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Showing posts with label neuroophthalmology. Show all posts
Showing posts with label neuroophthalmology. Show all posts

Understanding Myasthenia Gravis: Causes, Symptoms, Diagnosis, and Treatment

Myasthenia gravis is a chronic autoimmune disorder that causes weakness and fatigue in the skeletal muscles of the body. The disorder is characterized by the formation of antibodies that attack the acetylcholine receptors, which are responsible for transmitting signals from the nerves to the muscles. As a result, the muscles fail to receive the necessary signals, leading to muscle weakness, which can worsen with physical activity and improve with rest. In this article, we will provide a detailed overview of the causes, symptoms, diagnosis, and treatment of myasthenia gravis.

Causes:

The exact cause of myasthenia gravis is not yet fully understood. However, it is believed to be an autoimmune disorder, which means that the immune system mistakenly attacks the body's own tissues. In myasthenia gravis, the immune system produces antibodies that attack the acetylcholine receptors, which are responsible for transmitting signals from the nerves to the muscles. The attack on these receptors leads to a decrease in the number of functioning receptors, which in turn leads to muscle weakness and fatigue.

In some cases, myasthenia gravis may be associated with other autoimmune disorders such as rheumatoid arthritis, lupus, or thyroid disorders. There may also be a genetic component to the disorder, as it tends to run in families.

Symptoms:

The symptoms of myasthenia gravis vary from person to person, depending on the severity and distribution of muscle weakness. Some common symptoms of myasthenia gravis include:

  1. Muscle weakness: The most common symptom of myasthenia gravis is muscle weakness, which can affect any muscle group in the body. The weakness tends to be more pronounced during physical activity and improves with rest.
  2. Eye problems: Myasthenia gravis can affect the muscles that control eye movements, causing double vision (diplopia), drooping eyelids (ptosis), and difficulty focusing.
  3. Difficulty speaking: Myasthenia gravis can also affect the muscles used for speech, making it difficult to speak clearly or loudly.
  4. Difficulty swallowing: In some cases, myasthenia gravis can affect the muscles used for swallowing, leading to difficulty eating and drinking.
  5. Fatigue: People with myasthenia gravis may experience fatigue, particularly after physical activity.

Diagnosis:

Diagnosing myasthenia gravis can be challenging, as the symptoms can be similar to those of other neuromuscular disorders. A thorough medical history and physical examination are often the first steps in diagnosing myasthenia gravis. Additional tests may include:

  1. Electromyography (EMG): This test measures the electrical activity of the muscles and can help detect muscle weakness.
  2. Blood tests: Blood tests can detect the presence of antibodies that are associated with myasthenia gravis.
  3. Edrophonium test: This test involves injecting a medication called edrophonium, which can temporarily improve muscle weakness in people with myasthenia gravis.
  4. Imaging tests: Imaging tests such as CT or MRI scans may be used to detect abnormalities in the thymus gland, which is often enlarged in people with myasthenia gravis.

Treatment:

The treatment of myasthenia gravis typically involves a combination of medications and lifestyle modifications.

Medications:

There are several medications that can be used to treat myasthenia gravis, including:

  1. Cholinesterase inhibitors: These medications help increase the levels of acetylcholine, which can improve muscle function. Examples include pyridostigmine (Mestinon) and neostigmine (Prostigmin).
  2. Immunosuppressants: These medications help suppress the immune system, reducing the production of antibodies that attack the acetyl choline receptors. Examples include prednisone and azathioprine.
  3. Intravenous immunoglobulin (IVIG): IVIG is a medication that contains antibodies that can help reduce the production of harmful antibodies in the body.
  4. Plasmapheresis: Plasmapheresis is a procedure that involves removing the plasma from the blood and replacing it with a solution that does not contain the harmful antibodies.

Lifestyle modifications:

In addition to medications, there are several lifestyle modifications that can help manage the symptoms of myasthenia gravis, including:

  1. Rest: Rest is important for people with myasthenia gravis, as muscle weakness tends to worsen with physical activity and improve with rest.
  2. Diet: A healthy, balanced diet can help support overall health and well-being. People with myasthenia gravis may also benefit from small, frequent meals to help prevent fatigue during meals.
  3. Exercise: While excessive physical activity can worsen symptoms, regular exercise can help maintain muscle strength and overall health. It is important to work with a healthcare provider to develop an exercise plan that is appropriate for your level of muscle weakness.
  4. Assistive devices: Assistive devices such as walkers, canes, and braces can help support weak muscles and improve mobility.

Prognosis:

The prognosis for myasthenia gravis varies depending on the severity of the symptoms and the age at onset. In some cases, the symptoms may improve over time, while in others they may worsen. In rare cases, myasthenia gravis can be life-threatening if it affects the muscles used for breathing. With proper treatment and management, however, most people with myasthenia gravis are able to lead normal, active lives.

In conclusion, myasthenia gravis is a chronic autoimmune disorder that causes muscle weakness and fatigue. While the exact cause of the disorder is not fully understood, it is believed to be an autoimmune disorder in which the immune system attacks the acetylcholine receptors in the muscles. The symptoms of myasthenia gravis vary from person to person and can affect any muscle group in the body. Treatment typically involves a combination of medications and lifestyle modifications, and the prognosis varies depending on the severity of the symptoms and the age at onset.

What is Concomitant and Incomitant deviations in squint ?


Concomitant Deviation

  1. The Angle of deviation are the same in all fields of gaze.
  2. Congenital or chronic.
  3. Congenital or early onset strabismus or Chronic.
  4. Suppression associated with amblyopia.
  5. Develop diplopia later is life.

Incomitant Deviation
  1. Angle of deviation is different fields of gaze.
  2. Incomitant deviation mainly seen in patients with acquired problems-looking to right no problem.
  3. Straight also less problematic but looking to right produce diplopia.indicating deviation vary with gaze.
  4. Acquired and causes diplopia.
  5. Long standing incomitant deviation become comitant.

What are the causes of Horizontal and Vertical Diplopia

The following are the causes of Horizontal and Vertical Diplopia

Horizontal Diplopia
  1. Myasthenia Gravis
  2. CN 6th palsy
  3. CN 3rd palsy
  4. Divergence Insufficiency
  5. Internuclear Ophthalmoplegia
  6. Convergence Insufficiency
  7. Decompensated Strabismus
Vertical Diplopia

Differential Diagnosis of Monocular Diplopia

Following are differential diagnosis of Monocular Diplopia.
(a) Anterior segment causes, (b) Retinal abnormalities, (c) Cortical Diplopia

Anterior segment
  1. Refractive error
  2. Cataracts
  3. Keratoconus
  4. Astigmatism
  5. Corneal opacities
  6. Post-op Cataract surgery
Retinal abnormalities
  1. Retinal folds
  2. Retinal hemorrhage
  3. Epiretinal membrane
Cortical Diplopia

What are Beilchowski’s three step test ?

Step 1 
Find the resting position misalignment.
Due to diplopia patient have tilting of eye first correct it. For example if the patient has the Left eye low right eye up. Problem can be Either depressors are weak on the right side i.e. Right IR(inferior Rectus)  or SO(superior Oblique).Or elevators of the left eye could be at fault.

Step 2
To find out where is the maximum misalignment.
Ask the patient to look to the right and left.
Misalignment is maximum to looking towards the left side. For example, if the patient has Right eye is up and left eye is down and maximum separation is looking towards the left so the right superior oblique is weak.
Problem is Right superior oblique is weak.
OR Left superior rectus is weak.
Adducted eye is up on right and abducted eye is down in left .

Step 3
Lateral rotation where is the maximum separation. For example, on turning to the right disconjugation is maximum. Turning to the right side you are putting the right intorters into action and left extorters into the action.
Right turning the introrters are SR and SO .when the Superior oblique is weak the eye right eye SR is acting and pushes the eye to upwards,on the left side if the superior recus is abnormal it is an intorter nothing will happen.
On turing to left the extorters acting nothing will happen.
The separation of the images increase when the head is tilted to the side of palsy.
Deficit improves when the head is tilted to the opposite side.

BeilchowskyJs head rotation test
Pitfalls of the three step test - namely, the conditions in which the rules breakdown.
  1. Restrictive ocular myopathies
  2. Long-standing strabismus
  3. Skew deviation
  4. Disorders involving more than one muscle.



What is primary and secondary deviation Squint?

Primary deviation is the deviation of the "lazy" or paretic eye, when the "good eye" or the non-paretic eye fixes on an object. 

Secondary deviation is the deviation of the “ good "or non- paretic eye, when the "lazy" eye or the"paretic eye" fixes on an object.

Secondary deviation is always greater than primary deviation in noncomitant strabismus because of Hering's law of equal innervation.

When the left eye is covered right eye has to move more to fixate.same innervation go to the left eye also.

How to find out which eye is producing the peripheral image in Diplopia?

Ask the patient to cover both eyes one by one-alternatively; ask him to notice the side of the eye, closure which results in disappearance of the periphera image. But it is tricky and patients sometimes wont be able to tell. Best and easy way is as bellow.

Red-Glass test

  1. Put a red glass in front of one eye: usually right eye.
  2. Now patient sees the image produced by the right as red.
  3. Ask patient to notice color of the peripheral image, ie normal or red.
  4. If red one is to the periphery, then the right eye is the culprit.
  5. If the normal image is to the periphery, left eye is the culprit.

.

Related articles

  1. What are the History you should ask in Diplopia?
  2. What is Concomitant and Incomitant deviations in squint ?
  3. What are the causes of Horizontal and Vertical Diplopia
  4. Differential Diagnosis of Monocular Diplopia
  5. What are Beilchowski’s three step test ?
  6. How to find out which eye is producing the peripheral image in Diplopia?
  7. How to know which muscle is affected in Diplopia?
  8. What are the clinical approach that need to take care on diplopia History taking?
  9. What causes the Pathophysiology of misalignment?
  10. What causes binocular diplopia?
  11. What are the symptom of diplopia and how to diagnose diplopia ?
  12. Clinical approach to DIPLOPIA (Binocular and Uniocular)

How to know which muscle is affected in Diplopia?

Diplopia is worse in the direction of action of the weak eye muscle.

Lateral rectus muscle weakness causes diplopia worse on looking to the side of the weak muscle and is worse at distance.

Medial rectus muscle weakness causes diplopia that is worse for near than for distance vision and is worse to the contralateral side.

Superior oblique weakness causes diplopia that is worse on looking downward to the side opposite the weak muscle and causes difficulty with tasks such as reading, watching television in bed, descending a staircase, and walking on uneven ground.

Yolk muscles work in unison, so that the images fall on corresponding parts of the retina. Diplopia indicates weakness of one of the yolk muscles.

For example : For looking to right side, the yolk muscles acting are right lateral rectus and the left medial rectus. On looking up and out to the right side, they are the right SR and left 10.

For Horizontal diplopia:
Find out whether diplopia is maximum to the right or left.
For example : if diplopia is maximum on looking to the left, it can be either left lateral rectus or right medial rectus (yolk muscles).
If the diplopia is worse on looking at far objects, it likely to left lateral rectus. If diplopia is more while reading (convergence), it is more likely to be right medial rectus.

For Vertical diplopia
Problems comes mainly with vertical diplopia. Vertical diplopia is caused by weakness of a depressor or elevator. If diplopia is worse in downgaze, the weak muscle is a depressor.
Either inferior rectus or superior oblique, if the diplopia is worse in upgaze, it is an elevator.
Either superior rectus or inferior oblique, If one image is tilted, then the weak muscle is more likely an oblique than a vertically acting rectus.

Related articles

  1. What are the History you should ask in Diplopia?
  2. What is Concomitant and Incomitant deviations in squint ?
  3. What are the causes of Horizontal and Vertical Diplopia
  4. Differential Diagnosis of Monocular Diplopia
  5. What are Beilchowski’s three step test ?
  6. How to find out which eye is producing the peripheral image in Diplopia?
  7. How to know which muscle is affected in Diplopia?
  8. What are the clinical approach that need to take care on diplopia History taking?
  9. What causes the Pathophysiology of misalignment?
  10. What causes binocular diplopia?
  11. What are the symptom of diplopia and how to diagnose diplopia ?
  12. Clinical approach to DIPLOPIA (Binocular and Uniocular)

What are the clinical approach that need to take care on diplopia History taking

1. Check on Mono-ocular or binocular ? 

2. Whether the diplopia is horizontal, vertical, or oblique. ? 

3. Whether one of the images is tilted or not?

4. Whether the diplopia is worse in a particular direction of gaze or with near or distant visual tasks?

Related articles

  1. What are the History you should ask in Diplopia?
  2. What is Concomitant and Incomitant deviations in squint ?
  3. What are the causes of Horizontal and Vertical Diplopia
  4. Differential Diagnosis of Monocular Diplopia
  5. What are Beilchowski’s three step test ?
  6. How to find out which eye is producing the peripheral image in Diplopia?
  7. How to know which muscle is affected in Diplopia?
  8. What are the clinical approach that need to take care on diplopia History taking?
  9. What causes the Pathophysiology of misalignment?
  10. What causes binocular diplopia?
  11. What are the symptom of diplopia and how to diagnose diplopia ?
  12. Clinical approach to DIPLOPIA (Binocular and Uniocular)

What causes the Pathophysiology of misalignment?

A) The misalignment can be due to

  1. Weakness of one of the EOMs
  2. Over action of one of the EOM
  3. The muscle is prevented by acting because of a problem with the antagonist
    a. The antagonist fails to relax (ocular neuromyotonia)
    b. Simultaneous unwanted contraction (aberrant reinnervation), or
    c. Restrictive ophthalmopathy (something preventing it from relaxing)

B) It can be by infiltration,

C) It can be by fibrosis of the muscle or muscle getting stuck by some means( eg: blow out fracture)

D) The misalignment need not always due to a eye movement problem

  • Failure to keep the eyes in the parallel position due to vestibulo- ocular dysfunction can also produce diplopia  Eg: Skew deviation

Related articles

  1. What are the History you should ask in Diplopia?
  2. What is Concomitant and Incomitant deviations in squint ?
  3. What are the causes of Horizontal and Vertical Diplopia
  4. Differential Diagnosis of Monocular Diplopia
  5. What are Beilchowski’s three step test ?
  6. How to find out which eye is producing the peripheral image in Diplopia?
  7. How to know which muscle is affected in Diplopia?
  8. What are the clinical approach that need to take care on diplopia History taking?
  9. What causes the Pathophysiology of misalignment?
  10. What causes binocular diplopia?
  11. What are the symptom of diplopia and how to diagnose diplopia ?
  12. Clinical approach to DIPLOPIA (Binocular and Uniocular)


What causes binocular diplopia?

Why should the images fall on non-corresponding parts of retina?

The images fall on non-corresponding parts of the retina, because of mis-alignment of the eyes.

This mis-alignment may be in the primary position or when patient looks in to one direction.

Diplopia will not occur in cases of long standing misalignment because brain learns to suppress one image: eg congenital squint. Hence, diplopia is a symptom of a recent acquired misalignment.

Related articles

  1. What are the History you should ask in Diplopia?
  2. What is Concomitant and Incomitant deviations in squint ?
  3. What are the causes of Horizontal and Vertical Diplopia
  4. Differential Diagnosis of Monocular Diplopia
  5. What are Beilchowski’s three step test ?
  6. How to find out which eye is producing the peripheral image in Diplopia?
  7. How to know which muscle is affected in Diplopia?
  8. What are the clinical approach that need to take care on diplopia History taking?
  9. What causes the Pathophysiology of misalignment?
  10. What causes binocular diplopia?
  11. What are the symptom of diplopia and how to diagnose diplopia ?
  12. Clinical approach to DIPLOPIA (Binocular and Uniocular)

What are the symptom of diplopia and how to diagnose diplopia ?

Patients with diplopia may not always complain of double vision.

Symptom

Most of the complaints from the patients can be 

  1. Dizziness.
  2. Imbalance.
  3. Defective eye-hand coordination.
  4. Overlapping images (ghosting).
  5. Difficulty in negotiating stairs.

How you can diagnose diplopia in the above situations?

You can ask the patient to close one eye and ask them whether symptoms that they have disappear.

Related articles

  1. What are the History you should ask in Diplopia?
  2. What is Concomitant and Incomitant deviations in squint ?
  3. What are the causes of Horizontal and Vertical Diplopia
  4. Differential Diagnosis of Monocular Diplopia
  5. What are Beilchowski’s three step test ?
  6. How to find out which eye is producing the peripheral image in Diplopia?
  7. How to know which muscle is affected in Diplopia?
  8. What are the clinical approach that need to take care on diplopia History taking?
  9. What causes the Pathophysiology of misalignment?
  10. What causes binocular diplopia?
  11. What are the symptom of diplopia and how to diagnose diplopia ?
  12. Clinical approach to DIPLOPIA (Binocular and Uniocular)

Clinical approach to DIPLOPIA (Binocular and Uniocular)

Diplopia

Detailed examination reveals no obvious extra ocular muscle weakness.

Diplopia is due to failure of fusion of images.

Types of diplopia : There are two types

  1. Binocular
  2. Uniocular

Uniocular

  1.     Diplopia that persists even when patient closes one eye.
  2.     Diplopia improves with pin-hole

What are the causes of Uniocular

  1. Ocular causes: Example : Refractive errors
  2. Occipital lobe lesions
  3. Functional cause

Binocular

Patients with diplopia may not always have the issue of double vision.

What are the causes of  Binocular
  1. Diplopia is due failure of fusion of images.
  2. Normally fusion can occur only when the images fall on corresponding
  3. parts of the retina and when the images are similar.

What is See-Saw Nystagmus?

What is See-Saw Nystagmus?

In see-saw nystagmus one eye moves up + intorts & other eye moves down +extorts

Torsional component is conjugate

Vertical component is dysconjugate

1. Wave form is pendular or jerk

What are the types of See-Saw Nystagmus?

Pendular see-saw nystagmus

Seen in

  1. Suprasellar lesion
  2. Visual loss
  3. Joubert's syndrome

Jerk see-saw nystagmus: (Hemi see-saw nystagmus)

Half cycle is pendular with corrective half cycle jerky

Seen in

  1. lesions of INC (caudal thalamus-rostral midbrain)

See-Saw Nystagmus Pathogenesis:

Midbrain

Unilateral inactivation of INC

Sparing of riMLF

Afferent

  1. Bitemporal hemianopia.
  2. Visual loss-visuo-vestibular fibres
  3. Chiasmal miswiring

What are the causes of Acquired Pendular nystagmus ?

What are the causes of Acquired Pendular nystagmus ?

  1. Acquired Pendular nystagmus can be seen in the following conditions
  2. Oculo-palatal myoclonus
  3. See-saw nystagmus
  4. Oculomasticatory myorhythmia
  5. Visual loss
  6. Spasmus nutans

What is Convergence-Retraction Nystagmus?

Convergence-Retraction Nystagmus is characterised by rapid convergence with synchronous

retraction of both globes slow divergence.

It is due simultaneous contraction of all EOM

This is best detected by:

  1. Looking up
  2. OKN

What is the site of lesion in convergence retraction nystagmus

Dorsal midbrain


Reference Notes 

What is See-Saw Nystagmus ?
What are the causes of Acquired Pendular nystagmus ?
What is Convergence-Retraction Nystagmus ?
Dissociated Jerk Nystagmus and causes
What is Rebound nystagmus and its causes?
What is Bruns's nystagmus?
What is Gaze evoked nystagmus?
Down-beat nystagmus and its causes
Upbeat nystagmus and its causes
What is the basic Pathophysiology of Nystagmus
Alexanders law in Nystagmus - A brief

Dissociated Jerk Nystagmus and causes

Dissociated Jerk Nystagmus and causes

Dissociated Jerk Nystagmus and causes

Dissociated Jerk Nystagmus ,nystagmus is different in both eyes

INO (Internuclear ophthalmoplegia)

Ipsilateral adduction deficit with contralateral abduction nystagmus

Vertical nystagmus can occur in INO

What is Rebound nystagmus and its causes?

 Rebound nystagmus is a Gaze evoked nystagmus reverses direction in the eccentric gaze.

  • In Primary position - No nystagmus
  • Lateral gaze - Initiates nystagmus

        On return from lateral gaze, nystagmus reverses direction.
        Occasionally reverses direction while maintaining prolonged lateral gaze.

What are the causes of Rebound nystagmus?

It is seen in

  1. Cerebellar disorder
  2. Medullary lesion
  3. Lesions of NPH