Ahd   neuro-opthalmology - v. patel - nystagmus (1)
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Ahd neuro-opthalmology - v. patel - nystagmus (1)






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    Ahd   neuro-opthalmology - v. patel - nystagmus (1) Ahd neuro-opthalmology - v. patel - nystagmus (1) Presentation Transcript

    • Overview of NYSTAGMUSVivek Patel MD
    • OBJECTIVES Definition, description Neuroanatomical basis Instrinsic localizing value Representative cases
    • DEFINITION Disorder of ocular motor instability resulting inspontaneous, involuntary, rhythmic oscillationsof the eyes Congenital vs. acquired “jerk” nystagmus vs. pendular “true” nystagmus vs. nystagmoid movements
    •  Conjugate vs. disconjugate vs. dissociated Trajectory may be horizontal, vertical, torsional,or mixed Description of amplitude, frequency, velocity,and intensity may vary with changes in gaze position May be influenced by the integrity of theafferent visual system May exhibit a “null” point
    •  3 main mechanism of maintaining steadygaze: 1) fixation: a) prevent retinal image driftb) suppress unwanted saccades 2) VOR 3) eccentric gaze holding
    •  Pulse (phasic) and step (tonic) outputs must bebalanced for appropriate gaze-holding. Significant cerebellar (vermis) calibration Horizontal: phasic = PPRFtonic = NPH, MVN = neural integratorsVertical: phasic = riMLFtonic = iNC = neural integrator
    • NEUROANATOMICAL BASISLeigh & Zee, Neurology of Eye Movements, 3rded., 1998Leigh & Zee, Neurology of Eye Movements, 3rded., 1998
    • Not always a sign of disease… Physiological: Usually conjugate Preserves clear vision during self-rotation unsustained end-point nystagmus Vestibular nystagmus (brief sustained rot.) OKN (visually driven….uses pursuit mech.)
    • CHILDHOOD NYSTAGMUS Congenital nystagmus: usually recognized in first few months of life – life long May have good vision or poor vision Most often occurs in isolation (motor), but may be associatedwith albinism, LCA, achromatopsia, or optic atrophy Uniplanar, horizontal trajectory irrespective of gaze position No oscillopsia Reversal of OKN direction Exponential increase in slow phase velocity Conjugate Null point (may have resultant head turn) Amplified by attempted fixation (distant) Dampened by convergence and darkness Absent in sleep Association with esotropia
    •  Latent nystagmus: Usually appears within first few months of life Horizontal jerk nystagmus appearing onlyunder monocular viewing conditions Fast phase beats away from occluded eye Strong association with esotropia Usually poor stereopsis May explain subnormal visual acuity testedmonocularly Manifest latent nystagmus: Present even when both eyes are open Loss of peripheral fusion
    •  Monocular nystagmus of childhood: Usually monocular, vertical, low amplitude oscillation Eye with nystagmus may have afferent visual dysfunction Requires neuroimaging (chiasmal glioma) Spasmus Nutans: Asymmetric or monocular low-amplitude oscillations May be horizontal, vertical or torsional Head nodding Torticollis or abnormal head posture Begins in infancy, usually resolved by age 3 to 5 Requires neuroimaging
    • PERIPHERAL VS. CENTRALVESTIBULAR NYSTAGMUSPERIPHERAL Severe vertigo Days to weeks duration Hearing loss, tinnitusassociated Usually horizontal withtorsion Very rarely purely vertical ortorsional Dampened with visualfixation Commonly peripheralvestibular organ dysfunction:labyrynthitis, meniere’sCENTRAL• None or mild vertigo• Often chronic• May be purely vertical ortorsional• visual fixation usually has noeffect• Etiologies commonlyvascular, demyelination,pharmacologic, toxic• Downbeat, upbeat, torsional
    •  Gaze evoked nystagmus: One of the most common forms of centralnystagmus Inability to maintain eccentric gaze “leaky integrator” -- miscalibration between pulseand step inputs Symmetric cerebellar flocculus implicated Age, anti-convulsant therapy, alcoholicdegeneration, stroke, demyelination Baclofen effective
    •  Downbeat nystagmus: Defect in vertical gaze holding Asymmetric inputs from vertical semi-circularcanals produce upward slow drift of eyes Defect in fastigial nuclei calibration Secondary downward corrective fast phase Obeys Alexander’s law Localizes to cervico-medullary junction Arnold-Chiari malformation Treatment with baclofen, clonazepam, base-outprisms
    •  Upbeat nystagmus: Present in primary position or upgaze Classically localizes to a lesion of anterior cerebellarvermis More generally implicates posterior fossa disease Etiologies include stroke, cerebellar degeneration,demyelination, toxic exposures Periodic alternating nystagmus: Horizontal oscillation characterized by a periodic reversalin the direction of nystagmus due a shift in the null point Duration of cycles from 30 seconds to 6 minutes Classically a lesion of the cerebellar nodulus MS, drugs, ethanol, paraneoplastic syndromes Baclofen effective
    • •Bruns nystagmus:• associated with CPA tumors• high frequency, low amplitudenystagmus (fast-phase away from lesion)• low frequency, large amplitudenystagmus on ipsilateral gaze (fast phasetoward lesion)• shift from eye movement response tovestibular imbalance to that of defectivegaze holding
    •  See-saw nystagmus: Disconjugate vertical nystagmus (pendular vs. jerk) Upward moving eye intorts while downard eye extorts Localizes to lesions of diencephalon Visual fields may be useful (disruption of afferents to cerebellum) Ocular flutter/opsoclonus: Burst-like, incoordinated saccadic excursions with high frequency,low amplitude No intersaccadic latency Purely horizontal: ocular flutter Multiplanar: opsoclonus Reflect pause cell dysfunction (pons) Must consider paraneoplastic etiology: SCC of lung, ovarian,breast CA Neuroblastoma in children
    • Acquired pendular nystagmus: Can be vertical, horizontal, torsional, or anycombination (usually one predominates) Usually disconjugate or dissociated Oscillopsia ++ MS, whipple’s, oculopalatal myoclonus Combination of afferent dysfunction andcerebellar calibration
    •  Oculopalatal myoclonus: Vertical pendular eye movements associated with rhythmicupward movement of palate Caudal brainstem pathology: red nucleus, inferior olive, anddentate nuc. Convergence-retraction nystagmus: Commonly associated with dorsal midbrain syndrome May be associated with other Parinaud’s findings Not a true nystagmus: co-contraction of horizontal recti onattempted upgaze Localizes to pretectal area, posterior commissure, INC Pineal cyst or tumor, demyelination, stroke
    • SUMMARY Recognize physiologic vs. pathological Appropriate characterization important Presence of nystagmus may correlate with significantafferent visual dysfunction Recognition of nystagmus may facilitate subsequentneurological or medical investigations (know where tolook) Treatment options do exist