Spasmus nutans is a benign clinical entity characterized by the triad of nystagmus, head nodding, and an abnormal head position (1). The nystagmus is of low amplitude and high frequency and is often asymmetrical in the two eyes. It generally begins between 4 and 12 months of age (1) and is more common in the African American and Hispanic populations (2). Most cases are idiopathic, and its natural history is one of the spontaneous resolutions. In some children, however, it can signal the presence of chiasmal glioma or underlying retinal disease. We examined an infant with spasmus nutans whose unusual clinical course provides a cautionary note for the clinical management of this condition.
A healthy 8-month-old Caucasian infant with spasmus nutans was referred for evaluation of nystagmus, which was first noted at 2 months of age. The nystagmus intensified, and he began bobbing and tilting his head at 3 months of age. His head movements became more pronounced when trying to focus on objects of interest. He was born 4 weeks prematurely weighing 6 lb 11 ounces at birth. The parents had noted no photophobia or difficulty seeing in dim illumination. He had no family history of nystagmus and was neurodevelopmentally normal. On examination, he followed optokinetic stimuli and maintained fixation with either eye, and had normal pupillary responses to light with no relative afferent pupillary defect. He had fine symmetrical shimmery nystagmus, which was associated with vertical head bobbing and a chin-down head when viewing objects at near. Retinoscopy showed a mildly hyperopic refractive error. Retinal examination disclosed no optic disc swelling or pallor, and a normal retina in both eyes.
Magnetic resonance imaging showed bilobed thickening of the optic chiasm extending anteriorly to involve both intracranial optic nerves (Fig. 1). The tumor extended posteriorly to involve the optic tracts and showed additional extension into the right anterior midbrain and mesial temporal lobe. Endocrinologic testing disclosed no abnormalities. Over the next 2 months, his nystagmus and head nodding gradually resolved. Neuro-oncology evaluation was performed, and it was elected to observe him given the absence of associated neurological findings. On follow-up examination at 16 months of age, all signs of spasmus nutans were completely resolved, and repeat neuroimaging showed no change in the tumor size.
The rare association of chiasmal glioma with spasmus nutans is usually signaled by one or more of the following clinical findings: 1) a relative afferent pupillary defect; 2) optic atrophy or disc swelling; 3) large head size; 4) café-au-lait spots; and 5) coexistent neurological dysfunction or emaciation (3,4). Because these clinical findings were absent in this infant, the decision was almost made to forego neuroimaging. More surprising was the finding that the spasmus nutans completely resolved on follow-up examination, although 2 subsequent neuroimaging studies over a 10-month period showed no change in the tumor size. If we had seen the child after the spasmus nutans had resolved, neuroimaging would certainly have been deemed unnecessary.
This case history highlights 3 critical points in the clinical management of spasmus nutans. First, the early onset of spasmus nutans should raise particular concern about chiasmal glioma. Second, the absence of “red flag” systemic or neuro-ophthalmologic signs in the infant with spasmus nutans does not definitively rule out the possibility of chiasmal glioma (5,6). Finally, even the spontaneous resolution of spasmus nutans does not rule out chiasmal glioma as the underlying cause.
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