3.12.14 Clinical Eye and Ear Flashcards
Describe the effects of Parasympathetic ANS on the pupils
Constriction
Describe the effects of Sympathetic ANS on the pupils
Dilation
Describe the afferent limb of the Parasympathetic pupillary response.
Lens > retina > optic nerve > optic tract > PRETECTAL NUCLEUS (midbrain) > Edinger-Westphal nucleus
Describe the efferent limb of the Parasympathetic pupillary response.
Edinger-Westphal > CN3 > ciliary ganglion > SHORT ciliary nerves > constrictor muscles
Which important nucleus redirects afferent fibers to the Edinger-Westphal nucleus for the pupillary light reflex?
Pretectal nucleus
Which carries Parasympathetic fibers to the eyes: the long or short ciliary nerve?
Short ciliary nerve
Which carries Sympathetic fibers to the eyes: the long or short ciliary nerve?
Long ciliary nerve
What might cause dilated and unreactive pupils?
Damage to the efferent limb caused by:
- Compression of CN3
- Cavernous sinus fistula
- Stroke in the midbrain (pretectal nucleus; Edinger-Westphal nucleus)
What is Marcus-Gunn? Symptoms?
What might cause it?
(Marcus-Gunn pupil) = afferent limb damage in Parasympathetic ANS control of pupil
Eye is less reactive to swinging light test; caused by:
- Stroke in optic nerve
- Unilateral cataract
- Optic neuritis
Describe the afferent limb of the Sympathetic pupillary response.
Cortex or posterior hypothalamus:
- Emotional response
- Pain sensation
Describe the efferent limb of the Sympathetic pupillary response.
Posterior hypothalmus > reticular formation (brainstem) > ciliospinal center (preganglionic sympathetic neurons of C8-T1) > T1/T2 nerves > across APEX OF THE LUNG > superior cervical ganglion > carotid sheath > cavernous sinus > long ciliary nerves and nasociliary nerves > radial dilator muscles
What is the name for a set of symptoms characterized by the loss of the efferent limb of sympathetic fibers that control the eye? Causes?
Horner’s syndrome; this also would include other sympathetic innervation of one side of the face:
Vasodilation, anhydrosis, miosis, ptosis
Caused by:
- Tumor in apex of the lung
- Surgery on carotid artery (fibers along the sheath)
- Brainstem stroke
What would cause ipsilateral blindness (entire field)?
Damage to the optic nerve
What sort of vision loss would accompany an optic tract lesion?
Contralateral homonymous heminaopsia (field opposite of the lesion)
What sort of vision loss would accompany an optic chiasm lesion?
Bitemporal hemianopsia (loss of lateral fields)
What sort of vision loss would accompany a lesion of Meyer’s loop (which lobe)?
(Temporal lobe)
Contralateral homonymous superior quadrantanopsia
What sort of vision loss would accompany a lesion of the parietal lobe?
Contralateral homonymous inferior quadrantanopsia
What sort of vision loss would accompany a lesion of the occipital lobe?
Contralateral homonymous hemianopsia
What sort of vision loss would accompany posterior cerebral artery occlusion?
Contralateral homonymous hemianopsia with macular sparing
What accounts for macular sparing in posterior cerebral artery occlusion?
A small branch of the middle cerebral artery (some people) to the tip of the occipital lobe
What is hippus?
Normal, rhythmic variation in pupil size
What is physiologic anisocoria?
Normal difference in pupillary size (same person)
- Usually not more than one or two millimeters
What is pharmacologic mydriasis
Dilation of the pupils pharmacologically
What is Argyll-Robertson?
(Argyll-Robertson pupil)
aka “Prostitute’s pupil” - accomodates, but doesn’t react; neurosyphilis
Pupils will constrict when focusing on a close object; will not constrict in response to light
Describe the path of CN3
- Exits ventral midbrain
- Courses near the posterior communicating artery beneath the cerebellar tentorium
- Goes through cavernous sinus to the orbit
Cavernous sinus lesions and transtentorial herniation are associated with dysfunction of…
Cranial nerve III (Oculomotor)
If the patient is found leaning to one side, stating that this helps his vision, what might you expect?
Lesion of CN4, opposite to the side which he is leaning (compensates for loss of down and out movement)
Which cranial nerve exits the brainstem dorsally (after crossing internally)
Cranial nerve IV (Trochlear)
What motion of the eyes does the frontal lobe control (i.e. the right frontal lobe)
Directs eyes to move conjugately in the opposite direction (i.e. right frontal lobe controls looking to the left)
- Right frontal lobe cues the left lateral rectus (abducens); conjugate movement is coordinated by the medial longitudinal fasciculus (MLF)
What is internuclear ophthalmoplegia? What location is affected? Describe the result of a unilateral lesion?
- A deficit of conjugate movement of the eyes.
- The medial longitudinal fasciculus (MLF) coordinates these movements.
- Lesion to the MLF affects ipsilateral adduction (info from the contralateral abducens nucleus crosses over and ascends the MLF to the oculomotor nucleus)
What structures may be affected in sensorineural hearing loss?
Cochlea (hair cells), cochlear nerve, cochlear nucleus, etc. (cochlear and retrocochlear)
What structures may be affected in conductive hearing loss?
External auditory canal, tympanic membrane, ossicles (outer ear and middle ear)
What is the Weber test? What results would you expect normally? Sensorineural hearing loss? Conductive?
Tuning fork to the vertex of the head. Sound lateralizes to (is louder in) one ear or the other
- Normally: equilateral hearing/no lateralization
- Sensorineural: Sound lateralizes to the unaffected ear
- Conductive: Sound lateralizes to the affected ear (overcompensation of nerves)
What is the Rinne test? What results would you expect normally? Sensorineural hearing loss? Conductive?
A test of bone versus air conduction of sound
- Normally: Air > Bone (both ears)
- Sensorineural: Air > Bone (both ears)
- Conductive: Bone > Air (affected ear)
What might you find by otoscopic examination?
Cerumen impactation
Otitis externa
Otitis media
Tympanic membrane perforations
What can be diagnosed by audiometry?
- Conductive vs. Sensorineural hearing loss
- Frequencies sensed
- Deficits (in decibels) of frequencies
What is BAER’s? What does it test?
Brainstem Auditory Evoked Potentials
BAER’s helps in anatomical localization of lesions of the auditory nerve or brainstem
What is electrocochleography (ECochG)?
Compound action potential (AP)?
Summating potential (SP)?
Interpretation of the ratio?
Measurement of the electrical activity within the cochlea after acoustic stimulation
AP = combined recording of numerous individual nerve action potentials
SP = potential arising from displacement of the basilar membrane
SP:AP is normally less than 0.5; increased pressure of the inner ear fluid will increase the ratio
What six tests are commonly used to test cochlear nerve function/hearing?
Weber, Rinne, Otoscopic examination, Audiometry, BAER’s, Electrocochleography (ECochG)
What are the three tests commonly used to test vestibular nerve function?
Rotational test, Caloric test, Electronystagmography (ENG)
With respect to a rotational test spinning the pt to the right, what would you expect of the direction of:
Endolymph flow?
Slow phase nystagmus?
Fast phase nystagmus?
Endolymph: to the right (continuing the motion of the spin)
Slow: along with the endolymph
Fast: opposite of the endolymph (resetting vision)
What is the mnemonic for normal caloric testing results?
COWS:
Cold = opposite (fast phase of nystagmus)
Warm = same (slow phase of nystagmus)
What direction should the fast phase of nystagmus with peripheral lesion? Central lesion?
Peripheral: opposite of the lesion
Central: toward the lesion
Vertigo is due to pathology of what structures?
Labyrinths (peripheral) Vestibular nerve (peripheral) Vestibular nuclei (central)
Sensation of impending faint (near syncope) is usually caused by…
Cardiovascular disorders
Dysequilibrium is usually caused by…
Anxiety, multiple sensory deficits, or cerebellar dysfunction
Ill-defined light-headedness is usually due to…
Hyperventilation or anxiety
Peripheral conditions involving CN8 vestibular function include (6):
Labyrinthitis Meningitis Trauma Meniere's syndrome Benign positional vertigo Cerebellopontine Angle (CPA) tumors
Meniere’s syndrome =
Idiopathic disorder
Paroxysmal attacks of hearing loss, vertigo, and tinnitus
Cerebellopontine Angle tumors
usually acoustic Schwannomas
Vertigo, tinnitus, retrocochlear sensorineural hearing loss
Involvement of CN5 and CN7
Central conditions involving CN8 vestibular function include (3):
Multiple sclerosis
Vascular (stroke)
Neoplasms
