Case Presentation: A 6-month-old term female with history of mild reflux presented to the pediatric emergency department for seizure-like activity. Her mother described three episodes of eyes jerking and head bobbing, each occurring on waking from a nap and lasting about 30 seconds. She reported the patient’s eyes jerking rapidly to the right and slower back to the left and described the head movement “like a very fast bobble head doll.” There was no postictal period, recent illness, trauma, medication use or concern for ingestion. The infant had normal growth and development, but her mother noted she took longer to fix eye gaze than her siblings. There was an unremarkable birth, family, and social history. Exam found a smiling, babbling infant sitting supported with hands followed by a complete normal physical exam. An episode was not witnessed. Complete blood count, comprehensive metabolic panel, and coagulation studies were unrevealing. A brief literature search of the carefully described episodes presented a possible diagnosis of infantile nystagmus, including spasmus nutans. The mother was shown a video of spasmus nutans and reported it was exactly as her baby appeared. During admission, the patient completed a normal EEG, ophthalmologic exam, and MRI brain with and without contrast and was diagnosed with spasmus nutans. She is now almost one year old with occasional episodes and continued healthy development.
Discussion: Infantile nystagmus may be idiopathic or represent an underlying sensory deficit or oculomotor abnormality. Specific types of nystagmus may indicate unique ophthalmologic deficits or brain lesions. Opsoclonus, while not a true nystagmus, may suggest a diagnosis of neuroblastoma. A triad of ocular oscillations, head titubation, and torticollis characterizes spasmus nutans, a rare and idiopathic pediatric disorder. All three are not required for diagnosis, with torticollis being less common. Head nodding is a compensatory act for nystagmus. Spasmus nutans is considered transient, with the age of onset usually 6 to 12 months and resolution by 4 years of age, but great variability has been reported. The nystagmus of spasmus nutans is often unilateral in nature and if bilateral, dysconjugate, a feature distinguishing it from congenital nystagmus. However, clinical exam cannot differentiate spasmus nutans from underlying retinal disease such as achromotopsia and Bardet-Biedl syndrome, or even tumors in about 1 percent of cases, including chiasmal glioma, ependymomas of the fourth ventricle, or posterior thalamic tumors. Thus, ophthalmologic evaluation and MRI brain are indicated in a presentation suggestive of spasmus nutans. Spasmus nutans carries an excellent prognosis with 20/50 vision or better in most. A higher incidence of strabismus and amblyopia is associated in followed cases compared to controls.
Conclusions: This case highlights the importance of obtaining a descriptive history in the evaluation of seizure-like activity. This added infantile nystagmus, including spasmus nutans, to a differential, which initially considered more common etiologies of seizure-like activity in an infant. Nystagmus is a symptom or sign, not a diagnosis, and raises a unique differential in pediatric patients. Spasmus nutans is a rare, idiopathic disorder with good prognosis, but should only be a clinical diagnosis of exclusion following ophthalmologic exam and MRI brain.