The Twins Who Share A Brain

Channel 4 recently broadcast an interesting documentary as part of their 'Bodyshock' series, dealing with a set of twins who are joined at the head. I wrote some notes while watching the documentary:

Tatiana and Krista Hogan are regarded as a 'medical marvel'. While instances of twins being born joined at the heads are rare, ithis particular case is certainly a marvel in living memory. Their mother, Felicia Hogan, discovered this information at her 21-week scan. As she was 21 years of age at the time and already had two older children, the medical staff offered her the option to have a termination in view of the weight of responsibilities she would have if she went through with the birth. Felicia opted against the offer and, at the time of birth, doctors were surprised at the survival of both mother and babies. They also noticed something strange: when one twin was injected, the other spontaneously cried. Further observations from family as the twins were growing up, such as one twin 'zoning out' when looking at something while the other twin's eyes twitched, made them speculate as to whether the twins shared senses.

How could this be possible? Four months after the twins were born, they underwent a CT scan to check for any indications. It was found that they shared brain matter and arterial structures in an interconnected fashion, so there could be no possibility of surgical separation as sometimes occurs in other cases of conjoined twins. Furthermore, it was discovered that both twins shared the same thalamus, which is the brain structure responsible for processing sensory inputs and relaying them to other structures - a communications control room.

(Tatiana, bottom left, and Krista, bottom right, with their mother Felicia, top left.
Image courtesy: Macleans.ca)

The documentary followed the progress of the Hogan twins over the course of a year or so. At around age 2 years and 4 months, the twins weren't able to walk but could stand with support, and had begun to talk using simple expressions like "stop that!" in response to stimulation. Also, it was possible to see the birthing of two distinct personalities.

Tatiana's qualities include being the more "intellectual" of the two (whatever that means for a 2 year old child!), and is very loving, engages in frequent hugging and kissing behaviours, of a happy disposition. By contrast, Krista, who can also be loving and happy, tends to be more hot-tempered, exhibiting protest (crying) behaviours and is more aggressive, will scream to get what she wants and can even be a bit of a "bully" according to Felicia. However, separate personalities though they are, they are already beginning to learn the value of cooperation and they work together on simple tasks such as coordinating movement to stand up and attempt to walk. If you tickle Krista, Tatiana giggles.

Some of the usual medical problems affecting many pairs of conjoined twins also affect the Hogans. Despite being smaller and thinner, Tatiana's heart pumps for both of them and is thus at risk of enlargement and possible failure. Tatiana's heart also works twice as hard to supply the brain's arterial system with blood. Over time, her heart rate has thankfully dropped and is much closer to Krista's, but the possibility of further complications as the twins age always looms.

It was also discovered that when the twins slept, Tatiana would stop breathing for up to 20 seconds. A surgical operation was needed to remove the huge adenoids that were causing the problem, but when Tatiana was anaesthetised it was observed that she was borrowing a large amount of blood to keep her going. The trouble with this was that Krista didn't have enough blood to be anaesthetised herself, which meant she had to be awake (and suffer pain?) when Tatiana went under the knife.

The rest of the documentary focused largely on the Hogan family's meeting with another pair of craniopagus twins, Lori and George Schappell, who are also joined at the head but have separate brains. The Schappells have enjoyed fame to an extent by appearing on a variety of talk shows, television dramas and singing contests, and were able to discuss their situations and give advice for the Hogans in matters of parenting and how to engage the Hogan twins in relationship skills.

At a later date, further tests were carried out to investigate further the possibility of shared senses. They concluded that the "brain of one twin records signals from the other's visual field". The explanation proffered for this told about how images entering the eyes of a twin travel along a "neuron highway" to the other's visual cortex, meaning that one twin can see what the other witnesses. Fascinating.

Virginia Woolf's Last Letter

Virginia Woolf (1882-1941) was one of the foremost literary figures of the 20th Century, having produced several novels, short stories, and diaries. A number of traumatic events in her life, such as the death of her parents in her teens and sexual abuse at the hands of her half-brothers, may have contributed to the depression that plagued her throughout her life. Although her literary output remains largely unaffected, she was subject to periodic mood swings and associated illnesses until her suicide at age 59.

In a letter to her husband, regarded as her suicide note, she revealed a glimpse of life as a voice-hearer:


Transcript:

Tuesday.

Dearest,

I feel certain that I am going mad again. I feel we can't go through another of those terrible times. And I shan't recover this time. I begin to hear voices, and I can't concentrate. So I am doing what seems the best thing to do. You have given me the greatest possible happiness. You have been in every way all that anyone could be. I don't think two people could have been happier till this terrible disease came. I can't fight any longer. I know that I am spoiling your life, that without me you could work. And you will I know. You see I can't even write this properly. I can't read. What I want to say is I owe all the happiness of my life to you. You have been entirely patient with me and incredibly good. I want to say that - everybody knows it. If anybody could have saved me it would have been you. Everything has gone from me but the certainty of your goodness. I can't go on spoiling your life any longer.

I don't think two people could have been happier than we have been.

V.

Foot Discovered In Baby Brain

Ok guys, for the first time I have something that's

NSFW!

Pity that isn't my own work, I'm lazy right now and nicked this via Joanne Manaster and KevinMD.com. Still, you gotta admit this story treads the fine line between Whoa and Pass-Me-That-Buckettttt. The Denver Channel is running a story about a medical first - a foot found growing inside a newborn's brain. I have nothing to add so I'm just gonna post the entire article here. Graphic image ahead, you have been warned:

COLORADO SPRINGS, Colo. -- A Colorado Springs family is part of one of the strangest cases in medical history.

Dr. Paul Grabb, a pediatric brain surgeon, said he was surprised when he discovered a small foot growing inside the brain of 3-day-old Sam Esquibel. "The foot literally popped out of the brain," Grabb told TheDenverChannel Wednesday.

The appendage threatened the newborn's life.

When Grabb performed the life-saving surgery at Memorial Hospital for Children in Colorado Springs, he was in for another surprise: he also found what appeared to be parts of an intestine in the folds of the infant's tiny brain, in addition to another developing foot, hand and thigh. "I've never seen anything like it before," Grabb told the Colorado Springs Gazette. "It looked like the breach delivery of a baby coming out of the brain."


Sam was delivered on Oct. 1, within hours of an ultrasound that showed what appeared to be a tumor developing in the brain of the fetus. Three days later, Grabb performed the surgery to remove it. The reason for the strange growth was not clear at first. It was thought to be a teratoma -- a congenital brain tumor composed of foreign tissue such as muscle, hair or teeth -- or a fetus in fetu, which is a developmental abnormality in which a fetal twin begins to form within the other.

Grabb, the only pediatric brain surgeon in southern Colorado, said that the formal pathology report identified the mass as a teratoma because of how perfectly formed the structure was but there is a fine line between that and the fetus in fetu. "So it's unclear if a fetal twin began to form within another," Grabb said.

Grabb said he sees a teratoma once every few years but it doesn't compare to Sam's. Teratoma tumors do not usually grow as complex as a foot. "You show those pictures to the most experienced pediatric neurosurgeons in the world, and they've never seen anything like it," Grabb told the Gazette. "This is completely abnormal."

Grabb said neurologically, Sam is expected to do well. Sam's brain tumor can come back so he will be monitoring that in the months and years to come.

Mom Says Baby A Miracle

Sam's mom, Tiffnie, told TheDenverChannel on Wednesday that her son is doing well but that she didn't want to appear on camera because she doesn't want to exploit her child and make him appear like a freak in the eyes of the world.

"This is our baby," Tiffnie explained, in tears.

She said when she first talked to the Gazette, she thought the story would only appear in the small-town paper. But it has circled the globe and she is getting calls from national and international media outlets. "I am so overwhelmed right now ... We've been bombarded with calls," Tiffnie said.

DenverChannel.com Reporter Jane Slater held the infant with the baby blue eyes and round face and said "he is the cutest baby I've ever seen." Sam's at a healthy weight -- as evidenced by his pudgy arms and legs -- which explains why family members call him the "Michelin Man," Slater said.

He was alert and happy, with a barely visible inch-long scar which stretched from his hairline to the top of his cheek. Sam is still recovering from the surgery and shows weakness on one side of his body and some trouble with higher-level eye functions. He is already undergoing rehabilitation.

Tiffnie had said that her pregnancy was easy and there were no signs of complications until the ultrasound on Oct. 1. She and her husband had given up on the idea of having any children after years of trying and then Sam was conceived. Tiffnie said she doesn't mind driving to the hospital every week or month for Sam's MRI and blood checks, considering that he is healthy and happy.

"It's a miracle," she said.

In the meantime, Grabb wonders about the possibilities for medical science. "How does the body form complete extremities? Who is to say we can't grow a heart, leg or foot?" Grabb asked the Denver Post earlier. "This could show a window of what's possible."

"It's always impressive to see these sorts of things but it's not as unsual as you would think," said Dr. Rich Gustafson, with Cherry Creek Pediatrics. "Teratomas can be found in abdomens or other parts of the body ... what made this case so unusual is how perfectly formed the foot was and being in the skull as well. Usually, it's a totally safe and benign tumor. Often, it gets picked up in adulthood but now with ultrasound, you're actually picking more up as they are getting fetal ultrasounds."

Thugs left man with half a head

I don't often read tabloids, but I noticed this intriguing report in The Sun lately:

Thugs left man with half a head

By STAFF REPORTER

Published: 11 Sep 2009

VICIOUS thugs who punched this man so hard he was left with HALF A HEAD have got off scot free.

Horrified Steve Gator had to have the front of his skull removed by stunned surgeons after his head was smashed against a pavement in the sickening attack. And now the 26-year-old has been told that the teen attackers who disfigured him will escape justice after his case was dropped.

Steve, of Romford, Essex, was attacked after confronting one of the yobs who had been taunting him about his cousin. Another of the violent louts hit him so hard that he was sent flying and struck his head on the path. Steve plunged into a coma for two weeks as his shattered mum and distraught family kept a bedside vigil at Queen's Hospital, Romford.

His brain quickly began swelling and surgeons were forced to remove the front half of his skull just hours after he was admitted.

Grief-stricken mum Nina Gator was warned her son had just a terrifying 15 per cent chance of survival. Two days later cops charged a pair of teenage boys with the savage attack which shocked the neighbourhood. Steve, who has had to quit his job, was left seriously brain damaged and now suffers frequent seizures, has difficulty talking, and his memory is seriously impaired. Mrs Gator, who is his main carer, last night blasted the shock move. The 47-year-old said: "I can't believe it. Everyone is entitled to their day in court."

CPS lawyers claim they needed more proof before going ahead with the case. But Mrs Gator stormed: "Our boy is walking around with half a head - what more evidence do they need? "His sparkle is totally gone. He used to be so independent but he can't work any more and he can't drive." She added: "He's got half a head and he's completely lost his confidence. There's absolutely nothing protecting his brain now it's just under his skin."

Just from looking at the picture, it seems obvious that with this traumatic brain injury (TBI) his frontal lobes are practically destroyed and quite possibly the front parts of his midbrain. The frontal lobe is an extremely important structure responsible for a variety of functions. It is the 'Command HQ' for emotions, and controls and regulates functions such as memory, language, movement, and problem-solving. It is also responsible for more subtle things like judgment, planning, reasoning, spontaneity or impulse control, and some effects on social and sexual behaviour. As such, the frontal lobe administrates much of our very personality and sense of identity. It is also the largest 'lobe' structure, meaning that there is more of it to carry a greater risk of damage. As the story mentions, Gator's "sparkle is totally gone". It is tempting to draw parallels with the tale of Phineas Gage, another individual dubiously famed for frontal lobe damage.

A friend, The Neurocritic, pointed out that Gator may need several cranioplasties in order to rebuild his skull, and highlighted a recent Neurosurgical Focus literature review that discusses the types of post-operative complications associated with the surgical procesure underwent by Gator. Known as a decompressive craniectomy, and consisting of a partial removal of the skull in order to allow the swelling brain to expand without being squeezed, we start with contusion blossoming; the surgery leaves massive bruises which can be observed via pre-op and post-op CT scans.

Lesions - a mass lesion may develop on the opposite side of the brain to the injury or elsewhere in the brain. As Gator's frontal lobes were destroyed, it is possible that a lesion may develop around the back end and possibly affect the parietal lobes, which deals generally with perception, orientation and recognition.

Herniation - a small protrusion (or more) of neural tissue may remain in the early period after swelling subsides, sometimes through the cranial defect as is observed with 'normal' skin hernias. Gator has no such defect though, as the front of the skull was smashed.

Subdural Effusions - a collection of pus beneath the outer lining of the brain. This condition usually results from bacterial meningitis, but because craniectomies affect the circulation of cerebrospinal fluid (CSF) it is possible that buildups may accumulate. Similar to blood clots. Hygromas may also occur, which are buildups of CSF without blood. To counteract these, a craniectomy should be accompanied with a duraplasty, a reconstructive operation on the dura mater, the outermost and fibrous membrance covering the brain and spinal cord. Duraplasties have been observed to lower the incidence of subdural effusions occurring.

Infection - this may seem a rather obvious effect of any medical procedure, to guard against, but craniectomies (bone removal) will necessitate cranioplasties (bone reconstruction). As such, opening old scars and exposing the brain upto or after a month after the incident runs the risk of contracting infection and delaying healing. The review suggests a minimum wait of 3 months before replacing the bone, and that storage of the bone in a freezer can also increase the risk of infection.

Hydrocephalus - "water on the brain", refers to accumulations of CSF in neural cavities. This is unfortunately a common occurrence beyond a month after the injury, and will need specialised procedures (shunt treatment) to deal with it if it occurs.

Syndrome of the Trephined - another unfortunate common occurrence after decompressive craniectomies, of which common symptoms include dizziness, headaches, concentration difficulties, mood disturbances, irritability, and memory problems. Because Gator's particular situation involved the destruction of his frontal lobes, he will unfortunately suffer much worse symptoms than these. However, in general terms when the motor functions are affected, this then becomes known as motor trephine syndrome.

Bone resorption - when one undergoes a decompressive craniectomy, you're likely to have stray bone fragments swimming around and there's around a 50% chance that bone resorption will occur, which is when bone cells (known as osteoclasts) break down the bone and release minerals like calcium directly into the blood.

Persistent vegetative state - clearly the saddest effect of all extreme brain injuries. While decompressive craniectomies are effective at ameliorating intra-cranial pressure and reducing the risk of death, they offer no guarantee of restoring brain function once the patient suffers a TBI. The risks of surviving into a vegetative or minimally conscious state after undergoing craniectomy range upwards of 15-20%.

It may be that Steve Gator's clinicians need to be vigilant and ensure that his treatment is as risk-free as possible. And of course, wishing him all the best to recover well.
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Stiver, S. (2009). Complications of decompressive craniectomy for traumatic brain injury Neurosurgical FOCUS, 26 (6) DOI: 10.3171/2009.4.FOCUS0965

If You Had Half a Brain..

A great story made its way onto the interwebz lately. The Daily Mail reports:

"A 10-year-old girl born with half a brain has both fields of vision in one eye, scientists said today. The youngster, from Germany, has the power of both a right and left eye in the single organ in the only known case of its kind in the world.

"University of Glasgow researchers used Functional Magnetic Resonance Imaging (fMRI) to reveal how the girl’s brain had rewired itself in order to process information from the right and left visual fields in spite of her not having a whole brain."

BBC News goes further with:

"In the case of the German girl, her left and right field vision is almost perfect in one eye. Scans on the girl showed that the retinal nerve fibres carrying visual information from the back of the eye which should have gone to the right hemisphere of the brain diverted to the left ... 'Despite lacking one hemisphere, the girl has normal psychological function and is perfectly capable of living a normal and fulfilling life. She is witty, charming and intelligent.'"

Get that? The only known case in the world where brain plasticity (the ability of the brain to reorganise itself after injury) is displayed for all to see. Plasticity doesn't always work this way, there are many cases where plasticity effects haven't achieved the mark of restoring all or most of the impaired brain function. Epilepsy patients, for example, who undergo a hemispherectomy (removal of a half of a brain) in order to prevent the onset of severe seizures, among other things tend to lose an entire field of vision in both eyes; they only see people and objects in one half of their visual field, as in the illustration below:



Neither was this a case of brain injury; the anonymous girl (known only as 'AH') failed to adequately develop her cerebral right hemisphere in the womb. As a result, she is without a right-brain and also without the use of her right eye. She also has a slight left-hemiparesis (weakness affecting half of the body) but close to normal vision in both hemifields of her normal left eye.

In a study published by the Proceedings of the National Academy of Sciences (PNAS), a team led by Lars Muckli of the University of Glasgow used fMRI to investigate how the visual cortex had remapped itself. In a healthy individual, the cerebral cortex contains "maps" for vision, sound, motion and touch, which develop and modify over time dependent on several factors including genetic cues and neural activity. In the mammalian brain (that is, human brain) the visual cortex is made up of distinct sections dealing with vision, the main one being an area known simply as 'V1', the primary visual cortex. 'V2' deals with quarterfield representations in the area of vision, effectively dealing with the 'up' and 'down' areas of both the right and left hemispheres of vision, while 'V3' is a structure in front of V2 that, among other things, performs a supporting role for V2. There is also the question of retinotopic maps, a direct mapping of the spatial arrangement of the retina, located in visual structures including the cortex and thalamus.

As per materials provided by the University of Glasgow, "visual information is gathered by the retina at the back of the eye and images are inverted when they pass through the lens of the pupil so that images in your left field of vision are received on the right side of the retina, and images from the right are received on the left." The part of the retina close to the nose is known as the nasal retina whereas the other part is referred to as the temporal retina, being in proximity to the temples. Both halves transmit received information through separate nerve fibres. In a normal situation, the nerve fibres of the nasal retina cross over in the optic chiasm, a brain structure located at the bottom of the brain near the hypothalamus, and are processed by the hemisphere on the opposite side. The nerve fibres of the temporal retina remain in the same hemisphere (ipsilateral), meaning that the left and right visual fields described earlier are processed by opposite sides of the brain.



[DIGRESSION]Vision is not the only modality to be processed in this strange way. It actually reflects the larger processing activities of the intact brain which tends to process all other modalities in opposite sides of the brain. To wit, touch and hearing for example that is "entered" into the right side of the body (right body, right ear) are processed by the left-brain, and touch/hearing entered into the left body/ear is processed by the right-brain. This is generally referred to as contralateral processing, when input is processed by the 'opposite' half of the brain. Those inputs processed by the 'same' side of the brain is known as ipsilateral processing. For more information, please read about Basic Visual Pathways.[/DIGRESSION]

The MRI scan displays the complete lack of a right-hemisphere: The optic chiasm is shown here (top l-r) in the transverse and enlarged transverse planes, and (bottom l-r) in the coronal and saggital planes. A rudimentary optic nerve is pointed out in the enlargement by the green arrow but with no discernible optic tract, and it can also be seen how the left-hemisphere is spilling over into the right-domain. The vacant right-hemisphere is filled with cerebrospinal fluid (CSF).

In AH's fascinating case, it was found that the nasal retinal nerve had connected to her left-brain. A possible interpretation for AH's condition is suggested by the authors: The lack of a right-brain prevented an opposite connection from being made, which led the optic nerve fibers to "connect" with ipsilateral structures instead.

Remembering that normal cases require a crossing in the optic chiasm, and AH's connections were essentially ipsilateral, how exactly does AH see both visual fields with only one eye? After all, if the entire right hemisphere is missing, AH should see only the left hemifield. The answer lies with the Lateral Geniculate Nucleus (LGN), a structure that is embedded deep in the thalamus and which processes visual information from the retina. In AH, both the nasal and temporal retina would need to be mapped onto the LGN to allow for the processing of both hemifields. Again a similar suggestion of ipsilateral projections were presented as being the solution, instead of the usual contralateral connections, and that a mirror-symmetric representation of the hemifields would be received and processed by the thalamus. Similar cases have been seen in achiasmatic dogs where optic nerve fibres terminated in the ipsilateral LGN.

'Islands' were also found to have formed in the left-hemisphere to deal especially with processing of the left hemifield, to compensate for the missing right-brain activity.

The loss of AH's right-hemisphere was discovered at age 3 when she was treated for brief seizures and twitching taking place on her left side. It is speculated that the right-brain failed to develop between Day 28 and Day 49 of embryonic development. Despite the situation, she is able to engage quite capably in activities that require a fair amount of balance, such as riding a bicycle or roller-skating. Truly an extraordinary case in more ways than one.

For a professional view, please see Dr. Steven Novella's entry on this case.
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Muckli, L., Naumer, M., & Singer, W. (2009). Bilateral visual field maps in a patient with only one hemisphere Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.0809688106