Respiratory challenge MRI: Practical aspects.

Respiratory challenge MRI is the modification of arterial oxygen (PaO2) and/or carbon dioxide (PaCO2) concentration to induce a change in cerebral function or metabolism which is then measured by MRI. Alterations in arterial gas concentrations can lead to profound changes in cerebral haemodynamics which can be studied using a variety of MRI sequences. Whilst such experiments may provide a wealth of information, conducting them can be complex and challenging.

Oxygen challenge magnetic resonance imaging in healthy human volunteers.

Oxygen challenge imaging involves transient hyperoxia applied during deoxyhaemoglobin sensitive (T2*-weighted) magnetic resonance imaging and has the potential to detect changes in brain oxygen extraction. In order to develop optimal practical protocols for oxygen challenge imaging, we investigated the influence of oxygen concentration, cerebral blood flow change, pattern of oxygen administration and field strength on T2*-weighted signal. Eight healthy volunteers underwent multi-parametric magnetic resonance imaging including oxygen challenge imaging and arterial spin labelling using two oxygen concentrations (target FiO of 100 and 60%) administered consecutively (two-stage challenge) at both 1.

Magnesium in the management of catecholamine-secreting glomus tumours with intracranial extension.

Purpose: Catecholamine-secreting glomus jugulare tumours are uncommon and their anesthetic management can be challenging. The authors present the first description of the use of magnesium sulfate in the management of two patients with catecholamine-secreting glomus jugulare tumours where there was significant intracranial extension.

Clinical Features: Patient 1 underwent a transmastoid transoccipital excision of a catecholamine-secreting glomus tumour.