Good morning and welcome to your Thursday dose of Your Daily Meds.
Bonus Review: With respect to the physiology of muscle contraction, what is a motor unit?
Answer: So the unit consists of a single anterior horn alpha-motor neurone, its axon and all the muscle fibres it innervates. This is considered the functional unit of contraction, as the stimulation of that motor neurone results in the contraction of all those muscle fibres.
Then of course the number of fibres in a single motor unit varies. Muscles involved in small movements with fine control have few fibres per motor axon, while large muscles controlling gross movements may have 150 fibres per motor axon.
Investigation:
Alright. So a 36-year-old male comes to the Emergency Department complaining of generalised weakness. His ECG is shown below:
Which of the following correctly describes the most likely diagnosis?
Inferior infarction
Hypokalaemia
Hyperkalaemia
Mobitz I heart block
Atrial flutter
Have a think.
Scroll for the chat.
Quick Question:
When considering ankylosing spondylitis, which of the following features is most suggestive of poor prognosis?
Enthesitis on plain x-ray
Thoracic spine involvement
Age <25 at onset of symptoms
Presence of night pain
Hip involvement
Have a think.
Google enthesitis. Stupid word.
More scroll for more chat.
The Squiggly Line Heart Thing:
This ECG shows sinus bradycardia at a rate of approximately 70 bpm. There are widespread ST-segment abnormalities, such as ST-segment depression and T wave inversion. There is also a biphasic appearance to the ST-segments and T waves, with U waves present, that appear to be merging into one another such that it is difficult to tell where one wave ends and the next begins.
The combination of widespread ST-segment depression and T wave inversion, with prominent U waves and a long interval between the time of onset of the QRS complex to the end of the U wave, is suggestive of hypokalaemia.
An inferior infarction may be noticed on the ECG with ST-segment elevation in the inferior leads of II, III and aVF.
Hyperkalaemia is often characterised on ECG by a combination of bradycardia, flattening of P waves, QRS broadening and tenting of T waves.
A Mobitz I heart block, or Wenckebach rhythm, is characterised by the progressive elongation of the PR interval eventually resulting in a non-conducted P wave. These rhythms are usually benign and asymptomatic patients do not require treatment.
Atrial flutter is characterised by a narrow complex tachycardia with regular atrial activity at approximately 300 bpm, often described as ‘sawtooth’ waves.
Spines and Stiffness:
Ankylosing spondylitis (AS) is predominantly a disorder of men and affects up to 0.5% of the general population. The inflammation in AS is focussed, initially, at the sacroiliac joints before moving to the lumbar, thoracic and cervical spine. Enthesitis, inflammation at an insertion point of tendon or ligament to bone, is a common feature of the disease.
Ankylosing spondylitis is characterised by a gradual onset of symptoms before age 40, with a duration of symptoms longer than 3 months, prolonged morning stiffness and night pain. The symptom of pain tends to improve with physical activity and fails to improve with rest. Pain secondary to ankylosing spondylitis tends to respond to nonsteroidal anti-inflammatory drugs (NDAIDs).
The features predictive of poor prognosis in ankylosing spondylitis include:
Hip involvement
Age <16 years at onset of symptoms
Presence of 3 of the following factors within 2 years of onset of symptoms
ESR >30mm/h or CRP >6mg/L
Limitation of spinal movement
Dactylitis
Peripheral oligoarthritis
Inadequate symptom relief from NSAIDs
So of our options, hip involvement is most suggestive of poor prognosis when diagnosing ankylosing spondylitis.
Bonus: What are the functions of the skin?
Answer in tomorrow’s dose.
Closing:
Thank you for taking your Meds and we will see you tomorrow for your MANE dose. As always, please contact us with any questions, concerns, tips or suggestions. Have a great day!
Luke.
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