Laboratory Studies
Laboratory investigation usually is not required for infantile nystagmus.
Exceptions include workup for metabolic or infectious etiology in congenital cataracts, serology in suspected toxoplasmosis, toxicology in optic atrophy, endocrine assay for pituitary dysfunction in optic nerve hypoplasia, and others.
Children with opsoclonus who otherwise are well should undergo measurement of urine vanillylmandelic acid (and abdominal CT scan) to rule out neuroblastoma.
Imaging Studies
Infantile nystagmus may indicate underlying neurologic disease. Neuroimaging is indicated when a space-occupying lesion or brain malformation is suspected, as in cortical visual impairment or ocular motor disturbance.
Patients presenting with spasmus nutans should undergo MRI to rule out glioma if evidence suggests an anterior visual pathway or hypothalamic disease.
Patients with sporadic (as opposed to familial) aniridia are at risk of developing Wilms tumor and should undergo periodic renal ultrasound. The need for this may be modified with increasing availability of genetic testing.
Patients with optic nerve hypoplasia are at increased risk for other midline CNS abnormalities, such as absence of the corpus callosum or pituitary ectopia; MRI may be indicated to assess the need for endocrine evaluation.
Ocular ultrasonography is indicated in nystagmus patients with persistent hyperplastic primary vitreous (PHPV), cataract, Peters anomaly, and other disorders in which the ocular fundus cannot be visualized. It also is useful to assess the status of the retina in advanced retinopathy of prematurity, familial exudative vitreoretinopathy, and perinatal trauma.
Other Tests
Electroretinography is an essential component of evaluation if intrinsic retinal diseases such as Leber congenital amaurosis, achromatopsia, congenital stationary night blindness, or other disorders are suspected.
Visual-evoked response (VER) has limited use in the evaluation of infantile nystagmus due to the inability of infants to perform pattern VER. Flash VER provides little insight into visual pathway dysfunction but may be of some value in documenting abnormal chiasmal crossing in albinism.
Genetic testing is poised to provide increasing diagnostic insight for patients with nystagmus and many other ocular disorders. However, because of its low diagnostic yield, routine FRMD7 gene mutation screening is not recommended in isolated cases of idiopathic infantile nystagmus syndrome. Nonetheless, it may be considered in patients with a pedigree that indicates X-linked inheritance. [4]
Eye movement recordings can be done to measure the amplitude and frequency of nystagmus, but they mainly are used for research purposes. Pendular waveforms are often punctuated by brief foveation periods on such recordings. Jerk waveforms have highly characteristic increasing velocity slow phases. [4]
Procedures
Examination under anesthesia may be required to adequately evaluate ocular structures in the workup of infantile nystagmus.
Sedation may be required to perform ocular ultrasonography, electroretinography, VER, and neuroimaging.
