Pills of knowledge in Ophthalmology- Squint and refractive errors

1.A refractive error should be thoroughly assessed prior to surgical squint correction or the squint may recur.

2. Divergent squint occurs in myopes as the divergent system of muscles is more active during far vision. So, the far vision in myopes being hampered, the eyes try to diverge more.

3. Same goes for hypermetropes. They end up with a convergent squint if left uncorrected.

-That's all!

Sushrut Dongargaonkar

Differentiating peroneal neuropathy, sciatic nerve injury and L5 radiculopathy

This post is on differentiating weak dorsiflexion of foot - I made a little algorithm on it. (I'll add images later)

If there's weakness in foot dorsiflexion, check plantar flexion and inversion.

If plantar flexion and inversion is normal: Peroneal neuropathy.

If plantar flexion and inversion is weak: Check hip movements.

If weakness at hip joint: S5 radiculopathy.

If no weakness at hip joint: Sciatic nerve compression.

You can differentiate based on sensory levels and reflexes too but this is easier.

Conclusion:
Peroneal nerve supplies the dorsiflexors and evertors of the foot. There will be no weakness in plantar flexion and inversion in peroneal nerve injury.

Hip abduction is an action of Gluteus medius and minimus muscles. These are Superior gluteal nerve innervated muscles. This nerve arises from L4, L5 and S1 roots . If there is hip abduction deficit with foot drop, it means pathology at the radicular ( root) level. 

Here's the reading material.

Common peroneal neuropathy presentation:
- Acute foot drop (difficulty dorsiflexing the foot against resistance or gravity).
- Patients describe the foot as limp; there is a tendency to trip over it unless they compensate by flexing the hip higher when walking, producing what is called a "steppage" gait.
- Patients may also complain of paresthesias and/or sensory loss over the dorsum of the foot and lateral shin.
- Examination typically reveals weakness in foot dorsiflexion and foot eversion (deep and superficial peroneal nerve-innervated, respectively), with normal inversion and plantar flexion (posterior tibial nerve).
- Sensory disturbance is confined to the dorsum of the foot, including the web space between digits 1 and 2 and the lateral shin.
- Reflexes are normal.

Sciatic nerve injury presentation:
- Weakness affecting most of the lower leg musculature, including the hamstrings.
- Hip flexion, extension, abduction and adduction, and knee extension are normal.
- Sensory loss involves the entire peroneal, tibial, and sural territories.
- In the lower leg, however, the medial calf and arch of the foot may be spared secondary to innervation by the preserved saphenous nerve (a branch of the femoral nerve). Sensation is also spared above the knee both anteriorly and posteriorly.
- The knee jerk is normal, but the ankle jerk is unobtainable.

L5 radiculopathy presentation:
- Back pain that radiates down the lateral aspect of the leg into the foot.
- On examination, strength can be reduced in foot dorsiflexion, toe extension, foot inversion, and foot eversion.
- Mild weakness in leg abduction may also be evident in severe cases due to involvement of gluteus minimus and medius. Atrophy may be subtle; it is most readily observed in extensor digitorum brevis.
- Sensory loss is confined to the lateral shin and dorsum of the foot.
- Reflexes are generally normal.

That's all!
-IkaN

Alvarado Score Parameters Mnemonic ; For Appendicitis

Alvarado score is one of the most famous scores to clinically diagnose Appendicitis. Without further adieu let us delve into it.

            Anorexia or ketones in urine           - 1 
            Leukocytosis >10,000                      -2  
            Vomiting/Nausea                             -1
     migrAtory pain to right iliac fossa            -1
           Rebound tenderness                         -1
 temperAture above 37.3 celsius                 -1
      tenDerness in right iliac fossa              -2
   neutrOphilia >70%                                 -1

Of these the second parameter from above and second parameter from below have 2 points credited for each. Every other parameter is credited with 1 point each.

The overall aggregate comes out of 10, which the highest possible score for Alvarado score.

If, the aggregate is,

<3 - Low risk for appendicitis
4-6 - Mid risk for appedicitis
>=7 - High risk for appendicitis

In some hospitals where a differential count is difficult to find, use a modified score with 9.

That's all guys, if you find any mistake let me know.

With love,
Jay~

P.S. - yayyy.....missed me much awesomites? I was away from the blog for the last 6 months from posting, because I had very disastrous scores for surgery in my university and I didn't feel worthy enough to write for you guys. (So my activity was largely concentrated in the Whatsapp Medicowesome groups, and the Author's page.) Anyways, I had to take a remedial exam for Surgery 2 weeks ago. And BAAM!!!!.....the results were released today, and yayyyyy.....I passed surgery! :)

I must thank all my Medicowesome admin/author collegues for tolerating my rants and, help me to push through the hellish scary time together. Thanks everyone. Finally I'm through it, and I'm back to writing for you all guys. So thought to start the first post after returning, with a General Surgery Diagnosing score with the help of Schwartz Textbook of Surgery.

See ya soon peepz! :)

Pills of knowledge in Ophthalm- Posterior staphyloma

A posterior staphyloma is common because the durability of the layers of the eye where the optic nerve enters the eye is lesser in comparison.

-That's all!

Sushrut Dongargaonkar

Pills of knowledge in Ophthalm- Moxifloxacin

Moxifloxacin is the preferred antibiotic in Ophthalmic surgeries and pathologies because it gets concentrated into the anterior chamber and the aqueous.

That's all!


-Sushrut Dongargaonkar

EMG and NCS - Review

Hello there!

Today we'll see some important points on Electromyography (EMG) and Nerve conduction studies (NCS).

EMG evaluates abnormal electrical activity in muscles, and NCS investigates how electricity flows through a nerve.

They help to locate and determine the causes of diseases that affect muscles and peripheral nerves.

Procedure:
In EMG, a small needle is inserted into a muscle, to measure its electrical activity. In NCS, electrodes are placed on the skin overlying a nerve, and other recording electrodes are attached at a different point over the same nerve and a small shock is applied, and the electrical impulse is recorded​.

Understanding the terminologies and results of these tests-

 Amplitude: The electrical signal is represented as a wave, and the amplitude is its height.

ConductionVelocity (CV): The conduction velocity describes the speed at which the electrical impulse travels along the nerve.D

Duration This describes the width of an electrical wave.

ConductionBlock: The diminution of signal across an anatomical region such as the wrist. This suggests nerve entrapment.

So when a nerve stimulates a muscle to contract, there is a brief burst of electrical activity called a motor unit action potential (MUP).

Some of the abnormal responses seen are:

1)Fibrillations & positive sharp waves on the monitor seen in diseases of peripheral nerves.

Muscles sometimes start having spontaneous activity on their own.

2)Fasciculations: Sometimes the abnormality causes visible muscle twitches.

3)Abnormally large MUPS : These are seen If a nerve has been injured and then regrows.

 On regeneration the nerve tends to branch out to include a wider area of the muscle and hence we get large motor unit potentials on the screen.

4) Abnormally small MUPS: When they're  abnormally small or brief it suggests the presence of a disease of a muscle (a myopathy) where the muscle is unable to contract to and fails to provide the normal amplitude of the wave.

5)"Recruitment pattern":  As a muscle is contracted, nerve fibers signal more and more bits of muscle (called motor units) to join in and help. 

In a neuropathic disorder, the amplitude of different motor units is strong, but there are fewer of them because the nerve is unable to connect to as many units.

 In myopathies, the number of motor units is normal, but the amplitude is smaller

You may never come across an actual EMG for an interpretation,but it is always good to know the investigation.

The interpretation of EMG and NCSs is not always straightforward and may not always lead to just one possible diagnosis — but the tests can reduce the number of diagnostic possibilities.

Hope this was helpful!

Let's Learn Together!

-Medha.

New TB Risk Factor

People with low levels of vitamin A who live with individuals who were sick with tuberculosis were 10 times more likely to develop the disease than people with high levels of the nutrient, according to research led by investigators at Harvard Medical School.

Vit A rich foods: Liver, fish, hard-boiled egg(not omelette), cheese, butter, cheddar etc

And now some vegetables: Sweet potato, Carrot, Squash, Spinach, Lettuce

Some fruits: Mango, Papaya, Guava, Watermelon, Apricot, Passion fruit

Another reason to love Mango!

-VM

Research update: Statins may increase risk of Parkinsons' disease

Hey Awesomites

A new research by neuroscientists has updated our knowledge about the association between high cholesterol levels in people and prevalence of neurodegenerative diseases such as the Parkinson's.

Mind - wandering : How your body reacts to it?

Hey Awesomites

First lets have a word about mind - wandering.. "Mind- wandering (or task-unrelated thoughts) is an experience of thoughts which are totally unrelated to the task you are doing right now, especially when it demands attention. It involves activities such as reading, driving, attending lectures, etc."

Dibucaine Number.

Hello !
Let's see what this Dibucaine number is.

So Dibucaine is a local anesthetic.

Dibucaine inhibits 80% of the normal Pseudocholinesterase enzyme and 20% of the Atypical enzyme.

The number is determined by measuring the percentage of Pseudocholinesterase enzyme that remains unchanged in the blood of individuals administered a standard dose of Dibucaine intravenously.

Normal Dibucaine number is 70-80% i.e 70-80%of normal enzyme is inhibited by Dibucaine.
If there is a point mutation in the enzyme making it a Atypical Pseudocholinesterase then Dibucaine will not be able to inhibit it and the number will decrease.

This number is used to measure the activity of Atypical Pseudocholinesterase,and to assess the likely hood of prolonged apnea after succinylcholine administration.

Sodium Fluoride can also be used in place of Dibucaine.

If you know more on it Add to this information.

Let's learn Together!
-Medha.

Contraindications for Noninvasive Ventilation Mnemonic

Hey guys

This is one of my rare mnemonic posts. I don't post much on this coz most of my mnemonics are kinda personal if not socially inappropriate :p

So Noninvasive ventilation, imagine having a mask on ur face, all air tight, almost strangulating and as if this isn't enough, with multiple tiny outlets giving jets of air which are titillating your highly itchable nasal area.

Unpleasant, right?

Talking of unpleasant, you do remember Hitler, right?
He GAAASED the Jews, since that's not a possibility for us since we all love Zuckerberg let's think about something on a similar note.

"GAAAS the HOEs"

G- GI bleeding
A- Aspiration
A- Angina( including MI)
A- Arrest( Cardiac and Respiratory)
S- Surgery on ur face

H- Haemodynamic instability
O- Obstruction ( in upper airway)
E- Encephalopathy ( Severe)
S- _____

I've left the last one blank for the reader to fill up. Hint: It has something to do with​ obstruction of the lower airways.

Hope this is helpful!

-VM

Study Group Discussion: Salisbury Phenomenon

Whats Salisbury effect?

It's a very interesting phenomenon.

It states that when coronary collaterals develop in the face of myocardial ischemia, they improve the blood supply. However they physically restrict left ventricular dilation and thereby raise LVEDP(LV end diastolic pressure) and reduce LV compliance.
This is because they act like tendrils/scaffold which prevent ventricular dilation.

Nice one!

-VM

Ductus Arteriosus : Review of Key Points

Hi everyone ! Just a short review on Ductus Arteriosus.

- Ductus Arteriosus is basically a communication between the Pulmonary trunk and the Systemic Aorta.
- This communication is between pulmonary trunk and the end of Arch of aorta. Just after the Brachiocephalic trunk , and Left Common carotid and Subclavian have branched off.
- In embryonic life this communication helps transport blood from RV- Pulmonary artery to the Systemic circulation.

So ,
Remember :
Prostaglandins Persist

-Prostaglandins, especially PGE1 , act on the Ductal muscle tissue and keep it Open.
-So the Ductus arteriosus stays open.

-This is important in certain Duct dependent lesions
- Duct dependent heart lesions are those which need the presence of an Open ductus to receive blood in systemic / Pulmonary circulation.

- For example -->
✓ Duct dependent lesions for Systemic Circulation are those that cause obstruction to the Left side heart to pump blood into the aorta. These include :

- Coarctation of Aorta ( especially pre Ductal ) : Here there is a constriction of the aorta just before the ductus Arteriosus. So , a persistent Ductus would transport blood from pulmonary circulation into the systemic. 
If ductus gets closed , there would be minimal blood flow to the Lower limbs and abdomen.

- Critical Aortic stenosis.
- Left side Hypoplastic heart.

~~~~~~~~~~~~~~~~~~~~~~~~~

✓ Duct dependent lesions for pulmonary circulation
-These are lesions where pulmonary blood flow would be severely reduced due to some RV- Outflow tract Abnormality and the only source to the lungs would be through the ductus shunting some blood from aorta into the pulmonary vein.

- These include : 

- Critical Pulmonary Stenosis
- Hypoplastic Right heart syndrome
- Tetrology of Fallot
- Tricuspid Atresia
- Ebstein Anomaly

Another important disease is Transposition of the great vessels where this sort of corrects the defect.
~~~~~~~~~~~~~~~~~~~~~~~~~

So. We've seen in what conditions we'd like to keep the Ductus Arteriosus open / persistent.
Normally this Ductus closes functionally within 24 hours of birth. And anatomically between 10 and 14 days post natally.

If this persists on its own for a long time it causes a Congenital Heart Disease called Patent Ductus Arteriosus.
This defect is characterised by shunting of blood into the pulmonary trunk constantly during systole and diastole causing a Continuous murmur.

To close this ductus , we could try using Indomethacin / Ibuprofen especially in preterm children.
These drugs inhibit Prostaglandin synthesis , thus causing Ductus Smooth muscle to constrict and eventually close.

So that's all about the ductus !

Happy studying !
And Stay Awesome !

~ A.P.Burkholderia