History of polyneuropathy

As one of my mentors taught, polyneuropathy is all about history taking. The rest might be physical examination. Finally some lab tests. Before you then dare enter the neurophysiological approach all the data before should be ready, so that you can do a proper electrophysiological workup.

So here is my mental structure for the initial approach of polyneuropathy.

1. What is the time course of complaints?
2. Which fiber types are affected and how (positive and negative symptoms)?
3. What distribution pattern do the symptoms have?
4. What is the pathophysiology of the symptoms? (axonal vs demyelinative)
5. What other disease might the patient have?
6. What drugs and toxins did the patient suffer?
7. What is the family history?

Here is a list of positive and negative symptoms for the various fiber types (see 2):

Fiber type	Negative	Positive
Motor	Weakness, Hyporeflexia, Hypotonia, Deformities	Fasciculations, Crampi, restless legs
Sensory, large fiber	Hypesthesia, Hypotonia, Pallhypesthesia, Ataxia	Tingling, pins and needles
Sensory, small fiber	Hypalgesia, Thermhypesthesia	Burning, Jabbing, Shooting
Autonomic	Orthostatic hypotension, Arrhythmia, decreased sweating, constipation, impotence, urinary retention, …	Labile blood pressure, arrhythmia, increased sweating, diarrhea, urge incontinence, …

There are a few special cases of polyneuropathy with only limited differential:

1. Acute polyneuropathies: GBS, porphyria, diphtheria, drugs (dapson, nitrofurantoin, vincristine), toxins (arsenic, thallium), Lyme, vasculitis
2. Predominantly motor polyneuropathy: lead poisoning, porphyria, CMT, CIDP/GBS
3. Pure sensory polyneuropathy: paraneoplastic, postinfectious, Sjögren, B6 hypervitaminosis, inherited, Friedreich
4. Predominantly small fiber: diabetes, amyloid, toxic (alcohol), drugs (DDI, DDC), hypertriglyceridemia, hereditary, M. Tangier, M. Fabry, AIDS, idiopathic
5. Predominantly proximal polyneuropathy: diabetes, prophyria, CIDP
6. Asymmetric: mononeuritis multiplex, CIDP or PNP + entrapment/radiculopathy
7. Mononeuritis multiplex: vasculitis, diabetes, CIDP, HNPP, infectious (leprosy, Lyme, HIV), infiltrative (sarcoid, meningeosis)
8. Painful: small fiber, vasculitis, GBS
9. Demyelinating acquired: GBS, CIDP (+- HIV, IgM, anti-MAG, myeloma/Waldenström), GM1, diphtheria, toxic (amiodarone, arsenic)

Filed under: Neurology, Polyneuropathy

Polio

It is really tough to come up with a good case for polio that I could have experienced in order to talk about this disease that dominated much of the 20th century, led to the practice of mechanical ventilation, the invention of ICUs (somehow, at least) and showed that the WHO is more than a toothless tiger.

I use a case of suspected post-polio-syndrome to discuss the epidemiology, pathophysiology and sequelae of polio, then spend some time on the eradication program and it’s successes so far and finally cover the post polio discussion.

Filed under: General medicine, Neurology

Information management

I always was a fierce defendant of evidence-based medicine. After all, what harm is there in finding, using and being able to reject the available evidence for a particular question. Although we never learned it in medical school, I did some postgrad courses on medical literature appraisal, ploughed through the User’s Guide and tried to understand the mechanics of metaanalysis. I also follow most of the relevant Neurology journals. Still, I am unable to answer any given bedside clinical question in the way EBM would have it. It just takes too long and I am too dumb. Properly reading a study takes hours and then I am not able to find all weaknesses that internet blogs find in it.

So either I am unsuited for  EBM or it does not work. Also, it just explains how to answer questions, not how to raise them.

With these fears in the background, I stumbled upon this paper and this talk, explaining a basic approach to what I would call informed medicine. I would add to the information in the article some core principles of work with medical literature:

1. Try to stay current with the big journals (because they matter), but beware of their pharma influence.
2. Try to stay current with some more independent and small journals (such as in PMC and the British journals).
3. Follow informed discussions on the web (such as CCML, emcrit, …) in places where you reliably found good doctors.
4. Don’t be an early adopter, unless a study has very small NNTs and has been replicated.
5. Mistrust studies with thousands of participants, unless their (so-called scientific) results have been replicated in clinical practice.
6. If facing a patient with a problem, read up in good textbooks written by people you trust and who are too old to be influenced by every small whiff of medical wind.
7. Then confront this with something like uptodate.
8. Finally read some reviews.

As a final remark, I offer the following strategy for finding a treatment for your patient: do a search on RCT with limits to 1970-1990 on your subject – you will find many rightfully abandoned approaches, but also some gems to be recovered.

Filed under: General medicine, Professionalism

The 5 fingers of stroke

Did you get the stroke etiology right?

I love checklists with 5 items – 5 things to ask for in CHF, 2 x 5 things to remember in delirium. By looking at any of your hands, you can understand and work down the checklist. So here is my 5 item checklist for acute stroke care – designed for handovers.

1. Stroke characteristics:
   1. syndrome
   2. localization
   3. imaging results
   4. pattern
   5. confidence (couldn’t it be a mimic?)
2. Acute stroke treatment: tPA? endovascular therapy? Any early neurological deterioration?
3. Etiology: determines secondary prevention measures. I use ASCO
   1. risk factors
   2. atherosclerosis (big vessels – ultrasound results? CTA/MRA?),
   3. small vessels aka microangiopathy (CT/MRI)
   4. cardiac (ECG, monitor, further results)
   5. other etiologies
4. Complications: the big 5 are
   1. infection
   2. cardiac (rhythm, troponin)
   3. pressure
   4. gut problems
   5. thrombosis
5. Rehabilitation
   1. physiotherapy
   2. ergotherapy
   3. logopedic (aka SLT) therapy
   4. social services?
   5. rehabilitation planned?

Filed under: Neurology, Stroke

Strong acid base

Peter Stewart – the inventor of the quantitative (“ignore H+”) approach to acid base

I grew up with the German approach to acid base (“no clue – ask someone else”), then learned the Boston way (with all their compensation formulas). In parallel I tried to understand the Stewart style of quantitative acid base treatment, always missing the easy rule-of-thumb calculations I so loved in the anion gap calculations. So I really enjoyed the developments of the last years, where simple formulas for the strong ion gap proved to be adequate.

I will not delve into the discussion of the pros and cons of Stewart’s “H+ is not the point of acid base”, but happily accept that the old anion gap (if corrected for albumin) and the physicochemical approach yield the same results, if by different means. Scott Weingart at emcrit.org has devised a simple algorithm to deal with metabolic acid base disturbances, that I have adopted – you can enter all that stuff into acidbase.org’s calculator.

1. Labs: BGA (Na, Cl, K, pH, pCO2, base deficit = -base excess, lactate) plus albumin
2. Determine the sum effect of all acid base disorders:
   • pH < 7,35 = acidosis
   • pH > 7,45 = alkalosis
3. Determine the respiratory effect (might be compensation)
   • pCO2 > 45 = respiratory acidosis
   • pCO2 < 35 = respiratory alkalosis
4. Determine the strong ion effect: SID = Na – Cl
   • SID < 38 = low SID acidosis: get urinary anion gap (UAG) = urine Na + K – Cl
     • fluid administration with low SID fluids (saline, D5W)
     • renal tubular acidosis if UAG > 0
       • type I: urinary pH > 5,55
       • type II: urinary pH < 5,55
       • type IV: hyperkalemic, pH < 5,55
   • SID > 38 = high SID alkalosis (nasogastric suction, diuretics, hyperaldosteronism, fluid depletion)
5. Determine the lactate effect (due to hypoxia or toxicity with Metformin, Propofol, Linezolid, amphetamines, Valproate, HIV drugs, …)
6. Determine the albumine effect: 2,5 * (4,2 – [Alb in g/dl])
7. Add all the metabolic components into the Strong Ion Gap:
   • SIG = base deficit + SID – 38 + Albumine effect – Lactate
   • SIG > 2 = SIG metabolic acidosis: calculate osmolar gap = measured – 2 * Na + Gluc/18 + Urea/2,8 (> 10 is pathological)
     • Uremia, diabetic ketoacidosis, alcoholic ketoacidosis
     • Toxins: ASS, alcohols (methanol, mannitol, propylene glycol as in benzo or dilantin preparations), iron
     • Short gut syndrome (D-Lactate)
   • SIG < 0 = overdose with cations (Lithium, Bromide, Hyper-K, Hyper-Mg, Hyper-Ca, Nitrates, Immunoglobulins)
8. Check adequacy of compensation for chronic primary acid base disorders
   • In respiratory: expected delta SID = 0,4 * delta CO2
   • In metabolic acidosis: delta CO2 = base deficit
   • In metabolic alkalosis: delta CO2 = 0,6 * base excess

Recommended reading

• Please listen to Scott Weingart’s podcasts on acid base
• Read Kellum’s book on Stewart’s approach
• There is an excellent Swiss summary of the Stewart controversy and all the above in this German language review.

Filed under: General medicine, Acid base disorders, Critical care

A manifest checklist

We had a few near misses and annoyed team members the last weeks, so we did some probing, asked around and tried to identify what went wrong. It turns out – as so often – that team communication had deteriorated over the last months, so that the various members did not understand eachother anymore. This led to exchanges about our communication culture and to the project of a team timeout with a stroke team “preflight checklist” that we go through for each patient in the morning:

• What is the disease of the patient?
• Is he stable?
• What is the plan for today?
• Are all drugs ordered and ready?
• Have all labs been drawn?
• Is there any impediment to mobilization or oral nutrition?

We learned a lot from projects like the Provonost study and the surgical safety checklist. As far as I understand the author of “The checklist manifesto” – a Brigham and Women’s surgeon named Atul Gawande – checklists form the condensation point for interdisciplinary communication, allowing all team members to contribute to and understand the common goals and prioritize their work.

Of course, we will see how it works out but I have been fascinated by Gawande’s exposition and expect great results…

Filed under: General medicine, Professionalism

Stroke prevention – what patients can or should do

An aspirine a day, some statin, maybe more drugs (controlling BP, cholesterol, sugar) – we have a lot of ideas what to prescribe patients after their stroke. So what should they themselves do to prevent the next stroke?

I preach the five columns of stroke prevention behavior

1. Lose weight 
2. Move around (5 times 30 minutes a week)
3. Eat healthy (see recommendations by our German Nutritional Society)
4. Don’t smoke
5. Take your drugs (aka adherence)

This all sounds very well and we all suspect that properly following these instructions will reduce stroke risk in high risk situations (such as intracranial stenosis – see SAMMPRIS). Still, the evidence is scarce – as far as I know every attempt at showing that a particular diet is helpful for mortality failed. Studies for sports are rare. Even smoking studies are hard to come by.

We discuss the evidence and then develop a plan for a given patient.

Filed under: General medicine, Neurology, Stroke

The neurosurgical implications of PICA strokes

If your big PICA stroke gets worse, there are plenty of possible causes – here is a list:

1. Direct brainstem compression
   - typically affects the contralateral corticospinal tract, often above it’s crossin, so that an ipsilateral hemiparesis occurs
   - pontomedullary motor cranial nerves might be affected
   - vertigo, oculomotor abnormalities
2. Hydrocephalus from
   - Compression of the IIIrd ventricle
   - Compression of the aqueduct
   - Compression of the IVth ventricle
3. Ascending transtentorial herniation
   - Somnolence
   - Vertical oculomotor abnormalities
   - Vertigo
4. Transforaminal herniation
   - Vertigo
   - Nystagmus
   - Medullary brainstem signs

Filed under: Neurology, Stroke

The way of the lacune

Not a lacune but a lagoon

The terms lacune and lacunar are used at least 4 ways if not more:

1. A lacunar syndrome – neurologic deficits pointing (not reliably) to small lesions (the most famous are pure motor stroke, pure sensory stroke, dysarthria-clumsy hand, ataxic hemiparesis and – perhaps the worst: sensorimotor stroke)
2. A lacune as in small white matter lesion (e.g. < 1,5 cm, even < 1 cm sometimes)
3. A lacune as in a small hole in the brain (either an old bleeding or an old lacune in the previous sense, this is the term implied by status lacunaris)
4. A stroke with microangiopathic etiology (lacunar mechanism)

As for the geometry of interactions of these meanings:

• not every lacunar syndrome is due to a small lesion (might be bigger), so 1 does not imply 2 – this is obviously different for each lacunar syndrome but worst for sensorimotor stroke
• not every small lesion is due to microangiopathy (see below for more expansion on this)
• not every microangiopathic lesion is small (e.g., anterior choroid artery strokes are often microangiopathic, but mostly big)
• not every microangiopathic lesion or small lesions or small hole causes lacunar syndromes – you can even get aphasia from a small thalamic lesion

So I would suggest leaving out the term lacune altogether. Also you should cry out loud, throw yourself to the floor and start vomiting, whenever you hear it. If that doesn’t help, read on.

Tiny basal ganglia/capsula strokes are probably what we most associate with the above concepts – small, causing lacunar syndromes, often leaving holes in the brain. But they may be caused by at least three mechanisms:

1. microangiopathy: this is what has been termed arteriolosclerosis or lipohyalinosis, pathologically not very well described
   Implication: treat hypertension, stop smoking, improve risk factors, give aspirine
2. branch atheromatous disease: a plaque in the father vessel (MCA, BAS, PCA mostly) has either blocked the way to the branching endartery (hemodynamic) or lead to an embolus (arterioarterial embolism)
   Implication: treat large vessel disease aggressively (ASS + Clopidogrel for some time, high dose statins, treat risk factors, try to avoid stenting if possible)
3. cardiac or carotid embolism (obviously, if the blood can find it’s way into the basal ganglia, so can emboli)

Now there is a peculiar tendency of small lesions to fluctuate aggressively (the fluctuating lacune, throw myself to the floor!). If they do, we used to generously infuse heparin at varying doses, never ever actually achieving the proper PTT, but this seems not to be hip anymore. I personally favor Aggrastat (Tirofiban) for this indication and have excellent experience; also I can use the SATIS study to justify it’s off label use. Others use eptifibatide. But – as always – someone should do a study on this.

Other treatments include: induced hypertension and Mg sulfate.

References:

• Bailey. Pathology of Lacunar Ischemic Stroke in Humans— A Systematic Review. Brain pathology 2012 – an extensive review of all histopathological data out there, not very reassuring.
• Del Bene. Progressive lacunar stroke: Review of mechanisms, prognostic features, and putative treatments. Int J Stroke 2012 – what there is to know about progressive and fluctuating strokes.
• Norving. Lacunar infarcts. Practical Neurology 2008 – if there is a british review, read it in order to become more conservative…
• Micheli. Need for extensive diagnostic work-up for patients with lacunar stroke. J Neurol 2008 – the data for why you still have to do a regular workup for lacunes.
• Makin. Cognitive impairment after lacunar stroke: systematic review and meta-analysis of incidence, prevalence and comparison with other stroke subtypes. JNNP 2013 – even a small “lacune” can lead to cognitive impairment
• Chung. Branch Atheromatous Plaque: A Major Cause of Lacunar Infarction (High-Resolution MRI Study). Cerebrovascular Dis 2012 – how do you prove BAD? high resolution MRI – this is cool stuff

Filed under: Neurology, Stroke

Fluid responsiveness

Patients on non-intensive care wards (such as our stroke unit) are not as simple to understand as a patient with arterial and central line, with ultrasound and more high tech equipment around every corner.

So assume a lady with advanced heart failure, medium size stroke and a decent aspiration pneumonia, who is raised to your attention by a stroke nurse that is worried about the blood pressure of 78/28 mmHg with a heart rate of 109/min (sinus rhythm). What do we have by way of judging her fluid status? More precisely, is she going to benefit from a decent fluid bolus (say 500 ccs of NS or LR)?

From all evidence-based reviews on the history and physical, we know that a hemorrhagic patient might be identifiable by postural hypotension, tachycardia and postural dizziness. But this might be hard to check in a patient who is not able to sit or stand such as ours. Even more, both history and physical fare just as badly as flipping a coin (an AUC of the ROC curve of 56%), at least in the hands of an intensivist… Jugular venous pressure might be interesting for cardiological reasons, but the connection to right ventricular preload is difficult to judge as we don’t know the compliance of the system.

What remains are dynamic studies of responses to fluid challenges, such as

• Passive leg raising: flip the legs up to 45° and the trunk down to 0°, effectively keeping the standard angle of legs to trunk of about 30-45°, pushing about 400 ccs of blood up to the heart.
• Controlled respiration with volumes high above the usual aim of 6 ml/kg and with proper pressures (this yields vast changes in pressures, volumes and fluid compartmentalization around the heart and thorax)
• Saline bolus of 500 ccs.

So what are the physiological variables to monitor during such a maneuver? In order of increasing complexity and high-tech-yness

• Blood pressure (MAP), or even better pulse pressure (syst – diastol)
• Heart rate (if the carotid sinus reflex is intact and Bezold-Jarisch/Bainbridge keep quiet)
• Perfusion measurement of your oxygen saturation monitor (reflecting stroke volume in the periphery, which is worse than central stroke volume, but better than most measures)
• etCO2, if you happen to monitor it, reflecting minute volume
• PPV or SVV if measured by pulse contour analysis (PICCO = LIDCO, both better than Vigileo)
• Inferior vena cava diameter and collapsibility index
• Stroke volume (if measured by TEE or pulmonary catheter)
• Femoral artery (better carotid artery, but this hasn’t been studied) mean systolic velocity
• NICOM (thoracic impedance boosted)
• … many more devices I have never used

So on any normal ward with – say – a simple vital sign monitor, us Neurologists can do best with ultrasound of the IVC and the carotid artery and the pulse pressure plus (perhaps) heart rate during passive leg raise. But this isn’t too bad.

References:

• A recent review in Kidney International
• For high tech stuff see this article by Marik
• and this overview article by him

Filed under: General medicine, Intensive Care