From the Guidelines
Clinical Significance of Horizontal Gaze Nystagmus
Observing 6 points of horizontal gaze nystagmus is highly suggestive of a 6th nerve palsy, also known as abducens palsy, which typically presents with an acute onset of horizontal double vision, worse at distance than at near and worse laterally toward the side of the affected nerve 1.
- The majority of acute 6th nerve palsies in the adult population are vasculopathic, associated with risk factors such as diabetes and hypertension, and most resolve after 6 months, with about one-third resolving within 8 weeks 1.
- However, if no recovery is apparent by 6 months, approximately 40% of patients demonstrate a serious underlying pathology warranting further evaluation, such as giant cell arteritis, trauma, or neoplasm 1.
- Other common causes of 6th nerve palsy include trauma and neoplasm, which may present with additional neurologic changes, such as facial and extremity motor weakness, or visual field defects 1.
- It is essential to evaluate patients with 6th nerve palsy for associated neurologic or ocular findings, such as facial palsy, third- and fourth-cranial nerve involvement, or central acuity loss from optic nerve involvement, to determine the underlying cause and guide further management 1.
From the Research
Clinical Significance of Horizontal Gaze Nystagmus
The observation of 6 points of horizontal gaze nystagmus can be clinically significant in diagnosing and localizing lesions in the central nervous system, particularly in the brainstem and cerebellum.
- Horizontal gaze nystagmus can be associated with lesions in the pons, which is responsible for generating horizontal eye movements 2.
- The presence of horizontal nystagmus can also indicate cerebellar dysfunction, which can be caused by various factors such as drugs, chronic alcohol abuse, or neurodegenerative cerebellar disorders 2.
- In patients with multiple sclerosis, horizontal nystagmus can be attributed to brainstem disease, but lesions in other regions such as the cortex can also result in nystagmus 3.
- The direction and characteristics of nystagmus can provide clues about the underlying cause, such as benign positional vertigo, which can be treated with canalith repositioning maneuvers 4.
Diagnostic Considerations
When evaluating a patient with horizontal gaze nystagmus, it is essential to consider the following:
- A systematic clinical examination of eye movements, including eye position, range of eye movements, smooth pursuit, saccades, gaze-holding function, and optokinetic nystagmus 5, 2.
- The use of diagnostic tests such as head-impulse tests and diffusion tensor imaging to identify lesions and disrupt tracts in the neural integrator circuit 6, 3.
- A thorough medical history and physical examination to rule out other potential causes of nystagmus, such as vestibular disorders or neurological diseases 5, 2.