Non-nystagmus hyperkinetic eye movement disorders
Francesco Certo1,2, Giulia Salvucci1, Chiara Casellato1
1Clinical Neurology and Movement Disorders Units, San Paolo University Hospital, University of Milan, ASST Santi Paolo e Carlo, Via Antonio di Rudinì 8, Milan, 20142, Italy.
Background:
While nystagmus is an involuntary ocular movement relatively frequent, well described, and easily recognized by most practitioners, non-nystagmus hyperkinetic eye movement disorders (NHEMD) are less obvious and can be overlooked. NHEMD may arise from intrinsic abnormalities in ocular muscles and oculomotor nerves, brain and brainstem lesions, systemic diseases, dysimmune disorders, drugs or can even be functional in nature. Given that some treatable disorders initially manifest with NHEMD, their knowledge becomes crucial.
Aims:
This review aims to offer a practical and comprehensive guide to recognize specific types of NHEMD, to choose the appropriate diagnostic tests and treatments.
Results:
The review approaches individual NHEMD based on the location of anatomical lesions and the underlying pathophysiological mechanisms; therefore, it begins with those arising from abnormalities in extraocular muscles or oculomotor nerves (as for example, superior oblique myokymia and ocular neuromyotonia), then moves to NHEMD due to brainstem and brain involvement (as for example, ocular bobbing, opsoclonus, and tonic downward gaze deviation). Lastly, functional NHEMD and nonnystagmus ocular hyperkinesias associated with specific neurological disorders, such as Parkinson's disease or blepharospasm will be considered.
Conclusion:
Overall, the review offers a comprehensive reappraisal of hyperkinetic disorders of eye motility.
