus accumbens –
associated with pleasure/reward – similar results.
Tourette Syndrome
• It is an inherited neurological disorder with typical
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onset in childhood.
It is characterized by the presence of multiple
physical (motor) tics and vocal (phonic) tics.
These tics characteristically wax and wane.
People with Tourette's have normal life
expectancy and intelligence. Can reduce in teens.
Tourette's was once regarded as rare and bizarre,
most often associated with the exclamation of
obscene words – actually only a very small
proportion – also echoing & repeating.
Tourette Syndrome
• Treatment for mild cases – simply managing
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them – psycho behavioural therapy, education,
and reassurance.
No cure – different drugs help with different
types of the syndrome.
20% of persons with Tourette syndrome do not
recognize that they have tics.
Treatment problems due to intermittent
behaviour and lack of knowledge as to what
stimuli start them at a particular time.
Tourette Syndrome
• DBS has been used experimentally/successfully in a few
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patients with severe cases.
Study is needed to determine whether long term
benefits outweigh the risk.
Complications include "short battery life, abrupt
symptom worsening upon cessation of stimulation and
significant time and effort involved in optimizing
stimulation.
All cases experienced reduction in tics.
Lots of questions: There may be serious short- and longterm risks. Expert care &support required. Difficult to
assess exact electrode positioning.
Not so suitable for children – as it may go away.
Obsessive-Compulsive Disorder
• It is an anxiety disorder characterized by a
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subject's obsessive thoughts and related
compulsions (fituals) which attempt to neutralize
the obsessions.
It is listed by the WHO as one of the top 10
most disabling illnesses in terms diminished
quality of life.
A person who shows signs of infatuation or
fixation with a subject/object, or displays traits
such as perfectionism, does not necessarily have
OCD, a specific and well-defined condition.
Obsessions
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Recurrent and persistent thoughts or impulses that are
experienced as intrusive and that cause distress.
The person can attempt to ignore or suppress such
thoughts or impulses or to neutralize them with some
other thought or action.
It is important for the person to recognize that the
obsessional thoughts or impulses are a product of his
or her own mind, and are not based in reality.
The tendency is to haggle over small details that the
person is unable to permanently fix or change in any
way. This begins a mental pre-occupation with that
which is inevitable.
Compulsions
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Compulsions are repetitive behaviours that the person
simply must perform in response to an obsession according to rules that must be applied rigidly.
These behaviours are supposedly aimed at preventing
or reducing distress or preventing some terrible event
or situation,
The behaviours are not connected in a realistic way
with what they are designed to neutralize or prevent, or
are clearly excessive.
In addition, at some point, the sufferer must realize that
his/her obsessions or compulsions are unreasonable or
excessive. Moreover, the obsessions or compulsions can
be time-consuming, can cause distress, or cause
impairment in social functioning.
OCD – Examples 1
• Repeated hand washing.
• Repeated clearing of the throat, although nothing
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may need to be cleared.
Arranging objects in groups of three, grouping
objects in odd numbered groups.
Counting steps, e.g. the need to take 12 steps to
the car in the morning.
Aligning objects at absolute right angles or
perfectly parallel.
Having to "cancel out" bad thoughts with good
thoughts, e.g. Imagining harming a child and
having to imagine a child playing happily.
OCD – Examples 2
• Sexual Obsessions or unwanted sexual thoughts.
• Fear of contamination; fearing the presence of human body
secretions such as sweat or vomit or excretions such as urine
or feces. Fear that the soap they're using is contaminated.
• A need for both sides of the body to feel even. If one hand
gets wet, the sufferer may feel very uncomfortable if the
other is not. If the sufferer is walking and bumps into
something, he/she may hit the object or person back to feel a
sense of evenness. Conversely some sufferers would rather
things to be uneven.
• An obsession with numbers.Some people are obsessed with
even numbers, loathing odd numbers (causes anxiety and can
make the person very angry).
• Twisting the head on a toy around, then twisting it all the way
back.
DBS Treatment for OCD
• Tested and successful on extreme cases
only – where all else has failed.
• Procedure still questioned for this sort of
use.
• Little known as to what actual effects the
DBS is having in the brain.
• No long terms results yet.
• Side-effects still a research question.
Persistent pain
• Pain is categorized in a number of ways –
we are only interested here in extreme
cases – where DBS could be used.
• Phantom Limb pain
• Neuropathic pain
• Visceral (organ) pain
• Not so interested (yet) in somatic or
cutaneous pain
Visceral Pain
• Originates from body's viscera (organs).
• Nociceptors are located within body organs and internal cavities.
• The scarcity of nociceptors in these areas produces a pain that is
aching and of a longer duration than somatic pain.
• Visceral pain is difficult to localize, and injuries to visceral tissue can
exhibit referred pain, where the sensation is localized to an area
unrelated to the site of injury.
• Myocardial ischaemia (loss of blood flow to part of the heart muscle)
is a good example. The sensation can occur as an ache in the left
shoulder or hand.
• Referred pain can be explained by the findings that pain receptors in
the viscera also excite spinal cord neurons that are excited by
cutaneous tissue. Since the brain normally associates firing of these
spinal cord neurons with stimulation of somatic tissues in skin or
muscle, pain signals arising from the viscera are interpreted by the
brain as originating from the skin.
Phantom Limb Pain
• It is the sensation that an amputated or missing limb is still
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attached to the body and is moving along with other body
parts.
70% of amputees experience phantom sensations, the
majority report that the sensations are painful.
Phantom sensations, a referred pain, may also occur after
the removal of body parts other than the limbs, e.g. after
amputation of the breast, extraction of a tooth (phantom
tooth pain) or removal of an eye.
Phantom pains can occur in people who are paralysed or
born without limbs.
Sensations can include warmth, cold, itching, squeezing and
burning.
The missing limb often feels shorter and may feel as if it is
in a distorted and painful position. Occasionally, the pain
can be made worse by stress or weather changes.
Phantom Limb Pain
• The dominant theory for cause of phantom limbs used to
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be - irritation in the severed nerve endings. When a limb
is amputated, severed nerve endings are terminated at
the remaining stump. These nerve endings can become
inflamed, and may send anomalous signals to the brain.
These signals, being functionally nonsense, were
thought to be interpreted by the brain as pain.
Treatments based on this theory were failures.
Sometimes surgeons would perform a second
amputation, shortening the stump, hoping to remove the
inflamed nerve endings and cause temporary relief.
Instead, the phantom pains increased, and many were
left with the sensation of both the original phantom limb,
as well as a new phantom stump, with a pain all its own.
In some cases, surgeons cut the sensory nerves leading
into the spinal cord or in extreme cases removed the
part of the thalamus that receives sensory signals from
the body.
Neuropathic Pain
• Disease of the peripheral nerves
• Often results in numbness and neuralgia – very different
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from pain due to stubbing a toe.
Neuropathic pain is usually perceived as a steady
burning or like an electric shock. The difference is due to
the fact that "ordinary" pain stimulates only pain nerves,
while a neuropathy often results in the firing of both pain
and non-pain (touch, warm, cool) sensory nerves in the
same area, producing signals that the spinal cord and
brain do not normally expect to receive.
Only very extreme cases can be considered for DBS
Acts as a pain blocker
Problems/Side Effects?
• When using DBS to tackle a problem, various
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side-effects have been reported.
Examples: hallucinations, hyper sexuality,
compulsive gambling, depression, cognitive
dysfunction and apathy.
Extreme/few cases: voyeurism & suicide.
Could be due to shifting electrodes or bleeding
Possibly reversible conditions (not-suicide!)
Small %age of the total + compare with original
problem
May even have occurred anyway.
Comments
• DBS still in its infancy
• Presently only employed in more extreme
cases
• Very experimental – handful of surgeons
• Potentially could be used for many other
problems, e.g. arthritis.
• Electrode position, signal frequency and
magnitude are to be investigated
Next Lecture
• Human Enhancement