HINTS to diagnosing cerebellar stroke – A simple eye exam more sensitive than MRI? Part V-Final Installment
Kattah et al. (2009) describe a bedside eye movement exam thought to be very sensitive in differentiating acute vertigo patients with CS from those with peripheral vestibular disorders. The brief exam includes a combination of Head Impulse (Head Thrust) testing as described below, a review of nystagmus pattern , and examination for ocular misalignment (vertical skew deviation) using the cross cover test. The cross cover test involves having the patient look at an object in the distance, then alternately covering each eye. If there is a consistent eye movement to regain fixation on the object, then ocular misalignment is suspected. Some physicians use a Maddox Rod to provide a more objective evaluation of ocular misalignment.
This combination of eye exams, described as HINTS (Head Impulse test – Nystagmus – Test of Skew) is reported to be more sensitive than MRI in early identification of CS.
Head Thrust testing is almost always positive in patients with acute vertigo of labyrinthine origin, and almost always (approximately 90%) negative in patients suffering vertigo related to CS. Direction changing horizontal nystagmus is sometimes (approximately 20%) present with CS, but nystagmus is almost always direction fixed in acute labyrinthine disorders. Vertical skew deviation (ocular misalignment) is present in some (25%) of CS patients, but very rare (4%) in labyrinthine patients. When a patient presents with the combination of: 1. Normal Head Thrust exam, 2. Direction changing horizontal nystagmus, and 3. Positive Skew Deviation, there is a high probability (100% in the recent study) of brain or brainstem abnormality. Conversely, when this combination of exams is considered benign (e.g. positive head thrust, no nystagmus or direction fixed nystagmus, and negative test for skew deviation) there is a very small chance (4%) of central involvement. This exam has significantly better sensitivity (100% versus 72%), and comparable specificity (96% versus 100%) when compared to immediate MRI (Kattah et al., 2009). Because this exam can be done in one or two minutes and requires minimal equipment (infrared video or Frensel glasses), there is great interest in expanding and independently duplicating these findings. This concludes the five part series on acute vertigo and stroke. Next week we will take a look at recording techniques for nystagmus.
Kattah, J., Talkad, A., Wang, D., Hsieh, Y., & Newman-Toker, D. (2009). HINTS to diagnose stroke in the acute vestibular syndrome: three-step bedside oculomotor examination more sensitive than early MRI diffusion-weighted imaging. Stroke, 3504-3510