QuestionSBA
QuestionChoice
Multiple Sclerosis is a definite cause of a medical third nerve palsy. However, the normal MRI Head, lack of any previous neurological history and significant vascular risk factors in her history point towards a more vasculopathic process
32601
d
Multiple Sclerosis
QuestionChoice
This is the cause of a 'surgical' third nerve palsy. Note that this is a medical third nerve palsy which is pupillary sparing rather than a 'surgical' third nerve palsy where aneurysms, tumours and raised intracranial pressure can push on the outer autonomic fibres of the nerve, causing the pupil to dilate. In a medical third palsy, only the inner motor fibres are affected so the pupils are spared
32599
b
Cerebral artery Aneurysm
QuestionChoice
This patient has an oculomotor nerve palsy (cranial nerve III), and one of the common medical causes of this presentation is due to vasculopathic ischaemia to the third nerve. Note that this is a medical third nerve palsy which is pupillary sparing rather than a 'surgical' third nerve palsy where aneurysms, tumours and raised intracranial pressure can push on the outer autonomic fibres of the nerve, causing the pupil to dilate. In a medical third palsy, only the inner motor fibres are affected so the pupils are spared
32598
a
Diabetes
QuestionChoice
There are no real signs of raised intracranial pressure in this scenario. Also you would expect there to be pupillary dilatation secondary to pressure on the outer autonomic fibres of the third cranial nerve
32602
e
Raised intracranial pressure
QuestionChoice
Urinary tract infection is unlikely to be implicated in causing an isolated third nerve palsy
32600
c
Urinary tract infection
QuestionComment
what
38533
QuestionComment
what
57067
User
subscriber
Retrograde Hematoma
QuestionComment
what
62173
User
subscriber
Chronic Prognosis
User
subscriber
Imran
QuestionComment
wow
62180
User
subscriber
Warren
Concept
Chapter
# Summary

Diplopia is commonly caused by third, fourth, and sixth nerve palsies which refer to paralysis of the oculomotor, trochlear, and abducens nerves respectively. Each nerve controls different sets of extraocular muscles, contributing to various distinct clinical presentations. 

# Epidemiology

These nerve palsies are relatively rare, with an estimated prevalence ranging from 1 in 1,000 to 1 in 10,000 depending on the specific nerve involved. They can occur in all age groups but tend to be more prevalent in older adults due to higher rates of vascular disease and diabetes which are common aetiological factors.

# Aetiology

- **Third nerve palsy**: This condition can result from surgical lesions (compressive) such as a posterior communicating artery aneurysm, or medical lesions (non-compressive), such as multiple sclerosis or vascular causes like diabetes.
	- Compressive lesions compresse parasympathetic fibres which are at the outermost of the nerve, leads to unopposed sympathetic action which leads to fixed pupil dilatation. This doesn’t happen in medical pathologies as no physical compression of those outermost parasympathetic fibres. Please see section on medical third nerve palsy for more information
- **Fourth nerve palsy**: Common causes include ocular trauma and diabetes mellitus.
- **Sixth nerve palsy**: Common causes are diabetic neuropathy, stroke, infection, multiple sclerosis and trauma. It's known for being a 'false localizing sign' due to the path of the sixth nerve within the brain, making it easily compromised in a state of raised intracranial pressure.

# Signs and Symptoms

- **Third nerve palsy**: The eye's classic resting position is looking 'down and out'. Other features include ptosis, proptosis, and a fixed pupil dilatation if the lesion is compressive rather than medical.

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- **Fourth nerve palsy**: The presentation is a result of paralysis or partial paralysis of the superior oblique muscle. At rest, the eye points upwards and inwards, and the patient may present with a tilted head to compensate for the palsy. Patients present with double vision worse in the vertical plane, and potentially hypertropia.

- **Sixth nerve palsy**: The eye fails to ABduct due to paralysis of the abducens nerve. It may be medially deviated at rest, and diplopia worsens when the patient is asked to look horizontally away from the midline on the side of the lesion.

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# Differential Diagnosis 

The primary systemic differentials include:

- **Myasthenia gravis**: Presents with weakness that is exacerbated by continued use of the muscle. Patients often have ocular symptoms of diplopia and ptosis that worsen throughout the day or while watching television.
- **Strabismus**: Common cause of diplopia in children and occasionally in adults. Esotropia – a convergent squint – is the commonest type, where the malaligned eye diverges inwards towards the midline.
- **Thyroid eye disease**: Exophthalmos in Graves' disease can cause double vision through compression of the extraocular muscles and lack of space for the eye to rotate.

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# Investigations

- Typically, the workup includes a comprehensive ophthalmologic examination to evaluate eye movements, visual acuity, and pupillary function. 
- Neuro-imaging, such as MRI or CT scan, is often necessary, particularly for third nerve palsy, to identify any compressive lesions. 
- Additional tests depend on the suspected aetiology and may include blood tests, cerebrospinal fluid analysis (LP), and nerve conduction studies.

# Management

- Management strategies vary depending on the specific nerve involved, aetiology, and severity of symptoms. Initial management may include prismatic glasses to correct diplopia and use of occlusion for troublesome diplopia. 
- Definitive management may include strabismus surgery or treatment of the underlying cause (e.g. blood sugar control in diabetic neuropathy, immunosuppression in multiple sclerosis). 
- In some cases, spontaneous recovery can occur.

# References

1. Rucker JC. "Cranial Neuropathies: Oculomotor, Trochlear, and Abducens Nerve Palsies." In: Brazis PW, Masdeu JC, Biller J, editors. Localization in Clinical Neurology. 7th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2016. pp. 239-256.
   
2. Brazis PW. "Isolated palsies of cranial nerves III, IV, and VI." Semin Neurol. 2009;29(1):14-28. doi:10.1055/s-0028-1124022.

3. Malik SRK, Gupta AK, Choudhry S. "Strabismus and Ocular Paralysis." In: Clinical Ophthalmology: Modern Perspectives. New Delhi, India: Jaypee Brothers Medical Publishers; 2019. pp. 307-334.

4. Bahn RS. "Graves' ophthalmopathy." N Engl J Med. 2010;362(8):726-738. doi:10.1056/NEJMra0905750.


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The classic 'down and out' pupil and ptosis in oculomotor nerve palsy.
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An abducens palsy.
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A typical appearance of exophthalmos seen in a patient with grave's disease.
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2407
Cranial nerve palsies and the eye
Topic
34
Neurology
6520
Medical third nerve palsy, often caused by diabetes, involves damage to the oculomotor nerve, resulting in ptosis, ocular misalignment ("down and out" eye), and normal pupil reaction.
A 58-year-old female presents to the Emergency Department concerned she has had a stroke. Her past medical history includes hypertension, gout, recurrent urinary tract infections, chronic kidney disease (CKD) stage three, type two diabetes on insulin, and a previous N-STEMI. On examination, she is GCS 15/15 and talking in complete and coherent sentences. She has normal power, tone, sensation, reflexes and coordination in all four limbs. She has double vision and a mild ptosis. Her pupils are both symmetrical and equal.

An MRI Head is performed which is normal.

Which of the following is the most likely underlying cause of her presentation?
a