PhD defense by Casper Schwartz Riedel

The PhD investigated the fascinating links between intracranial pressure and sleep-disordered breathing.

The research was conducted under the supervision of

• Professor Marianne Juhler
• Professor Poul Jørgen Jennum, MD, DMSc

Opponents on the thesis were

• Professor Rigmor Højland Jensen, MD, DMSc (Chairperson)
• Professor Vesa Kiviniemi, MD, PhD,
  Oulu University, Finland
• Associate Professor Anders Rosendal Korshøj, MD, PhD,
  Aarhus University, Denmark

Thesis summary

Repetitive transient intracranial pressure (ICP) waveform elevations of up to 50 mmHg are often used to define pathological conditions and determine ICP-reducing treatment indications. Despite several attempts to identify background physiology, no general or partial explanation for these changes has been identified. This thesis investigated the prevalence of sleep-disordered breathing (SDB) in patients with hydrocephalus, and the associations between transient ICP elevations, sleep stages, pCO2, and SDB in “normal” subjects and patients with different hydrocephalus types and idiopathic intracranial hypertension (IIH) undergoing diagnostic ICP monitoring.

We included 48 patients with hydrocephalus in Study I for nocturnal polysomnography (PSG) sleep evaluation. Twenty-three with simultaneous pCO2 measurements. In studies II and III, PSG with simultaneous ICP monitoring was performed. In study II, we included 4 “normal” subjects. Normal subjects were treated for an unruptured aneurysm without ICP or cerebrospinal fluid dynamic disturbances. In Study III, we included 34 patients with hydrocephalus or IIH. Lastly, three patients in Study III were monitored with continuous positive airway pressure (CPAP) treatment for an additional night.

Our main findings are:

1. Patients with idiopathic normal-pressure hydrocephalus (iNPH) frequently have severe SDB, which is not found in other common forms of adult hydrocephalus.
2. In patients measured with transcutaneous (PTCCO2) or end-tidal (PETCO2), SDB was not associated with transient elevations of pCO2 or hypoventilation with pCO2 retention during sleep,
3. Transient ICP elevations are highly associated with SDB in “normal” subjects and patients with neurosurgical disorders.
4. High-amplitude ramp-type transient ICP elevations are related to SDB during REM sleep, and sinusoidal type with NREM sleep.
5. Many patients with IIH and pediatric-onset hydrocephalus exhibit similar ICP changes during REM sleep.
6. CPAP treatment can reduce the number of transient ICP elevations and change mean ICP during sleep. In conclusion, SDB is frequently found in patients with iNPH, and SDB is associated with a significant proportion of transient ICP elevations without changes in pCO2. However, several mechanisms are probably responsible for generating ICP elevations, particularly in REM sleep, when ICP is elevated, and in patients with reduced compliance.

Dive into the individual research papers below.