Cerebral venous system and anatomical predisposition to high-altitude headache

The Traumatic Brain Injury Centre, St Mary's Hospital, Imperial College, London, W1 2NY
Annals of Neurology (Impact Factor: 9.98). 03/2013; 73(3). DOI: 10.1002/ana.23796
Source: PubMed


As inspired oxygen availability falls with ascent to altitude, some individuals develop high-altitude headache (HAH). We postulated that HAH results when hypoxia-associated increases in cerebral blood flow occur in the context of restricted venous drainage, and is worsened when cerebral compliance is reduced. We explored this hypothesis in 3 studies.

In high-altitude studies, retinal venous distension (RVD) was ophthalmoscopically assessed in 24 subjects (6 female) and sea-level cranial magnetic resonance imaging was performed in 12 subjects ascending to 5,300m. Correlation of headache burden (summed severity scores [0-4]≤24 hours from arrival at each altitude) with RVD, and with cerebral/cerebrospinal fluid (CSF)/venous compartment volumes, was sought. In a sea-level hypoxic study, 11 subjects underwent gadolinium-enhanced magnetic resonance venography before and during hypoxic challenge (fraction of inspired oxygen=0.11, 1 hour).

In the high-altitude studies, headache burden correlated with both RVD (Spearman rho=0.55, p=0.005) and with the degree of narrowing of 1 or both transverse venous sinuses (r=-0.56, p=0.03). It also related inversely to both the lateral+third ventricle summed volumes (Spearman rho=-0.5, p=0.05) and pericerebellar CSF volume (r=-0.56, p=0.03). In the hypoxic study, cerebral and retinal vein engorgement were correlated, and rose as the combined conduit score fell (a measure of venous outflow restriction; r=-0.66, p<0.05 and r=-0.75, p<0.05, respectively).

Arterial hypoxemia is associated with cerebral and retinal venous distension, whose magnitude correlates with HAH burden. Restriction in cerebral venous outflow is associated with retinal distension and HAH. Limitations in cerebral venous efferent flow may predispose to headache when hypoxia-related increases in cerebral arterial flow occur.

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    • "Wilson first pointed out the analogy between the Space Adaptation Syndrome and the effects of altitude on the cerebral circulation, since they both lead to venous distension (Wilson et al., 2011). Wilson and colleagues suggest that venous distension plays an important role in high altitude headache (Wilson et al., 2013). Gabriel Willmann followed with a talk on the posterior part of the eye as a window on the brain in conditions of hypoxia (Willmann et al., 2014). "

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    • "Notably, the prevalence of intracranial venous sinus stenosis at magnetic resonance venography (MRV) was found to be much higher than that previously expected in both IIHWOP and CM [7, 8]. Sinus stenosis has been recently reported to be highly prevalent also in other primary headaches [9–11]. Sinus stenosis is considered a reliable marker of idiopathic intracranial hypertension (IIH) with a sensitivity and specificity of 93 % [12]. "
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    • "A related hypothesis proposes that fluid redistribution to the intracellular space leading to astrocytic swelling underlies the development of symptomatic AMS [9]. More recently, it has been suggested that high altitude headache may relate to restricted venous drainage following the hypoxia-associated increase in cerebral blood flow at altitude [10]. "
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