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.

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.

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.

Complex Regional Pain Syndrome

crps

Hypo/Hyperalgesia:Decreased/increased sensitivity to a usually-painful stimulus (e.g., pinprick).
Hypo/Hyperesthesia: Decreased/increased sensation to a usually-innocuous stimulus (e.g., light touch).
Allodynia: Sensation of pain from a usually-innocuous stimulus (e.g., light touch).

Complex Regional Pain Syndrome (CRPS) refers to a chronic neuropathic pain condition with a broad and varied range of  clinical presentations. CRPS patients experience severe pain out of proportion to their original injury, and this may start at the time of injury or weeks later. The pain is described as deep-seated and burning/aching/shooting. Sesnory changes are common, including hypo/hyperesthesia, hypo/hyperalgesia, and allodynia. For instance, many patients describe not being able to tolerate the sensation of bedsheets on their painful limb.

In the affected area, there is often marked edema, temperature asymmetry (usually cooler), and sweating changes (usually increased). Loss of hair and nail growth is common, and disuse of the limb can result in weakness, muscle atrophy, and contractures.

The diagnosis is made clinically, using the Budapest Criteria. Some pain physicians use a nuclear medicine test, three-phase bone scintigraphy, for CRPS diagnosis but this test is becoming less popular, since it has a low positive predictive value.

Budapest Criteria

  1. Pain, ongoing and disproportionate to any inciting event
  2. Symptoms: at least one symptom in three of the four categories:
    • Sensory: reports of hyperesthesia and/or allodynia
    • Vasomotor: reports of temperature asymmetry and/or skin color changes and/or skin color asymmetr
    • Sudomotor/edema: reports of edema and/or sweating changes and/or sweating asymmetry
    • Motor/trophic: reports of decreased range of motion and/or motor dysfunction (weakness, tremor, dystonia) and/or trophic changes (hair, nail, skin)
  3. Physical Signs: at least one sign at time of evaluation in two or more categories:
    • Sensory: evidence of hyperalgesia (to pinprick) and/or allodynia (to light touch and/or deep somatic pressure and/or 
joint movement)
    • Vasomotor: evidence of temperature asymmetry and/or skin color changes and/or asymmetry
    • Sudomotor/edema: evidence of edema and/or sweating changes and/or sweating asymmetry
    • Motor/trophic: evidence of decreased range of motion and/or motor dysfunction (weakness, tremor, dystonia) and/or trophic changes (hair, nail, skin)
  4. No other diagnosis better explains the signs and symptoms

CRPS is classified as Type I when there is no apparent history of nerve damage, and Type II when associated with definite peripheral nerve injury. CRPS most commonly occurs following fractures and immobilization, but can happen even with little to no trauma.The pathophysiology is thought to involve autonomic dysfunction and inflammation, but much is still unknown.

CRPS affects females about 2-4 times more often than males, and onset is usually in middle age (though there are rare pediatric cases reported). It is a progressive disease that can result in spread of pain, sensory disturbances, and physical changes to other limbs.

Treatment for CRPS may involve physiotherapy, complementary medicine (e.g., acupuncture, qi gong) psychological therapies, and a variety of pharmacologic (e.g., NSAIDs, anticonvulsants, antidepressants, opioids, ketamine, bisphosphonates) and interventional procedures (nerve blocks, sympathectomy, neurostimulators). As with all things CRPS, there isn’t great evidence for any particular intervention.

  • Harden RN, Bruehl S, Perez RSGM, Birklein F, Marinus J, Maihofner C, Lubenow T, Buvanendran A, Mackey S, Graciosa J, Mogilevski M, Ramsden C, Chont M, Vatine J-J. Validation of proposed diagnostic criteria (the “Budapest Criteria”) for Complex Regional Pain Syndrome. Pain; 150:268.
  • Hord E-D. Complex regional pain syndrome. In: Massachusetts General Hospital Handbook of Pain Management (Eds: Ballantyne JC, Fields HL). Lippincott Williams & Wilkins.
  • Moon JY, Park SY, Kim YC, Lee SC, Nahm FS, Kim H, Oh SW. 2012. Analysis of  patterns of three-phase bone scintigraphy for patients with complex regional pain syndrome diagnosed using the proposed research criteria (the ‘Budapest Criteria’). British Journal of Anesthesia; 108:655.
  • O’Connell NE, Wand BM, McAuley J, Marston L, Moseley GL. Interventions for treating pain and disability in adults with complex regional pain syndrome – an overview of systematic reviews. Cochrane Database of Systematic Reviews; 4:CD009416.
  • Schwartzman RJ, Erwin KL, Alexander GM. 2009. The natural history of complex regional pain syndrome. Clinical Journal of Pain; 25:273.
  • Smith H, Popp AJ. The patient with chronic pain syndromes. In: A Guide to the Primary Care of Neurological Disorders (Eds: Popp AJ, Deshaies EM). Thieme.
  • Tran DQH, Duong S, Bertini P, Finlayson RJ. Treatment of complex regional pain syndrome: a review of the evidence. Canadian Journal of Anesthesiology; 57:149.

Internuclear Opthalmoplegia

ino.v2Internuclear opthalmoplegia (INO) is an impairment in lateral conjugate gaze (both eyes looking toward one side), caused by a lesion in the medial longitudinal fasciculus (MLF), and associated with multiple sclerosis.

Lateral conjugate gaze requires coordination of adduction (medial rectus muscle, CN III) in one eye and abduction (lateral rectus muscle, CN VI) in the other eye. These movements are coordinated by the paramedian pontine reticular formation (PPRF), also known as the pontine gaze centre. The pathway is as follows:

  1. To look to the left, the right frontal eye field (FEF) sends a signal to the left PPRF.
  2. The left PPRF innervates the left abducens (CN VI) nucleus, which controls the left lateral rectus muscle and causes the left eye to abduct (gaze to the left).
  3. Additionally, the left CN VI nucleus innervates the right oculomotor (CN III) nucleus, which controls the right medial rectus muscle and causes the right eye to adduct (gaze to the left). The MLF is the tract connecting the CN VI nucleus to the contralateral CN III nucleus.

In INO, there is damage to the MLF, giving a deficit in adduction of the corresponding eye during conjugate lateral gaze, but convergence (eye crossing) is classically preserved because that is controlled by a different pathway. In very mild cases of INO, the only deficit is a slowed velocity of the affected eye. For naming, a right INO (as in the sketch) involves damage to the right MLF, which means that the right eye can’t adduct to look to the left, but can abduct to look to the right.

INO may also be associated with gaze abnormalities such as nystagmus, skew deviation, and even abduction or convergence deficits.

The causes of INO include: multiple sclerosis, pontine glioma, and stroke.

  • Flaherty AW, Rost NS. 2007. Eyes and vision. In: Massachusetts General Hospital Handbook of Neurology. Lippincott Williams & Wilkins.
  • Frohman EM, Frohman TC, Zee DS, McColl R, Galetta S. 2005. The neuro-opthalmology of multiple sclerosis. The Lancet Neurology; 4:111.
  • Ropper AH, Brown RH. 2005. Disorders of ocular movement and pupillary function. In: Adams and Victor’s Principles of Neurology. McGraw-Hill.
  • Wilkinson I, Lennox G. 2005. Cranial nerve disorders. In: Essential Neurology. Blackwell.

 

Severity (Classification) of Burns

burn_depth

Burns are typically classified by their depth into (or through) the skin.

  1. 1st degree: just in the epidermis
    • Pink, hot, no blisters
    • Like a typical sunburn
  2. 2nd degree: into dermis, painful, wet
    • Superficial: unruptured blisters, hair & glands spared, erythematous (red) but blanch with pressure
    • Deep: ruptured blisters, hair often gone, can convert to a 3rd
  3. 3rd degree: through the dermis aka full thickness
    • Lack vascularization, dry, leathery, no sensation

Zones of a Burn

A burn isn’t a homogenous spot on the skin; more heat means more damage (who knew!)

  • 40 – 44 C: enzymes malfunction, protein denature
  • >44 C: damage occurs faster than the cell can handle
  • Damage keeps going after the heat source is removed
  1. Zone of Coagulation: The cells are dead and their proteins have denatured. Denatured proteins coagulate – think fried eggs. This is what forms the eschar of the burn.
  2. Zone of Stasis: The cells aren’t quite dead but the blood supply isn’t the best. If the circulation gets worse (usually due to vessel constriction and thrombosis) the cells in this area will die too. This is why it can take a couple days for a burn to “declare” itself.
  3. Zone of Hyperemia: “Hyperemia” means an increase in blood flow, in this case because of vasodilation. The cells in this area are alive and generally recover.

The image above shows a superficial 2nd degree burn. 

The Standard Drink

standard_drink

A “standard drink” is a measure of pure ethanol consumed. One standard drink represents 10 grams of pure ethanol.

This means that based on the alcohol percentage of certain drinks, the “standard” size changes. The important thing to be aware of is to think of it as a Standard Drink because the size that equals 10 g of ethanol isn’t necessarily the standard size that is served. This is why it’s a good habit when asking “how many glasses of _______ do you drink” to ask about the size of the glass.

This design was actually originally made for an event, but I’m reposting it here because it’s useful and I like it and I haven’t had a chance to draw anything new recently.

Maculopapular Childhood Rashes

rashes

BUY THIS AS A STUDY CARD

A kid without a rash just isn’t a kid.

Chicken Pox

  • Incubation: 10-21d, infective until crusted over
  • Rash: vesicles on macules (dewdrops on rosepetals),
  • Very pruritic!
  • Other symptoms: 1-3d prodrome of fever and respiratory symptoms
  • Treatment: supportive, acyclovir for severe disease, VZIG for post-exposure prophylaxis
  • Complications: 1st or 2nd trimester = congenital varicella syndrome

Roseola

  • Incubation: 5-15d
  • Rash: pink macules and maculopapules, starts on neck.
  • Non-pruritic!
  • Other symptoms: HIGH FEVER, cough, respiratory symptoms, erythematous pharynx, tonsils & TMs
  • Treatment: supportive
  • Complications: febrile seizures
  • * Generally affects kids <5 years old

Measles

  • Incubation: 10-14d, dx with measles IgM
  • Rash: maculopapular, starts on face.
  • Non-pruritic!
  • Other symptoms: the 3 Cs
    • 1) Cough 2) Coryza (runny nose) 3) Conjunctivitis
    • Koplik spots in mouth 1-2d before rash
  • Treatment: supportive, prophylactic Ig
  • Complications: secondary bacterial infection, encephalitis (1:1000), subacute sclerosing panencephalitis (1:100000)

Rubella aka German Measles

  • Incubation: 14-21d, infective 5d before rash and 7d after
  • Rash: pink maculopapular, starts on face.
  • Pruritic!
  • Other symptoms: non-specific
  • Treatment: supportive
  • Complications: congenital rubella syndrome (very bad*), first four months of pregnancy highest risk (this is why we check rubella immunity status in prenatal screening)

* Congenital Rubella Syndrome
“Blueberry muffin baby” (purpura). Cataracts/congenital glaucoma, congenital heart disease, hepatosplenomegaly, jaundice, microcephaly, developmental delay

Fifth Disease aka Erythema Infectiosum

  • Incubation: 4-14d, infective prior to onset of rash
  • Rash: slapped cheeks (raised uniform maculopapular lesions on cheeks), may appear on extensor surfaces
  • Usually not pruritic
  • Other symptoms: flu-like illness ~3d prior to rash
  • Treatment: supportive, blood transfusions if aplastic crisis
  • Complications: arthritis (10%), vasculitis
    • Aplastic crisis: reticulocytopenia, not bad in normal people, very bad anemia if you already have chronic hemolytic anemia
    • During pregnancy: fetal hydrops/fetal loss

* This is a good one to actually know the virus name! PARVOVIRUS B19

Other rash descriptors to think about

  • Sandpaper rash: scarlet fever (Group A Strep), they also have strawberry tongue, fever and sore throat
  • Pink macules with central clearing: erythema marginatum (one of the major Jones criteria for rheumatic fever)
  • Palpable purpura: Henoch-Schonlein Purpura
  • Non-blanching petechiae: BAD (meningococcal disease), could be other things too, but need to rule out meningitis
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