Intracranial Pressure in Experimental Models of Headache

The purpose of this study is to determine whether increased pressure in the head is elevated in people who suffer from High Altitude Headache. We hypothesise that head pressure will be elevated in people with High Altitude Headache.

High Altitude Headache is the primary symptom of Acute Mountain Sickness. However, at present the reason why some individuals suffer from High Altitude Headache and others do not remains unknown. It is widely believed that elevated pressure within the brain leads to stretching of pain sensitive fibres and thus headache. However, evidence of raised intracranial pressure during High Altitude Headache is currently unavailable. Therefore, this study aims to examine a proxy measure of intracranial pressure (Optic Nerve Sheath Diameter) in persons visiting High Altitude, half of whom have been given the drug acetazolamide that is known to reduce headache symptoms.

Arm 1: ACETAZOLAMIDE (250mg) will be given to subjects at fifteen, twenty and thirty two hours post hypoxic exposure (3777m).

Placebo (LACTOSE MONOHYDRATE) will be given to subjects at fifteen, twenty and thirty two hours post hypoxic exposure (3777m).

During a forty eight hour hypoxic exposure (3777m), subjects will be given either acetazolamide or placebo at hours fifteen, twenty and thirty two.

During a forty eight hour hypoxic exposure (3777m), subjects will be given either acetazolamide or placebo at hours fifteen, twenty and thirty two.

Baseline is defined as the average of the 3 hour and 12 hour normoxia measurement. 24 hours is defined at the 24 hour hypoxia measurement. Optic nerve sheath diameter obtained by ultrasonography of the eye. Increased optic nerve sheath diameter suggests greater intra cranial pressure.

Baseline is defined as the average of the 3 hour and 12 hour normoxia measurement. 24 hours is defined at the 24 hour hypoxia measurement. Outcome measured using visual analogue scale, where 0 mm is no headache and 100 mm is maximum headache.

Baseline is defined as the average of the 3 hour and 12 hour normoxia measurement. 24 hours is defined at the 24 hour hypoxia measurement.

Baseline is defined as the average of the 3 hour and 12 hour normoxia measurement. 24 hours is defined at the 24 hour hypoxia measurement. Urine output was recorded by 24 hour urine collection and fluid intake by 24 hour food diaries. Fluid balance was calculated as: (urine output (L) / fluid intake (L) ) * 100.

Baseline is defined as the average of the 3 hour 12 hour normoxia measurements. 3 hours is defined at the 3 hour hypoxia measurement.

Baseline is defined as the average of the 3 hour 12 hour normoxia measurements. 12 hours is defined at the 12 hour hypoxia measurement.

Baseline is defined as the average of the 3 hour and 12 hour normoxia measurements. 36 hours is defined at the 36 hour hypoxia measurement.

Inclusion Criteria: Member of the Italian High Altitude Research Expeditions Exclusion Criteria: Are under the age of 18years; sulfonamide allergy Liver or kidney disfunction Have any other uncontrolled medical condition Or are unable to give consent.

Lawley JS, Oliver SJ, Mullins P, Morris D, Junglee NA, Jelleyman C, Macdonald JH. Optic nerve sheath diameter is not related to high altitude headache: a randomized controlled trial. High Alt Med Biol. 2012 Sep;13(3):193-9. doi: 10.1089/ham.2012.1019.