Ver el código de «Fourth nerve palsy»

==Background==
*Also called the 4th cranial nerve (CN IV)
*Trochlea innervates superior oblique muscle
**Intorts, depresses and abducts the globe
*Trochlear nerve palsy causes an inability to move the eye in inward rotation, downward, and laterally. <ref name="rosen">Marx JA, Hockberger RS, Walls RM, et al., eds. Rosen's Emergency Medicine: Concepts and Clinical Practice. Philadelphia, PA: Mosby/Elsevier; 2013</ref>
*Most common cause of vertical diplopia <ref name="medscape">Sheik Z. Trochlear Nerve Palsy Treatment and Management on emedicine.medscape.com/article/1200187 Accessed on 8/29/2015</ref>

===Etiology===
*[[Head trauma]] <ref name="book">Disorders of Ocular Movement and Pupillary Function In: Adams and Victor's Principles of Neurology. 10th ed. Accessed on AccessMedicine.com on 8/29/2015. Chapter 14 </ref>
*Mechanisms that increase intraocular pressure
**Practically never involved by aneurysm
*[[Herpes zoster]] opthalmicus
*[[Meningitis]]
*Diabetic neuropathy
*[[Lupus]]/Sjogren syndrome

==Clinical Features==
*Vertical, torsional, or oblique diplopia.
**Worse on downward gaze and gaze away from affected muscle <ref name="medscape">Sheik Z. Trochlear Nerve Palsy Treatment and Management on emedicine.medscape.com/article/1200187 Accessed on 8/29/2015</ref>
*Head-tilt
**Tilt typically away from affected side (~70%) to overcome inward rotation of affected eye to create wider separation of images. Can be paradoxical, where patient tilts head toward affected side (~3%) <ref name="rosen">Marx JA, Hockberger RS, Walls RM, et al., eds. Rosen's Emergency Medicine: Concepts and Clinical Practice. Philadelphia, PA: Mosby/Elsevier; 2013</ref> <ref name="brazis">Brazis, PW. Isolated palsies of cranial nerves III, IV, and VI. Seminars in neurology. 2009 Feb. 29(1):14</ref>
**Bielschowsky phenomenon - head tilt to affected side reveals inability to intort, diplopia
*Ask about history of fever, stiff neck, headache, diabetes, hypertension, other sensory and motor symptoms
[[File:trochlear nerve palsy.jpg|thumbnail]]

==Differential Diagnosis==
*''Increased intracranial pressure (ICP)'': [[Pseudotumor cerebri]] 
*''Vascular'': [[Stroke (main) | Stroke]], [[subarachnoid hemorrhage]], aneurysm (extremely rare), microvasculopathy signs and symptoms to diabetes, atherosclerosis or hypertension<ref name="brazis">Brazis, PW. Isolated palsies of cranial nerves III, IV, and VI. Seminars in neurology. 2009 Feb. 29(1):14</ref>
*''Neoplastic'': Tumor in the subarachnoid space 
*''Degenerative/deficiency'': Vitamin B deficiency, [[Wernicke-Korsakoff syndrome]]
*''Idiopathic'': Most common cause of acquired trochlear nerve palsy. 
*''Infection'': [[Meningitis]], [[herpes zoster]]
*''Congenital'': Signs/symptoms of dysgenesis of trochlear nerve nucleus or abnormal peripheral nerve
*''Autoimmune'': [[Myasthenia gravis]], [[multiple sclerosis]], [[systemic lupus erythematosus]], [[giant cell arteritis]], [[Sjogren’s]]
*''Trauma'': Its long course makes it susceptible to traumatic injury. [[Head trauma (adult)]] is the second most common cause. Is generally severe with loss of consciousness. Consider underlying structural abnormalities if results after minor trauma. 
*''Endocrine'': Thyroid ophthalmopathy <ref name="medscape">Sheik Z. Trochlear Nerve Palsy Treatment and Management on emedicine.medscape.com/article/1200187 Accessed on 8/29/2015</ref> <ref name="brazis">Brazis, PW. Isolated palsies of cranial nerves III, IV, and VI. Seminars in neurology. 2009 Feb. 29(1):14</ref> 
*[[Third nerve palsy]]
*[[Abducens nerve palsy]]

==Diagnostic==
===Labs and Tests===
*+/- POC glucose, CBC, and other labs depending on suspected diagnosis
*+/- LP after negative neuroimaging if suspect subarachnoid hemorrhage or meningitis. 
===Imaging===
*CT Head if traumatic, suspect stroke, or subarachnoid hemorrhage (rare).
*MRI is study of choice, although there no increased yield from MRI vs CT scan. <ref name="medscape">Sheik Z. Trochlear Nerve Palsy Treatment and Management on emedicine.medscape.com/article/1200187 Accessed on 8/29/2015</ref> <ref name="brazis">Brazis, PW. Isolated palsies of cranial nerves III, IV, and VI. Seminars in neurology. 2009 Feb. 29(1):14</ref>

==Management==
*Address any acute causes like stroke, trauma
*May require surgical correction
*+/- Neurology consult

==Disposition==
*'''Vasculopathic''': Observation for improvement over 6-8 weeks. Often resolve spontaneously in 4-6 months.
*'''Traumatic''':  Observation for improvement over 6-8 weeks. Often resolves spontaneously. If progressing or lack of improvement – neuroimaging with MRI 
*'''Isolated, idiopathic cases''' very rarely have an underlying etiology after prolonged follow-up, and most resolve spontaneously in weeks to months. If no improvement in 2 months, consider neuroimaging. <ref name="brazis">Brazis, PW. Isolated palsies of cranial nerves III, IV, and VI. Seminars in neurology. 2009 Feb. 29(1):14</ref>

==See Also==
*[[Ocular palsy]]
*[[Cranial nerves]]

==External Links==
[http://emedicine.medscape.com/article/1200187-overview Medscape: Trochlear Nerve Palsy]

==References==
<references/>

[[Category:Ophthalmology]]
[[Category:Neurology]]