Neurology India, Vol. 59, No. 3, May-June, 2011, pp. 493
Intermittent herniation of brain causing intermittent cerebrospinal fluid rhinorrhea
Department of Neurology, Medical College, Calicut, India
Correspondence Address: K Saifudheen Department of Neurology, Medical College, Calicut India firstname.lastname@example.org
Date of Submission: 01-May-2011
Code Number: ni11153
I read with interest the article 'Intermittent herniation of brain: A rare cause of intermittent cerebrospinal fluid rhinorrhea.'  I have a few concerns: The authors presume that intermittent cerebral herniation is leading to intermittent cerebrospinal fluid (CSF) rhinorrhea but have not taken sufficient pains to exclude idiopathic intracranial hypertension (IIH), which has important role in the mechanism of herniation and its management. One of the most common cause of spontaneous CSF rhinorrhea is IIH, even though IIH presenting as CSF rhinorrhea is rare. 
In IIH, the long-standing effect of pulsatile CSF under high pressure leads to expansion and eventual rupture of the arachnoid sleeve surrounding the olfactory filaments which pass through the pits in the cribriform plate, resulting CSF rhinorrhea. So during high pressure, gyrus rectus may herniate. Once pressure is relived by the CSF rhinorrhea, the hernia may resolve. Moreover, to exclude IIH, the authors have quoted a study that showed that empty sella has a 60% incidence  in spontaneous CSF rhinorrhea and 76% incidence in females with spontaneous CSF rhinorrhea; however, the CSF pressure was not measured in this study.
Interestingly, empty sella has a 100% incidence in spontaneous CSF rhinorrhea in another study and the authors of that study concluded that empty sella probably represents a sign of elevated intracranial pressure, which leads to idiopathic spontaneous CSF leaks.  The most likely theory for the development of an empty sella is that it is due to impaired CSF absorption. Approximately 80% of patients with empty sella have obstruction to normal CSF absorption at the arachnoid villi.  Maira et al. showed elevated intracranial pressure in 73% patients with idiopathic empty sella.  Therefore, in any case of spontaneous CSF rhinorrhea with some features of IIH on magnetic resonance imaging, the CSF pressure should be measured even if there is no clinical suspicion of IIH.
Copyright 2011 - Neurology India