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Saturday, September 17, 2016
Subcortical vascular dementiaVascular dementia is the loss of mental faculties caused by a problem in the blood vessels in the brain.
art of me was almost hoping that the rumors about Hillary Clinton having subcortical vascular dementia (SVD) were true. Not because I would wish it on anyone, not even Satan him- or herself, but because vascular dementia is my third most favorite disease, right after Alzheimer's and Parkinson's.
The supposed medical report says that in 2013 she was diagnosed with early onset SVD. I'd never heard of such a thing, but there actually is a report of it, and it says they get psychiatric symptoms well before the appearance of cognitive deterioration. But it's not easy to figure out what kind of dementia somebody has, because there's so much overlap. Anyway, she was 66 and that's not what most people would call ‘early.’
You wouldn't diagnose SVD by MMSE as the document says. MMSE only tells you about global cognitive function; it's better to use NINDS-AIREN criteria, but if you're going to tell somebody they're going to die horribly in three years, you better have an MRI to back it up (either FLAIR or T2-weighted spin-echo MRI with a TE of 40–60 ms. Or diffusion tensor MRI, which works even better).
Considering all this, it's almost certainly a misdiagnosis. But as the commercial used to say, only her neurologist knows for sure, So maybe it's too early to give up hope. Or maybe not. But damn it, Jim, I'm going to talk about SVD anyway.
It's been suggested that the philosopher Nietzsche suffered from an inherited form of SVD called cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy. They call it CADASIL for the obvious reason that by the time your doctor gets through explaining what all those words mean you'd be dead. CADASIL really is early onset. But it's just one of many varieties of this fascinating thing called SVD.
Vascular dementia is the second most common kind of dementia. The term simply means loss of mental faculties caused by some problem in the blood vessels in the brain, like a blood clot or a hemorrhage. In subcortical dementia the lower parts of the brain, including the basal ganglia, and brainstem, or the inner parts of the cerebrum, which have a lot of white matter, are damaged.
White matter is the long-distance connections or wiring in the brain. It's white because it's covered with a type of insulation called myelin, which is white. The myelin also speeds up the signals, so if there's less of it your brain works more slowly. That's one of the things that happens when you get multiple sclerosis, which is a demyelinating disorder.
There are four kinds of SVD, depending on what's going on:
The second kind is what we're talking about, and there are two types of it. One is what we call Binswanger's disease. The other is the lacunar type.
Pathologists will tell you there are many signs of SVD (or SIVD, where they added the term ischemic) on the cellular level. Unfortunately, these are only detectable on autopsy, so you never see them until it's too late. But it's easy to see a stroke or complete infarct in MRI, as it shows up as a round hole or lacune up to 15 mm or so in diameter.
There can also be a partial occlusion of a vessel, which leads to an incomplete infarct. These white matter lesions show up in a FLAIR or T2-weighted MRI as bilaterally symmetric areas of hyperintensities (bright spots). They're very common in elderly people: they increase exponentially after age 65, and 62–95% of elderly people have some of those bright spots. A partial occlusion causes hypoperfusion, or insufficient blood flow, and that's what people think is going on in Binswanger's.
Just to make things tough, though, some patients have both holes and bright spots. What's more, some have a combination of different kinds of dementia.
In a white matter lesion, the wiring between neurons, not the cell bodies of the neurons themselves, is destroyed first. This is different from what happens in other dementias like Alzheimer's and Parkinson's. But eventually neurons in the hippocampus, which processes and stores spatial memories, are destroyed too. In SVD patients the hippocampus is 18.2% smaller than normal subjects but 11% bigger than Alzheimer subjects. But some of the symptoms, like crying and apathy, look more like prefrontal area injury.
The symptoms are typical of what we stereotypically associate with old people: gait impairment and cognitive dysfunction. They are physically slower and are abulic, which means they have trouble making decisions.
One way to distinguish SIVD from, say multi-infarct dementia or Alzheimer's, is to give them acetazolamide or 1.8% carbon dioxide. Blood vessels react to CO2, and patients with SIVD will have an impaired vasoreactive response, which can be detected in a PET scan.
Other symptoms are impairment of executive control, which includes planning, inhibition of inappropriate responses, and impairment of working memory and complex goal-directed purposeful activity. Depending on where the lesion is located, there could be apathy or other behavioral changes instead. There could also be Parkinson-like changes, like facial weakness and arm drift. SVD patients have a short-stepped, apraxic gait with freezing and a frequent tendency to fall. Seizures may occur. In its early stages it can be mistaken for depression.
One simple test for SVD is to write the alphabet in upper case letters. If it takes more than 21 seconds, it means there could be cognitive slowing, which gives you a starting point for more definitive tests.
Most of the tests for dementia don't measure executive function, so it's easy to miss. SIVD patients have difficulty shifting from one idea to another, known as perseveration. They also get forced laughing and crying, dysphagia (trouble swallowing), rigidity and urinary disturbance. They often get respiratory infections and dehydration, and that gives them increased blood coagulation and platelet aggregation.
Unlike in Parkinson's, tremor is not generally present. Parkinson's is easy to spot: the patient has a shuffling gait and tremors. It's awful: I watched one guy taking about ten minutes to walk a few feet from one building to another. When he got there he could not open the door by himself. In SVD Parkinson-like shuffling gait is sometimes seen. It can be distinguished from Alzheimer's by the lesser amount of progressive memory loss and a more stepwise onset.
There are a few drug treatments: piracetam, the so-called smart drug, which supposedly works as a cognitive enhancer, and provigil, aka modafinil, which is used to treat apathy. Hillary's staff was said to have looked into that one. But these drugs show only modest efficacy. The best way is to treat the risk factors, which are diabetes and hypertension. Calcium channel blockers, which treat hypertension, reduce the incidence of dementia in some patients, but low blood pressure is also a risk, so BP needs to be monitored closely.
Acetylcholinesterase inhibitors like donepezil and galantamine, which are approved for Alzheimer's, also have been tested for symptomatic relief in SIVD. SSRIs such as sertraline and citalopram have been used to treat the depression and anxiety, but tricyclics or other drugs that produce hypotension are usually avoided.
Without seeing Hillary's MRI, there's no way to know whether she has SVD. But even if she released one, who would ever believe it was authentic? That's the risk of being a pathological liar: any attempt to squash a conspiracy theory only creates a new one.
Early-onset truth impairment syndrome
Truth serum, 50cc, i.v., q.i.d.
1 Behav Neurol. 1995;8(1):43–46. Psychiatric symptomatology in early-onset Binswanger's disease: two case reports. Lawrence RM, Hillam JC. Link
2 J Neurol Sci. 2010 Dec 15;299(1–2):9–10. Binswanger disease--an update. Caplan LR, Gomes JA. Link
3 Subcortical ischaemic vascular dementia. Román GC, Erkinjuntti T, Wallin A, Pantoni L, Chui HC. Lancet Neurol. 2002 Nov;1(7):426–436. Link
4 Neurol Clin. 2007 Aug;25(3):717–740, vi. Subcortical ischemic vascular dementia. Chui HC. Link
Last edited sep 21 2016, 7:42 pm
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