Amnesia for loss of consciousness in carotid sinus syndrome: implications for presentation with falls.

OBJECTIVES: The goal of this study was to compare the clinical characteristics of patients with carotid sinus syndrome who presented with falls with those who presented with syncope.
BACKGROUND: Carotid sinus syndrome presents with both falls and syncope. The reasons for this differential presentation are unknown, but amnesia for loss of consciousness may be the underlying cause.
METHODS: Two groups of 34 consecutive patients with carotid sinus syndrome as the sole cause of falls and syncope were recruited. Cognitive function and clinical characteristics were compared between the two groups.
RESULTS: Syncopal subjects with carotid sinus syndrome were more likely to be older males (18 [53%] vs. 7 [21%] years; p = 0.006) with a longer duration of symptoms (27.9 vs. 13.3 months; p = 0.009) and more soft tissue injuries (19 [56%] vs. 9 [26%]; p = 0.03). Duration of asystole during carotid sinus massage was similar in both groups (5.1 vs. 5.4 s; p = 0.42), but witnessed amnesia for loss of consciousness was more frequent in fallers than those with syncope (21 [95%] vs. 4 [12%]; p < 0.001). Clinical characteristics and cognitive function were otherwise similar in both groups.
CONCLUSIONS: Patients with carotid sinus syndrome have similar rates of witnessed loss of consciousness during laboratory testing regardless of symptoms. However, those presenting with falls are far less likely to perceive any disturbance of consciousness than those with syncope, showing for the first time the manner in which such patients manifest symptoms. Cognitive impairment does not explain the amnesia for loss of consciousness seen in fallers with carotid sinus syndrome.