Purpose: Joubert syndrome (Online Mendelian Inheritance in Man 213300) is a rare autosomal recessive congenital malformation of the brainstem and cerebellar vermis. Diagnosis is based on characteristic clinical features (e.g., hypotonia, episodic hyperpnea, developmental delay, progressive ataxia) and is confirmed by distinctive neuroradiologic findings (e.g., the "molar tooth" sign). Variable ophthalmic features have been mentioned in prior reports; however, most do not detail eye findings and the few that do were before the publication of suggested diagnostic criteria. The objective of the current study is to describe the ophthalmic phenotype in a cohort of patients with Joubert syndrome for whom the diagnosis was made using current diagnostic criteria.
Design: Prospective case series.
Participants: Eight children diagnosed clinically with radiologic confirmation.
Methods: Ophthalmic examination and visual electrophysiology.
Main outcome measures: Ocular and oculomotor examination (as allowed by patient cooperation), electroretinography, flash visual-evoked potential (fVEP).
Results: Patients' ages ranged from 7 months to 10 years. Saccadic dysfunction was observed in all cooperative patients (6/6); compensatory head thrusts or turns were present in all except the youngest patient (7 months of age). Most patients (5/8) had primary-position nystagmus (see-saw in 3/5). Abnormal pursuit (3/7) and a dystrophic retinal appearance (3/8) were also seen. One patient had bilateral asymmetric ptosis with unilateral lid elevation during ipsilateral abduction. Electroretinography findings were normal for all 8 patients. Seven patients underwent fVEP; 6 were abnormal (asymmetric) and one was not interpretable because of study artifact.
Conclusions: Ophthalmologists should be aware that saccadic dysfunction (typically with head thrusts) and primary position nystagmus (typically see-saw) in a developmentally delayed child suggest the diagnosis of Joubert syndrome, especially if a dystrophic retinal appearance is also present. Our findings of asymmetric fVEPs and see-saw nystagmus suggest an abnormality in optic nerve decussation, consistent with the concept that impaired axonal guidance occurs in patients with Joubert syndrome.
Financial disclosure(s): The author(s) have no proprietary or commercial interest in any materials discussed in this article.