Poor pupil reactivity and asymmetry are potential hallmarks of worsening intracranial injury in patients with acute neurological conditions. However, their clinical significance after intracranial surgery, when mass effect is less likely to directly affect midbrain pupillary pathways, is unclear. 

Of 24 patients, the mean age was 45.29 ± 19.23 years and 16 were male (66.7%). Thirteen patients received hemicraniectomies for stroke (N=7) or ICH (N=6; spontaneous or related to another injury), 9 had hemicraniectomy for acute subdural hemorrhage, and 2 underwent suboccipital craniectomies for posterior circulation ICH. For all patients, pupil abnormalities occurred in 53.82% of post-surgical measurements, as compared to 45.5% of available pre-surgical measurements. Within the subgroup of patients with ≥3 measurements before and after surgery (n=13), the median minimum NPi post-surgery was lower than pre-surgery (3.8 [2.7-3.39] v. 3.9 [2.7-3.51], p < 0.001). Post-surgery, decreased NPi was associated with loss of cranial nerves, motor decline, and refractory intracranial pressure.