B‐waves are present in patients without intracranial pressure disturbances

Abstract

Intracranial pressure (ICP) B‐waves are defined as short, repeating elevations of ICP of up to 50 mmHg with a frequency of 0.5–2 waves/min. The presence of B‐waves in overnight recordings is regarded as a pathological phenomenon. However, the physiology of B‐waves is still not fully understood and studies with transcranial Doppler, as a surrogate marker for ICP, have suggested that B‐waves could be a normal physiological phenomenon. We present four patients without known structural neurological disease other than a coincidentally found unruptured intracranial aneurysm. One of the patients had experienced well‐controlled epilepsy for several years, but was included because ICP under these conditions is unlikely to be abnormal. Following informed consent, all four patients had a telemetric ICP probe implanted during a prophylactic operation with closure of the aneurysm. They underwent overnight ICP monitoring with simultaneous polysomnography (PSG) sleep studies at 8 weeks after the operation. These patients exhibited nocturnal B‐waves, but did not have major structural brain lesions. Their ICP values were within the normal range. Nocturnal B‐waves occurred in close association with sleep‐disordered breathing (SDB) in rapid eye movement (REM) and non‐REM sleep stages. SDB during REM sleep was associated with ramp‐type B‐waves; SDB during non‐REM sleep was associated with the sinusoidal type of B‐wave. We propose that B‐waves are a physiological phenomenon associated with SDB and that the mechanical changes during respiration could have an essential and previously unrecognised role in the generation of B‐waves.

Evaluation of diurnal and postural intracranial pressure employing telemetric monitoring in idiopathic intracranial hypertension

“…The observed rise in mean ICP overnight is of interest, headache due to raised ICP is typically noted to be worse on waking whilst the patient is supine and to regress as the patient becomes ambulant in the day (with ICP falling in the standing position). Rising ICP overnight has not be observed in other conditions and may be a specific finding in IIH [8,16,[26][27][28][29][30][31].…”

Reference Values For Intracranial Pressure And Lumbar Cerebrospinal Fluid Pressure: A Systematic Review

“…The literature further indicates that age, weight, neck position, zeropoint for measurement-site, and monitoring equipment is of great importance in measurement of ICP and LCSF op [10,24,[37][38][39][40][41][42].…”

“…For daytime ICP, the established reference intervals were likewise based on a limited number of studies (n = 2) and study participants (n = 45) [42,57]. Furthermore, there are large interpersonal differences in the amount of time spend in an upright position during the day.…”

“…For nighttime, we were able to establish a reference interval from − 15.8 to 28.2 mmHg. Besides a limited number of studies (n = 3) and participants (n = 57) addressing the matter [42,57,58], body position during sleep may vary considerably among patients. Furthermore, the degree of sleep apnoe has also been found to highly impact ICP [42].…”

“…Besides a limited number of studies (n = 3) and participants (n = 57) addressing the matter [42,57,58], body position during sleep may vary considerably among patients. Furthermore, the degree of sleep apnoe has also been found to highly impact ICP [42]. Combined, this could potentially cause signi cant variations in measured ICP and, result in the very wide and clinical unuseful reference interval.…”