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(See also Autonomic Nervous System: Horner's Syndrome, see Nose and Paranasal Sinus Disorders, see Optic Nerve Disorders, and see Approach to the Neurologic Patient).
Dysfunction of certain cranial nerves may affect the eye, pupil, optic nerve, or extraocular muscles and their nerves; thus, they can be considered cranial nerve disorders, neuro-ophthalmologic disorders, or both. Neuro-ophthalmologic disorders may also involve dysfunction of the central pathways that control and integrate ocular movement and vision. Cranial nerve disorders can also involve dysfunction of smell, vision, chewing, facial sensation or expression, taste, hearing, balance, swallowing, phonation, head turning and shoulder elevation, or tongue movements (see Table 1: Neuro-ophthalmologic and Cranial Nerve Disorders: Cranial Nerves ). One or more cranial nerves may be affected.
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Table 1
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| Cranial Nerves |
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Nerve
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Function
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Possible Findings
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Possible Causes*
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Olfactory (1st)
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Provides sensory input for smell
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Anosmia
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Head trauma
Nasal disorders (eg, allergic rhinitis)
Neurodegenerative disorders (eg, Alzheimer disease, Parkinson disease)
Paranasal sinusitis
Tumors of the cranial fossa, nasal cavity, and paranasal sinuses
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Optic (2nd)
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Provides sensory input for vision
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Amaurosis fugax (transient monocular blindness)
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Embolism of retinal arteries
Ipsilateral internal carotid disease
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Anterior ischemic optic neuropathy
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Complications after cataract extraction
Connective tissue disease that causes arteritis (eg, temporal arteritis, antiphospholipid antibody syndrome)
Diabetes
Hypotension or hypovolemia if severe
Ipsilateral internal carotid artery obstruction
Migraine
Phosphodiesterase type 5 (PDE5) inhibitors (eg, sildenafil, tadalafil, vardenafil)
Retinal artery embolism
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Optic neuritis (papillitis and retrobulbar)
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Acute demyelinating disease (eg, multiple sclerosis, neuromyelitis optica)
Bacterial infections (eg, TB, syphilis, Lyme disease)
Postinfectious or disseminated encephalomyelitis
Uveitis
Viral infections (eg, HIV, herpes simplex, hepatitis B, cytomegalovirus)
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Toxic-nutritional optic neuropathy (toxic amblyopia)
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Drugs (chloramphenicol, ethambutol, isoniazid, streptomycin, sulfonamides, digitalis, chlorpropamide, ergot, disulfiram)
Methanol ingestion
Nutritional deprivation if severe
Organic mercury
Vitamin B12 deficiency
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Bitemporal hemianopia
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Craniopharyngioma
Meningioma of tuberculum sellae
Saccular aneurysm in the cavernous sinus
Suprasellar extension of pituitary adenoma
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Oculomotor (3rd)
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Raises eyelids
Moves eyes up, down, and medially
Adjusts amount of light entering eyes
Focuses lenses
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Palsies
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Aneurysm of posterior communicating artery
Ischemia of the 3rd cranial nerve (often due to small-vessel disease as occurs in diabetes) or of the midbrain
Transtentorial herniation due to intracranial mass (eg, subdural hematoma, tumor, abscess)
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Trochlear (4th)
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Moves eye in and down via the superior oblique muscle
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Palsies
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Often idiopathic
Head trauma
Infarction often due to small-vessel disease (eg, in diabetes)
Tentorial meningioma
Pinealoma
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Trigeminal (5th)
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Provides sensory input from the eye surface, tear glands, scalp, forehead, and upper eyelids
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Neuralgia
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Vascular loop compressing the nerve root, occasionally multiple sclerosis
Lesions of cavernous sinus or superior orbital fissure
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Provides sensory input from the teeth, gums, lip, lining of palate, and skin of the face
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Neuralgia
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Lesions of cavernous sinus or superior orbital fissure
Multiple sclerosis (occasionally)
Vascular loop compressing the nerve root
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Moves masticatory muscles (chewing, grinding the teeth)
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Neuropathy
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Carcinomatous or lymphomatous meningitis
Connective tissue disorders
Meningiomas, schwannomas, or metastatic tumors at the skull base
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Abducens (6th)
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Moves the eye outward (abduction) via the lateral rectus muscle
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Palsies
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Often idiopathic
Head trauma
Increased intracranial pressure
Infarction (may be mononeuritis multiplex)
Infections or tumors affecting the meninges
Multiple sclerosis
Nasopharyngeal carcinoma
Pontine or cerebellar tumors
Pontine infarction
Wernicke encephalopathy
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Facial (7th)
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Moves muscles of facial expression
Proximal branches: Innervate tear glands and salivary glands and provide sensory input for taste on the anterior two thirds of the tongue
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Palsies
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Vestibular schwannoma
Basilar skull fracture
Bell palsy
Guillain-Barré syndrome
Infarcts and tumors of the pons
Lyme disease
Melkersson-Rosenthal syndrome
Ramsay Hunt syndrome
Sarcoidosis
Tumors that invade the temporal bone
Uveoparotid fever (Heerfordt syndrome)
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Hemifacial spasm
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Artery loop compressing the nerve root
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Vestibulocochlear (8th)
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Provides sensory input for equilibrium and hearing
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Tinnitus, vertigo, sense of fullness in the ear, and hearing loss
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Meniere disease
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Benign positional vertigo
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Ear surgery
Labyrinthine concussion
Occlusion of the anterior vestibular artery
Otitis media
Otolithic aggregation in semicircular canal related to aging
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Vestibular neuronitis
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Viral infection
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Hearing loss or disturbance
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Acoustic neuromas
Aging
Barotrauma
Cerebellopontine angle tumors
Congenital rubella infection
Exposure to loud noises
Hereditary disorders
Meningitis
Viral infection (possibly)
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Glossopharyngeal (9th)
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Provides sensory input from the pharynx, tonsils, posterior tongue, and carotid arteries
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Glossopharyngeal neuralgia
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Ectatic artery or tumor (less common) compressing the nerve
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Moves muscles of swallowing and salivary glands
Helps regulate BP
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Glossopharyngeal neuropathy
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Tumor or aneurysm in the posterior fossa or jugular foramen
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Vagus (10th)
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Moves vocal cords and muscles for swallowing
Transmits impulses to the heart and smooth muscles of visceral organs
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Hoarseness, dysphonia, and dysphagia
Vasovagal syncope
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Entrapment of recurrent laryngeal nerve by mediastinal tumor
Herpes zoster
Infectious or carcinomatous meningitis
Medullary tumors or ischemia (eg, lateral medullary syndrome)
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Accessory (11th)
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Turns the head
Shrugs the shoulders
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Partial or complete paralysis of the sternocleidomastoid and trapezius
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Iatrogenic (eg, due to lymph node biopsy in posterior triangle of the neck)
Idiopathic
Trauma
Tumors at the skull base or near the meninges
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Hypoglossal (12th)
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Moves the tongue
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Atrophy and fasciculation of tongue
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Intramedullary lesions (eg, motor neuron disease, tumors)
Lesions of the basal meninges or occipital bones (eg, platybasia, Paget disease of skull base)
Surgical trauma (eg, due to endarterectomy)
Motor neuron disease (eg, amyotrophic lateral sclerosis)
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*Systemic disorders (eg, myasthenia gravis, botulism, variant Guillain-Barré syndrome, poliomyelitis with bulbar involvement, progressive supranuclear palsy) can cause diffuse cranial nerve dysfunction. Amyotrophic lateral sclerosis may cause prominent tongue fasciculations.
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Causes and symptoms of neuro-ophthalmologic and cranial nerve disorders overlap. Both types of disorders can result from tumors, inflammation, trauma, systemic disorders, and degenerative or other processes, causing such symptoms as vision loss, diplopia, ptosis, pupillary abnormalities, periocular pain, facial pain, or headache.
Diagnosis
Evaluation includes the following:
Visual system examination includes ophthalmoscopy and testing of visual acuity, visual fields (see Table: Approach to the Ophthalmologic Patient: Visual field testing), pupils (see Table 2: Neuro-ophthalmologic and Cranial Nerve Disorders: Common Pupillary Abnormalities), and eye movements (ocular motility—see Table 3: Neuro-ophthalmologic and Cranial Nerve Disorders: Common Disturbances of Ocular Motility). As part of this testing, the 2nd, 3rd, 4th, and 6th cranial nerves are examined (see also Approach to the Neurologic Patient: Cranial nerves). Neuroimaging with CT or MRI is also usually required.
The following parts of the visual examination are of particular interest in diagnosing neuro-ophthalmologic and cranial nerve disorders.
Pupils are inspected for size, equality, and regularity. Normally, the pupils constrict promptly (within 1 sec) and equally during accommodation and during exposure to direct light and to light directed at the other pupil (consensual light reflex). Testing pupillary response to consensual light via a swinging flashlight test can determine whether a defect is present. Normally, the degree of pupillary constriction does not change as the flashlight is swung from eye to eye.
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Table 2
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| Common Pupillary Abnormalities |
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Finding
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Explanation
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Asymmetry of 1–2 mm between pupils, preserved light responses, and no symptoms
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Normal variant (physiologic anisocoria)
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Asymmetry, impaired light responses, and preserved response to accommodation (light-near dissociation or Argyll Robertson pupil)
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Neurosyphilis (possibly)
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Bilateral constriction
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Opioids
Miotic eye drops for glaucoma (most common; causing unilateral constriction if single eye is dosed)
Pontine hemorrhage
Organophosphate or cholinergic toxins
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Bilateral dilation with preserved light reflexes
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Hyperadrenergic states (eg, withdrawal syndromes, drugs such as sympathomimetics or cocaine, thyrotoxicosis)
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Bilateral dilation with impaired light response
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Mydriatic eye drops such as sympathomimetics (eg, phenylephrine) and cycloplegics (eg, cyclopentolate, tropicamide, homatropine, atropine)
Brain herniation
Hypoxic or ischemic encephalopathy
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Unilateral dilation with afferent pupillary defect
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Lesions of the eye, retina, or 2nd cranial (optic) nerve
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Unilateral dilation with efferent pupillary defect
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Third cranial (oculomotor) nerve palsies, often due to compression (eg, due to aneurysm of the posterior communicating artery or to transtentorial herniation)
Iris trauma (also irregular pupil)
Mydriatic eye drops*
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Unilateral dilation with minimal or slow direct and consensual light reflexes and pupil constriction in response to accommodation
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Tonic (Adie) pupil†
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*Transtentorial herniation and use of mydriatic eye drops can often be distinguished by instilling a drop of pilocarpine ocular solution into the dilated pupil; no constriction in response suggests mydriatic eye drops.
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†Tonic pupil is permanent but nonprogressive abnormal dilation of the pupil due to damage of the ciliary ganglion. It typically occurs in women aged 20 to 40. Onset is usually sudden. The only findings are slight blurring of vision, impaired dark adaptation, and sometimes absent deep tendon reflexes.
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Eye movements are checked by having the patient hold the head steady while tracking the examiner's finger as it moves to the far right, left, upward, downward, diagonally to either side, and inward toward the patient's nose (to assess accommodation). However, such examination may miss mild paresis of ocular movement sufficient to cause diplopia.
Diplopia may indicate a defect in bilateral coordination of eye movements (eg, in neural pathways) or in the 3rd (oculomotor), 4th (trochlear), or 6th (abducens) cranial nerve. If diplopia persists when one eye is closed (monocular diplopia), the cause is probably a nonneurologic eye disorder (see Symptoms of Ophthalmologic Disorders: Diplopia). If diplopia disappears when either eye is closed (binocular diplopia), the cause is probably a disorder of ocular motility. The 2 images are furthest apart when the patient looks in the direction served by the paretic eye muscle (eg, to the left when the left lateral rectus muscle is paretic). The eye that, when closed, eliminates the more peripheral image is paretic. Placing a red glass over one eye can help identify the paretic eye. When the red glass covers the paretic eye, the more peripheral image is red (see also Symptoms of Ophthalmologic Disorders: Physical examination).
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Table 3
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| Common Disturbances of Ocular Motility |
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Clinical Finding
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Syndrome
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Common Causes
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Pareses
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Paresis of horizontal gaze in one direction
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Conjugate horizontal gaze palsy
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Lesion in the ipsilateral pontine horizontal gaze center or in the contralateral frontal cortex
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Paresis of horizontal gaze in both directions
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Complete (bilateral) horizontal gaze palsy
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Wernicke encephalopathy
Large bilateral pontine lesion affecting both horizontal gaze centers
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Bilateral paresis of all horizontal eye movements except for abduction of the eye contralateral to the lesion; convergence unaffected
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One-and-a-half syndrome
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Lesion in the medial longitudinal fasciculus and ipsilateral pontine horizontal gaze center
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Unilateral or bilateral paresis of eye adduction in horizontal lateral gaze but not in convergence
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Internuclear ophthalmoplegia
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Lesion in the medial longitudinal fasciculus
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Bilateral paresis of upward eye movement with dilated pupils, loss of the pupillary light response despite preservation of pupillary accommodation and constriction with convergence, downward gaze preference, and downbeating nystagmus
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Parinaud syndrome (a type of conjugate vertical gaze palsy)
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Pineal tumor
Midbrain infarct
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Bilateral paresis of downward eye movements
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Conjugate downward gaze palsy
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Progressive supranuclear palsy
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Unilateral eye deviation (resting position is down and out); unilateral paresis of eye adduction, elevation, and depression; ptosis; and often a dilated pupil
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3rd cranial nerve palsy
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Aneurysms
Oculomotor nerve or midbrain ischemia
Trauma
Transtentorial herniation
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Unilateral paresis of downward and inward (nasal) eye movement, which may be subtle, causing symptoms (difficulty looking down and inward)
Head tilt sign (patient tilts the head to the side opposite the affected eye)
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4th cranial nerve palsy
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Idiopathic
Head trauma
Ischemia
Congenital
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Unilateral paresis of eye abduction
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6th cranial nerve palsy
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Idiopathic
Infarct
Vasculitis
Increased intracranial pressure
Wernicke encephalopathy
Multiple sclerosis
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Skew deviation (vertical misalignment of the eyes)
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Partial and unequal involvement of 3rd cranial nerve nuclei, vertical gaze center, or median longitudinal fasciculus
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Brain stem lesion anywhere from midbrain to medulla
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Weakness or restriction of all extraocular muscles
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External ophthalmoplegia
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Dysfunction of eye muscles or of neuromuscular junction
Usually caused by the following:
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Involuntary or abnormal movements
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Rhythmic involuntary movements, usually bilateral
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Nystagmus
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see Sidebar 1: Approach to the Patient With Ear Problems: Nystagmus
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Fast downward jerk and slow upward return to midposition
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Ocular bobbing
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Extensive pontine destruction or dysfunction
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Gaze overshoot followed by several oscillations
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Ocular dysmetria
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Cerebellar pathway disorders
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Burst of rapid horizontal oscillations about a point of fixation
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Ocular flutter
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Many causes:
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Rapid, conjugate, multidirectional, chaotic movements, often with widespread myoclonus
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Opsoclonus
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Many causes (same as for ocular flutter, above)
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Treatment
Treatment of neuro-ophthalmologic and cranial disorders depends on the cause.
Last full review/revision July 2012 by Michael Rubin, MDCM
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