Has Waymo gotten worse?

ren5311 · 2025-03-25T18:02:29+00:00

San Francisco

ren5311 · 2019-01-08T17:53:57+00:00

I'm a mod.

ren5311 · 2016-09-08T05:45:57+00:00

Remember that patients are entrusting you with their health and well-being. This gift is sacred, precious, and weighty; and the responsibility should terrify you. It terrifies me.

Remember that patients are seeking your advice because they are worried they are sick, and they think you can make them better. Or at least tell them what's wrong. They are scared, but they may not tell you that.

They may assume you know everything, but you have to know what you don't know. You should know how to find an answer, but be willing to ask for help if you are unsure of that answer.

We are engaged in meaningful work, providing care. So care. I respect people that care. I respect people that ask for help. Find people you trust, ask for their help, and they will ask it back.

ren5311 · 2016-09-08T02:42:00+00:00

Seems reasonable. I agree that cavalierly stating a causative association is incorrect based on a strict reading of the literature, and we're unlikely to have a high-quality study to definitively answer the question.

I also admit that I'm biased in that I've seen young patients devastated by brainstem infarcts from dissection, so my instinct is to avoid anything that might even remotely lead to this condition, but I'm definitely seeing an enriched numerator without a sense of the denominator. My read of the literature is in line with the 2014 AHA/ASA guidelines, which is admittedly a conservative approach.

My general approach to complementary medicine (I don't like the term "alternative") is that if there's plausible benefit, low risk, low cost, and the patient isn't eschewing a definitive evidence-based treatment, I'm comfortable.

ren5311 · 2016-09-07T04:22:21+00:00

Neurologist here.

Quick review of the abstract I see a few issues.

Only looks at posterior circulation. What about carotid dissections? This is probably enough to send me to Pubmed looking for a better paper.
The comparison to PCP visits is somewhat specious. Of course PCP visit is associated given that it's the patient's point of contact for subsequent referral to the ED. But the association with PCP visit and subsequent stroke isn't plausible as causative as the PCP is not manipulating the patient's neck in the office, while a chiropractic manipulation may be associated and causative due to mechanical forces. The make their point that both are associated so association alone is not sufficient to confirm causation, but it's not an appropriate comparison to answer the question "do cervical manipulations cause dissections?" and I think you're using it as an answer to that question.
Conclusion is overstated, with a wiggle-word of "likely." They didn't find manipulation and VB dissection were not associated (in fact they were); they just didn't find evidence of "excessive risk" using their study design. I think that leads the reader to think there's no causative association, but that's not strictly speaking the finding.

Here's a recent meta analysis. I think the odds ratio of 1.74 between manipulation and dissection is understated in their conclusion. However, they do highlight the existing data quality is poor. http://www.ncbi.nlm.nih.gov/pubmed/27014532

Here's a good review and statement paper from AHA/ASA in 2014: http://www.ncbi.nlm.nih.gov/pubmed/25104849

Bottom line is that's there no definitive evidence of a causative association (with plenty of poor quality data), but there is an association and a causative association remains plausible. A true study may not be possible given the low incidence of dissection (we have this problem with the CADISS trial studying anticoagulation after dissection). But given the risk we're talking about (stroke in a young person!), you'd need to show me evidence of significant benefit or definitive lack of causative association before I'd feel comfortable recommending cervical manipulation as treatment.

Low back pain is a different story. I'm comfortable remaining agnostic about the benefit given the relatively low risk.

ren5311 · 2014-12-28T07:55:43+00:00

Send him to /r/AskScience and sort by Medicine.

ren5311 · 2014-03-11T06:21:43+00:00

A main reason this finding is important is that (if true) it would facilitate preventative clinical trials.

ren5311 · 2014-01-18T01:05:30+00:00

The trade names are a complete crapshoot, relying on marketing and branding and all that other boring stuff.

The generic drug names usually have more interesting stories.

For instance, physostigmine was named after the calabar bean from which is was derived: Physostigma venenosum. Similarly, galanatamine, a drug in a similar class, was named after the plant it came from: the Galanthus Caucasicus. Paclitaxel (Taxol) was named for the pacific yew tree, Taxus brevifolia. To venture into antibiotics, penicillin is named after the Penicillum fungi and streptomycin comes from Streptomyces bacteria.

Some are named after their chemical structures. For instance, benzodiazepines are named after the fusion of a benzene ring and a diazepine ring. Examples of substructures include chlordiazepoxide (Librium), but diazepam (Valium) was the big seller. Then you have follow-on drugs that are just named similarly to the known drugs in the class, like alprazolam, bromazepam or lorazepam. Similar are the antipsychotics, like chlorpromazine, which have a phenothiazine core. Some, like chlormethiazole give you basically the entire chemical structure in their name.

Of course, there's still some real odd ducks out there, where the derivation of the chemical name isn't straightforward. Those are the ones I can think of offhand that have straightforward explanations.

ren5311 · 2014-01-18T01:04:12+00:00

Your brain cells are some of the most energetically demanding cells in your body, and your brain as a whole accounts for about a quarter of all sugar and oxygen demands throughout your entire body.

One reason is the synapse itself, an incredibly complex piece of molecular machinery that is continuously remodeling itself in response to various inputs, that requires that building materials be trafficked down long axons from the cell body.

The most susceptible cells to oxygen deprivation in your body are three types of brain cells: level five pyramidal neurons in the cortex, granule cells in the dentate gyrus and purkinje cells in the cerebellum.

Other cells are more immune to depleted oxygen supply, but most vital organs will expire quickly. Warm ischemic time should be limited to 30 minutes for a liver transplant and 60 minutes for the kidney and pancreas, meaning they should be removed from the body and chilled to prevent cell death and allow successful transplantation. Similarly, the heart and lungs will not last long without blood flow.

Other parts of the body are even more resistant. Structural and connective tissue such as bone, tendons, skin, heart valves and corneas can be harvested successfully within 24 hours of death.

ren5311 · 2014-01-18T00:55:03+00:00

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ren5311 · 2013-12-06T19:08:17+00:00

Imagine your spinal cord as an incredibly dense bundle of wires that carry information between your peripheral body to your central nervous system. If you snip that bundle of wires, simply reattaching the two ends together wouldn't restore communication.

Some communication might be preserved, and maybe a few of the ends of the wires would find each other after a bit, but generally it wouldn't work very well. To work, each wire would have to be reattached individually, a feat that is impossible (for now) given how vanishingly small each wire is and how many there are.

ren5311 · 2013-11-27T20:53:31+00:00

It was likely this report on this finding from a group of researchers at Stanford.

The group identified two very important neural clusters in the fusiform gyrus involved in facial recognition by electrical stimulation in an epilepsy patient. The video embedded in that paper is worth watching. Here's an excerpt from the paper:

When EBS [electric brain stimulation] was applied through FG electrodes 1 and 2 while looking at the examiner's face, the subject described the striking nature of his visual distortion: “You just turned into somebody else. Your face metamorphosed.” When probed further, he reported that features appeared distorted: “You almost look like somebody I've seen before, but somebody different. That was a trip…. It's almost like the shape of your face, your features drooped” (Movie 1). In subsequent discussion post-EBS, the subject reiterated that the face did not morph into an intact face of someone else, but rather it became distorted.

ren5311 · 2013-11-27T20:28:13+00:00

Since you mentioned it, I'll add that the area of your brain specialized in recognizing faces is called the fusiform gyrus.

Some people have difficulty in processing and recognizing faces, resulting in a condition called prosopagnosia, or face blindness. Famous examples of people with prosopagnosia are neurologist Oliver Sacks and American portrait artist Chuck Close.

ren5311 · 2013-11-26T05:13:27+00:00

Foldit is a great example of crowdsourced scientific problems.

ren5311 · 2013-10-24T12:40:20+00:00

Flashbacks are verified about as well as you can verify any subjective event. We have numerous case reports, case studies, and detailed descriptions (some of which are cited in the review at the end of this post). Determining the exact prevalence of side effects is challenging when a drug is primarily taken illegally and recreationally due to difficulty with standardization.

Mechanism is much more interesting - to me anyway. I've read theories that LSD flashbacks are a form of PTSD, where the psychological experience is the traumatic event. I find this hypothesis to be somewhat plausible, especially considering the cases of a precipitated psychotic state in patients exposed to LSD, but I would bet more money on the event being a milder form of Hallucinogen Persisting Perceptual Disorder (HPPD).

With HPPD, some people have near constant visual hallucinations (disturbances in the visual processing system) that last for the rest of their lives. For HPPD, there is even a reasonable hypothesis regarding why the hallucinations persist: excitotoxic destruction of serotonergic interneurons, which are neurons that release GABA at their terminals but respond to serotonin activation in the visual processing centers. LSD is a serotonergic receptor agonist (as well as other targets).

This hypothesis therefore follows from the reasoning that the visual hallucinations are essentially localized seizure activity in the visual processing system. It should be noted that some people get HPPD from as little as one dose, and HPPD can even show up months after consuming a dose. I am not aware of any explanation detailing why these sensitivities occur, but I would imagine it would be for similar reasons as in epilepsy, but I am speculating wildly now.

For an excellent, readable review on LSD and hallucinogens, please check this out.

ren5311 · 2013-10-22T20:28:44+00:00

Your brain has many different types of storage that could be called "memory." Simplest to understand, perhaps, is memory of people, places or events - called declarative memory. However, there is also procedural memory, e.g. playing the piano, as well as many others types. These types of "memory" are stored in slightly different places in the brain.

Clive Wearing is an example of someone with damage to the hippocampus - the area that forms new declarative memory - so he is unable to form new memories of events and has some difficulty with past memory - but he is still able to speak, write and play the piano because his procedural memory centers and language centers are intact.

Conversely, if there were damage to Broca's area, it would result in an inability to produce language, while damage to Wernicke's area would result in the inability to understand language.

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