Nystagmus Associated with Infantile Esotropia

Fig. 8.12  (a) Two-year-old boy with thalamic glioma and Russell diencephalic syndrome. Courtesy of William F. Hoyt, M.D.

(b) MR scan demonstrating chiasmal glioma and hydrocephalus in child with Russell diencephalic syndrome. Courtesy of Neil R. Miller, M.D.

treated patients. The natural history of Russell diencephalic syndrome following radiation therapy is extremely variable,116 however, with survival of up to 12 years having been documented.96,416

Monocular Nystagmus

In 1956, Cogan106 stated that spasmus nutans is the most common, if not the only, cause of unilateral horizontal nystagmus in infancy. With the added caveat that chiasmal gliomas can present with paradigmatic spasmus nutans,180 this generalization still applies to most infants with monocular nystagmus (Table 8.6). Rarely, severe unilateral visual loss causes a slow, unilateral horizontal nystagmus in the affected eye.77,223,224

In the second decade of life, a monocular vertical oscillation may develop in an eye with reduced vision (20/200 or less) of long duration (the Heimann–Bielschowsky phenomenon). Yee et al592 described the vertical drift with monocular visual loss as small-amplitude, low-frequency, pendular and accentuated by refixation or eccentric gaze. Smith et al507 subsequently described this oscillation as large in amplitude and low in frequency. Pritchard et al457 attempted to reconcile these two views by demonstrating that some patients have small rapid oscillations superimposed on larger oscillations of lower frequency. There is

Table 8.6  Monocular nystagmus in children

Spasmus nutans

Chiasmal/hypothalamic glioma

Heimann–Bielschowsky phenomenon

Congenital unilateral visual loss

some suggestion that the amplitude of the larger waveform may correlate with the duration of visual loss.457 In our experience, most affected patients display a slow-velocity and large-amplitude oscillation that makes it easily distinguishable from other forms of nystagmus. One report documented successful treatment of this condition with oral gabapentin.459 Episodic monocular nystagmus can also be a rare manifestation of epilepsy.303

Nystagmus Associated with Infantile Esotropia

Torsional Nystagmus

Infants with esotropia may display a subtle conjugate torsional nystagmus with no horizontal component. This fine conjugate torsional rotation seems to be a progenitor to latent nystagmus and does not carry additional neurological significance.86,143