Internship Learning Points Flashcards
A woman develops weakness in all four limbs.
How, on examination, can you tell if this is UMNL / LMNL?
Reflexes:
If brisk - in the brainstem / high C spine
If sluggish - peripheral neuropathy
Sensation:
If glove and stocking - peripheral neuropathy
Describe the pathway of the DCML
Receptors of first order sensory nerves in peripheral tissue
Cell bodies are in the dorsal root ganglia
Travel up the ipsilateral side of the dorsal columns
Synapse with second order neurons in the gracrile (LL) and cuneate (UL) nuclei in the medulla
Decussate and up the medial leminscus
Synapse in the VPL nucleus in the thalamus
Then project to the somatorsensory cortex in the parietal lobe, posterior to the central sulcus
Describe how a ‘glove and stocking’ pattern of sensory loss comes about
Peripheral neuropathy
Affects the longest nerves first
What is the Modification of Diet in Chronic Renal Disease equation?
What variables does it include?
Variables include: age, sex and race (i.e. not weight)
What is the difference in variables between the MDRD and Cockroft Gault equations?
Therefore, what is the diffenece in the units?
CG includes weight*
Therefore, the MDRD has to include body surface area in it’s units.
Remember _C_reatnine _C_learance = _C_ockroft Gault
C shape looks like central adiposity / weight
*NB - another difference is that MDRD includes race
What does the DCML pathway convey?
Proprioception and vibration
What might fasciculations signify?
LMNL
Think of disease of the anterior horn cell first
Describe upper and lower motor neuron lesions
What does the spinothalamic tract convey?
Pain and temperature
What is creatinine used to measure, and what is creatine kinase used to measure?
Creatinine is used to measure kidney function
- It is a breakdown product produced at a constant rate from the muscles and excreted by the kidneys, hence why it is used to measure kidney function
Creatine kinase is used to measure muscle damage
- There are two sub-units of CK: muscle (M) type and brain (B) type.
- There are therefore three isoenzymes: CK-MM, CK-BB and CK-MB
- Skeletal muscle expresses 99% CK-MM and 1% CK-MB
- Myocardium expresses 70% CK-MM and 30% CK-MB
- CK-BB is predominantly expressed by the brain and smooth muscle
Comment on tone / reflexes in upper motor neuron lesions
Note that in the early phases of UMNL - can get reduced tone and sluggish reflexes
As disease progresses - get increased tone (and clonus) and brisk reflexes
What pathway conveys pain and temperature?
Spinothalamic tract
What percentage of right handers are left hemisphere dominant?
What percentage of left handers are left hemisphere dominant?
Why is this significant, if for example a patient suddenly loses power of the right arm and leg?
99%
60-70%
You assume the patient has had a stroke. If the arm and leg are involved you assume it is a rather large stroke if it’s involving the arm and the leg. However, if that patient is right handed (or even if they’re left handed) and the weakness is NOT associated with dysphasia, you might think that this is in the brainstem - rather than cortical.
In what conditions would you expect elevated levels of creatine kinase, and which isoenzyme specifically?
- In conditions causing skeletal muscle damage, you would expect elevated CK levels, specifically CK-MM.
UpToDate RE rhabdomyolysis:
- “The CK is generally entirely or almost entirely of the MM or skeletal muscle fraction; a small proportion of the total CK may be from the MB or myocardial fraction. The presence of MB reflects the small amount found in skeletal muscle rather than the presence of myocardial disease.”*
2. In AMI, CK-MB is raised.
Used to be used as a marker of cardiac myocyte damage, however troponin more sensitive and specific.
How do you describe movements at the 1st MCP joint?
Because the 1st MCP joint is rotated 90 degrees:
When the body is in the anatomical position
Ab/adduction is in the frontal plane
Flexion/extension is in the coronal plane
Which aminotransferase is most specific to the liver?
Which is also in other organs?
- Alanine aminotransferase (ALT) is present primarily in the liver, and thus is a more specific marker of hepatocellular cell injury
- Asparate aminotransferase (AST) is present in the liver and other organs including cardiac muscle, skeletal muscle, kidney, and brain.
- Remember L for ‘liver’*
- Remember S for ‘several other organs’*
What is the characteristic triad of symptoms in rhabdomyolysis?
- Muscle pain
- Weakness
- Dark urine
What are the units of Creatinine Clearance?
mls / minute
What is the difference between creatinine, creatine and creatine kinase?
- Creatine is a protein, synthesized by the liver from amino acids
- Creatine is stored in muscle, it is used to form phosphophocreatine (as well as convert ATP to ADP) by the enzyme creatine kinase. See below.
- Creatinine is a waste product, excreted by the kidneys
When does juvenille myoclonic epilepsy begin?
What is it characterised by?
Usually begins in teenage years.
CHaracterised in ints early stages by early morning myoclonic jerksm usually in the morning within one hour of waking up, or after a nap.
What does AProf Stark say about a sensory examination?
Never do a sensory examination until you know what you’re looking for.
Describe the pathway of the spinothalamic tract
First order neurons have receptors in the tissue
Cell bodies in the DRG
Synapse in the doral horn
Second order neurons decussate at the same level or a level above or below
Then travel up the lateral spinal tract
Second order neuons synapse with third order neurons in the thalamus
Then project up to S1, in the parietal lobe posterior to the central sulcus
What is the Cockroft Gault equation?
What variables does it include?
Includes the variables age, weight and sex.
Consider the Numerator:
Therefore, the older you are and less you weigh (and if you are female), the worse your creatnine clearance is for a given serum creatinine level.
The younger you are and the more you weigh (muscle mass), the better your creatnine clearance is for a given serum creatinine level.
Consider the Denominator:
The higher your plasma creatinine, the worse your creatnine clearance.
When assessing power in carpal tunnel syndrome:
What muscle / movement is always supplied by the median nerve?
What can you use as a ‘negative control’ to ensure that this is not a C8/T1 nerve root issue?
Abductor policis brevis (1st MCP joint abduction) is always supplied by the median nerve
2nd dorsal interosseus (2nd finger abduction) is always supplied by the ulnar nerve and therefore a good negative control
Which neurons decussate in the spinothalamic tract?
Which neurons decussate in the DCML tract?
And where?
In both cases, the second order neurons.
In the spinothalamic tract at the level of the entry of the nerve to the spinal cord (or a few levels above / below).
In the DCML, at the level of the medulla.
What is the scale of the vertical axis on an ECG?
1mV = 10mm / 1cm
1mV = 2 big squares
What is the scale of the horizontal axis on an ECG?
1 square = 0.5cm / 5mm
5mm = 0.2 seconds
5 small squares = 1 second
What is the strict definition of sinus rhythm?
(Both physiologically and on an ECG)
When depolarisation of the heart commences at the sinoatrial node.
Sinus rhythm can be identified by the presence of normally shaped p waves preceding every QRS complex with a normal PR interval.
Note that some people say that the only requirement to diagnose sinus rhythm is to identify a p wave before every QRS complex. This is not strictly true. The presence of abnormally shaped p waves or short PR intervals may indicate an ectopic atrial rhythm, where depolarisation of the heart is commencing somewhere in the atrial muscle that is not the SA node proper.
Describe the sequence of action potential propogation from the SA node to the AV node
Anterior, middle and posterior internodal pathways
Anterior = Bachman’s bundle*
(*also conducts AP to left atrium)
Middle = Wenkebach’s bundle
Posterior = Thorell’s bundle
How are the right and left atria synchronised?
Bachman’s bundle
Describe the anatomy of the conducting system from the AV node
AV node
–>
Bundle of His / AV bundle
–>
Left bundle branch
(which divides into an anterior and posterior fasicle)
OR
Right bundle branch
–>
Purkinje fibres
What does rouleaux look like on a blood film?
Stacks or aggregations of erythrocytes which form because of the unique discoid shape of the cells in vertebrates.
(Looks like a stack of coins or tokens at the casino)
What causes rouleux formation, seen on a blood film?
This can occur in any disease where there is increased levels of fibrinogen or total proteins or whatever cause (eg monoclonal or polycloncal gammaopathies).
Most commonly known to be present in multiple myeloma.
Why does rouleux formation cause an increased ESR?
Because having RBCs stacked like this increases their rate of sedimentation
From what lineage does a plasma cell come?
Lymphoid –> Lymphoblast –> B lymphocyte –> Plasma cell
Describe what MGUS is to multiple myeloma?
The first step in the pathway to the development of multiple myeloma (MM) is the establishment of the premalignant plasma cell proliferative disorder known as monoclonal gammopathy of undetermined significance (MGUS)
What is Smoldering Myeloma?
An intermediate stage between MGUS and MM
What is the diagnostic criteria of MGUS / SM / MM?
What is a Bence Jones protein?
A light chain paraprotein, found in the urine.
Is the M protein of MM in 15-20% of cases.
Kappa is the predominant light chain isotype compared with lambda, by a factor of 2 to 1
