Congenital Nystagmus: Eyes jump around

Congenital Nystagmus; Horizontal Jerk Nystagmus; Optokinetic Nystagmus Absent; Infantile Nystagmus SyndromeEyes jump aroundThis 14 year old boy was born one month premature weighing 6 pounds 5 ounces. The top of his head failed to close until age 6. In addition he had only half a clavicle and stunted growth. Diagnosis: Cleidocranial dysostosis. He was referred by his endocrinologist for evaluation of difficulty reading and his "eyes jump around". Jason was noted to have spontaneous movements of his eyes when he was quite small, and his mother commented that his eyes tended to oscillate when he was tired but she is now more aware of the eyes jiggling in the past year and felt it might be getting worse. Three years ago he was examined by an ophthalmologist for glasses and his mother was told, at that time, that nystagmus must have been present at birth. Ocular motility examination: Slight head turn to the left Eyes slightly deviated to the right Visual acuity 20/30 OU in null position Primary position, right beating nystagmus With gaze approximately 40 degrees to the right, the nystagmus almost stopped and eyes in the null position. On gaze to the left, large amplitude gaze evoked nystagmus. No vertical nystagmus on up or downgaze No latent nystagmus Electronystagmogram and videonystagmogram: • Spontaneous and gaze-evoked nystagmus with eyes open with fixation on a target. • No nystagmus with the eyes opened in complete darkness. • The nystagmus did not have the appearance of vestibular (jerk) nystagmus, as the waveform was composed of hyperbolic slow phase components joined by a peak directed rightward. Saccades - Normal with superimposed background nystagmus. Pursuit Tracking (horizontal and vertical): 0.2 Hertz: sinusoidal with superimposed background nystagmus 0.3 Hertz: Sinusoidal with superimposed background nystagmus. OptokineticTracking (horizontal and vertical) - Normal Positional Testing: Dix-Hallpike Tests - No dizziness with superimposed background nystagmus. Static Positional Tests (eyes opened in darkness) - No nystagmus or dizziness. Static Positional Tests (eyes closed) - No nystagmus or dizziness. Summary: - Abnormal study because of spontaneous nystagmus in both eyes best seen in the presence of a fixation target. Careful inspection of the eye movements revealed a hyperbolic slow phase eye movement waveform with peak directed rightward. Diagnosis: Infantile Nystagmus SyndromeThis boy with Infantile Nystagmus Syndrome has: • A slight head turn to the right • Right beating nystagmus in primary gaze • Large amplitude left beating nystagmus gaze left • Smaller amplitude right beating nystagmus gaze right • No lid nystagmus • No nystagmus on full downgaze • No nystagmus on convergence • No latent nystagmus • Vertical pursuit smooth • Horizontal pursuit disrupted by nystagmus Patient told us that he had oscillopsia at distance but not for near objects and had no difficulty reading. Classification: The Classification of Eye Movement Abnormalities and Strabismus Working Group has recommended new names for nystagmus that begins during infancy. Three categories have been defined: 1. Infantile Nystagmus Syndrome (INS), which corresponds to what had previously been called motor or sensory forms of congenital nystagmus. 2. Fusional Maldevelopment Nystagmus Syndrome (FMNS), which corresponds to latent nystagmus occurring in association with amblyopia and strabismus and 3. Spasmus Nutans Syndrome (SNS). Diagnostic features of each of these syndromes are summarized in (ref 6). Box 10-11 Clinical features of Infantile Nystagmus Syndrome (See Chp 10, p513) Box 10-12 Clinical features of Latent Nystagmus (FMNS) (See Ch 10 p517) Box 10-13 Clinical features of Spasmus Nutans Syndrome (See Chp 10 p519) The congenital ‘nystagmus' of INS maybe present at birth but usually develops during infancy. Although variable in wave form (the commonest are increasing-velocity and pendular), certain clinical features usually differentiate INS from other ocular oscillations. • INS is almost always conjugate and mainly horizontal, even on up or downgaze. • A torsional component to the nystagmus is probably common but may be difficult to identify clinically. • Less commonly the nystagmus of INS is mainly seesaw and such patients may have underlying disease of the retina, visual pathways or cerebellum. • Life long nystagmus that is vertical is not typical of INS, and consideration should be given to other diagnoses such as the calcium channelopathies. • Nystagmus of INS is usually accentuated by the attempt to fixate on an object, and by attention or anxiety. • Eyelid closure or convergence, usually suppress it, but occasionally the nystagmus is evoked by viewing a near target. • Often nystagmus decreases when the eyes are moved into a particular position in the orbit; this is called the null point or zone, and corresponds to the range of eye position within which slow-phase eye velocity is at a minimum. • In some patients, especially albinos, the nystagmus periodically reverses direction, but this reversal seldom occurs in the regular manner seen in the acquired form of PAN. Stereovision: is usually degraded, even in children lacking strabismus, partly due to retinal image motion. Oscillopsia: Children with congenital nystagmus rarely complain of movement of visual images (oscillopsia). Head turns: Head turns are common in INS and are used to bring the eye and the orbit close to the null point or zone, which nystagmus is minimal. The presence of such head turns in childhood photographs is often useful evidence in diagnosing INS. Nystagmus blockage syndrome: Another strategy used by patients with either INS or the latent nystagmus of FMNS is to purposely induce an esotropia (nystagmus blockage syndrome) in order to suppress the nystagmus; such an esotropia requires a head turn to direct the viewing eye at the object of interest. Head oscillations: Some patients with INS also show head oscillations. Such head movements are not compensatory and tend to increase when the individual attends to an object, an effort that also increases the nystagmus. It seems possible, therefore, that in most patients head tremor and ocular oscillations represent the output of a common neural mechanism. Associated visual system defects: Overall, most children with congenital forms of nystagmus have no associated visual system defects. (See Table 10-7 Visual system disorders associated with INS Chp 10 p513. (ref 6)). Familial INS: INS either, with or without associated visual system abnormalities may be familial. Autosomal dominant, and sex-linked recessive forms of inheritance have been reported. In x-linked forms, the mother may show subtle ocular motor abnormalities. The hereditary forms of INS, with the characteristic wave forms should be differentiated from other genetic disorders that produce forms of nystagmus typical of cerebellar dysfunction.CongenitalSurgical procedures for congenital nystagmus are discussed in (ref 6).1. Abel, L.A., Wang, Z.I. and Dell'Osso, L.F.: Wavelet Analysis in Infantile Nystagmus Syndrome: Limitations and Abilities. Invest. Ophthalmol. Vis. Sci. 2008. (In Press). http://www.ncbi.nlm.nih.gov/pubmed/18450585 2. Averbuch-Heller L, Dell'Osso LF, Leigh RJ, Jacobs JB, Stahl JS. The torsional component of ‘horizontal' congenital nystagmus. J Neuro-ophthalmol 2002;22:22-32. http://www.ncbi.nlm.nih.gov/pubmed/11937902 3. Classification of Eye Movement Abnormalities and Strabismus (CEMAS) Working Group. http://www.nei.nih.gove/news/statements/cemas 2003. 4. Cogan D. Neurology of the Ocular Muscles, 2nd Edition. Charles C. Thomas Publisher, Springfield, Ill. 1956. 5. Hertle RW, Maldanado VK, Maybodi M, Yang D. Clinical and ocular motor analysis of the infantile nystagmus syndrome in the first 6 months of life. Br J Ophthalmol 2002;86:670-675. http://www.ncbi.nlm.nih.gov/pubmed/12034691 6. Leigh JR, Zee DS. Diagnosis of Nystagmus and Saccadic Instrusions. Chp 10; 475-558. In: The Neurology of Eye Movements, Fourth Edition. Oxford University Press, NY 2006. 7. Shibasaki H, Motomura S. Suppression of congenital nystagmus. J Neurol Neurosurg Psychiatry 1978;41:1078-1083. http://www.ncbi.nlm.nih.gov/pubmed/731252VBcranialdysotosescraniosynotosis; horizontaljerknystagmu