From the Research
Phencyclidine (PCP) can cause rotary nystagmus, which is an involuntary rhythmic movement of the eyes in a circular or rotational pattern, as evidenced by studies showing nystagmus as a common abnormality in PCP intoxication 1. This is one of the characteristic neurological effects of PCP intoxication, along with vertical and horizontal nystagmus. PCP is a dissociative anesthetic that acts primarily as an NMDA receptor antagonist in the brain, disrupting normal glutamate signaling.
Key Points
- The presence of rotary nystagmus in a patient with altered mental status, hypertension, hyperthermia, and agitation should raise suspicion for PCP intoxication.
- Other substances that can cause nystagmus include ketamine, alcohol, and certain anticonvulsants, but the combination of vertical, horizontal, and rotary nystagmus is particularly characteristic of PCP.
- This finding can be useful in emergency settings when evaluating patients with unknown drug ingestions or unusual neurological presentations, as noted in a study of 27 cases of PCP intoxication confirmed by urine assay 1.
Clinical Considerations
- Nystagmus was present in 85% of patients with confirmed PCP intoxication, making it a key diagnostic feature 1.
- The most common serious medical complication requiring hospitalization in PCP intoxication is rhabdomyolysis, which may occur more frequently than previously recognized and should be excluded in patients with PCP intoxication 1.