Amyotrophic Lateral Sclerosis (ALS) & the corticospinal tract

corticospinal_tract

Amyotrophic Lateral Sclerosis (ALS) is a degenerative disease of the motor neurons in the brain and spinal cord. It progressively affects all the muscles in the body but there is no known cause and no treatment. Only about 5-10% of cases are inherited while the rest are sporadic.

The neurons ALS affects are primarily the upper motor neurons. These are the ones that originate in the brain and travel down the spinal cord. These neurons then synapse with the lower motor neurons in the ventral horn, and it is the lower motor neurons that go directly to the muscles.

In ALS there are both upper motor neuron and lower motor neuron symptoms. As the neurons die, a constellation of symptoms including numbness, weakness and paralysis emerge. Eventually the paralysis progresses leading to inability to speak, swallow and breath. There is no cure for ALS and treatments only help with the symptoms, they do not slow the progression of the disease.

So you may have seen a lot of ice bucket challenges over the last few weeks but please support this cause as it is a horrible disease that up until now had almost no recognition or support. So please donate to The ALS Association (alas.org).

And in case you get tired or jaded seeing your social media full of these videos, watch this one of my father doing it. He’s not an emotional guy, but he has lost more than his fair share of friends to this disease.

donate to help fund ALS research and support from Ali & Mike on Vimeo.

Side Effects of Atypical Antipsychotics

antipsychoticsAtypical (a.k.a., “second-generation”) antipsychotics are commonly used in the treatment of psychotic disorders, and mood disorders as well. Compared to typical (first-generation) antipsychotics, the atypical antipsychotics have lower affinity for dopamine D2 receptors, and they also act at serotonin (5-HT) receptors (they are antagonists for these receptors). Other neurotransmitter receptors are affected as well, and each atypical antipsychotic preferentially antagonizes different receptors.

When atypical antipsychotics were first introduced, it was hoped that they would be more effective than typical antipsychotics and have fewer extrapyramidal side effects (see below). While these expectations may have been somewhat overblown and atypicals are not markedly superior in decreasing psychosis symptoms, most atypicals certainly have a lower risk of developing extrapyramidal side effects. However, they do come with their own array of side effects.

Extrapyramidal side effects (EPSE): These are movement-related side effects caused by dopamine antagonism. These include acute dystonia (torticollis, an uncomfortable muscular spasm of the neck; as well as spasms of the eyes, tongue, jaw), akathisia (motor restlessness and a need to remain in motion), tardive dyskinesia (repetitive, involuntary movements usually involving facial muscles), parkinsonian symptoms (resting tremor, rigidity, slowed movements), and neuroleptic malignant syndrome (potentially fatal!).
Elevated prolactin (PRL): This can lead to gynecomastia (breast growth) and galactorrhea (milk-production), which can be very distressing for male patients! Can also cause infertility and sexual dysfunction. It also happens with typical antipsychotics.
Weight gain: This can be very a troublesome symptom, and may lead to diabetes in some patients.
Sedation: This may prevent patients from engaging in their usual activities and work.
Orthostatic hypotension: Drop in blood pressure after standing from sitting position.

Some antipsychotics have especially severe side effects. Clozapine, for example, is extremely effective in treating psychosis but can lead to fatal agranulocytosis (drop in white blood cells), as well as tremendous weight gain and sedation. Ziprasidone use can lead to QTc prolongation and increase the risk for serious cardiac arrhythmia.

The above chart shows the relative side effect profiles of eight atypical antipsychotics (aripiprazole, clozapine, lurasidone, olanzepine, paliperidone, quetiapine, risperidone, ziprasidon) versus two typical antipsychotics (chlorpromazine, haloperidone).

  • Haddad PM, Sharma SG. 2007. Adverse effects of atypical antipsychotics: Differential risk and clinical  implications. CNS drugs; 21:911.
  • Leucht S, Cipriani A, Spineli L, Mavridis D, Orey D, Richter F, Samara M, Barbui C, Engel RR, Geddes JR, Kissling W, Stapf MP, Lassig B, Salanti G, Davis JM. 2013. Comparative efficacy and tolerability of 15 antipsychotic drugs in schizophrenia: A multiple treatments meta-analysis. Lancet; 382:951.
  • Meltzer HY. 2013. Update on typical and atypical antipsychotic drugs. Annual Review of Medicine: 64:393.
  • Sadock BJ, Sadock VA (Eds.). 2007. Serotonin-dopamine antagonists: Atypical antipsychotics. In: Kaplan & Sadock’s Synopsis of Psychiatry. Lippincott Williams & Wilkins, Philadelphia PA.

Treatment of scaphoid fractures

scaphoid-flow-chart

Scaphoid fractures are very common but due to its weird blood supply, the scaphoid is prone to not healing well (review the anatomy of the scaphoid in this doodle). This is why fractures of the scaphoid and even SUSPECTED fractures of the scaphoid are treated very conservatively.

Even if you’re suspicious of a fracture but don’t see one on x-ray, that’s enough to subject someone to a cast for 2 weeks and then bring them back to re-x-ray.

This doodle goes through the basic algorithm for treating scaphoid fractures centred around a timeline to show how long the treatment course can be. There are of course nuances to the management, so take a person’s work and hobbies and handedness into consideration. Also, don’t be afraid to consult your friendly hand/wrist specialist.

Scaphoid bone anatomy and fractures

scaphoid_fracturesThe scaphoid bone is one of the eight carpal bones of the wrist (you can check out this doodle for a refresher).

The scaphoid is the most commonly fractured carpal bone, accounting for almost 70% of fractures. It tends to be young males who break their scaphoid this is both an anatomical thing: younger kids get ligament injuries and older folks break their distal radius and a lifestyle thing: falling on outstretched hands (skateboarding, snowboarding) or throwing a punch both place a lot of force across the scaphoid leading to fractures.

The bad thing about scaphoid fractures is that the blood supply (from a branch of the radial artery) comes from distal to proximal. Since most fractures happen at the waist of the scaphoid the likelihood of having poor blood supply to the fracture site is quite high. It doesn’t help matters that around 80% of the scaphoid is articular surface (joint surface), so if it doesn’t heel well, it can lead to problems with arthritis of the wrist later on.

 

Presentation

Scaphoid fractures present with a pretty classic story and the person is usually swollen and bruised and will have tenderness in their “snuffbox.” So even if the x-ray doesn’t show a fracture, it’s best to treat with a cast for comfort and safety and then recheck them in 2 week’s time (this will be discussed in a separate post).

Z Plasty

z-plasty

The Z-Plasty is one of the most fundamental local flaps. It’s a variation of a transposition flap (meaning simply that it was rotated into a defect right next to it).

The trick is that all three limbs need to be equal and that the angles should be equal.

If the angle between the central limb and the lateral limb is 60°, then there should be an increase of the central limb by 75% (ex: 2cm -> 3.5cm)*

Since the Z-Plasty lengthens and changes the line of tension, it is great for releasing scar contractures.

 

* If you want you can measure the doodle, it’s pretty close to a 75% increase which I found really cool (in that I created it by rotating the flaps). MATHMAGIC!

Mechanical Ventilation Basics

ventilator

Volume control (VC) and pressure control (PC) are two common modes of positive pressure mechanical ventilation. In VC, the clinician sets the tidal volume that is given for every breath; pressure is allowed to vary over the course of the breath. In PC, the ventilator is programmed to deliver the same pressure throughout inspiration, so tidal volume is allowed to vary based on the pressure and timing settings, as well as the patient’s own lung compliance.

The timing of ventilation can be set according to a trigger. Continuous mandatory ventilation (CMV) involves setting the respiratory rate and having the ventilator deliver breaths at exactly that rate. This is generally used in paralyzed patients (e.g., general anesthesia), where the patient is not expected to trigger any breaths. In Synchronized Intermittent Mandatory Ventilation (SIMV), mandatory breaths are still given but they are synchronized to the patients’ own respiratory efforts (if present). Also, the patient is allowed to take additional breaths on their own. SIMV is often used to wean patients from the ventilator, by decreasing the rate of mandatory breaths and having patients take more of their breaths spontaneously.

Pressure support (PS) is another mode that is used for weaning. No mandatory breaths are programmed. The patient actively takes their own breaths, and the ventilator simply gives an additional boast of inspiratory pressure to help them out.

Positive End Expiratory Pressure (PEEP) is a setting that is used to prevent alveolar collapse, increase functional residual capacity, and generally improve gas exchange. PEEP involves programming a small amount of additional airway pressure (often ~5-10 cmH2O) to be present at the end of expiration.

  • Nugent K, Nourbaksh E (Eds.). 2011. A bedside guide to mechanical ventilation. Createspace.
  • Owens W. 2012. The ventilator book. First Draught.
  • Kacmarek RM, Hess DR. 2008. Mechanical ventilation for the surgical patient. In: Anesthesiology (Longnecker DE, Brown DL, Newman MF, Zapol WM, Eds.). McGraw Hill, New York.

 

Acquired Nevomelanocytic Nevi (aka moles)

nevomelanocytic-nevi

Nevi (or moles) are very, very common. They are generally well-circumscribed dark spots (or “papules” to use the dermatological terminology) that can appear at any time in someone’s life.

Histologically they are composed of groups of melanocytic nevus cells and can be found in the epidermis, dermis or both.

The problem with nevi is that they are pigmented and people tend to get worried about pigmented things on the skin (for good reason as melanoma can be a pretty scary disease).

Common acquired nevi are grouped into three categories (I’ll leave out congenital and dysplastic nevi for now)

  1. Junctional: the nevus cells are completely in the epidermis, just above the dermal-epidermal junction. Clinically they are <1 cm, flat or minimally elevated and dark in colour.
  2. Compound: the nevus cells are in both the epidermis and the papillary dermis (top layer of the dermis), and cross the basement membrane. Clinically they are raised, and a medium-brown colour.
  3. Dermal: the nevus cells are completely in the dermis. Clinically they are raised and almost always pigment less as the cells lose their capacity for melanization when in the dermis. They usually have telangectasia and may or may not have hair. They don’t tend to appear until the 2nd or 3rd decades of life.

Pierre-Robin Sequence

pierre-robin-sequence

Pierre-Robin Sequence is not a syndrome, it’s a sequence. While it is a collection of features, one happens because of the one that came before.

The features are:

  • Retrognathia/micrognathia (posterior mandible or very small mandible)
  • Glossoptosis (downwards/posterior displacement of the tongue due to the small mandible
  • Airway obstruction (because the tongue is in the way)

Pierre-Robin Sequence is associated with cleft palate (50% of children with the sequence have cleft palate). There are two proposed theories:

  1. The first is that the tongue simply gets in the way of the palate from fusing
  2. The second is that the tongue prevents the newly fused palate from staying fused (this is currently the more popular theory)

PRS, though not a syndrome itself, is associated with multiple syndromes including Stickler Syndrome, velocardiofacial syndrome, fetal alcohol syndrome and Treacher Collins Syndrome.

PHACE Syndrome (hemangiomas)

PHACE_syndromeThere are no shortage of congenital syndromes that are acronyms arranged into some sort of vaguely pronounceable word. There will be lots of doodles about these, but we’ll start off with a more uncommon one – PHACE Syndrome.

PHACE Syndrome is a collection of findings that go along with large infantile hemangiomas. They’re the more worrisome (but less obviously disfiguring) things you need to look for when you see a baby with a large hemangioma on the face or multiple hemangiomas.

  • Posterior fossa brain malformations
  • Hemangiomas
  • Arterial anomalies
  • Cardiac anomalies and coarctation of the aorta
  • Eye abnormalities
  • Sternal cleft

The most common symptom of PHACE is cerebrovascular abnormalities, followed by cardiac anomalies (coarctation, aortic arch anomalies, VSDs). If you suspect PHACE, do clinical exam of the skin and eyes and MRI of the head, neck and chest.

Other cool facts

  • PHACE occurs in full-term normal birth weight infants (other hemangiomas tend to occur in preterm infants)
  • Quite common, more girls than boys (8:1)
  • Don’t confuse it with Strurge-Weber (port wine stain, associated with the facial dermatomes)
    • Port wine stains don’t proliferate and then regress like an infantile hemangioma

Brachial Plexus Part 1 – anatomical relations

brachial_plexus

The brachial plexus is the bane of many med students’ existence during any sort of neuro block. So many nerves, so many connections, so many seemingly arbitrary names of different sections. It’s just a woven mess of misery. (especially when they start getting into the “where is the lesion” questions)

Thus I’ve decided to have a couple posts about the brachial plexus, hopefully demystifying it to some extent. This first doodle is about the brachial plexus and its anatomical relationship to some of the structures that show why anatomists who named the parts weren’t as crazy as they seem.

Important structures to remember because they explain why parts are named the way they are:

  1. Vertebrae
  2. Anterior and posterior scalene muscles
  3. Subclavian artery
  4. The arm (in its anatomical position)

Vertebrae: There are 7 cervical vertebrae and 12 thoracic vertebrae. To make things confusing the cervical spinal nerves exit ABOVE their named vertebrae (except for C8) while the thoracic, lumbar and sacral exit BELOW. This messes up the whole numbering system because there are SEVEN cervical vertebrae but there are EIGHT cervical spinal nerve roots. The brachial plexus generally includes the nerve roots C5-T1*
* I say generally because there’s are anatomical variations such as a “prefixed” plexus that goes from C4-C8 and a “postfixed” plexus that goes from C6-T2

Scalene Muscles: The brachial plexus is nestled between the scalenes in the neck. At this point the plexus is oriented up and down and therefore the trunks are superior (closest to your noggin), middle, and inferior.

Subclavian Artery/Anatomical Position: The artery is in front of the plexus at the level of the trunks and then the plexus starts to wrap around it (or at least seems to because we don’t keep our arms straight out to our sides in “anatomical position” at all times). The cords are named for their relationship to the artery. One is lateral (again, if the arm was held out to the side), one is posterior and one is medial (think closest to armpit).

 

Subdivisions of the Brachial Plexus

The parts are: Roots/Trunks/Divisions/Cords/Branches or, as I remember them being a classy east coast Canadian: Real/Truckers/Drink/Cold/Beer

Then you might think, “But how do I remember which of the terminal branches comes off where?” For that I think of the two “M” branches being on the M: Musculocutaneous, Median and (M)Ulnar and that the whole thing together can just be said as “MARMU” Pick the mnemonics you want, the brachial plexus is rife with them. I personally just like the sound of the word marmu.

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