Congenital Nystagmus: Oscillations of the Eyes-2

Congenital Nystagmus; Horizontal Pendular Nystagmus; Infantile Nystagmus Syndrome; Optokinetic Nystagmus AbsentOscillations of the EyesThis child was noted to have oscillations of the eyes in infancy and was given a diagnosis of congenital nystagmus.This little boy with Infantile Nystagmus Syndrome has: • Horizontal pendular nystagmus in primary gaze • No head turn • No latent nystagmus 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 7). 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 Neutans 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 7)). 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 mothers 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 71. Abadi RV, Dickinson CM. Waveform characteristics in congenital nystagmus. Documents Ophthalmologica 1986;64:153-167. http://www.ncbi.nlm.nih.gov/pubmed/3608756 2. 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 3. Averbuch-Heller L, Dell'Osso LF, Leigh RJ, Jacobs JB, Stahl JS. The torsional component of ‘horizontal' congenital nystagmus. J Neuroophthalmol 2002;22:22-32. http://www.ncbi.nlm.nih.gov/pubmed/11937902 4. Classification of Eye Movement Abnormalities and Strabismus (CEMAS) Working Group. http://www.nei.nih.gove/news/statements/cemas 2003. 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. Hertle RW, Maybodi M, Mellow SD, Yang D. Clinical and oculographic response to Tenuate Dospan (diethylpropionate) in a patient with congenital nystagmus. Am J Ophthalmol 2002;133:159-160. http://www.ncbi.nlm.nih.gov/pubmed/11755862 7. Leigh JR, Zee DS. Diagnosis of Nystagmus and Saccadic Instrusions. In The Neurology of Eye Movements, Fourth Edition. Oxford University Press, NY 2006; Chp 10; 475-558. 8. Shibasaki H, Motomura S. Suppression of congenital nystagmus. J Neurol Neurosurg Psychiatry 1978;41:1078-1083. http://www.ncbi.nlm.nih.gov/pubmed/731252 9. Stevens DJ, Hertle RW. Relationships between visual acuity and anomalous head posture in patients with congenital nystagmus. J Pediatr Ophthalmol Strabismus 2003;40:259-264. http://www.ncbi.nlm.nih.gov/pubmed/14560831curriculum_fellow; MTcongenitalvsacquirednystagmus; MTcongenitalmotornystagmus; horizontaljerknystagmu