Acquired pendular nystagmus: its characteristics, localising value and pathophysiology

Area of Science:

• Neuroscience
• Ophthalmology
• Neurology

Background:

• Acquired pendular nystagmus (APN) is an involuntary eye movement disorder.
• APN can be associated with various neurological conditions, including multiple sclerosis and cerebrovascular accidents.

Purpose of the Study:

• To investigate the characteristics of APN in patients.
• To review literature cases of APN.
• To explore the underlying mechanisms and prognosis of APN.

Main Methods:

• Clinical investigation of 16 patients with APN.
• Review of 32 previously reported APN cases.
• Spectral analysis to characterize nystagmus amplitude, frequency, and inter-eye coherence.

Main Results:

• Common causes included multiple sclerosis (2/3) and cerebrovascular events (1/3).
• Nystagmus varied in form (monocular/binocular, conjugate/disconjugate) and frequency (2.5-6 Hz).
• Associated signs included squint, convergence failure, skew deviation, and internuclear ophthalmoplegia.

Conclusions:

• APN likely originates from a mechanism near oculomotor nuclei, affecting conjugate eye movements.
• Neuronal instability may cause the nystagmus periodicity and associated somatic tremors.
• Prognosis for APN is generally poor; suppression with hyoscine had significant side effects.