Transient intracranial pressure elevations are associated with sleep apnea

Background: Repetitive transient intracranial pressure waveform elevations up to 50 mmHg (ICP B-waves) are often used to define pathological conditions and determine intracranial pressure-reducing treatment indications. We recently showed that nocturnal transient ICP elevations are present in patients without structural brain lesions or hydrocephalus in whom they are associated with sleep apnea. However, whether this signifies a general association between intracranial pressure patterns and sleep apnea is still unknown. Methods We included 34 patients with hydrocephalus, or idiopathic intracranial hypertension (IIH), referred to the Neurosurgical Department, Copenhagen, Denmark, from 2017 to 2021. Every patient underwent a diagnostic overnight intracranial pressure monitoring on clinical indications with simultaneous polysomnography (PSG) sleep studies. All transient ICP elevations were objectively quantified for all patients. Three patients were monitored with continuous positive airway pressure (CPAP) treatment for an additional night. Results All patients had transient intracranial pressure elevations associated with sleep apnea. The mean temporal delay from sleep apnea to transient intracranial pressure elevations for all patients was 3.6 seconds (SEM 0.2 seconds). High amplitude ramp-type transient intracranial pressure elevations were associated with rapid eye movement (REM) sleep and sinusoidal-type elevations with non-REM (NREM) sleep. CPAP treatment reduced the number of transient intracranial pressure elevations in all three patients (mean 37%). CPAP treatment elevated the mean intracranial pressure during sleep in two patients by 1.2 and 5.6 mmHg, respectively, and reduced the mean intracranial pressure in one patient with a ventriculoperitoneal shunt by 1.0 mmHg. Conclusion The findings suggest that sleep apnea causes a significant proportion of transient intracranial pressure elevations, and sleep apnea should be considered in intracranial pressure evaluation. Continuous positive airway pressure (CPAP) treatment can reduce their occurrence. However, CPAP may concurrently elevate the mean intracranial pressure. More research is needed on the impact of slow oscillating mechanisms on transient intracranial pressure elevations during high intracranial pressure and REM sleep.