Timothy C. Hain, MD . • Page last modified: July 17, 2009
While many ENG abnormalities are blamed on "central" pathology, usually this just means "not peripheral". Here we show the ENG findings in a man with a large, old right parietal CVA (see above). The CVA is very extensive and easily seen as the white area on the left lower part of the image above. The main finding shown here is due to inattention to the left visual space.
Caloric testing is usually normal in persons with cortical strokes. Here there is no RVR, but there is a DP, with left-beating responses being 40% stronger than right. This sort of pattern could be also due to a strong spontaneous nystagmus (which he doesn't have). Strong DP's are occasionally seen in persons with large strokes, but far more commonly they occur in persons without any clear source of lesions.
Here there is a clear cut left-beating nystagmus. Spontaneous nystagmus is sometimes found in parietal lobe lesions.
The interaction between vibration and parietal lobe lesions has so far gone unreported. In this patient, vibration reduced the intensity of the nystagmus on the right, and incrased it on the left, as well as provoked an upbeating nystagmus.
Here smooth pursuit is reduced in both directions, but there is inattention to targets in the left visual space. Because of this, pursuit just stops once the target gets into the left visual space. Once you have excluded techical problems (i.e. tracker not working to left), this is a very specific finding for parietal lobe injury.
Saccades to the left, into the field where the patient is not attending, are multistep. This is a very nonspecific finding.