The disorder
Clinical features
Two complaints carry the diagnosis: “I’m unsteady, and it’s far worse in the dark,” and “my vision jumps when I move my head.” The spinning that brings most vertigo patients in is conspicuously absent.
The cardinal features
People feel unsteady on their feet, especially in the dark or on soft or uneven ground, and their sight blurs or bounces whenever they move their head — making it hard to read signs while walking or to recognise faces in a moving car. There is usually no spinning. Tap each feature below.
The cluster is: chronic gait imbalance that worsens in darkness or on compliant ground; oscillopsia on head movement and while walking; and characteristically little or no spinning vertigo at rest, because the loss is symmetric.1 Many also report a heavy attentional cost to staying upright and difficulty with spatial orientation.
The burden is easy to underestimate: oscillopsia and imbalance impose a quality-of-life cost comparable to major chronic disease, and the falls risk is real.2 Watch for the patient who became unsteady during or after an ICU admission or a course of intravenous antibiotics — gentamicin vestibulotoxicity is easily missed because it often spares hearing and produces no spinning to flag it.3
At the bedside
The examination is the screen. The VOR failure shows as a positive head impulse test to both sides (overt catch-up saccades on each horizontal thrust) and as a marked drop in dynamic visual acuity — several lines lost on the chart when the head is gently oscillated. Postural signs follow the same theme: the Romberg test worsens sharply with eyes closed, and tandem gait is unsteady, especially in the dark. Crucially there is usually no spontaneous nystagmus, because the loss is symmetric.
The full battery and technique are covered in Bedside clinical tests and HINTS; the instrumented version of the head impulse is the video head impulse test.
Key points
- Imbalance worse in the dark and oscillopsia on head movement are the cardinal symptoms.
- Little or no spinning vertigo and usually no spontaneous nystagmus — the loss is symmetric.
- Bedside: bilateral head-impulse catch-up saccades, reduced dynamic visual acuity, Romberg worse eyes-closed, unsteady gait.
- Suspect gentamicin vestibulotoxicity after IV aminoglycosides or an ICU stay — it often spares hearing.