Approach to Nystagmus
Two general categories of nystagmus are jerk versus pendular.
Jerk nystagmus is what we are usually referring to when we say horizontal or vertical nystagmus and is described by the trajectory and the provoking factor (e.g., gaze-evoked positional). Examples of this are upbeat or vertical, downbeat, horizontal, or torsional.
Pendular nystagmus have a sinusoidal oscillation (think a sine wave as depicted below). The important fact here is that there is never a fast phase here or a “jerking.” It can move in a torsional, horizontal, vertical, or combination of these that results in various patterns (e.g., circular, elliptical). We discussed pendular nystagmus in the discussion of oculomasticatory myorhythmia seen in Whipple’s disease – more on this later.
Causes of Vertical Nystagmus
The primary source of data regarding causes of vertical nystagmus is from Baloh et al’s 1989 paper in ze French literature (Revue neurologique) that reviewed the clinical features of 106 patients (86 with vertical nystagmus) from UCLA’s Eye Movement Laboratories. The n is arguably small but the largest cohort of data that we have currently.
Key takeaways include:
- Brainstem/cerebellar stroke + cerebellar degeneration account for almost half of the cases.
- This finding on physical exam should prompt further evaluation for primary CNS etiologies and may include prompt advanced imaging.
Here is the summary of their findings:
- Brainstem/cerebellar stroke (n=23, 27%)
- Cerebellar degeneration – acquired or hereditary (n=17, 20%)
- Demyelination – mostly MS and small proportion is focal demyelination (n=14, 16%)
- Tumor/structural lesion – for example, brainstem gliomas and mets (n=10, 12%)
- Infection – viral meningitis/encephalitis and tuberculoma (n=4, 4%)
- Metabolic – Wernicke’s encephalopathy (n=3, 3%)
- The rest (which account independently for n=1 or < 1%)
- Vascular malformations – A-V, aneurysm
- Inflammation – sarcoid, Behcet’s
- Autoimmune conditions – paraneoplastic antibodies, anti-glutamic acid decarboxylase antibodies
- Meds – anticonvulsants, opiates, anticholinesterase insecticides
- Congenital NOS
- Pathognomonic for Whipple’s disease.
- Pendular oscillations of the eyes that diverge and converge when a patient is looking at the examiner that is associated with synchronous masticatory contractions.
- Usually associated with vertical and horizontal gaze palsy.
- Of note, if this finding is present there is no indication for jejunal biopsy nor blood or CSF PCR for Trophyeryma whippelii before initiating treatment with trimethoprim-sulfamethoxazole.