Ah yes, that peculiar one-legged balance. I do that because several doctors had grave doubts that I would ever balance again, and forbade outdoor activities. The balance is also a way for me to check how well my cerebellum is functioning, before I begin a descent**, because…
I’m Missing Part of My Brain –
Have You
Seen It?
On March 8, 2002, I had an ischemic stroke in my right cerebellum and brainstem, at the age of 47. I get asked a lot of questions about the stroke; here are some answers (Most written in 2004).
2018 update: I wrote this originally in 2004. A lot has happened
over the years, and some of my speculations have been confirmed. A
lot of web links
have broken, and I need to update.
What caused the stroke?
The probable cause is either:
(1) a small hole between the upper chambers of my heart. This patent foramen ovale (PFO) may have allowed a clot to pass from the right side circulation (where clots are normal), to the left, where the clot could make a fast track to the brain. The hole has since been closed via catheter surgery.
(2) a neck injury, which might have stretched a neck artery (the
right
vertebral), causing a clot to form on a tear inside the artery. The
clot might
then have broken loose and traveled to my cerebellum, blocking blood
flow t the inferior branch of my SCA (superior Cerebellar Artery). I had several harsh neck
injuries
in the week before the stroke. 2018 update: It is now believed that >50% of the strokes in
people
<50 y.o. are due to artery
dissections. 2019: originally the radiologists thought
the PICA (posterior inferior cerebellar artery) was blocked. I looked
back at the radiology in 2019 and realized they were incorrect; and I
re-read the reports from an MRI in late 2018 which confirmed it was the
SCA, not the PICA. Those funny radiologists!
Why don’t we know the cause? Part of the problem is that one
time-critical
bit of radiology – an "MRA" – was mistakenly done on the wrong (very
wrong) portion of my brain. I requested the MRA films and found this
error
myself, and later had the error confirmed by doctors. 2018 update: I
continue to be amazed by how often radiology is screwed up in Las
Vegas. I did
my PhD thesis at MIT in radiochemistry/geochemistry, and I spent
many years
calculating radiation absorption in materials. We used MRI/MRA in
our research
on fluid flow. I learned a lot about anatomy and reading radiology
from my
rather negative experiences in 2002. Much of the problem with bad
radiology
comes from sloppy transcription errors by the gatekeepers, and the
refusal of
the gatekeepers to allow questions of the radiology staff; if they
do it
incorrectly, chances are the insurance will pay to do it over. Many
medical
doctors are really not up on radiology, and will simply trust the
radiologists'
written reports.
Few MDs understand some of the nasty details: for
example, if you
request an MRA of the head, you won’t get the neck; will get the
data down to
the C1 or C2 vertebrae. But
an MRI
request for the head usually includes the neck.
Are cerebellar strokes common?
No. They make up about 1.5% of all strokes, perhaps 15-20% of strokes
in
"the young" (meaning, "not elderly"). This point is
important, since most people -- including many doctors -- treat me as
if I had
a cerebral stroke (the common type of stroke). Many people will tell
me about
their experiences with other stroke "victims;" I am always grateful
to hear stories of people who overcome adversity. But it is important
to
understand that strokes vary hugely, and other strokers
have experiences vastly different from mine. Did you have any
risk
factors?
I had no traditional risk factors. My blood pressure is ~110/70, my pulse is less than 50, I am fit, my total cholesterol* is ~149 and my HDL is ~61. I never smoked, I have no plaque build-up in my arteries (atherosclerosis), and am not diabetic, nor do I have any known clotting disorders. My CRP (C-reactive protein) and homocysteine are low. I did, however, have "migraine with aura" combined with a PFO, which makes for a non-traditional risk factor (still controversial). Recent results show that patients who have "migraine with aura" tend to have 15 times as many cerebellar lesions as controls, and patients who have both a PFO and "migraine with aura" are much more likely to have a stroke, than are controls. (Tsimikas, editorial in JACC Vol. 45, No. 4, 2005, February 15, 2005 pp 496–8). In this view, some migraines may be like mini-strokes, perhaps caused when a clot passes through the PFO and lands on part of the brain. I had suffered some peculiar cerebellar deficits in the years before the stroke, perhaps as clots were occasionally lodging in the small cerebellar arteries.
I did have one ironic “risk” factor. My heart is/was quite strong, with a very high ejection fraction; thus I was able to over-pressurize the right atrium, which probably made it easier to force a clot through the PFO. Normally, a high ejection fraction is considered a good thing.
(In the last few years, another possible cause has come to light, again, associated with migraine. There is medical evidence, not yet backed up by double-blind studies, that people who are susceptible to migraines --and take strong decongestants-- are far more likely to have ischemic strokes. At the time of the stroke, I had a severe sinus infection, and was taking strong prescription decongestants.)
What does the cerebellum do?
Traditionally, the cerebellum was thought to contribute mainly to fine coordination, as might be needed for speech and handwriting; it also controls some parts of peripheral vision. In the last few years, a more important role has been seen for this part of the brain; it contributes to procedural memory, and may indirectly prevent dyslexia and dysgraphia. The cerebellum is small, but is packed with nerve endings -- more than all other parts of the brain, combined. The cerebellum does not have much redundancy in the blood supply, and the left part of the cerebellum won't take over for damaged parts of the right side. Here are more links, varying in degree of obfuscation:
As hinted, the cerebellum has perhaps 50-60% of the total brain inventory of neurons, despite being only 10% of the mass. However, the cerebellum lacks the intense connectivity of the cerebrum. The cerebrum "white matter" is almost entirely used for "networking" among its thought centers, and makes up the lion's share of cerebral mass. The cerebellum, on the other hand, is mainly devoted to intercepting or initiating signals that pass in nerves at its anterior; a great deal of its signals are purely inhibitory, telling muscles when to stop. I think of the cerebellum as crudely analogous to the cache, pre-fetch queue, and predictive execution features of a modern microprocessor; you can disable all these components, and the CPU will still function, but may become incredibly slow. Personally, when I use my cerebrum to take over some of the "sudden stop" signals, I am constantly sparking the "fight-or-flight" reaction that normally takes place through interaction of the cerebrum, amygdala and brainstem; simply writing a page with my affected hand is an exercise in tiring and disturbing overstimulation. Normally, the cerebellum would handle these functions below my level of consciousness. To minimize such problems, I am currently learning to write with my left hand, a very interesting and bizarre process -- e.g. I have been losing my ability to distinguish right and left.
2018 update: I found out the hard way that it is NOT easy to change
handedness if you have a cerebellar stroke. People who simply lose a
dominant
hand in an accident, still have the cerebellum and neural
connections
associated with that hand; with training, the brain recruits the
cerebellum
associated with the (now missing) dominant hand, and assigns it to
work with
the other hand. This
doesn’t happen if
that cerebellum is simply gone from a stroke. I can write fairly
well with my
left hand; but slowly, and my right foot twitches and the right part
of my tongue
burns if I use my left hand for writing.
What does the brainstem do?
It keeps you alive by controlling autonomic functions like heartbeat and breathing. The nausea and swallow reflexes, and the down-regulation of fight-or-flight, are partly controlled on the brainstem. Since many neural pathways cross on the brainstem, damage to the brainstem can greatly affect balance (pathways from inner ears) and some seemingly disparate functions. Initially, the doctors gave me less than even hope of survival, because the damaged cerebellum swelled and compressed my brainstem. The artery blocked by my stroke (the PICA) also supplies blood to the lateral parts of the medulla, so I had some initial brainstem damage, before the swelling.
What deficits did/do you have?
Initially, I couldn’t walk, and I had to stop and pronounce every syllable separately, and I choked a lot. I was unable to write at all, and had absolutely no balance. I’ve regained my balance pretty well, and have improved my speech and handwriting a lot. (I did many things to improve my balance – e.g. I walked 200 miles on curbs.) However, I can speak for one or two days only, before I have to rest for a few days. Some days, I lose my speech after just 1 hour of intense conversation. I still scan every sentence in my head, before I speak, to look for words that might be difficult to pronounce; I pull off this trick so well, that many people assume I am speaking with complete spontaneity. I write perhaps 1/3 as fast as I once did, and my tongue and hand compete for the same parts of my brain; thus, all muscles controlled by that part of cerebellum are activated and "twitch" as if by electrical cross-talk. Thus if I write a lot -- just a page will do it -- my tongue gets tired; and if I talk a lot, I cannot write. Moreover, I don't simply get tired; my tongue begins to burn, and my hand gets wildly spastic. The good news is that these functions are still improving some, more than 2 years later. And I need a lot more sleep than I used to; if I talk a lot and use my hands actively during a hike (say, climb rocks or part scrub brush), for example, I may need 12 hours of sleep the next night.
However, my "large" muscles are pretty fit; I can do 27 good pull-ups in a single set, and 100 good push-ups (touching my chest on every one) per set -- when I am not injured (more on that below). I can punch a speed bag, and can do some hand exercises much faster than most people. When the weather is good, I often run 10 miles at a shot. My right foot is still partly paralyzed, but since we don’t do many detailed motions with our feet, that deficit is generally not obvious.
Unfortunately, I am much more likely to injure my right side, because I try so hard to achieve the same speed as my left side, without the fine motor controls to prevent overextension. Hence I have "golfer's elbow" at this writing, primarily because I must do an exaggerated swing of my right arm, from the elbow, to write or type with any speed. I have ripped my right hamstring 3 times in the last year.
But the most difficult deficits were in my expression and perception. I can do analytical work just as before – e.g. I have no trouble with abstract thought, and can derive closed-form solutions for difficult math and engineering problems. My ability to program (a computer) is unaffected. However, I am curiously dysgraphic; I start writing something, and the spelling that comes out of my fingertips may be bizarrely different from what I intended. Sometimes I begin to say a word, and my tongue doesn’t seem to get the correct word, or pronunciation. I have learned to pay extra attention to my right peripheral vision, and have practiced doing crossword puzzles with just my right eye, to force my attention. Often I must ignore talkative people to my right, so I can focus on more essential functions, like driving a car (nowadays, a person has to be really talkative!). I don't mean to be impolite, but I know that the right side of my perception is easily overloaded, and some of the behavior isn't intentional -- it just happens. In reality, I've replaced many of my automatic cerebellar functions with cerebral, higher-brain thought -- a very inefficient process, which absorbs a lot of my attention span. When I hike cross-country, I must consciously commit objects on my right side to memory, so I will remember the way back (e.g., I say to myself, "note that odd-looking tree"). Hence my use of a GPS, which served as an electronic memory, but is becoming less necessary with time. For a long time, I would get sudden extreme sleepiness, which I learned to fight. I believe that sleepiness was organic; I would deal with a crisis, then the down-regulation of "fight-or-flight" by my brainstem would go a bit overboard.
But I see you climbing mountains – doesn’t that mean you are
"back 100%"?
A blind man climbed
Hiking through rough territory is about the best exercise I can get; I use my right hand to part brush, to hold a GPS, to climb rocks; and I talk with my friends in a measured, off-and-on fashion. I hardly notice my deficit till it comes time to sign my name in a register, or until my tongue gets tired enough to slur words. The constant decision-making and navigation through a 3D environment helps my right-side neglect.
============
*I'm rather skeptical as to whether cholesterol has any bearing on ischaemic stroke:
**I started thinking that this ritual was no longer necessary. Then on January 1, 2006, I felt peculiar wooziness and unsteadiness in my right foot, which I ignored. Then on descent, 10 minutes later, the gravelly ground under my right foot broke away, and I lacked the normal reaction time to "find my center". I fell perhaps 20 feet, righting myself and landing on all fours. I've started jumping in the air on mountaintops, as an additional test of my right leg response time.
